[oweals/gnunet.git] / src / include / gnunet_fs_service.h

/*
     This file is part of GNUnet
     (C) 2004--2013 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 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/
/**
 * @file include/gnunet_fs_service.h
 * @brief API for file-sharing via GNUnet
 * @author Christian Grothoff
 */
#ifndef GNUNET_FS_LIB_H
#define GNUNET_FS_LIB_H

#include "gnunet_util_lib.h"
#include "gnunet_scheduler_lib.h"

#ifdef __cplusplus
extern "C"
{
#if 0                           /* keep Emacsens' auto-indent happy */
}
#endif
#endif

/**
 * Version number of the implementation.
 * History:
 *
 * 1.x.x: initial version with triple GNUNET_hash and merkle tree
 * 2.x.x: root node with mime-type, filename and version number
 * 2.1.x: combined GNUNET_EC_ContentHashKey/3HASH encoding with 25:1 super-nodes
 * 2.2.x: with directories
 * 3.0.x: with namespaces
 * 3.1.x: with namespace meta-data
 * 3.2.x: with collections
 * 4.0.x: with expiration, variable meta-data, kblocks
 * 4.1.x: with new error and configuration handling
 * 5.0.x: with location URIs
 * 6.0.0: with support for OR in KSKs
 * 6.1.x: with simplified namespace support
 * 9.0.0: CPS-style integrated API
 * 9.1.1: asynchronous directory scanning
 * 9.2.0: unified K-Block and S-block format (#2564)
 */
#define GNUNET_FS_VERSION 0x00090200


/* ******************** URI API *********************** */

#define GNUNET_FS_URI_PREFIX "gnunet://fs/"
#define GNUNET_FS_URI_KSK_INFIX "ksk/"
#define GNUNET_FS_URI_SKS_INFIX "sks/"
#define GNUNET_FS_URI_CHK_INFIX "chk/"
#define GNUNET_FS_URI_LOC_INFIX "loc/"


/**
 * How often do we signal applications that a probe for a particular
 * search result is running? (used to visualize probes).
 */
#define GNUNET_FS_PROBE_UPDATE_FREQUENCY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 250)

/**
 * A Universal Resource Identifier (URI), opaque.
 */
struct GNUNET_FS_Uri;


/**
 * Identifier for a GNUnet pseudonym (the public key).
 * Q-point, Q=dp.
 */
struct GNUNET_PseudonymIdentifier
{
  /**
   * Q consists of an x- and a y-value, each mod p (256 bits),
   * given here in affine coordinates.
   */
  unsigned char q_x[256 / 8];

  /**
   * Q consists of an x- and a y-value, each mod p (256 bits),
   * given here in affine coordinates.
   */
  unsigned char q_y[256 / 8];

};


/**
 * Handle for a pseudonym (private key).
 */
struct GNUNET_PseudonymHandle;


/**
 * Signature made with a pseudonym (includes the full public key).
 * The ECDSA signature is a pair (r,s) with r = x1 mod n where
 * (x1,y1) = kG for "random" k and s = k^{-1}(z + rd) mod n,
 * where z is derived from the hash of the message that is being
 * signed.
 */
struct GNUNET_PseudonymSignature
{
  
  /**
   * Who created the signature? (public key of the signer), 'd' value in NIST P-256.
   */
  struct GNUNET_PseudonymIdentifier signer;

  /**
   * Binary ECDSA signature data, r-value.  Value is mod n, and n is 256 bits.
   */
  unsigned char sig_r[256 / 8];

  /**
   * Binary ECDSA signature data, s-value.  Value is mod n, and n is 256 bits.
   */
  unsigned char sig_s[256 / 8];
};


/**
 * Purpose for signature made with a pseudonym.
 */
struct GNUNET_PseudonymSignaturePurpose
{
  /**
   * How many bytes are being signed (including this header)?
   */
  uint32_t size;

  /**
   * What is the context/purpose of the signature?
   */
  uint32_t purpose;
};


/**
 * Iterator over keywords
 *
 * @param cls closure
 * @param keyword the keyword
 * @param is_mandatory is the keyword mandatory (in a search)
 * @return GNUNET_OK to continue to iterate, GNUNET_SYSERR to abort
 */
typedef int (*GNUNET_FS_KeywordIterator) (void *cls, const char *keyword,
                                          int is_mandatory);




/**
 * Create a pseudonym.
 *
 * @param filename name of the file to use for storage, NULL for in-memory only
 * @return handle to the private key of the pseudonym
 */
struct GNUNET_PseudonymHandle *
GNUNET_PSEUDONYM_create (const char *filename);


