arg
[oweals/gnunet.git] / src / fs / fs_download.c
index 29501070386e1e69abc864a1482f09d108403309..1565f9a3d5e2a6a5b97a7e57768fdb8286001956 100644 (file)
@@ -1,10 +1,10 @@
 /*
      This file is part of GNUnet.
-     (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008, 2009, 2010 Christian Grothoff (and other contributing authors)
+     (C) 2001-2011 Christian Grothoff (and other contributing authors)
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 2, or (at your
+     by the Free Software Foundation; either version 3, or (at your
      option) any later version.
 
      GNUnet is distributed in the hope that it will be useful, but
  * @author Christian Grothoff
  *
  * TODO:
- * - handle recursive downloads (need directory & 
- *   fs-level download-parallelism management)
- * - handle recursive downloads where directory file is
- *   NOT saved on disk (need temporary file instead then!)
- * - location URI suppport (can wait, easy)
- * - check if blocks exist already (can wait, easy)
- * - check if iblocks can be computed from existing blocks (can wait, hard)
- * - persistence (can wait)
+ * - different priority for scheduling probe downloads?
  */
 #include "platform.h"
 #include "gnunet_constants.h"
 
 #define DEBUG_DOWNLOAD GNUNET_NO
 
+/**
+ * Determine if the given download (options and meta data) should cause
+ * use to try to do a recursive download.
+ */
+static int
+is_recursive_download (struct GNUNET_FS_DownloadContext *dc)
+{
+  return  (0 != (dc->options & GNUNET_FS_DOWNLOAD_OPTION_RECURSIVE)) &&
+    ( (GNUNET_YES == GNUNET_FS_meta_data_test_for_directory (dc->meta)) ||
+      ( (dc->meta == NULL) &&
+       ( (NULL == dc->filename) ||            
+         ( (strlen (dc->filename) >= strlen (GNUNET_FS_DIRECTORY_EXT)) &&
+           (NULL !=
+            strstr (dc->filename + strlen(dc->filename) - strlen(GNUNET_FS_DIRECTORY_EXT),
+                    GNUNET_FS_DIRECTORY_EXT)) ) ) ) );              
+}
+
+
 /**
  * We're storing the IBLOCKS after the DBLOCKS on disk (so that we
  * only have to truncate the file once we're done).
@@ -50,8 +61,7 @@
  * 
  * @param fsize overall file size
  * @param off offset of the block in the file
- * @param depth depth of the block in the tree
- * @param treedepth maximum depth of the tree
+ * @param depth depth of the block in the tree, 0 for DBLOCK
  * @return off for DBLOCKS (depth == treedepth),
  *         otherwise an offset past the end
  *         of the file that does not overlap
 static uint64_t
 compute_disk_offset (uint64_t fsize,
                     uint64_t off,
-                    unsigned int depth,
-                    unsigned int treedepth)
+                    unsigned int depth)
 {
   unsigned int i;
   uint64_t lsize; /* what is the size of all IBlocks for depth "i"? */
   uint64_t loff; /* where do IBlocks for depth "i" start? */
   unsigned int ioff; /* which IBlock corresponds to "off" at depth "i"? */
   
-  if (depth == treedepth)
+  if (depth == 0)
     return off;
   /* first IBlocks start at the end of file, rounded up
      to full DBLOCK_SIZE */
   loff = ((fsize + DBLOCK_SIZE - 1) / DBLOCK_SIZE) * DBLOCK_SIZE;
-  lsize = ( (fsize + DBLOCK_SIZE-1) / DBLOCK_SIZE) * sizeof (struct ContentHashKey);
+  lsize = ( (fsize + DBLOCK_SIZE - 1) / DBLOCK_SIZE) * sizeof (struct ContentHashKey);
   GNUNET_assert (0 == (off % DBLOCK_SIZE));
   ioff = (off / DBLOCK_SIZE);
-  for (i=treedepth-1;i>depth;i--)
+  for (i=1;i<depth;i++)
     {
       loff += lsize;
       lsize = (lsize + CHK_PER_INODE - 1) / CHK_PER_INODE;
@@ -89,56 +98,23 @@ compute_disk_offset (uint64_t fsize,
 
 
 /**
- * Given a file of the specified treedepth and a block at the given
- * offset and depth, calculate the offset for the CHK at the given
- * index.
- *
- * @param offset the offset of the first
- *        DBLOCK in the subtree of the 
- *        identified IBLOCK
- * @param depth the depth of the IBLOCK in the tree
- * @param treedepth overall depth of the tree
- * @param k which CHK in the IBLOCK are we 
- *        talking about
- * @return offset if k=0, otherwise an appropriately
- *         larger value (i.e., if depth = treedepth-1,
- *         the returned value should be offset+DBLOCK_SIZE)
- */
-static uint64_t
-compute_dblock_offset (uint64_t offset,
-                      unsigned int depth,
-                      unsigned int treedepth,
-                      unsigned int k)
-{
-  unsigned int i;
-  uint64_t lsize; /* what is the size of the sum of all DBlocks 
-                    that a CHK at depth i corresponds to? */
-
-  if (depth == treedepth)
-    return offset;
-  lsize = DBLOCK_SIZE;
-  for (i=treedepth-1;i>depth;i--)
-    lsize *= CHK_PER_INODE;
-  return offset + k * lsize;
-}
-
-
-/**
- * Fill in all of the generic fields for 
- * a download event.
+ * Fill in all of the generic fields for a download event and call the
+ * callback.
  *
  * @param pi structure to fill in
  * @param dc overall download context
  */
-static void
-make_download_status (struct GNUNET_FS_ProgressInfo *pi,
-                     struct GNUNET_FS_DownloadContext *dc)
+void
+GNUNET_FS_download_make_status_ (struct GNUNET_FS_ProgressInfo *pi,
+                                struct GNUNET_FS_DownloadContext *dc)
 {
   pi->value.download.dc = dc;
   pi->value.download.cctx
     = dc->client_info;
   pi->value.download.pctx
     = (dc->parent == NULL) ? NULL : dc->parent->client_info;
+  pi->value.download.sctx
+    = (dc->search == NULL) ? NULL : dc->search->client_info;
   pi->value.download.uri 
     = dc->uri;
   pi->value.download.filename
@@ -155,8 +131,16 @@ make_download_status (struct GNUNET_FS_ProgressInfo *pi,
     = GNUNET_TIME_calculate_eta (dc->start_time,
                                 dc->completed,
                                 dc->length);
+  pi->value.download.is_active = (dc->client == NULL) ? GNUNET_NO : GNUNET_YES;
+  if (0 == (dc->options & GNUNET_FS_DOWNLOAD_IS_PROBE))
+    dc->client_info = dc->h->upcb (dc->h->upcb_cls,
+                                  pi);
+  else
+    dc->client_info = GNUNET_FS_search_probe_progress_ (NULL,
+                                                       pi);
 }
 
+
 /**
  * We're ready to transmit a search request to the
  * file-sharing service.  Do it.  If there is 
@@ -174,136 +158,6 @@ transmit_download_request (void *cls,
                           void *buf);
 
 
-/**
- * Schedule the download of the specified
- * block in the tree.
- *
- * @param dc overall download this block belongs to
- * @param chk content-hash-key of the block
- * @param offset offset of the block in the file
- *         (for IBlocks, the offset is the lowest
- *          offset of any DBlock in the subtree under
- *          the IBlock)
- * @param depth depth of the block, 0 is the root of the tree
- */
-static void
-schedule_block_download (struct GNUNET_FS_DownloadContext *dc,
-                        const struct ContentHashKey *chk,
-                        uint64_t offset,
-                        unsigned int depth)
-{
-  struct DownloadRequest *sm;
-  uint64_t off;
-
-#if DEBUG_DOWNLOAD
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Scheduling download at offset %llu and depth %u for `%s'\n",
-             (unsigned long long) offset,
-             depth,
-             GNUNET_h2s (&chk->query));
-#endif
-  off = compute_disk_offset (GNUNET_ntohll (dc->uri->data.chk.file_length),
-                            offset,
-                            depth,
-                            dc->treedepth);
-  if ( (dc->old_file_size > off) &&
-       (dc->handle != NULL) &&
-       (off  == 
-       GNUNET_DISK_file_seek (dc->handle,
-                              off,
-                              GNUNET_DISK_SEEK_SET) ) )
-    {
-      // FIXME: check if block exists on disk!
-      // (read block, encode, compare with
-      // query; if matches, simply return)
-    }
-  if (depth < dc->treedepth)
-    {
-      // FIXME: try if we could
-      // reconstitute this IBLOCK
-      // from the existing blocks on disk (can wait)
-      // (read block(s), encode, compare with
-      // query; if matches, simply return)
-    }
-  sm = GNUNET_malloc (sizeof (struct DownloadRequest));
-  sm->chk = *chk;
-  sm->offset = offset;
-  sm->depth = depth;
-  sm->is_pending = GNUNET_YES;
-  sm->next = dc->pending;
-  dc->pending = sm;
-  GNUNET_CONTAINER_multihashmap_put (dc->active,
-                                    &chk->query,
-                                    sm,
-                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
-
-  if ( (dc->th == NULL) &&
-       (dc->client != NULL) )
-    dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
-                                                 sizeof (struct SearchMessage),
-                                                 GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                                 GNUNET_NO,
-                                                 &transmit_download_request,
-                                                 dc);
-}
-
-
-/**
- * We've lost our connection with the FS service.
- * Re-establish it and re-transmit all of our
- * pending requests.
- *
- * @param dc download context that is having trouble
- */
-static void
-try_reconnect (struct GNUNET_FS_DownloadContext *dc);
-
-
-/**
- * Compute how many bytes of data should be stored in
- * the specified node.
- *
- * @param fsize overall file size
- * @param totaldepth depth of the entire tree
- * @param offset offset of the node
- * @param depth depth of the node
- * @return number of bytes stored in this node
- */
-static size_t
-calculate_block_size (uint64_t fsize,
-                     unsigned int totaldepth,
-                     uint64_t offset,
-                     unsigned int depth)
-{
-  unsigned int i;
-  size_t ret;
-  uint64_t rsize;
-  uint64_t epos;
-  unsigned int chks;
-
-  GNUNET_assert (offset < fsize);
-  if (depth == totaldepth)
-    {
-      ret = DBLOCK_SIZE;
-      if (offset + ret > fsize)
-        ret = (size_t) (fsize - offset);
-      return ret;
-    }
-
-  rsize = DBLOCK_SIZE;
-  for (i = totaldepth-1; i > depth; i--)
-    rsize *= CHK_PER_INODE;
-  epos = offset + rsize * CHK_PER_INODE;
-  GNUNET_assert (epos > offset);
-  if (epos > fsize)
-    epos = fsize;
-  /* round up when computing #CHKs in our IBlock */
-  chks = (epos - offset + rsize - 1) / rsize;
-  GNUNET_assert (chks <= CHK_PER_INODE);
-  return chks * sizeof (struct ContentHashKey);
-}
-
-
 /**
  * Closure for iterator processing results.
  */
@@ -333,11 +187,108 @@ struct ProcessResultClosure
   /**
    * Type of data.
    */
-  uint32_t type;
+  enum GNUNET_BLOCK_Type type;
+
+  /**
+   * Flag to indicate if this block should be stored on disk.
+   */
+  int do_store;
   
 };
 