/**
 * Create a pseudonym, from a file that must already exist.
 *
 * @param filename name of the file to use for storage, NULL for in-memory only
 * @return handle to the private key of the pseudonym
 */
struct GNUNET_PseudonymHandle *
GNUNET_PSEUDONYM_create_from_existing_file (const char *filename);


/**
 * Get the handle for the 'anonymous' pseudonym shared by all users.
 * That pseudonym uses a fixed 'secret' for the private key; this
 * construction is useful to make anonymous and pseudonymous APIs
 * (and packets) indistinguishable on the network.  See #2564.
 *
 * @return handle to the (non-secret) private key of the 'anonymous' pseudonym
 */
struct GNUNET_PseudonymHandle *
GNUNET_PSEUDONYM_get_anonymous_pseudonym_handle (void);


/**
 * Destroy a pseudonym handle.  Does NOT remove the private key from
 * the disk.
 *
 * @param ph pseudonym handle to destroy
 */
void
GNUNET_PSEUDONYM_destroy (struct GNUNET_PseudonymHandle *ph);


/**
 * Cryptographically sign some data with the pseudonym.
 *
 * @param ph private key used for signing (corresponds to 'x' in #2564)
 * @param purpose data to sign
 * @param seed hash of the plaintext of the data that we are signing, 
 *             used for deterministic PRNG for anonymous signing;
 *             corresponds to 'k' in section 2.7 of #2564
 * @param signing_key modifier to apply to the private key for signing;
 *                    corresponds to 'h' in section 2.3 of #2564.
 * @param signature where to store the signature
 * @return GNUNET_SYSERR on failure
 */
int
GNUNET_PSEUDONYM_sign (struct GNUNET_PseudonymHandle *ph,
                       const struct GNUNET_PseudonymSignaturePurpose *purpose,
                       const struct GNUNET_HashCode *seed,
                       const struct GNUNET_HashCode *signing_key,
                       struct GNUNET_PseudonymSignature *signature);


/**
 * Given a pseudonym and a signing key, derive the corresponding public
 * key that would be used to verify the resulting signature.
 *
 * @param pseudonym the public key (g^x in DSA, dQ in ECDSA)
 * @param signing_key input to derive 'h' (see section 2.4 of #2564)
 * @param verification_key resulting public key to verify the signature
 *        created from the 'ph' of 'pseudonym' and the 'signing_key';
 *        the value stored here can then be given to GNUNET_PSEUDONYM_verify.
 * @return GNUNET_OK on success, GNUNET_SYSERR on error
 */
int
GNUNET_PSEUDONYM_derive_verification_key (struct GNUNET_PseudonymIdentifier *pseudonym,
                                          const struct GNUNET_HashCode *signing_key,
                                          struct GNUNET_PseudonymIdentifier *verification_key);


/**
 * Verify a signature made with a pseudonym.
 *
 * @param purpose data that was signed
 * @param signature signature to verify
 * @param verification_key public key to use for checking the signature;
 *                    corresponds to 'g^(x+h)' in section 2.4 of #2564.
 * @return GNUNET_OK on success (signature valid, 'pseudonym' set),
 *         GNUNET_SYSERR if the signature is invalid
 */
int
GNUNET_PSEUDONYM_verify (const struct GNUNET_PseudonymSignaturePurpose *purpose,
                         const struct GNUNET_PseudonymSignature *signature,
                         const struct GNUNET_PseudonymIdentifier *verification_key);


/**
 * Get the identifier (public key) of a pseudonym.
 *
 * @param ph pseudonym handle with the private key
 * @param pseudonym pseudonym identifier (set based on 'ph')
 */
void
GNUNET_PSEUDONYM_get_identifier (struct GNUNET_PseudonymHandle *ph,
                                 struct GNUNET_PseudonymIdentifier *pseudonym);



/**
 * Iterator over all known pseudonyms.
 *
 * @param cls closure
 * @param pseudonym hash code of public key of pseudonym
 * @param name name of the pseudonym (might be NULL)
 * @param unique_name unique name of the pseudonym (might be NULL)
 * @param md meta data known about the pseudonym
 * @param rating the local rating of the pseudonym
 * @return GNUNET_OK to continue iteration, GNUNET_SYSERR to abort
 */
typedef int (*GNUNET_PSEUDONYM_Iterator) (void *cls,
                                          const struct GNUNET_PseudonymIdentifier *pseudonym,
                                          const char *name,
                                          const char *unique_name,
                                          const struct GNUNET_CONTAINER_MetaData *md, 
                                          int32_t rating);


/**
 * Change the rank of a pseudonym.
 *
 * @param cfg overall configuration
 * @param pseudonym identity of the pseudonym
 * @param delta by how much should the rating be changed?
 * @return new rating of the pseudonym
 */
int
GNUNET_PSEUDONYM_rank (const struct GNUNET_CONFIGURATION_Handle *cfg,
                       const struct GNUNET_PseudonymIdentifier *pseudonym, 
                       int32_t delta);


/**
 * Add a pseudonym to the set of known pseudonyms.
 * For all pseudonym advertisements that we discover
 * FS should automatically call this function.
 *
 * @param cfg overall configuration
 * @param pseudonym the pseudonym identifier
 * @param meta metadata for the pseudonym
 * @return GNUNET_OK on success, GNUNET_SYSERR on failure
 */
int
GNUNET_PSEUDONYM_add (const struct GNUNET_CONFIGURATION_Handle *cfg,
                      const struct GNUNET_PseudonymIdentifier *pseudonym,
                      const struct GNUNET_CONTAINER_MetaData *meta);


/**
 * List all known pseudonyms.
 *
 * @param cfg overall configuration
 * @param iterator function to call for each pseudonym
 * @param iterator_cls closure for iterator
 * @return number of pseudonyms found
 */
int
GNUNET_PSEUDONYM_list_all (const struct GNUNET_CONFIGURATION_Handle *cfg,
                           GNUNET_PSEUDONYM_Iterator iterator, 
                           void *iterator_cls);


/**
 * Handle for a discovery callback registration.
 */
struct GNUNET_PSEUDONYM_DiscoveryHandle;


/**
 * Register callback to be invoked whenever we discover
 * a new pseudonym.
 *
 * @param cfg our configuration
 * @param iterator function to invoke on discovery
 * @param iterator_cls closure for iterator
 * @return registration handle
 */
struct GNUNET_PSEUDONYM_DiscoveryHandle *
GNUNET_PSEUDONYM_discovery_callback_register (const struct GNUNET_CONFIGURATION_Handle *cfg,
                                              GNUNET_PSEUDONYM_Iterator iterator, 
                                              void *iterator_cls);


/**
 * Unregister pseudonym discovery callback.
 *
 * @param dh registration to unregister
 */
void
GNUNET_PSEUDONYM_discovery_callback_unregister (struct GNUNET_PSEUDONYM_DiscoveryHandle *dh);


/**
 * Return unique variant of the pseudonym name.  Use after
 * GNUNET_PSEUDONYM_id_to_name() to make sure that name is unique.
 *
 * @param cfg configuration
 * @param pseudonym cryptographic ID of the pseudonym
 * @param name name to uniquify
 * @param suffix if not NULL, filled with the suffix value
 * @return NULL on failure (should never happen), name on success.
 *         Free the name with GNUNET_free().
 */
char *
GNUNET_PSEUDONYM_name_uniquify (const struct GNUNET_CONFIGURATION_Handle *cfg,
                                const struct GNUNET_PseudonymIdentifier *pseudonym, 
                                const char *name, 
                                unsigned int *suffix);


/**
 * Get pseudonym name, metadata and rank. This is a wrapper around
 * internal read_info() call, and ensures that returned data is not
 * invalid (not NULL).  Writing back information returned by this
 * function will give a name "no-name" to pseudonyms that have no
 * name. This side-effect is unavoidable, but hardly harmful.
 *
 * @param cfg configuration
 * @param pseudonym cryptographic ID of the pseudonym
 * @param ret_meta a location to store metadata pointer. NULL, if metadata
 *        is not needed. Destroy with GNUNET_CONTAINER_meta_data_destroy().
 * @param ret_rank a location to store rank. NULL, if rank not needed.
 * @param ret_name a location to store human-readable name. Name is not unique.
 *        NULL, if name is not needed. Free with GNUNET_free().
 * @param name_is_a_dup is set to GNUNET_YES, if ret_name was filled with
 *        a duplicate of a "no-name" placeholder
 * @return GNUNET_OK on success. GNUENT_SYSERR if the data was
 *         unobtainable (in that case ret_* are filled with placeholders - 
 *         empty metadata container, rank -1 and a "no-name" name).
 */
int
GNUNET_PSEUDONYM_get_info (const struct GNUNET_CONFIGURATION_Handle *cfg,
                           const struct GNUNET_PseudonymIdentifier *pseudonym, 
                           struct GNUNET_CONTAINER_MetaData **ret_meta,
                           int32_t *ret_rank, 
                           char **ret_name, 
                           int *name_is_a_dup);