 
+/**
+ * Iterator over entries in the pending requests in the 'active' map for the
+ * reply that we just got.
+ *
+ * @param cls closure (our 'struct ProcessResultClosure')
+ * @param key query for the given value / request
+ * @param value value in the hash map (a 'struct DownloadRequest')
+ * @return GNUNET_YES (we should continue to iterate); unless serious error
+ */
+static int
+process_result_with_request (void *cls,
+                            const GNUNET_HashCode * key,
+                            void *value);
+
+
+/**
+ * We've found a matching block without downloading it.
+ * Encrypt it and pass it to our "receive" function as
+ * if we had received it from the network.
+ * 
+ * @param dc download in question
+ * @param chk request this relates to
+ * @param dr request details
+ * @param block plaintext data matching request
+ * @param len number of bytes in block
+ * @param do_store should we still store the block on disk?
+ * @return GNUNET_OK on success
+ */
+static int
+encrypt_existing_match (struct GNUNET_FS_DownloadContext *dc,
+                       const struct ContentHashKey *chk,
+                       struct DownloadRequest *dr,
+                       const char * block,                    
+                       size_t len,
+                       int do_store)
+{
+  struct ProcessResultClosure prc;
+  char enc[len];
+  struct GNUNET_CRYPTO_AesSessionKey sk;
+  struct GNUNET_CRYPTO_AesInitializationVector iv;
+  GNUNET_HashCode query;
+  
+  GNUNET_CRYPTO_hash_to_aes_key (&chk->key, &sk, &iv);
+  if (-1 == GNUNET_CRYPTO_aes_encrypt (block, len,
+                                      &sk,
+                                      &iv,
+                                      enc))
+    {
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
+    }
+  GNUNET_CRYPTO_hash (enc, len, &query);
+  if (0 != memcmp (&query,
+                  &chk->query,
+                  sizeof (GNUNET_HashCode)))
+    {
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Matching block for `%s' at offset %llu already present, no need for download!\n",
+             dc->filename,
+             (unsigned long long) dr->offset);
+#endif
+  /* already got it! */
+  prc.dc = dc;
+  prc.data = enc;
+  prc.size = len;
+  prc.type = (0 == dr->depth) 
+    ? GNUNET_BLOCK_TYPE_FS_DBLOCK 
+    : GNUNET_BLOCK_TYPE_FS_IBLOCK;
+  prc.query = chk->query;
+  prc.do_store = do_store;
+  process_result_with_request (&prc,
+                              &chk->key,
+                              dr);
+  return GNUNET_OK;
+}
+
+
+/**
+ * We've lost our connection with the FS service.
+ * Re-establish it and re-transmit all of our
+ * pending requests.
+ *
+ * @param dc download context that is having trouble
+ */
+static void
+try_reconnect (struct GNUNET_FS_DownloadContext *dc);
+
+
 /**
  * We found an entry in a directory.  Check if the respective child
  * already exists and if not create the respective child download.
@@ -355,43 +306,7 @@ trigger_recursive_download (void *cls,
                            const struct GNUNET_FS_Uri *uri,
                            const struct GNUNET_CONTAINER_MetaData *meta,
                            size_t length,
-                           const void *data)
-{
-  struct GNUNET_FS_DownloadContext *dc = cls;  
-  struct GNUNET_FS_DownloadContext *cpos;
-
-  if (NULL == uri)
-    return; /* entry for the directory itself */
-  cpos = dc->child_head;
-  while (cpos != NULL)
-    {
-      if ( (GNUNET_FS_uri_test_equal (uri,
-                                     cpos->uri)) ||
-          ( (filename != NULL) &&
-            (0 == strcmp (cpos->filename,
-                          filename)) ) )
-       break;  
-      cpos = cpos->next;
-    }
-  if (cpos != NULL)
-    return; /* already exists */
-  if (data != NULL)
-    {
-      /* determine on-disk filename, write data! */
-      GNUNET_break (0); // FIXME: not implemented
-    }
-  /* FIXME: filename MAY be NULL => make one up! */
-  GNUNET_FS_download_start (dc->h,
-                           uri,
-                           meta,
-                           filename, /* FIXME: prepend directory name! */
-                           0,
-                           GNUNET_FS_uri_chk_get_file_size (uri),
-                           dc->anonymity,
-                           dc->options,
-                           NULL,
-                           dc);
-}
+                           const void *data);
 
 
 /**
@@ -425,9 +340,6 @@ full_recursive_download (struct GNUNET_FS_DownloadContext *dc)
     }
   else
     {
-      /* FIXME: need to initialize (and use) temp_filename
-        in various places in order for this assertion to
-        not fail; right now, it will always fail! */
       GNUNET_assert (dc->temp_filename != NULL);
       h = GNUNET_DISK_file_open (dc->temp_filename,
                                 GNUNET_DISK_OPEN_READ,
@@ -464,232 +376,938 @@ full_recursive_download (struct GNUNET_FS_DownloadContext *dc)
 
 
 /**
- * Iterator over entries in the pending requests in the 'active' map for the
- * reply that we just got.
+ * Check if all child-downloads have completed (or trigger them if
+ * necessary) and once we're completely done, signal completion (and
+ * possibly recurse to parent).  This function MUST be called when the
+ * download of a file itself is done or when the download of a file is
+ * done and then later a direct child download has completed (and
+ * hence this download may complete itself).
  *
- * @param cls closure (our 'struct ProcessResultClosure')
- * @param key query for the given value / request
- * @param value value in the hash map (a 'struct DownloadRequest')
- * @return GNUNET_YES (we should continue to iterate); unless serious error
+ * @param dc download to check for completion of children
  */
-static int
-process_result_with_request (void *cls,
-                            const GNUNET_HashCode * key,
-                            void *value)
+static void
+check_completed (struct GNUNET_FS_DownloadContext *dc)
 {
-  struct ProcessResultClosure *prc = cls;
-  struct DownloadRequest *sm = value;
-  struct GNUNET_FS_DownloadContext *dc = prc->dc;
-  struct GNUNET_CRYPTO_AesSessionKey skey;
-  struct GNUNET_CRYPTO_AesInitializationVector iv;
-  char pt[prc->size];
   struct GNUNET_FS_ProgressInfo pi;
-  uint64_t off;
-  size_t app;
-  int i;
-  struct ContentHashKey *chk;
-  char *emsg;
-
-  if (prc->size != calculate_block_size (GNUNET_ntohll (dc->uri->data.chk.file_length),
-                                        dc->treedepth,
-                                        sm->offset,
-                                        sm->depth))
+  struct GNUNET_FS_DownloadContext *pos;
+
+  /* first, check if we need to download children */
+  if ( (dc->child_head == NULL) &&
+       (is_recursive_download (dc)) )
+    full_recursive_download (dc);  
+  /* then, check if children are done already */
+  pos = dc->child_head;
+  while (pos != NULL)
     {
-#if DEBUG_DOWNLOAD
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                 "Internal error or bogus download URI (expected %u bytes, got %u)\n",
-                 calculate_block_size (GNUNET_ntohll (dc->uri->data.chk.file_length),
-                                       dc->treedepth,
-                                       sm->offset,
-                                       sm->depth),
-                 prc->size);
-#endif
-      dc->emsg = GNUNET_strdup ("Internal error or bogus download URI");
-      /* signal error */
-      pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
-      make_download_status (&pi, dc);
-      pi.value.download.specifics.error.message = dc->emsg;
-      dc->client_info = dc->h->upcb (dc->h->upcb_cls,
-                                    &pi);
-      /* abort all pending requests */
-      if (NULL != dc->th)
-       {
-         GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
-         dc->th = NULL;
-       }
-      GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
-      dc->client = NULL;
-      return GNUNET_NO;
-    }
-  GNUNET_assert (GNUNET_YES ==
-                GNUNET_CONTAINER_multihashmap_remove (dc->active,
-                                                      &prc->query,
-                                                      sm));
-  GNUNET_CRYPTO_hash_to_aes_key (&sm->chk.key, &skey, &iv);
-  GNUNET_CRYPTO_aes_decrypt (prc->data,
-                            prc->size,
-                            &skey,
-                            &iv,
-                            pt);
-  off = compute_disk_offset (GNUNET_ntohll (dc->uri->data.chk.file_length),
-                            sm->offset,
-                            sm->depth,
-                            dc->treedepth);
-  /* save to disk */
-  if ( (NULL != dc->handle) &&
-       ( (sm->depth == dc->treedepth) ||
-        (0 == (dc->options & GNUNET_FS_DOWNLOAD_NO_TEMPORARIES)) ) )
+      if ( (pos->emsg == NULL) &&
+          (pos->completed < pos->length) )
+       return; /* not done yet */
+      if ( (pos->child_head != NULL) &&
+          (pos->has_finished != GNUNET_YES) )
+       return; /* not transitively done yet */
+      pos = pos->next;
+    }
+  /* All of our children are done, so mark this download done */
+  dc->has_finished = GNUNET_YES;
+  if (dc->job_queue != NULL)
     {
-      emsg = NULL;
-#if DEBUG_DOWNLOAD
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                 "Saving decrypted block to disk at offset %llu\n",
-                 (unsigned long long) off);
-#endif
-      if ( (off  != 
-           GNUNET_DISK_file_seek (dc->handle,
-                                  off,
-                                  GNUNET_DISK_SEEK_SET) ) )
-       GNUNET_asprintf (&emsg,
-                        _("Failed to seek to offset %llu in file `%s': %s\n"),
-                        (unsigned long long) off,
-                        dc->filename,
-                        STRERROR (errno));
-      else if (prc->size !=
-              GNUNET_DISK_file_write (dc->handle,
-                                      pt,
-                                      prc->size))
-       GNUNET_asprintf (&emsg,
-                        _("Failed to write block of %u bytes at offset %llu in file `%s': %s\n"),
-                        (unsigned int) prc->size,
-                        (unsigned long long) off,
-                        dc->filename,
-                        STRERROR (errno));
-      if (NULL != emsg)
-       {
-         dc->emsg = emsg;
-         // FIXME: make persistent
+      GNUNET_FS_dequeue_ (dc->job_queue);
+      dc->job_queue = NULL;
+    }
+  GNUNET_FS_download_sync_ (dc);
 
-         /* signal error */
-         pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
-         make_download_status (&pi, dc);
-         pi.value.download.specifics.error.message = emsg;
-         dc->client_info = dc->h->upcb (dc->h->upcb_cls,
-                                        &pi);
+  /* signal completion */
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_COMPLETED;
+  GNUNET_FS_download_make_status_ (&pi, dc);
 