/**
 * Get the pseudonym ID belonging to the given pseudonym name.
 *
 * @param cfg configuration to use
 * @param ns_uname unique (!) human-readable name for the pseudonym
 * @param pseudonym set to pseudonym ID based on 'ns_uname'
 * @return GNUNET_OK on success, GNUNET_SYSERR on failure
 */
int
GNUNET_PSEUDONYM_name_to_id (const struct GNUNET_CONFIGURATION_Handle *cfg,
                             const char *ns_uname,
                             struct GNUNET_PseudonymIdentifier *pseudonym);


/**
 * Set the pseudonym metadata, rank and name.
 *
 * @param cfg overall configuration
 * @param pseudonym id of the pseudonym
 * @param name name to set. Must be the non-unique version of it.
 *        May be NULL, in which case it erases pseudonym's name!
 * @param md metadata to set
 *        May be NULL, in which case it erases pseudonym's metadata!
 * @param rank rank to assign
 * @return GNUNET_OK on success, GNUNET_SYSERR on failure
 */
int
GNUNET_PSEUDONYM_set_info (const struct GNUNET_CONFIGURATION_Handle *cfg,
                           const struct GNUNET_PseudonymIdentifier *pseudonym, 
                           const char *name,
                           const struct GNUNET_CONTAINER_MetaData *md, 
                           int32_t rank);


/**
 * Remove pseudonym from the set of known pseudonyms.
 *
 * @param cfg overall configuration
 * @param id the pseudonym identifier
 * @return GNUNET_OK on success, GNUNET_SYSERR on failure
 */
int
GNUNET_PSEUDONYM_remove (const struct GNUNET_CONFIGURATION_Handle *cfg,
    const struct GNUNET_PseudonymIdentifier *id);


/**
 * Get a unique key from a URI.  This is for putting URIs
 * into HashMaps.  The key may change between FS implementations.
 *
 * @param uri uri to convert to a unique key
 * @param key wherer to store the unique key
 */
void
GNUNET_FS_uri_to_key (const struct GNUNET_FS_Uri *uri, struct GNUNET_HashCode * key);


/**
 * Convert a URI to a UTF-8 String.
 *
 * @param uri uri to convert to a string
 * @return the UTF-8 string
 */
char *
GNUNET_FS_uri_to_string (const struct GNUNET_FS_Uri *uri);


/**
 * Convert keyword URI to a human readable format
 * (i.e. the search query that was used in the first place)
 *
 * @param uri ksk uri to convert to a string
 * @return string with the keywords
 */
char *
GNUNET_FS_uri_ksk_to_string_fancy (const struct GNUNET_FS_Uri *uri);


/**
 * Add the given keyword to the set of keywords represented by the URI.
 * Does nothing if the keyword is already present.
 *
 * @param uri ksk uri to modify
 * @param keyword keyword to add
 * @param is_mandatory is this keyword mandatory?
 */
void
GNUNET_FS_uri_ksk_add_keyword (struct GNUNET_FS_Uri *uri, const char *keyword,
                               int is_mandatory);


/**
 * Remove the given keyword from the set of keywords represented by the URI.
 * Does nothing if the keyword is not present.
 *
 * @param uri ksk uri to modify
 * @param keyword keyword to add
 */
void
GNUNET_FS_uri_ksk_remove_keyword (struct GNUNET_FS_Uri *uri,
                                  const char *keyword);


/**
 * Convert a UTF-8 String to a URI.
 *
 * @param uri string to parse
 * @param emsg where to store the parser error message (if any)
 * @return NULL on error
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_parse (const char *uri, char **emsg);

/**
 * Free URI.
 *
 * @param uri uri to free
 */
void
GNUNET_FS_uri_destroy (struct GNUNET_FS_Uri *uri);


/**
 * How many keywords are ANDed in this keyword URI?
 *
 * @param uri ksk uri to get the number of keywords from
 * @return 0 if this is not a keyword URI
 */
unsigned int
GNUNET_FS_uri_ksk_get_keyword_count (const struct GNUNET_FS_Uri *uri);


/**
 * Iterate over all keywords in this keyword URI.
 *
 * @param uri ksk uri to get the keywords from
 * @param iterator function to call on each keyword
 * @param iterator_cls closure for iterator
 * @return -1 if this is not a keyword URI, otherwise number of
 *   keywords iterated over until iterator aborted
 */
int
GNUNET_FS_uri_ksk_get_keywords (const struct GNUNET_FS_Uri *uri,
                                GNUNET_FS_KeywordIterator iterator,
                                void *iterator_cls);