-         /* abort all pending requests */
-         if (NULL != dc->th)
-           {
-             GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
-             dc->th = NULL;
-           }
-         GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
-         dc->client = NULL;
-         GNUNET_free (sm);
-         return GNUNET_NO;
+  /* let parent know */
+  if (dc->parent != NULL)
+    check_completed (dc->parent);  
+}
+
+
+/**
+ * We got a block of plaintext data (from the meta data).
+ * Try it for upward reconstruction of the data.  On success,
+ * the top-level block will move to state BRS_DOWNLOAD_UP.
+ *
+ * @param dc context for the download
+ * @param dr download request to match against
+ * @param data plaintext data, starting from the beginning of the file
+ * @param data_len number of bytes in data
+ */ 
+static void
+try_match_block (struct GNUNET_FS_DownloadContext *dc,
+                struct DownloadRequest *dr,
+                const char *data,
+                size_t data_len)
+{
+  struct GNUNET_FS_ProgressInfo pi;
+  unsigned int i;
+  char enc[DBLOCK_SIZE];
+  struct ContentHashKey chks[CHK_PER_INODE];
+  struct ContentHashKey in_chk;
+  struct GNUNET_CRYPTO_AesSessionKey sk;
+  struct GNUNET_CRYPTO_AesInitializationVector iv;
+  size_t dlen;
+  struct DownloadRequest *drc;
+  struct GNUNET_DISK_FileHandle *fh;
+  int complete;
+  const char *fn;
+  const char *odata;
+  size_t odata_len;
+  
+  odata = data;
+  odata_len = data_len;
+  if (BRS_DOWNLOAD_UP == dr->state)
+    return;
+  if (dr->depth > 0)
+    {
+      complete = GNUNET_YES;
+      for (i=0;i<dr->num_children;i++)
+       {
+         drc = dr->children[i];
+         try_match_block (dc,
+                          drc,
+                          data, data_len);
+         if (drc->state != BRS_RECONSTRUCT_META_UP)
+           complete = GNUNET_NO;
+         else
+           chks[i] = drc->chk;
        }
+      if (GNUNET_YES != complete)
+       return;
+      data = (const char*) chks;
+      dlen = dr->num_children * sizeof (struct ContentHashKey);
     }
-  if (sm->depth == dc->treedepth) 
+  else
     {
-      app = prc->size;
-      if (sm->offset < dc->offset)
+      if (dr->offset > data_len) 
+       return; /* oops */
+      dlen = GNUNET_MIN (data_len - dr->offset,
+                        DBLOCK_SIZE);
+    }
+  GNUNET_CRYPTO_hash (&data[dr->offset],
+                     dlen,
+                     &in_chk.key);
+  GNUNET_CRYPTO_hash_to_aes_key (&in_chk.key, &sk, &iv);
+  if (-1 == GNUNET_CRYPTO_aes_encrypt (&data[dr->offset], dlen,
+                                      &sk,
+                                      &iv,
+                                      enc))
+    {
+      GNUNET_break (0);
+      return;
+    }
+  GNUNET_CRYPTO_hash (enc, dlen, &in_chk.query);
+  switch (dr->state)
+    {
+    case BRS_INIT:
+      dr->chk = in_chk;
+      dr->state = BRS_RECONSTRUCT_META_UP;
+      break;
+    case BRS_CHK_SET:
+      if (0 != memcmp (&in_chk,
+                      &dr->chk,
+                      sizeof (struct ContentHashKey)))
        {
-         /* starting offset begins in the middle of pt,
-            do not count first bytes as progress */
-         GNUNET_assert (app > (dc->offset - sm->offset));
-         app -= (dc->offset - sm->offset);       
+         /* other peer provided bogus meta data */
+         GNUNET_break_op (0);
+         break;
        }
-      if (sm->offset + prc->size > dc->offset + dc->length)
+      /* write block to disk */
+      fn = dc->filename != NULL 
+       ? dc->filename 
+       : dc->temp_filename;
+      fh = GNUNET_DISK_file_open (fn,
+                                 GNUNET_DISK_OPEN_READWRITE | 
+                                 GNUNET_DISK_OPEN_CREATE | 
+                                 GNUNET_DISK_OPEN_TRUNCATE,
+                                 GNUNET_DISK_PERM_USER_READ |
+                                 GNUNET_DISK_PERM_USER_WRITE |
+                                 GNUNET_DISK_PERM_GROUP_READ |
+                                 GNUNET_DISK_PERM_OTHER_READ);     
+      if (fh == NULL)
        {
-         /* end of block is after relevant range,
-            do not count last bytes as progress */
-         GNUNET_assert (app > (sm->offset + prc->size) - (dc->offset + dc->length));
-         app -= (sm->offset + prc->size) - (dc->offset + dc->length);
+         GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                                   "open",
+                                   fn);
+         GNUNET_asprintf (&dc->emsg,
+                          _("Failed to open file `%s' for writing"),
+                          fn);
+         GNUNET_DISK_file_close (fh);
+         dr->state = BRS_ERROR;
+         pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+         pi.value.download.specifics.error.message = dc->emsg;
+         GNUNET_FS_download_make_status_ (&pi, dc); 
+         return;
        }
-      dc->completed += app;
-
-      if ( (0 != (dc->options & GNUNET_FS_DOWNLOAD_OPTION_RECURSIVE)) &&
-          (GNUNET_NO != GNUNET_FS_meta_data_test_for_directory (dc->meta)) )
+      if (data_len != 
+         GNUNET_DISK_file_write (fh,
+                                 odata,
+                                 odata_len))
        {
-         GNUNET_FS_directory_list_contents (prc->size,
-                                            pt,
-                                            off,
-                                            &trigger_recursive_download,
-                                            dc);         
+         GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                                   "write",
+                                   fn);              
+         GNUNET_asprintf (&dc->emsg,
+                          _("Failed to open file `%s' for writing"),
+                          fn);
+         GNUNET_DISK_file_close (fh);
+         dr->state = BRS_ERROR;
+         pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+         pi.value.download.specifics.error.message = dc->emsg;
+         GNUNET_FS_download_make_status_ (&pi, dc);      
+         return;
        }
-
+      GNUNET_DISK_file_close (fh);
+      /* signal success */      
+      dr->state = BRS_DOWNLOAD_UP;
+      dc->completed = dc->length;
+      GNUNET_FS_download_sync_ (dc);
+      pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
+      pi.value.download.specifics.progress.data = data;
+      pi.value.download.specifics.progress.offset = 0;
+      pi.value.download.specifics.progress.data_len = dlen;
+      pi.value.download.specifics.progress.depth = 0;
+      GNUNET_FS_download_make_status_ (&pi, dc);
+      if ( (NULL != dc->filename) &&
+          (0 != truncate (dc->filename,
+                          GNUNET_ntohll (dc->uri->data.chk.file_length))) )
+       GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
+                                 "truncate",
+                                 dc->filename);
+      check_completed (dc);      
+      break;
+    default:
+      /* how did we get here? */
+      GNUNET_break (0);
+      break;
     }
+}
 