/**
 * Obtain the identity of the peer offering the data
 *
 * @param uri the location URI to inspect
 * @param peer where to store the identify of the peer (presumably) offering the content
 * @return GNUNET_SYSERR if this is not a location URI, otherwise GNUNET_OK
 */
int
GNUNET_FS_uri_loc_get_peer_identity (const struct GNUNET_FS_Uri *uri,
                                     struct GNUNET_PeerIdentity *peer);


/**
 * Obtain the URI of the content itself.
 *
 * @param uri location URI to get the content URI from
 * @return NULL if argument is not a location URI
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_loc_get_uri (const struct GNUNET_FS_Uri *uri);


/**
 * Obtain the expiration of the LOC URI.
 *
 * @param uri location URI to get the expiration from
 * @return expiration time of the URI
 */
struct GNUNET_TIME_Absolute
GNUNET_FS_uri_loc_get_expiration (const struct GNUNET_FS_Uri *uri);


/**
 * Construct a location URI (this peer will be used for the location).
 *
 * @param baseUri content offered by the sender
 * @param cfg configuration information (used to find our hostkey)
 * @param expiration_time how long will the content be offered?
 * @return the location URI, NULL on error
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_loc_create (const struct GNUNET_FS_Uri *baseUri,
                          const struct GNUNET_CONFIGURATION_Handle *cfg,
                          struct GNUNET_TIME_Absolute expiration_time);


/**
 * Merge the sets of keywords from two KSK URIs.
 *
 * @param u1 first uri
 * @param u2 second uri
 * @return merged URI, NULL on error
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_ksk_merge (const struct GNUNET_FS_Uri *u1,
                         const struct GNUNET_FS_Uri *u2);


/**
 * Duplicate URI.
 *
 * @param uri the URI to duplicate
 * @return copy of the URI
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_dup (const struct GNUNET_FS_Uri *uri);


/**
 * Create an FS URI from a single user-supplied string of keywords.
 * The string is broken up at spaces into individual keywords.
 * Keywords that start with "+" are mandatory.  Double-quotes can
 * be used to prevent breaking up strings at spaces (and also
 * to specify non-mandatory keywords starting with "+").
 *
 * Keywords must contain a balanced number of double quotes and
 * double quotes can not be used in the actual keywords (for
 * example, the string '""foo bar""' will be turned into two
 * "OR"ed keywords 'foo' and 'bar', not into '"foo bar"'.
 *
 * @param keywords the keyword string
 * @param emsg where to store an error message
 * @return an FS URI for the given keywords, NULL
 *  if keywords is not legal (i.e. empty).
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_ksk_create (const char *keywords, char **emsg);


/**
 * Create an FS URI from a user-supplied command line of keywords.
 * Arguments should start with "+" to indicate mandatory
 * keywords.
 *
 * @param argc number of keywords
 * @param argv keywords (double quotes are not required for
 *             keywords containing spaces; however, double
 *             quotes are required for keywords starting with
 *             "+"); there is no mechanism for having double
 *             quotes in the actual keywords (if the user
 *             did specifically specify double quotes, the
 *             caller should convert each double quote
 *             into two single quotes).
 * @return an FS URI for the given keywords, NULL
 *  if keywords is not legal (i.e. empty).
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_ksk_create_from_args (unsigned int argc, const char **argv);


/**
 * Test if two URIs are equal.
 *
 * @param u1 one of the URIs
 * @param u2 the other URI
 * @return GNUNET_YES if the URIs are equal
 */
int
GNUNET_FS_uri_test_equal (const struct GNUNET_FS_Uri *u1,
                          const struct GNUNET_FS_Uri *u2);


/**
 * Is this a namespace URI?
 *
 * @param uri the uri to check
 * @return GNUNET_YES if this is an SKS uri
 */
int
GNUNET_FS_uri_test_sks (const struct GNUNET_FS_Uri *uri);


/**
 * Handle to one of our namespaces.
 */
struct GNUNET_FS_Namespace;


/**
 * Create an SKS URI from a namespace and an identifier.
 *
 * @param ns namespace
 * @param id identifier
 * @param emsg where to store an error message
 * @return an FS URI for the given namespace and identifier
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_sks_create (struct GNUNET_FS_Namespace *ns, const char *id,
                          char **emsg);


/**
 * Create an SKS URI from a namespace ID and an identifier.
 *
 * @param pseudonym pseudonym to use
 * @param id identifier
 * @return an FS URI for the given namespace and identifier
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_sks_create_from_nsid (struct GNUNET_PseudonymIdentifier *pseudonym, 
                                    const char *id);