-  pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
-  make_download_status (&pi, dc);
-  pi.value.download.specifics.progress.data = pt;
-  pi.value.download.specifics.progress.offset = sm->offset;
-  pi.value.download.specifics.progress.data_len = prc->size;
-  pi.value.download.specifics.progress.depth = sm->depth;
-  dc->client_info = dc->h->upcb (dc->h->upcb_cls,
-                                &pi);
-  GNUNET_assert (dc->completed <= dc->length);
-  if (dc->completed == dc->length)
-    {
+
+/**
+ * Type of a function that libextractor calls for each
+ * meta data item found.  If we find full data meta data,
+ * call 'try_match_block' on it.
+ *
+ * @param cls our 'struct GNUNET_FS_DownloadContext*'
+ * @param plugin_name name of the plugin that produced this value;
+ *        special values can be used (i.e. '&lt;zlib&gt;' for zlib being
+ *        used in the main libextractor library and yielding
+ *        meta data).
+ * @param type libextractor-type describing the meta data
+ * @param format basic format information about data 
+ * @param data_mime_type mime-type of data (not of the original file);
+ *        can be NULL (if mime-type is not known)
+ * @param data actual meta-data found
+ * @param data_len number of bytes in data
+ * @return 0 to continue extracting, 1 to abort
+ */ 
+static int
+match_full_data (void *cls,
+                const char *plugin_name,
+                enum EXTRACTOR_MetaType type,
+                enum EXTRACTOR_MetaFormat format,
+                const char *data_mime_type,
+                const char *data,
+                size_t data_len)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+
+  if (type != EXTRACTOR_METATYPE_GNUNET_FULL_DATA) 
+    return 0;
 #if DEBUG_DOWNLOAD
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                 "Download completed, truncating file to desired length %llu\n",
-                 (unsigned long long) GNUNET_ntohll (dc->uri->data.chk.file_length));
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Found %u bytes of FD!\n",
+             (unsigned int) data_len);
 #endif
-      /* truncate file to size (since we store IBlocks at the end) */
-      if (dc->handle != NULL)
-       {
-         GNUNET_DISK_file_close (dc->handle);
-         dc->handle = NULL;
-         if (0 != truncate (dc->filename,
-                            GNUNET_ntohll (dc->uri->data.chk.file_length)))
-           GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
-                                     "truncate",
-                                     dc->filename);
+  if (GNUNET_FS_uri_chk_get_file_size (dc->uri) != data_len)
+    {
+      GNUNET_break_op (0);
+      return 1; /* bogus meta data */
+    }
+  try_match_block (dc,
+                  dc->top_request,
+                  data,
+                  data_len);
+  return 1;
+}
+
+
+/**
+ * Set the state of the given download request to
+ * BRS_DOWNLOAD_UP and propagate it up the tree.
+ *
+ * @param dr download request that is done
+ */
+static void
+propagate_up (struct DownloadRequest *dr)
+{
+  unsigned int i;
+
+  do
+    {
+      dr->state = BRS_DOWNLOAD_UP;
+      dr = dr->parent;
+      if (dr == NULL)
+       break;
+      for (i=0;i<dr->num_children;i++)
+       if (dr->children[i]->state != BRS_DOWNLOAD_UP)
+         break;
+    }
+  while (i == dr->num_children);
+}
+
+
+/**
+ * Try top-down reconstruction.  Before, the given request node
+ * must have the state BRS_CHK_SET.  Afterwards, more nodes may
+ * have that state or advanced to BRS_DOWNLOAD_DOWN or even
+ * BRS_DOWNLOAD_UP.  It is also possible to get BRS_ERROR on the
+ * top level.
+ *
+ * @param dc overall download this block belongs to
+ * @param dr block to reconstruct
+ */
+static void
+try_top_down_reconstruction (struct GNUNET_FS_DownloadContext *dc,
+                            struct DownloadRequest *dr)
+{
+  uint64_t off;
+  char block[DBLOCK_SIZE];
+  GNUNET_HashCode key;
+  uint64_t total;
+  size_t len;
+  unsigned int i;
+  unsigned int chk_off;
+  struct DownloadRequest *drc;
+  uint64_t child_block_size;
+  const struct ContentHashKey *chks;
+  int up_done;
+  
+  GNUNET_assert (dc->rfh != NULL);
+  GNUNET_assert (dr->state == BRS_CHK_SET);
+  total = GNUNET_FS_uri_chk_get_file_size (dc->uri);
+  GNUNET_assert (dr->depth < dc->treedepth);
+  len = GNUNET_FS_tree_calculate_block_size (total,
+                                            dr->offset,
+                                            dr->depth);
+  GNUNET_assert (len <= DBLOCK_SIZE);
+  off = compute_disk_offset (total,
+                            dr->offset,
+                            dr->depth);
+  if (dc->old_file_size < off + len) 
+    return; /* failure */
+  if (off  != 
+      GNUNET_DISK_file_seek (dc->rfh,
+                            off,
+                            GNUNET_DISK_SEEK_SET) ) 
+    {
+      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
+                               "seek",
+                               dc->filename);
+      return; /* failure */
+    }
+  if (len != 
+      GNUNET_DISK_file_read (dc->rfh,
+                            block,
+                            len)) 
+    {
+      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
+                               "read",
+                               dc->filename);
+      return; /* failure */
+    }
+  GNUNET_CRYPTO_hash (block, len, &key);
+  if (0 != memcmp (&key,
+                  &dr->chk.key,
+                  sizeof (GNUNET_HashCode)))
+    return; /* mismatch */
+  if (GNUNET_OK !=
+      encrypt_existing_match (dc,
+                             &dr->chk,
+                             dr,
+                             block,
+                             len,
+                             GNUNET_NO))
+    {
+      /* hash matches but encrypted block does not, really bad */
+      dr->state = BRS_ERROR;
+      /* propagate up */
+      while (dr->parent != NULL)
+       {
+         dr = dr->parent;
+         dr->state = BRS_ERROR;
+       }
+      return;
+    }
+  /* block matches */
+  dr->state = BRS_DOWNLOAD_DOWN;
+
+  /* set CHKs for children */
+  up_done = GNUNET_YES;
+  chks = (const struct ContentHashKey*) block;
+  for (i=0;i<dr->num_children;i++)
+    {
+      drc = dr->children[i];
+      GNUNET_assert (drc->offset >= dr->offset);
+      child_block_size = GNUNET_FS_tree_compute_tree_size (drc->depth);
+      GNUNET_assert (0 == (drc->offset - dr->offset) % child_block_size);
+      chk_off = (drc->offset - dr->offset) / child_block_size;
+      if (drc->state == BRS_INIT)      
+       {
+         drc->state = BRS_CHK_SET;
+         drc->chk = chks[chk_off];
+         try_top_down_reconstruction (dc, drc);
+       }
+      if (drc->state != BRS_DOWNLOAD_UP)
+       up_done = GNUNET_NO; /* children not all done */
+    } 
+  if (up_done == GNUNET_YES)
+    propagate_up (dr); /* children all done (or no children...) */
+}
+
+
+/**
+ * Schedule the download of the specified block in the tree.
+ *
+ * @param dc overall download this block belongs to
+ * @param dr request to schedule
+ */
+static void
+schedule_block_download (struct GNUNET_FS_DownloadContext *dc,
+                        struct DownloadRequest *dr)
+{
+  unsigned int i;
+
+  switch (dr->state)
+    {
+    case BRS_INIT:
+      GNUNET_assert (0);
+      break;
+    case BRS_RECONSTRUCT_DOWN:
+      GNUNET_assert (0);
+      break;
+    case BRS_RECONSTRUCT_META_UP:
+      GNUNET_assert (0);
+      break;
+    case BRS_RECONSTRUCT_UP:
+      GNUNET_assert (0);
+      break;
+    case BRS_CHK_SET:
+      /* normal case, start download */
+      break;
+    case BRS_DOWNLOAD_DOWN:
+      for (i=0;i<dr->num_children;i++)
+       schedule_block_download (dc, dr->children[i]);
+      return;
+    case BRS_DOWNLOAD_UP:
+      /* We're done! */
+      return;
+    case BRS_ERROR:
+      GNUNET_break (0);
+      return;
+    }
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Scheduling download at offset %llu and depth %u for `%s'\n",
+             (unsigned long long) dr->offset,
+             dr->depth,
+             GNUNET_h2s (&dr->chk.query));
+#endif
+  if (GNUNET_NO !=
+      GNUNET_CONTAINER_multihashmap_contains_value (dc->active,
+                                                   &dr->chk.query,
+                                                   dr))
+    return; /* already active */
+  GNUNET_CONTAINER_multihashmap_put (dc->active,
+                                    &dr->chk.query,
+                                    dr,
+                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+  if (dc->client == NULL)
+    return; /* download not active */
+  GNUNET_CONTAINER_DLL_insert (dc->pending_head,
+                              dc->pending_tail,
+                              dr);
+  dr->is_pending = GNUNET_YES;
+  if (NULL == dc->th)
+    dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
+                                                 sizeof (struct SearchMessage),
+                                                 GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                 GNUNET_NO,
+                                                 &transmit_download_request,
+                                                 dc);
+}
+
+
+#define GNUNET_FS_URI_CHK_PREFIX GNUNET_FS_URI_PREFIX GNUNET_FS_URI_CHK_INFIX
+
+/**
+ * We found an entry in a directory.  Check if the respective child
+ * already exists and if not create the respective child download.
+ *
+ * @param cls the parent download
+ * @param filename name of the file in the directory
+ * @param uri URI of the file (CHK or LOC)
+ * @param meta meta data of the file
+ * @param length number of bytes in data
+ * @param data contents of the file (or NULL if they were not inlined)
+ */
+static void 
+trigger_recursive_download (void *cls,
+                           const char *filename,
+                           const struct GNUNET_FS_Uri *uri,
+                           const struct GNUNET_CONTAINER_MetaData *meta,
+                           size_t length,
+                           const void *data)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;  
+  struct GNUNET_FS_DownloadContext *cpos;
+  char *temp_name;
+  char *fn;
+  char *us;
+  char *ext;
+  char *dn;
+  char *pos;
+  char *full_name;
+  char *sfn;
+
+  if (NULL == uri)
+    return; /* entry for the directory itself */
+  cpos = dc->child_head;
+  while (cpos != NULL)
+    {
+      if ( (GNUNET_FS_uri_test_equal (uri,
+                                     cpos->uri)) ||
+          ( (filename != NULL) &&
+            (0 == strcmp (cpos->filename,
+                          filename)) ) )
+       break;  
+      cpos = cpos->next;
+    }
+  if (cpos != NULL)
+    return; /* already exists */
+  fn = NULL;
+  if (NULL == filename)
+    {
+      fn = GNUNET_FS_meta_data_suggest_filename (meta);
+      if (fn == NULL)
+       {
+         us = GNUNET_FS_uri_to_string (uri);
+         fn = GNUNET_strdup (&us [strlen (GNUNET_FS_URI_CHK_PREFIX)]);
+         GNUNET_free (us);
+       }
+      else if (fn[0] == '.')
+       {
+         ext = fn;
+         us = GNUNET_FS_uri_to_string (uri);
+         GNUNET_asprintf (&fn,
+                          "%s%s",
+                          &us[strlen (GNUNET_FS_URI_CHK_PREFIX)], ext);
+         GNUNET_free (ext);
+         GNUNET_free (us);
+       }
+      /* change '\' to '/' (this should have happened
+       during insertion, but malicious peers may
+       not have done this) */
+      while (NULL != (pos = strstr (fn, "\\")))
+       *pos = '/';
+      /* remove '../' everywhere (again, well-behaved
+        peers don't do this, but don't trust that
+        we did not get something nasty) */
+      while (NULL != (pos = strstr (fn, "../")))
+       {
+         pos[0] = '_';
+         pos[1] = '_';
+         pos[2] = '_';
+       }
+      filename = fn;
+    }
+  if (dc->filename == NULL)
+    {
+      full_name = NULL;
+    }
+  else
+    {
+      dn = GNUNET_strdup (dc->filename);
+      GNUNET_break ( (strlen (dn) >= strlen (GNUNET_FS_DIRECTORY_EXT)) &&
+                    (NULL !=
+                     strstr (dn + strlen(dn) - strlen(GNUNET_FS_DIRECTORY_EXT),
+                             GNUNET_FS_DIRECTORY_EXT)) );
+      sfn = GNUNET_strdup (filename);
+      while ( (strlen (sfn) > 0) &&
+             (filename[strlen(sfn)-1] == '/') )
+       sfn[strlen(sfn)-1] = '\0';
+      if ( (strlen (dn) >= strlen (GNUNET_FS_DIRECTORY_EXT)) &&
+          (NULL !=
+           strstr (dn + strlen(dn) - strlen(GNUNET_FS_DIRECTORY_EXT),
+                   GNUNET_FS_DIRECTORY_EXT)) )      
+       dn[strlen(dn) - strlen (GNUNET_FS_DIRECTORY_EXT)] = '\0';      
+      if ( (GNUNET_YES == GNUNET_FS_meta_data_test_for_directory (meta)) &&
+          ( (strlen (filename) < strlen (GNUNET_FS_DIRECTORY_EXT)) ||
+            (NULL ==
+             strstr (filename + strlen(filename) - strlen(GNUNET_FS_DIRECTORY_EXT),
+                     GNUNET_FS_DIRECTORY_EXT)) ) )
+       {
+         GNUNET_asprintf (&full_name,
+                          "%s%s%s%s",
+                          dn,
+                          DIR_SEPARATOR_STR,
+                          sfn,
+                          GNUNET_FS_DIRECTORY_EXT);
+       }
+      else
+       {
+         GNUNET_asprintf (&full_name,
+                          "%s%s%s",
+                          dn,
+                          DIR_SEPARATOR_STR,
+                          sfn);
+       }
+      GNUNET_free (sfn);
+      GNUNET_free (dn);
+    }
+  if ( (full_name != NULL) &&
+       (GNUNET_OK !=
+       GNUNET_DISK_directory_create_for_file (full_name)) )
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                 _("Failed to create directory for recursive download of `%s'\n"),
+                 full_name);
+      GNUNET_free (full_name);
+      GNUNET_free_non_null (fn);
+      return;
+    }
+
+  temp_name = NULL;
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Triggering recursive download of size %llu with %u bytes MD\n",
+             (unsigned long long) GNUNET_FS_uri_chk_get_file_size (uri),
+             (unsigned int) GNUNET_CONTAINER_meta_data_get_serialized_size (meta));
+#endif
+  GNUNET_FS_download_start (dc->h,
+                           uri,
+                           meta,
+                           full_name, temp_name,
+                           0,
+                           GNUNET_FS_uri_chk_get_file_size (uri),
+                           dc->anonymity,
+                           dc->options,
+                           NULL,
+                           dc);
+  GNUNET_free_non_null (full_name);
+  GNUNET_free_non_null (temp_name);
+  GNUNET_free_non_null (fn);
+}
+
+
+/**
+ * (recursively) free download request structure
+ *
+ * @param dr request to free
+ */
+void
+GNUNET_FS_free_download_request_ (struct DownloadRequest *dr)
+{
+  unsigned int i;
+
+  if (dr == NULL)
+    return;
+  for (i=0;i<dr->num_children;i++)
+    GNUNET_FS_free_download_request_ (dr->children[i]);
+  GNUNET_free_non_null (dr->children);
+  GNUNET_free (dr);
+}
+
+
+/**
+ * Iterator over entries in the pending requests in the 'active' map for the
+ * reply that we just got.
+ *
+ * @param cls closure (our 'struct ProcessResultClosure')
+ * @param key query for the given value / request
+ * @param value value in the hash map (a 'struct DownloadRequest')
+ * @return GNUNET_YES (we should continue to iterate); unless serious error
+ */
+static int
+process_result_with_request (void *cls,
+                            const GNUNET_HashCode *key,
+                            void *value)
+{
+  struct ProcessResultClosure *prc = cls;
+  struct DownloadRequest *dr = value;
+  struct GNUNET_FS_DownloadContext *dc = prc->dc;
+  struct DownloadRequest *drc;
+  struct GNUNET_DISK_FileHandle *fh = NULL;
+  struct GNUNET_CRYPTO_AesSessionKey skey;
+  struct GNUNET_CRYPTO_AesInitializationVector iv;
+  char pt[prc->size];
+  struct GNUNET_FS_ProgressInfo pi;
+  uint64_t off;
+  size_t bs;
+  size_t app;
+  int i;
+  struct ContentHashKey *chk;
+
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Received block `%s' matching pending request at depth %u and offset %llu/%llu\n",
+             GNUNET_h2s (key),
+             dr->depth,
+             (unsigned long long) dr->offset,
+             (unsigned long long) GNUNET_ntohll (dc->uri->data.chk.file_length));
+             
+#endif
+  bs = GNUNET_FS_tree_calculate_block_size (GNUNET_ntohll (dc->uri->data.chk.file_length),
+                                           dr->offset,
+                                           dr->depth);
+  if (prc->size != bs)
+    {
+      GNUNET_asprintf (&dc->emsg,
+                      _("Internal error or bogus download URI (expected %u bytes at depth %u and offset %llu/%llu, got %u bytes)\n"),
+                      bs,
+                      dr->depth,
+                      (unsigned long long) dr->offset,
+                      (unsigned long long) GNUNET_ntohll (dc->uri->data.chk.file_length),
+                      prc->size);
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                 "%s", 
+                 dc->emsg);
+      while (dr->parent != NULL)
+       {
+         dr->state = BRS_ERROR;
+         dr = dr->parent;
        }
+      dr->state = BRS_ERROR;
+      goto signal_error;
+    }
 
-      if ( (0 != (dc->options & GNUNET_FS_DOWNLOAD_OPTION_RECURSIVE)) &&
-          (GNUNET_NO != GNUNET_FS_meta_data_test_for_directory (dc->meta)) )
-       full_recursive_download (dc);
-      if (dc->child_head == NULL)
+  (void) GNUNET_CONTAINER_multihashmap_remove (dc->active,
+                                              &prc->query,
+                                              dr);
+  if (GNUNET_YES == dr->is_pending)
+    {
+      GNUNET_CONTAINER_DLL_remove (dc->pending_head,
+                                  dc->pending_tail,
+                                  dr);
+      dr->is_pending = GNUNET_NO;
+    }
+
+
+  GNUNET_CRYPTO_hash_to_aes_key (&dr->chk.key, &skey, &iv);
+  if (-1 == GNUNET_CRYPTO_aes_decrypt (prc->data,
+                                      prc->size,
+                                      &skey,
+                                      &iv,
+                                      pt))
+    {
+      GNUNET_break (0);
+      dc->emsg = GNUNET_strdup (_("internal error decrypting content"));
+      goto signal_error;
+    }
+  off = compute_disk_offset (GNUNET_ntohll (dc->uri->data.chk.file_length),
+                            dr->offset,
+                            dr->depth);
+  /* save to disk */
+  if ( ( GNUNET_YES == prc->do_store) &&
+       ( (dc->filename != NULL) ||
+        (is_recursive_download (dc)) ) &&
+       ( (dr->depth == dc->treedepth) ||
+        (0 == (dc->options & GNUNET_FS_DOWNLOAD_NO_TEMPORARIES)) ) )
+    {
+      fh = GNUNET_DISK_file_open (dc->filename != NULL 
+                                 ? dc->filename 
+                                 : dc->temp_filename, 
+                                 GNUNET_DISK_OPEN_READWRITE | 
+                                 GNUNET_DISK_OPEN_CREATE,
+                                 GNUNET_DISK_PERM_USER_READ |
+                                 GNUNET_DISK_PERM_USER_WRITE |
+                                 GNUNET_DISK_PERM_GROUP_READ |
+                                 GNUNET_DISK_PERM_OTHER_READ);    
+      if (NULL == fh)
        {
-         /* signal completion */
-         pi.status = GNUNET_FS_STATUS_DOWNLOAD_COMPLETED;
-         make_download_status (&pi, dc);
-         dc->client_info = dc->h->upcb (dc->h->upcb_cls,
-                                        &pi);
+         GNUNET_asprintf (&dc->emsg,
+                          _("Download failed: could not open file `%s': %s\n"),
+                          dc->filename,
+                          STRERROR (errno));
+         goto signal_error;
+       }      
+#if DEBUG_DOWNLOAD
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Saving decrypted block to disk at offset %llu\n",
+                 (unsigned long long) off);
+#endif
+      if ( (off  != 
+           GNUNET_DISK_file_seek (fh,
+                                  off,
+                                  GNUNET_DISK_SEEK_SET) ) )
+       {
+         GNUNET_asprintf (&dc->emsg,
+                          _("Failed to seek to offset %llu in file `%s': %s\n"),
+                          (unsigned long long) off,
+                          dc->filename,
+                          STRERROR (errno));
+         goto signal_error;
        }
-      GNUNET_assert (sm->depth == dc->treedepth);
+      if (prc->size !=
+         GNUNET_DISK_file_write (fh,
+                                 pt,
+                                 prc->size))
+       {
+         GNUNET_asprintf (&dc->emsg,
+                          _("Failed to write block of %u bytes at offset %llu in file `%s': %s\n"),
+                          (unsigned int) prc->size,
+                          (unsigned long long) off,
+                          dc->filename,
+                          STRERROR (errno));
+         goto signal_error;
+       }
+      GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fh));
+      fh = NULL;
     }
-  // FIXME: make persistent
-  if (sm->depth == dc->treedepth
+
+  if (dr->depth == 0
     {
-      GNUNET_free (sm);      
+      /* DBLOCK, update progress and try recursion if applicable */
+      app = prc->size;
+      if (dr->offset < dc->offset)
+       {
+         /* starting offset begins in the middle of pt,
+            do not count first bytes as progress */
+         GNUNET_assert (app > (dc->offset - dr->offset));
+         app -= (dc->offset - dr->offset);       
+       }
+      if (dr->offset + prc->size > dc->offset + dc->length)
+       {
+         /* end of block is after relevant range,
+            do not count last bytes as progress */
+         GNUNET_assert (app > (dr->offset + prc->size) - (dc->offset + dc->length));
+         app -= (dr->offset + prc->size) - (dc->offset + dc->length);
+       }
+      dc->completed += app;
+
+      /* do recursive download if option is set and either meta data
+        says it is a directory or if no meta data is given AND filename 
+        ends in '.gnd' (top-level case) */
+      if (is_recursive_download (dc))
+       GNUNET_FS_directory_list_contents (prc->size,
+                                          pt,
+                                          off,
+                                          &trigger_recursive_download,
+                                          dc);         
+           
+    }
+  dr->state = BRS_DOWNLOAD_DOWN;
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
+  pi.value.download.specifics.progress.data = pt;
+  pi.value.download.specifics.progress.offset = dr->offset;
+  pi.value.download.specifics.progress.data_len = prc->size;
+  pi.value.download.specifics.progress.depth = dr->depth;
+  GNUNET_FS_download_make_status_ (&pi, dc);
+  GNUNET_assert (dc->completed <= dc->length);
+  if (dr->depth == 0) 
+    propagate_up (dr);
+
+  if (dc->completed == dc->length)
+    {
+      /* download completed, signal */
+#if DEBUG_DOWNLOAD
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Download completed, truncating file to desired length %llu\n",
+                 (unsigned long long) GNUNET_ntohll (dc->uri->data.chk.file_length));
+#endif
+      /* truncate file to size (since we store IBlocks at the end) */
+      if (dc->filename != NULL)
+       {
+         if (0 != truncate (dc->filename,
+                            GNUNET_ntohll (dc->uri->data.chk.file_length)))
+           GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
+                                     "truncate",
+                                     dc->filename);
+       }
+      GNUNET_assert (dr->depth == 0);
+      check_completed (dc);
+    }
+  if (dr->depth == 0) 
+    {
+      /* bottom of the tree, no child downloads possible, just sync */
+      GNUNET_FS_download_sync_ (dc);
       return GNUNET_YES;
     }
+
 #if DEBUG_DOWNLOAD
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Triggering downloads of children (this block was at depth %u and offset %llu)\n",
-             sm->depth,
-             (unsigned long long) sm->offset);
+             dr->depth,
+             (unsigned long long) dr->offset);
 #endif
   GNUNET_assert (0 == (prc->size % sizeof(struct ContentHashKey)));
   chk = (struct ContentHashKey*) pt;
   for (i=(prc->size / sizeof(struct ContentHashKey))-1;i>=0;i--)
     {
-      off = compute_dblock_offset (sm->offset,
-                                  sm->depth,
-                                  dc->treedepth,
-                                  i);
-      if ( (off + DBLOCK_SIZE >= dc->offset) &&
-          (off < dc->offset + dc->length) ) 
-       schedule_block_download (dc,
-                                &chk[i],
-                                off,
-                                sm->depth + 1);
-    }
-  GNUNET_free (sm);
+      drc = dr->children[i];
+      switch (drc->state)
+       {
+       case BRS_INIT:
+         drc->chk = chk[i];
+         drc->state = BRS_CHK_SET;
+         schedule_block_download (dc, drc);
+         break;
+       case BRS_RECONSTRUCT_DOWN:
+         GNUNET_assert (0);
+         break;
+       case BRS_RECONSTRUCT_META_UP:
+         GNUNET_assert (0);
+         break;
+       case BRS_RECONSTRUCT_UP:
+         GNUNET_assert (0);
+         break;
+       case BRS_CHK_SET:
+         GNUNET_assert (0);
+         break;
+       case BRS_DOWNLOAD_DOWN:
+         GNUNET_assert (0);
+         break;
+       case BRS_DOWNLOAD_UP:
+         GNUNET_assert (0);
+         break;
+       case BRS_ERROR:
+         GNUNET_assert (0);
+         break;
+       default:
+         GNUNET_assert (0);
+         break;
+       }
+    }
+  GNUNET_FS_download_sync_ (dc);
   return GNUNET_YES;
+
+ signal_error:
+  if (fh != NULL)
+    GNUNET_DISK_file_close (fh);
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+  pi.value.download.specifics.error.message = dc->emsg;
+  GNUNET_FS_download_make_status_ (&pi, dc);
+  /* abort all pending requests */
+  if (NULL != dc->th)
+    {
+      GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
+      dc->th = NULL;
+    }
+  GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
+  dc->in_receive = GNUNET_NO;
+  dc->client = NULL;
+  GNUNET_FS_free_download_request_ (dc->top_request);
+  dc->top_request = NULL;
+  GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+  dc->active = NULL;
+  dc->pending_head = NULL;
+  dc->pending_tail = NULL;
+  GNUNET_FS_download_sync_ (dc);
+  return GNUNET_NO;
 }
 
 
@@ -703,7 +1321,7 @@ process_result_with_request (void *cls,
  */
 static void
 process_result (struct GNUNET_FS_DownloadContext *dc,
-               uint32_t type,
+               enum GNUNET_BLOCK_Type type,
                const void *data,
                size_t size)
 {
@@ -713,6 +1331,7 @@ process_result (struct GNUNET_FS_DownloadContext *dc,
   prc.data = data;
   prc.size = size;
   prc.type = type;
+  prc.do_store = GNUNET_YES;
   GNUNET_CRYPTO_hash (data, size, &prc.query);
 #if DEBUG_DOWNLOAD
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
@@ -786,145 +1405,740 @@ transmit_download_request (void *cls,
   struct GNUNET_FS_DownloadContext *dc = cls;
   size_t msize;
   struct SearchMessage *sm;
+  struct DownloadRequest *dr;
 
   dc->th = NULL;
   if (NULL == buf)
     {
+#if DEBUG_DOWNLOAD
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Transmitting download request failed, trying to reconnect\n");
+#endif
       try_reconnect (dc);
       return 0;
     }
   GNUNET_assert (size >= sizeof (struct SearchMessage));
   msize = 0;
   sm = buf;
-  while ( (dc->pending != NULL) &&
-         (size > msize + sizeof (struct SearchMessage)) )
+  while ( (NULL != (dr = dc->pending_head)) &&
+         (size >= msize + sizeof (struct SearchMessage)) )
     {
 #if DEBUG_DOWNLOAD
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                  "Transmitting download request for `%s' to `%s'-service\n",
-                 GNUNET_h2s (&dc->pending->chk.query),
+                 GNUNET_h2s (&dr->chk.query),
                  "FS");
 #endif
       memset (sm, 0, sizeof (struct SearchMessage));
       sm->header.size = htons (sizeof (struct SearchMessage));
       sm->header.type = htons (GNUNET_MESSAGE_TYPE_FS_START_SEARCH);
-      if (dc->pending->depth == dc->treedepth)
-       sm->type = htonl (GNUNET_DATASTORE_BLOCKTYPE_DBLOCK);
+      if (0 != (dc->options & GNUNET_FS_DOWNLOAD_OPTION_LOOPBACK_ONLY))
+       sm->options = htonl (1);
       else
-       sm->type = htonl (GNUNET_DATASTORE_BLOCKTYPE_IBLOCK);
+       sm->options = htonl (0);      
+      if (dr->depth == 0)
+       sm->type = htonl (GNUNET_BLOCK_TYPE_FS_DBLOCK);
+      else
+       sm->type = htonl (GNUNET_BLOCK_TYPE_FS_IBLOCK);
       sm->anonymity_level = htonl (dc->anonymity);
       sm->target = dc->target.hashPubKey;
-      sm->query = dc->pending->chk.query;
-      dc->pending->is_pending = GNUNET_NO;
-      dc->pending = dc->pending->next;
+      sm->query = dr->chk.query;
+      GNUNET_CONTAINER_DLL_remove (dc->pending_head,
+                                  dc->pending_tail,
+                                  dr);
+      dr->is_pending = GNUNET_NO;
       msize += sizeof (struct SearchMessage);
       sm++;
     }
-  if (dc->pending != NULL)
-    dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
-                                                 sizeof (struct SearchMessage),
-                                                 GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                                 GNUNET_NO,
-                                                 &transmit_download_request,
-                                                 dc); 
+  if (dc->pending_head != NULL)
+    {
+      dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
+                                                   sizeof (struct SearchMessage),
+                                                   GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                   GNUNET_NO,
+                                                   &transmit_download_request,
+                                                   dc); 
+      GNUNET_assert (dc->th != NULL);
+    }
+  if (GNUNET_NO == dc->in_receive)
+    {
+      dc->in_receive = GNUNET_YES;
+      GNUNET_CLIENT_receive (dc->client,
+                            &receive_results,
+                            dc,
+                            GNUNET_TIME_UNIT_FOREVER_REL);
+    }
   return msize;
 }
 