/**
 * Get the public key of a namespace from the given
 * namespace URI.
 *
 * @param uri the uri to get the namespace ID from
 * @param pseudonym where to store the public key of the namespace
 * @return GNUNET_OK on success
 */
int
GNUNET_FS_uri_sks_get_namespace (const struct GNUNET_FS_Uri *uri,
                                 struct GNUNET_PseudonymIdentifier *pseudonym);


/**
 * Get the content identifier of an SKS URI.
 *
 * @param uri the sks uri
 * @return NULL on error (not a valid SKS URI)
 */
char *
GNUNET_FS_uri_sks_get_content_id (const struct GNUNET_FS_Uri *uri);


/**
 * Convert namespace URI to a human readable format
 * (using the namespace description, if available).
 *
 * @param cfg configuration to use
 * @param uri SKS uri to convert
 * @return NULL on error (not an SKS URI)
 */
char *
GNUNET_FS_uri_sks_to_string_fancy (struct GNUNET_CONFIGURATION_Handle *cfg,
                                   const struct GNUNET_FS_Uri *uri);


/**
 * Is this a keyword URI?
 *
 * @param uri the uri
 * @return GNUNET_YES if this is a KSK uri
 */
int
GNUNET_FS_uri_test_ksk (const struct GNUNET_FS_Uri *uri);


/**
 * Is this a file (or directory) URI?
 *
 * @param uri the uri to check
 * @return GNUNET_YES if this is a CHK uri
 */
int
GNUNET_FS_uri_test_chk (const struct GNUNET_FS_Uri *uri);


/**
 * What is the size of the file that this URI
 * refers to?
 *
 * @param uri the CHK (or LOC) URI to inspect
 * @return size of the file as specified in the CHK URI
 */
uint64_t
GNUNET_FS_uri_chk_get_file_size (const struct GNUNET_FS_Uri *uri);


/**
 * Is this a location URI?
 *
 * @param uri the uri to check
 * @return GNUNET_YES if this is a LOC uri
 */
int
GNUNET_FS_uri_test_loc (const struct GNUNET_FS_Uri *uri);


/**
 * Construct a keyword-URI from meta-data (take all entries
 * in the meta-data and construct one large keyword URI
 * that lists all keywords that can be found in the meta-data).
 *
 * @param md metadata to use
 * @return NULL on error, otherwise a KSK URI
 */
struct GNUNET_FS_Uri *
GNUNET_FS_uri_ksk_create_from_meta_data (const struct GNUNET_CONTAINER_MetaData
                                         *md);


/* ******************** command-line option parsing API *********************** */

/**
 * Command-line option parser function that allows the user
 * to specify one or more '-k' options with keywords.  Each
 * specified keyword will be added to the URI.  A pointer to
 * the URI must be passed as the "scls" argument.
 *
 * @param ctx command line processor context
 * @param scls must be of type "struct GNUNET_FS_Uri **"
 * @param option name of the option (typically 'k')
 * @param value command line argument given
 * @return GNUNET_OK on success
 */
int
GNUNET_FS_getopt_set_keywords (struct GNUNET_GETOPT_CommandLineProcessorContext
                               *ctx, void *scls, const char *option,
                               const char *value);


/**
 * Command-line option parser function that allows the user to specify
 * one or more '-m' options with metadata.  Each specified entry of
 * the form "type=value" will be added to the metadata.  A pointer to
 * the metadata must be passed as the "scls" argument.
 *
 * @param ctx command line processor context
 * @param scls must be of type "struct GNUNET_CONTAINER_MetaData **"
 * @param option name of the option (typically 'k')
 * @param value command line argument given
 * @return GNUNET_OK on success
 */
int
GNUNET_FS_getopt_set_metadata (struct GNUNET_GETOPT_CommandLineProcessorContext
                               *ctx, void *scls, const char *option,
                               const char *value);



/* ************************* sharing API ***************** */


/**
 * Possible status codes used in the callback for the
 * various file-sharing operations.  On each file (or search),
 * the callback is guaranteed to be called once with "START"
 * and once with STOPPED; calls with PROGRESS, ERROR or COMPLETED
 * are optional and depend on the circumstances; parent operations
 * will be STARTED before child-operations and STOPPED after
 * their respective child-operations.  START and STOP signals
 * are typically generated either due to explicit client requests
 * or because of suspend/resume operations.
 */
enum GNUNET_FS_Status
{
  /**
   * Notification that we have started to publish a file structure.
   */
  GNUNET_FS_STATUS_PUBLISH_START = 0,

  /**
   * Notification that we have resumed sharing a file structure.
   */
  GNUNET_FS_STATUS_PUBLISH_RESUME = 1,