 
 /**
- * Reconnect to the FS service and transmit our queries NOW.
+ * Reconnect to the FS service and transmit our queries NOW.
+ *
+ * @param cls our download context
+ * @param tc unused
+ */
+static void
+do_reconnect (void *cls,
+             const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct GNUNET_CLIENT_Connection *client;
+  
+  dc->task = GNUNET_SCHEDULER_NO_TASK;
+  client = GNUNET_CLIENT_connect ("fs",
+                                 dc->h->cfg);
+  if (NULL == client)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                 "Connecting to `%s'-service failed, will try again.\n",
+                 "FS");
+      try_reconnect (dc);
+      return;
+    }
+  dc->client = client;
+  if (dc->pending_head != NULL)
+    {
+      dc->th = GNUNET_CLIENT_notify_transmit_ready (client,
+                                                   sizeof (struct SearchMessage),
+                                                   GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                   GNUNET_NO,
+                                                   &transmit_download_request,
+                                                   dc);
+      GNUNET_assert (dc->th != NULL);
+    }
+}
+
+
+/**
+ * Add entries to the pending list.
+ *
+ * @param cls our download context
+ * @param key unused
+ * @param entry entry of type "struct DownloadRequest"
+ * @return GNUNET_OK
+ */
+static int
+retry_entry (void *cls,
+            const GNUNET_HashCode *key,
+            void *entry)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct DownloadRequest *dr = entry;
+
+  dr->next = NULL;
+  dr->prev = NULL;
+  GNUNET_CONTAINER_DLL_insert (dc->pending_head,
+                              dc->pending_tail,
+                              dr);
+  dr->is_pending = GNUNET_YES;
+  return GNUNET_OK;
+}
+
+
+/**
+ * We've lost our connection with the FS service.
+ * Re-establish it and re-transmit all of our
+ * pending requests.
+ *
+ * @param dc download context that is having trouble
+ */
+static void
+try_reconnect (struct GNUNET_FS_DownloadContext *dc)
+{
+  
+  if (NULL != dc->client)
+    {
+#if DEBUG_DOWNLOAD
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Moving all requests back to pending list\n");
+#endif
+      if (NULL != dc->th)
+       {
+         GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
+         dc->th = NULL;
+       }
+      /* full reset of the pending list */
+      dc->pending_head = NULL;
+      dc->pending_tail = NULL;
+      GNUNET_CONTAINER_multihashmap_iterate (dc->active,
+                                            &retry_entry,
+                                            dc);
+      GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
+      dc->in_receive = GNUNET_NO;
+      dc->client = NULL;
+    }
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Will try to reconnect in 1s\n");
+#endif
+  dc->task
+    = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
+                                   &do_reconnect,
+                                   dc);
+}
+
+
+/**
+ * We're allowed to ask the FS service for our blocks.  Start the download.
+ *
+ * @param cls the 'struct GNUNET_FS_DownloadContext'
+ * @param client handle to use for communcation with FS (we must destroy it!)
+ */
+static void
+activate_fs_download (void *cls,
+                     struct GNUNET_CLIENT_Connection *client)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct GNUNET_FS_ProgressInfo pi;
+
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Download activated\n");
+#endif
+  GNUNET_assert (NULL != client);
+  GNUNET_assert (dc->client == NULL);
+  GNUNET_assert (dc->th == NULL);
+  dc->client = client;
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_ACTIVE;
+  GNUNET_FS_download_make_status_ (&pi, dc);
+  dc->pending_head = NULL;
+  dc->pending_tail = NULL;
+  GNUNET_CONTAINER_multihashmap_iterate (dc->active,
+                                        &retry_entry,
+                                        dc);
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Asking for transmission to FS service\n");
+#endif
+  if (dc->pending_head != NULL)
+    {
+      dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
+                                                   sizeof (struct SearchMessage),
+                                                   GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                   GNUNET_NO,
+                                                   &transmit_download_request,
+                                                   dc);    
+      GNUNET_assert (dc->th != NULL);
+    }
+}
+
+
+/**
+ * We must stop to ask the FS service for our blocks.  Pause the download.
+ *
+ * @param cls the 'struct GNUNET_FS_DownloadContext'
+ */
+static void
+deactivate_fs_download (void *cls)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct GNUNET_FS_ProgressInfo pi;
+
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Download deactivated\n");
+#endif  
+  if (NULL != dc->th)
+    {
+      GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
+      dc->th = NULL;
+    }
+  if (NULL != dc->client)
+    {
+      GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
+      dc->in_receive = GNUNET_NO;
+      dc->client = NULL;
+    }
+  dc->pending_head = NULL;
+  dc->pending_tail = NULL;
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_INACTIVE;
+  GNUNET_FS_download_make_status_ (&pi, dc);
+}
+
+
+/**
+ * (recursively) Create a download request structure.
+ *
+ * @param parent parent of the current entry
+ * @param depth depth of the current entry, 0 are the DBLOCKs,
+ *              top level block is 'dc->treedepth - 1'
+ * @param dr_offset offset in the original file this block maps to
+ *              (as in, offset of the first byte of the first DBLOCK 
+ *               in the subtree rooted in the returned download request tree)
+ * @param file_start_offset desired starting offset for the download
+ *             in the original file; requesting tree should not contain
+ *             DBLOCKs prior to the file_start_offset
+ * @param desired_length desired number of bytes the user wanted to access
+ *        (from file_start_offset).  Resulting tree should not contain
+ *        DBLOCKs after file_start_offset + file_length.
+ * @return download request tree for the given range of DBLOCKs at
+ *         the specified depth
+ */
+static struct DownloadRequest *
+create_download_request (struct DownloadRequest *parent,
+                        unsigned int depth,
+                        uint64_t dr_offset,
+                        uint64_t file_start_offset,
+                        uint64_t desired_length)
+{
+  struct DownloadRequest *dr;
+  unsigned int i;
+  unsigned int head_skip;
+  uint64_t child_block_size;
+  
+  dr = GNUNET_malloc (sizeof (struct DownloadRequest));
+  dr->parent = parent;
+  dr->depth = depth;
+  dr->offset = dr_offset;
+  if (depth > 0)
+    {
+      child_block_size = GNUNET_FS_tree_compute_tree_size (depth - 1);
+      
+      /* calculate how many blocks at this level are not interesting
+        from the start (rounded down), either because of the requested
+        file offset or because this IBlock is further along */
+      if (dr_offset < file_start_offset)
+       head_skip = file_start_offset / child_block_size;       
+      else
+       head_skip = dr_offset / child_block_size;       
+
+      /* calculate index of last block at this level that is interesting (rounded up) */
+      dr->num_children = file_start_offset + desired_length / child_block_size;
+      if (dr->num_children * child_block_size < file_start_offset + desired_length)
+       dr->num_children++; /* round up */
+
+      /* now we can get the total number of children for this block */
+      dr->num_children -= head_skip;
+      if (dr->num_children > CHK_PER_INODE)
+       dr->num_children = CHK_PER_INODE; /* cap at max */
+
+      /* why else would we have gotten here to begin with? (that'd be a bad logic error) */
+      GNUNET_assert (dr->num_children > 0); 
+
+      dr->children = GNUNET_malloc (dr->num_children * 
+                                   sizeof (struct DownloadRequest *));
+      for (i=0;i<dr->num_children;i++)
+       dr->children[i] = create_download_request (dr,
+                                                  depth - 1,
+                                                  dr_offset + i * child_block_size,
+                                                  file_start_offset,
+                                                  desired_length);      
+    }
+  return dr;
+}
+
+
+/**
+ * Continuation after a possible attempt to reconstruct
+ * the current IBlock from the existing file.
+ *
+ * @param cls the 'struct ReconstructContext'
+ * @param tc scheduler context
+ */
+static void
+reconstruct_cont (void *cls,
+                 const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+
+  /* clean up state from tree encoder */
+  if (dc->te != NULL)
+    {
+      GNUNET_FS_tree_encoder_finish (dc->te, NULL, NULL);
+      dc->te = NULL;
+    }
+  if (dc->task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (dc->task);
+      dc->task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  if (dc->rfh != NULL)
+    {
+      GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (dc->rfh));
+      dc->rfh = NULL;
+    }
+  /* start "normal" download */
+  schedule_block_download (dc, 
+                          dc->top_request);
+}
+
+
+/**
+ * Task requesting the next block from the tree encoder.
+ *
+ * @param cls the 'struct GNUJNET_FS_DownloadContext' we're processing
+ * @param tc task context
+ */
+static void
+get_next_block (void *cls,
+               const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+
+  dc->task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_FS_tree_encoder_next (dc->te);
+}
+
+
+
+/**
+ * Function called asking for the current (encoded)
+ * block to be processed.  After processing the
+ * client should either call "GNUNET_FS_tree_encode_next"
+ * or (on error) "GNUNET_FS_tree_encode_finish".
  *
- * @param cls our download context
- * @param tc unused
+ * This function checks if the content on disk matches
+ * the expected content based on the URI.
+ * 
+ * @param cls closure
+ * @param chk content hash key for the block
+ * @param offset offset of the block
+ * @param depth depth of the block, 0 for DBLOCK
+ * @param type type of the block (IBLOCK or DBLOCK)
+ * @param block the (encrypted) block
+ * @param block_size size of block (in bytes)
  */
-static void
-do_reconnect (void *cls,
-             const struct GNUNET_SCHEDULER_TaskContext *tc)
+static void 
+reconstruct_cb (void *cls,
+               const struct ContentHashKey *chk,
+               uint64_t offset,
+               unsigned int depth,
+               enum GNUNET_BLOCK_Type type,
+               const void *block,
+               uint16_t block_size)
 {
   struct GNUNET_FS_DownloadContext *dc = cls;
-  struct GNUNET_CLIENT_Connection *client;
-  
-  dc->task = GNUNET_SCHEDULER_NO_TASK;
-  client = GNUNET_CLIENT_connect (dc->h->sched,
-                                 "fs",
-                                 dc->h->cfg);
-  if (NULL == client)
+  struct GNUNET_FS_ProgressInfo pi;
+  struct DownloadRequest *dr;
+  uint64_t blen;
+  unsigned int chld;
+
+  /* find corresponding request entry */
+  dr = dc->top_request;
+  while (dr->depth > depth)
     {
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                 "Connecting to `%s'-service failed, will try again.\n",
-                 "FS");
-      try_reconnect (dc);
+      blen = GNUNET_FS_tree_compute_tree_size (dr->depth);
+      chld = (offset - dr->offset) / blen;
+      GNUNET_assert (chld < dr->num_children);
+      dr = dr->children[chld];
+    }
+  switch (dr->state)
+    {
+    case BRS_INIT:
+      break;
+    case BRS_RECONSTRUCT_DOWN:
+      break;
+    case BRS_RECONSTRUCT_META_UP:
+      break;
+    case BRS_RECONSTRUCT_UP:
+      break;
+    case BRS_CHK_SET:
+      if (0 == memcmp (chk,
+                      &dr->chk,
+                      sizeof (struct ContentHashKey)))
+       {
+         /* block matches, hence tree below matches; 
+            this request is done! */
+         dr->state = BRS_DOWNLOAD_UP;
+         /* calculate how many bytes of payload this block
+            corresponds to */
+         blen = GNUNET_FS_tree_compute_tree_size (dr->depth);
+         /* how many of those bytes are in the requested range? */
+         blen = GNUNET_MIN (blen,
+                            dc->length + dc->offset - dr->offset);
+         /* signal progress */
+         dc->completed += blen;
+         pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
+         pi.value.download.specifics.progress.data = NULL;
+         pi.value.download.specifics.progress.offset = offset;
+         pi.value.download.specifics.progress.data_len = 0;
+         pi.value.download.specifics.progress.depth = 0;
+         GNUNET_FS_download_make_status_ (&pi, dc);             
+       }
+      else
+       {
+       }
+      break; 
+    case BRS_DOWNLOAD_DOWN:
+      break; 
+    case BRS_DOWNLOAD_UP:
+      break;
+    case BRS_ERROR:
+      break;
+    default:
+      GNUNET_assert (0);
+      break;
+    }
+  if ( (dr == dc->top_request) &&
+       (dr->state == BRS_DOWNLOAD_UP) )
+    {
+      check_completed (dc);
       return;
     }
-  dc->client = client;
-  dc->th = GNUNET_CLIENT_notify_transmit_ready (client,
-                                               sizeof (struct SearchMessage),
-                                               GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                               GNUNET_NO,
-                                               &transmit_download_request,
-                                               dc);  
-  GNUNET_CLIENT_receive (client,
-                        &receive_results,
-                        dc,
-                        GNUNET_TIME_UNIT_FOREVER_REL);
+  dc->task = GNUNET_SCHEDULER_add_now (&get_next_block,
+                                      dc);
 }
 
 
 /**
- * Add entries that are not yet pending back to the pending list.
+ * Function called by the tree encoder to obtain a block of plaintext
+ * data (for the lowest level of the tree).
  *
- * @param cls our download context
- * @param key unused
- * @param entry entry of type "struct DownloadRequest"
- * @return GNUNET_OK
+ * @param cls our 'struct ReconstructContext'
+ * @param offset identifies which block to get
+ * @param max (maximum) number of bytes to get; returning
+ *        fewer will also cause errors
+ * @param buf where to copy the plaintext buffer
+ * @param emsg location to store an error message (on error)
+ * @return number of bytes copied to buf, 0 on error
  */
-static int
-retry_entry (void *cls,
-            const GNUNET_HashCode *key,
-            void *entry)
+static size_t
+fh_reader (void *cls,
+          uint64_t offset,
+          size_t max, 
+          void *buf,
+          char **emsg)
 {
   struct GNUNET_FS_DownloadContext *dc = cls;
-  struct DownloadRequest *dr = entry;
+  struct GNUNET_DISK_FileHandle *fh = dc->rfh;
+  ssize_t ret;
 
-  if (! dr->is_pending)
+  *emsg = NULL;
+  if (offset !=
+      GNUNET_DISK_file_seek (fh,
+                            offset,
+                            GNUNET_DISK_SEEK_SET))
     {
-      dr->next = dc->pending;
-      dr->is_pending = GNUNET_YES;
-      dc->pending = entry;
+      *emsg = GNUNET_strdup (strerror (errno));
+      return 0;
     }
-  return GNUNET_OK;
+  ret = GNUNET_DISK_file_read (fh, buf, max);
+  if (ret < 0)
+    {
+      *emsg = GNUNET_strdup (strerror (errno));
+      return 0;
+    }
+  return ret;
 }
 
 
 /**
- * We've lost our connection with the FS service.
- * Re-establish it and re-transmit all of our
- * pending requests.
+ * Task that creates the initial (top-level) download
+ * request for the file.
  *
- * @param dc download context that is having trouble
+ * @param cls the 'struct GNUNET_FS_DownloadContext'
+ * @param tc scheduler context
  */
-static void
-try_reconnect (struct GNUNET_FS_DownloadContext *dc)
+void
+GNUNET_FS_download_start_task_ (void *cls,
+                               const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  
-  if (NULL != dc->client)
+  struct GNUNET_FS_DownloadContext *dc = cls;  
+  struct GNUNET_FS_ProgressInfo pi;
+  struct GNUNET_DISK_FileHandle *fh;
+
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Start task running...\n");
+#endif
+  dc->task = GNUNET_SCHEDULER_NO_TASK;
+  if (dc->length == 0)
     {
-      if (NULL != dc->th)
+      /* no bytes required! */
+      if (dc->filename != NULL) 
        {
-         GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
-         dc->th = NULL;
+         fh = GNUNET_DISK_file_open (dc->filename, 
+                                     GNUNET_DISK_OPEN_READWRITE |
+                                     GNUNET_DISK_OPEN_CREATE |
+                                     ( (0 == GNUNET_FS_uri_chk_get_file_size (dc->uri)) 
+                                       ? GNUNET_DISK_OPEN_TRUNCATE : 0),
+                                     GNUNET_DISK_PERM_USER_READ |
+                                     GNUNET_DISK_PERM_USER_WRITE |
+                                     GNUNET_DISK_PERM_GROUP_READ |
+                                     GNUNET_DISK_PERM_OTHER_READ);
+         GNUNET_DISK_file_close (fh);
        }
-      GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                            &retry_entry,
-                                            dc);
-      GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
-      dc->client = NULL;
+      GNUNET_FS_download_sync_ (dc);
+      check_completed (dc);
+      return;
     }
-  dc->task
-    = GNUNET_SCHEDULER_add_delayed (dc->h->sched,
-                                   GNUNET_TIME_UNIT_SECONDS,
-                                   &do_reconnect,
-                                   dc);
+  if (dc->emsg != NULL)        
+    return;
+  if (dc->top_request == NULL)
+    {
+      dc->top_request = create_download_request (NULL, dc->treedepth - 1, 0,
+                                                dc->offset, dc->length);
+      dc->top_request->state = BRS_CHK_SET;
+      dc->top_request->chk = (dc->uri->type == chk) 
+       ? dc->uri->data.chk.chk
+       : dc->uri->data.loc.fi.chk;
+      /* signal start */
+      GNUNET_FS_download_sync_ (dc);
+      pi.status = GNUNET_FS_STATUS_DOWNLOAD_START;
+      pi.value.download.specifics.start.meta = dc->meta;
+      GNUNET_FS_download_make_status_ (&pi, dc);
+    }
+  GNUNET_FS_download_start_downloading_ (dc);
+  /* attempt reconstruction from disk */
+  if (GNUNET_YES == GNUNET_DISK_file_test (dc->filename))    
+    dc->rfh = GNUNET_DISK_file_open (dc->filename,
+                                    GNUNET_DISK_OPEN_READ,
+                                    GNUNET_DISK_PERM_NONE);    
+  if (dc->top_request->state == BRS_CHK_SET)
+    {
+      if (dc->rfh != NULL)
+       {
+         /* first, try top-down */
+#if DEBUG_DOWNLOAD
+         GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                     "Trying top-down reconstruction for `%s'\n",
+                     dc->filename);
+#endif
+         try_top_down_reconstruction (dc, dc->top_request);
+         switch (dc->top_request->state)
+           {
+           case BRS_CHK_SET:
+             break; /* normal */
+           case BRS_DOWNLOAD_DOWN:
+             break; /* normal, some blocks already down */
+           case BRS_DOWNLOAD_UP:
+             /* already done entirely, party! */
+             if (dc->rfh != NULL)
+               {
+                 /* avoid hanging on to file handle longer than 
+                    necessary */
+                 GNUNET_DISK_file_close (dc->rfh);
+                 dc->rfh = NULL;
+               }
+             return;      
+           case BRS_ERROR:
+             GNUNET_asprintf (&dc->emsg,
+                              _("Invalid URI"));
+             GNUNET_FS_download_sync_ (dc);
+             pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+             pi.value.download.specifics.error.message = dc->emsg;
+             GNUNET_FS_download_make_status_ (&pi, dc);
+             return;
+           default:
+             GNUNET_assert (0);
+             break;
+           }
+       }
+    }
+  /* attempt reconstruction from meta data */
+  if ( (GNUNET_FS_uri_chk_get_file_size (dc->uri) <= MAX_INLINE_SIZE) &&
+       (NULL != dc->meta) )
+    {
+#if DEBUG_DOWNLOAD
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Trying to find embedded meta data for download of size %llu with %u bytes MD\n",
+                 (unsigned long long) GNUNET_FS_uri_chk_get_file_size (dc->uri),
+                 (unsigned int) GNUNET_CONTAINER_meta_data_get_serialized_size (dc->meta));
+#endif
+      GNUNET_CONTAINER_meta_data_iterate (dc->meta,
+                                         &match_full_data,
+                                         dc);
+      if (dc->top_request->state == BRS_DOWNLOAD_UP)
+       {
+         if (dc->rfh != NULL)
+           {
+             /* avoid hanging on to file handle longer than 
+                necessary */
+             GNUNET_DISK_file_close (dc->rfh);
+             dc->rfh = NULL;
+           }
+         return; /* finished, status update was already done for us */
+       }
+    }
+  if (dc->rfh != NULL)
+    {
+      /* finally, try bottom-up */
+#if DEBUG_DOWNLOAD
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                 "Trying bottom-up reconstruction of file `%s'\n",
+                 dc->filename);
+#endif
+      dc->te = GNUNET_FS_tree_encoder_create (dc->h,
+                                             dc->old_file_size,
+                                             dc,
+                                             &fh_reader,
+                                             &reconstruct_cb,
+                                             NULL,
+                                             &reconstruct_cont);     
+      dc->task = GNUNET_SCHEDULER_add_now (&get_next_block,
+                                          dc);
+    }
+  else
+    {
+      /* simple, top-level download */
+       schedule_block_download (dc, 
+                                dc->top_request);
+    }
+  if (dc->top_request->state == BRS_DOWNLOAD_UP)
+    check_completed (dc);
+}
+
+
+/**
+ * Create SUSPEND event for the given download operation
+ * and then clean up our state (without stop signal).
+ *
+ * @param cls the 'struct GNUNET_FS_DownloadContext' to signal for
+ */
+void
+GNUNET_FS_download_signal_suspend_ (void *cls)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct GNUNET_FS_ProgressInfo pi;
+
+  if (dc->top != NULL)
+    GNUNET_FS_end_top (dc->h, dc->top);
+  while (NULL != dc->child_head)
+    GNUNET_FS_download_signal_suspend_ (dc->child_head);  
+  if (dc->search != NULL)
+    {
+      dc->search->download = NULL;
+      dc->search = NULL;
+    }
+  if (dc->job_queue != NULL)
+    {
+      GNUNET_FS_dequeue_ (dc->job_queue);
+      dc->job_queue = NULL;
+    }
+  if (dc->parent != NULL)
+    GNUNET_CONTAINER_DLL_remove (dc->parent->child_head,
+                                dc->parent->child_tail,
+                                dc);  
+  if (dc->task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (dc->task);
+      dc->task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_SUSPEND;
+  GNUNET_FS_download_make_status_ (&pi, dc);
+  if (dc->te != NULL)
+    {
+      GNUNET_FS_tree_encoder_finish (dc->te, NULL, NULL);      
+      dc->te = NULL;
+    }
+  if (dc->rfh != NULL)
+    {
+      GNUNET_DISK_file_close (dc->rfh);
+      dc->rfh = NULL;
+    }
+  GNUNET_FS_free_download_request_ (dc->top_request);
+  if (dc->active != NULL)
+    {
+      GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+      dc->active = NULL;
+    }
+  GNUNET_free_non_null (dc->filename);
+  GNUNET_CONTAINER_meta_data_destroy (dc->meta);
+  GNUNET_FS_uri_destroy (dc->uri);
+  GNUNET_free_non_null (dc->temp_filename);
+  GNUNET_free_non_null (dc->serialization);
+  GNUNET_free (dc);
 }
 
 
@@ -945,6 +2159,10 @@ try_reconnect (struct GNUNET_FS_DownloadContext *dc)
  * @param meta known metadata for the file (can be NULL)
  * @param filename where to store the file, maybe NULL (then no file is
  *        created on disk and data must be grabbed from the callbacks)
+ * @param tempname where to store temporary file data, not used if filename is non-NULL;
+ *        can be NULL (in which case we will pick a name if needed); the temporary file
+ *        may already exist, in which case we will try to use the data that is there and
+ *        if it is not what is desired, will overwrite it
  * @param offset at what offset should we start the download (typically 0)
  * @param length how many bytes should be downloaded starting at offset
  * @param anonymity anonymity level to use for the download
@@ -959,6 +2177,7 @@ GNUNET_FS_download_start (struct GNUNET_FS_Handle *h,
                          const struct GNUNET_FS_Uri *uri,
                          const struct GNUNET_CONTAINER_MetaData *meta,
                          const char *filename,
+                         const char *tempname,
                          uint64_t offset,
                          uint64_t length,
                          uint32_t anonymity,
@@ -966,18 +2185,17 @@ GNUNET_FS_download_start (struct GNUNET_FS_Handle *h,
                          void *cctx,
                          struct GNUNET_FS_DownloadContext *parent)
 {
-  struct GNUNET_FS_ProgressInfo pi;
   struct GNUNET_FS_DownloadContext *dc;
-  struct GNUNET_CLIENT_Connection *client;
 