  /**
   * Notification that we have suspended sharing a file structure.
   */
  GNUNET_FS_STATUS_PUBLISH_SUSPEND = 2,

  /**
   * Notification that we are making progress sharing a file structure.
   */
  GNUNET_FS_STATUS_PUBLISH_PROGRESS = 3,

  /**
   * Notification that an error was encountered  sharing a file structure.
   * The application will continue to receive resume/suspend events for
   * this structure until "GNUNET_FS_publish_stop" is called.
   */
  GNUNET_FS_STATUS_PUBLISH_ERROR = 4,

  /**
   * Notification that we completed sharing a file structure.
   * The application will continue to receive resume/suspend events for
   * this structure until "GNUNET_FS_publish_stop" is called.
   */
  GNUNET_FS_STATUS_PUBLISH_COMPLETED = 5,

  /**
   * Notification that we have stopped
   * the process of uploading a file structure; no
   * futher events will be generated for this action.
   */
  GNUNET_FS_STATUS_PUBLISH_STOPPED = 6,

  /**
   * Notification that we have started this download.
   */
  GNUNET_FS_STATUS_DOWNLOAD_START = 7,

  /**
   * Notification that this download is being resumed.
   */
  GNUNET_FS_STATUS_DOWNLOAD_RESUME = 8,

  /**
   * Notification that this download was suspended.
   */
  GNUNET_FS_STATUS_DOWNLOAD_SUSPEND = 9,

  /**
   * Notification about progress with this download.
   */
  GNUNET_FS_STATUS_DOWNLOAD_PROGRESS = 10,

  /**
   * Notification that this download encountered an error.
   */
  GNUNET_FS_STATUS_DOWNLOAD_ERROR = 11,

  /**
   * Notification that this download completed.  Note that for
   * directories, completion does not imply completion of all files in
   * the directory.
   */
  GNUNET_FS_STATUS_DOWNLOAD_COMPLETED = 12,

  /**
   * Notification that this download was stopped
   * (final event with respect to this action).
   */
  GNUNET_FS_STATUS_DOWNLOAD_STOPPED = 13,

  /**
   * Notification that this download is now actively being
   * pursued (as opposed to waiting in the queue).
   */
  GNUNET_FS_STATUS_DOWNLOAD_ACTIVE = 14,

  /**
   * Notification that this download is no longer actively
   * being pursued (back in the queue).
   */
  GNUNET_FS_STATUS_DOWNLOAD_INACTIVE = 15,

  /**
   * Notification that this download is no longer part of a
   * recursive download or search but now a 'stand-alone'
   * download (and may thus need to be moved in the GUI
   * into a different category).
   */
  GNUNET_FS_STATUS_DOWNLOAD_LOST_PARENT = 16,

  /**
   * First event generated when a client requests
   * a search to begin or when a namespace result
   * automatically triggers the search for updates.
   */
  GNUNET_FS_STATUS_SEARCH_START = 17,

  /**
   * Last event when a search is being resumed;
   * note that "GNUNET_FS_SEARCH_START" will not
   * be generated in this case.
   */
  GNUNET_FS_STATUS_SEARCH_RESUME = 18,

  /**
   * Event generated for each search result
   * when the respective search is resumed.
   */
  GNUNET_FS_STATUS_SEARCH_RESUME_RESULT = 19,

  /**
   * Last event when a search is being suspended;
   * note that "GNUNET_FS_SEARCH_STOPPED" will not
   * be generated in this case.
   */
  GNUNET_FS_STATUS_SEARCH_SUSPEND = 20,

  /**
   * This search has yielded a result.
   */
  GNUNET_FS_STATUS_SEARCH_RESULT = 21,

  /**
   * We have discovered a new namespace.
   */
  GNUNET_FS_STATUS_SEARCH_RESULT_NAMESPACE = 22,

  /**
   * We have additional data about the quality
   * or availability of a search result.
   */
  GNUNET_FS_STATUS_SEARCH_UPDATE = 23,

  /**
   * Signals a problem with this search.
   */
  GNUNET_FS_STATUS_SEARCH_ERROR = 24,

  /**
   * Signals that this search was paused.
   */
  GNUNET_FS_STATUS_SEARCH_PAUSED = 25,

  /**
   * Signals that this search was continued (unpaused).
   */
  GNUNET_FS_STATUS_SEARCH_CONTINUED = 26,

  /**
   * Event generated for each search result
   * when the respective search is stopped.
   */
  GNUNET_FS_STATUS_SEARCH_RESULT_STOPPED = 27,