-  GNUNET_assert (GNUNET_FS_uri_test_chk (uri));
+  GNUNET_assert (GNUNET_FS_uri_test_chk (uri) ||
+                GNUNET_FS_uri_test_loc (uri) );
+                
   if ( (offset + length < offset) ||
-       (offset + length > uri->data.chk.file_length) )
+       (offset + length > GNUNET_FS_uri_chk_get_file_size (uri)) )
     {      
       GNUNET_break (0);
       return NULL;
     }
-  // FIXME: add support for "loc" URIs!
 #if DEBUG_DOWNLOAD
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Starting download `%s' of %llu bytes\n",
@@ -1004,79 +2222,177 @@ GNUNET_FS_download_start (struct GNUNET_FS_Handle *h,
        GNUNET_DISK_file_size (filename,
                               &dc->old_file_size,
                               GNUNET_YES);
-      dc->handle = GNUNET_DISK_file_open (filename, 
-                                         GNUNET_DISK_OPEN_READWRITE | 
-                                         GNUNET_DISK_OPEN_CREATE,
-                                         GNUNET_DISK_PERM_USER_READ |
-                                         GNUNET_DISK_PERM_USER_WRITE |
-                                         GNUNET_DISK_PERM_GROUP_READ |
-                                         GNUNET_DISK_PERM_OTHER_READ);
-      if (dc->handle == NULL)
-       {
-         GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                     _("Download failed: could not open file `%s': %s\n"),
-                     dc->filename,
-                     STRERROR (errno));
-         GNUNET_CONTAINER_meta_data_destroy (dc->meta);
-         GNUNET_FS_uri_destroy (dc->uri);
-         GNUNET_free (dc->filename);
-         GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
-         GNUNET_free (dc);
-         return NULL;
-       }
     }
-  // FIXME: set "dc->target" for LOC uris!
+  if (GNUNET_FS_uri_test_loc (dc->uri))
+    GNUNET_assert (GNUNET_OK ==
+                  GNUNET_FS_uri_loc_get_peer_identity (dc->uri,
+                                                       &dc->target));
   dc->offset = offset;
   dc->length = length;
   dc->anonymity = anonymity;
   dc->options = options;
-  dc->active = GNUNET_CONTAINER_multihashmap_create (2 * (length / DBLOCK_SIZE));
-  dc->treedepth = GNUNET_FS_compute_depth (GNUNET_ntohll(dc->uri->data.chk.file_length));
+  dc->active = GNUNET_CONTAINER_multihashmap_create (1 + 2 * (length / DBLOCK_SIZE));
+  dc->treedepth = GNUNET_FS_compute_depth (GNUNET_FS_uri_chk_get_file_size(dc->uri));
+  if ( (filename == NULL) &&
+       (is_recursive_download (dc) ) )
+    {
+      if (tempname != NULL)
+       dc->temp_filename = GNUNET_strdup (tempname);
+      else
+       dc->temp_filename = GNUNET_DISK_mktemp ("gnunet-directory-download-tmp");    
+    }
+
 #if DEBUG_DOWNLOAD
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Download tree has depth %u\n",
              dc->treedepth);
 #endif
-  // FIXME: make persistent
-  
-  // FIXME: bound parallelism here!
-  client = GNUNET_CLIENT_connect (h->sched,
-                                 "fs",
-                                 h->cfg);
-  dc->client = client;
-  schedule_block_download (dc, 
-                          &dc->uri->data.chk.chk,
-                          0, 
-                          1 /* 0 == CHK, 1 == top */);
-  GNUNET_CLIENT_receive (client,
-                        &receive_results,
-                        dc,
-                        GNUNET_TIME_UNIT_FOREVER_REL);
-  pi.status = GNUNET_FS_STATUS_DOWNLOAD_START;
-  make_download_status (&pi, dc);
-  pi.value.download.specifics.start.meta = meta;
-  dc->client_info = dc->h->upcb (dc->h->upcb_cls,
-                                &pi);
-
+  if (parent == NULL)
+    {
+      dc->top = GNUNET_FS_make_top (dc->h,
+                                   &GNUNET_FS_download_signal_suspend_,
+                                   dc);
+    }
+  dc->task = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, 
+                                      dc);
   return dc;
 }
 
 
 /**
- * Free entries in the map.
+ * Download parts of a file based on a search result.  The download
+ * will be associated with the search result (and the association
+ * will be preserved when serializing/deserializing the state).
+ * If the search is stopped, the download will not be aborted but
+ * be 'promoted' to a stand-alone download.
  *
- * @param cls unused (NULL)
- * @param key unused
- * @param entry entry of type "struct DownloadRequest" which is freed
- * @return GNUNET_OK
+ * As with the other download function, this will store
+ * the blocks at the respective offset in the given file.  Also, the
+ * download is still using the blocking of the underlying FS
+ * encoding.  As a result, the download may *write* outside of the
+ * given boundaries (if offset and length do not match the 32k FS
+ * block boundaries). <p>
+ *
+ * The given range can be used to focus a download towards a
+ * particular portion of the file (optimization), not to strictly
+ * limit the download to exactly those bytes.
+ *
+ * @param h handle to the file sharing subsystem
+ * @param sr the search result to use for the download (determines uri and
+ *        meta data and associations)
+ * @param filename where to store the file, maybe NULL (then no file is
+ *        created on disk and data must be grabbed from the callbacks)
+ * @param tempname where to store temporary file data, not used if filename is non-NULL;
+ *        can be NULL (in which case we will pick a name if needed); the temporary file
+ *        may already exist, in which case we will try to use the data that is there and
+ *        if it is not what is desired, will overwrite it
+ * @param offset at what offset should we start the download (typically 0)
+ * @param length how many bytes should be downloaded starting at offset
+ * @param anonymity anonymity level to use for the download
+ * @param options various download options
+ * @param cctx initial value for the client context for this download
+ * @return context that can be used to control this download
  */
-static int
-free_entry (void *cls,
-           const GNUNET_HashCode *key,
-           void *entry)
+struct GNUNET_FS_DownloadContext *
+GNUNET_FS_download_start_from_search (struct GNUNET_FS_Handle *h,
+                                     struct GNUNET_FS_SearchResult *sr,
+                                     const char *filename,
+                                     const char *tempname,
+                                     uint64_t offset,
+                                     uint64_t length,
+                                     uint32_t anonymity,
+                                     enum GNUNET_FS_DownloadOptions options,
+                                     void *cctx)
 {
-  GNUNET_free (entry);
-  return GNUNET_OK;
+  struct GNUNET_FS_DownloadContext *dc;
+
+  if ( (sr == NULL) ||
+       (sr->download != NULL) )
+    {
+      GNUNET_break (0);
+      return NULL;
+    }
+  GNUNET_assert (GNUNET_FS_uri_test_chk (sr->uri) ||
+                GNUNET_FS_uri_test_loc (sr->uri) );             
+  if ( (offset + length < offset) ||
+       (offset + length > sr->uri->data.chk.file_length) )
+    {      
+      GNUNET_break (0);
+      return NULL;
+    }
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Starting download `%s' of %llu bytes\n",
+             filename,
+             (unsigned long long) length);
+#endif
+  dc = GNUNET_malloc (sizeof(struct GNUNET_FS_DownloadContext));
+  dc->h = h;
+  dc->search = sr;
+  sr->download = dc;
+  if (sr->probe_ctx != NULL)
+    {
+      GNUNET_FS_download_stop (sr->probe_ctx, GNUNET_YES);
+      sr->probe_ctx = NULL;      
+    }
+  dc->uri = GNUNET_FS_uri_dup (sr->uri);
+  dc->meta = GNUNET_CONTAINER_meta_data_duplicate (sr->meta);
+  dc->client_info = cctx;
+  dc->start_time = GNUNET_TIME_absolute_get ();
+  if (NULL != filename)
+    {
+      dc->filename = GNUNET_strdup (filename);
+      if (GNUNET_YES == GNUNET_DISK_file_test (filename))
+       GNUNET_DISK_file_size (filename,
+                              &dc->old_file_size,
+                              GNUNET_YES);
+    }
+  if (GNUNET_FS_uri_test_loc (dc->uri))
+    GNUNET_assert (GNUNET_OK ==
+                  GNUNET_FS_uri_loc_get_peer_identity (dc->uri,
+                                                       &dc->target));
+  dc->offset = offset;
+  dc->length = length;
+  dc->anonymity = anonymity;
+  dc->options = options;
+  dc->active = GNUNET_CONTAINER_multihashmap_create (1 + 2 * (length / DBLOCK_SIZE));
+  dc->treedepth = GNUNET_FS_compute_depth (GNUNET_ntohll(dc->uri->data.chk.file_length));
+  if ( (filename == NULL) &&
+       (is_recursive_download (dc) ) )
+    {
+      if (tempname != NULL)
+       dc->temp_filename = GNUNET_strdup (tempname);
+      else
+       dc->temp_filename = GNUNET_DISK_mktemp ("gnunet-directory-download-tmp");    
+    }
+
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+             "Download tree has depth %u\n",
+             dc->treedepth);
+#endif
+  dc->task = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, 
+                                      dc);
+  return dc;  
+}
+
+
+/**
+ * Start the downloading process (by entering the queue).
+ *
+ * @param dc our download context
+ */
+void
+GNUNET_FS_download_start_downloading_ (struct GNUNET_FS_DownloadContext *dc)
+{
+  if (dc->completed == dc->length)
+    return;
+  GNUNET_assert (dc->job_queue == NULL);
+  dc->job_queue = GNUNET_FS_queue_ (dc->h, 
+                                   &activate_fs_download,
+                                   &deactivate_fs_download,
+                                   dc,
+                                   (dc->length + DBLOCK_SIZE-1) / DBLOCK_SIZE);
 }
 
 
@@ -1091,39 +2407,64 @@ GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc,
                         int do_delete)
 {
   struct GNUNET_FS_ProgressInfo pi;
+  int have_children;
 
+  if (dc->top != NULL)
+    GNUNET_FS_end_top (dc->h, dc->top);
+
+
+  if (dc->task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (dc->task);
+      dc->task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  if (dc->search != NULL)
+    {
+      dc->search->download = NULL;
+      dc->search = NULL;
+    }
+  if (dc->job_queue != NULL)
+    {
+      GNUNET_FS_dequeue_ (dc->job_queue);
+      dc->job_queue = NULL;
+    }
+  if (dc->te != NULL)
+    {
+      GNUNET_FS_tree_encoder_finish (dc->te, NULL, NULL);
+      dc->te = NULL;
+    }
+  have_children = (NULL != dc->child_head) ? GNUNET_YES : GNUNET_NO;
   while (NULL != dc->child_head)
     GNUNET_FS_download_stop (dc->child_head, 
                             do_delete);
-  // FIXME: make unpersistent  
   if (dc->parent != NULL)
     GNUNET_CONTAINER_DLL_remove (dc->parent->child_head,
                                 dc->parent->child_tail,
-                                dc);
-  
+                                dc);  
+  if (dc->serialization != NULL)
+    GNUNET_FS_remove_sync_file_ (dc->h,
+                                ( (dc->parent != NULL)  || (dc->search != NULL) )
+                                ? GNUNET_FS_SYNC_PATH_CHILD_DOWNLOAD 
+                                : GNUNET_FS_SYNC_PATH_MASTER_DOWNLOAD , 
+                                dc->serialization);
+  if ( (GNUNET_YES == have_children) &&
+       (dc->parent == NULL) )
+    GNUNET_FS_remove_sync_dir_ (dc->h, 
+                               (dc->search != NULL) 
+                               ? GNUNET_FS_SYNC_PATH_CHILD_DOWNLOAD 
+                               : GNUNET_FS_SYNC_PATH_MASTER_DOWNLOAD,
+                               dc->serialization);  
   pi.status = GNUNET_FS_STATUS_DOWNLOAD_STOPPED;
-  make_download_status (&pi, dc);
-  dc->client_info = dc->h->upcb (dc->h->upcb_cls,
-                                &pi);
-
-  if (GNUNET_SCHEDULER_NO_TASK != dc->task)
-    GNUNET_SCHEDULER_cancel (dc->h->sched,
-                            dc->task);
-  if (NULL != dc->th)
+  GNUNET_FS_download_make_status_ (&pi, dc);
+  GNUNET_FS_free_download_request_ (dc->top_request);
+  dc->top_request = NULL;
+  if (dc->active != NULL)
     {
-      GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
-      dc->th = NULL;
+      GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+      dc->active = NULL;
     }
-  if (NULL != dc->client)
-    GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
-  GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                        &free_entry,
-                                        NULL);
-  GNUNET_CONTAINER_multihashmap_destroy (dc->active);
   if (dc->filename != NULL)
     {
-      if (NULL != dc->handle)
-       GNUNET_DISK_file_close (dc->handle);
       if ( (dc->completed != dc->length) &&
           (GNUNET_YES == do_delete) )
        {
@@ -1136,6 +2477,15 @@ GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc,
     }
   GNUNET_CONTAINER_meta_data_destroy (dc->meta);
   GNUNET_FS_uri_destroy (dc->uri);
+  if (NULL != dc->temp_filename)
+    {
+      if (0 != UNLINK (dc->temp_filename))
+       GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                                 "unlink",
+                                 dc->temp_filename);
+      GNUNET_free (dc->temp_filename);
+    }
+  GNUNET_free_non_null (dc->serialization);
   GNUNET_free (dc);
 }