  /**
   * Event generated for each search result
   * when the respective search is suspended.
   */
  GNUNET_FS_STATUS_SEARCH_RESULT_SUSPEND = 28,

  /**
   * Last message from a search; this signals
   * that there will be no further events associated
   * with this search.
   */
  GNUNET_FS_STATUS_SEARCH_STOPPED = 29,

  /**
   * Notification that we started to unindex a file.
   */
  GNUNET_FS_STATUS_UNINDEX_START = 30,

  /**
   * Notification that we resumed unindexing of a file.
   */
  GNUNET_FS_STATUS_UNINDEX_RESUME = 31,

  /**
   * Notification that we suspended unindexing a file.
   */
  GNUNET_FS_STATUS_UNINDEX_SUSPEND = 32,

  /**
   * Notification that we made progress unindexing a file.
   */
  GNUNET_FS_STATUS_UNINDEX_PROGRESS = 33,

  /**
   * Notification that we encountered an error unindexing
   * a file.
   */
  GNUNET_FS_STATUS_UNINDEX_ERROR = 34,

  /**
   * Notification that the unindexing of this file
   * was completed.
   */
  GNUNET_FS_STATUS_UNINDEX_COMPLETED = 35,

  /**
   * Notification that the unindexing of this file
   * was stopped (final event for this action).
   */
  GNUNET_FS_STATUS_UNINDEX_STOPPED = 36
};


/**
 * Handle for controlling an upload.
 */
struct GNUNET_FS_PublishContext;


/**
 * Handle for controlling an unindexing operation.
 */
struct GNUNET_FS_UnindexContext;


/**
 * Handle for controlling a search.
 */
struct GNUNET_FS_SearchContext;


/**
 * Result from a search.  Opaque handle to refer to the search
 * (typically used when starting a download associated with the search
 * result).
 */
struct GNUNET_FS_SearchResult;


/**
 * Context for controlling a download.
 */
struct GNUNET_FS_DownloadContext;


/**
 * Handle for detail information about a file that is being publishd.
 * Specifies metadata, keywords, how to get the contents of the file
 * (i.e. data-buffer in memory, filename on disk) and other options.
 */
struct GNUNET_FS_FileInformation;


/**
 * Argument given to the progress callback with
 * information about what is going on.
 */
struct GNUNET_FS_ProgressInfo
{

  /**
   * Values that depend on the event type.
   */
  union
  {

    /**
     * Values for all "GNUNET_FS_STATUS_PUBLISH_*" events.
     */
    struct
    {

      /**
       * Context for controlling the upload.
       */
      struct GNUNET_FS_PublishContext *pc;

      /**
       * Information about the file that is being publishd.
       */
      const struct GNUNET_FS_FileInformation *fi;

      /**
       * Client context pointer (set the last time by the client for
       * this operation; initially NULL on START/RESUME events).
       */
      void *cctx;

      /**
       * Client context pointer for the parent operation
       * (if this is a file in a directory or a subdirectory).
       */
      void *pctx;

      /**
       * Name of the file being published; can be NULL.
       */
      const char *filename;

      /**
       * How large is the file overall?  For directories,
       * this is only the size of the directory itself,
       * not of the other files contained within the
       * directory.
       */
      uint64_t size;

      /**
       * At what time do we expect to finish the upload?
       * (will be a value in the past for completed
       * uploads).
       */
      struct GNUNET_TIME_Relative eta;

      /**
       * How long has this upload been actively running
       * (excludes times where the upload was suspended).
       */
      struct GNUNET_TIME_Relative duration;

      /**
       * How many bytes have we completed?
       */
      uint64_t completed;

      /**
       * What anonymity level is used for this upload?
       */
      uint32_t anonymity;

      /**
       * Additional values for specific events.
       */
      union
      {

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_PUBLISH_PROGRESS events.
         */
        struct
        {

          /**
           * Data block we just published.
           */
          const void *data;

          /**
           * At what offset in the file is "data"?
           */
          uint64_t offset;

          /**
           * Length of the data block.
           */
          uint64_t data_len;

          /**
           * Depth of the given block in the tree;
           * 0 would be the lowest level (DBLOCKs).
           */
          unsigned int depth;

        } progress;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_PUBLISH_RESUME events.
         */
        struct
        {

          /**
           * Error message, NULL if no error was encountered so far.
           */
          const char *message;

          /**
           * URI of the file (if the download had been completed)
           */
          const struct GNUNET_FS_Uri *chk_uri;

        } resume;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_PUBLISH_COMPLETED events.
         */
        struct
        {

          /**
           * URI of the file.
           */
          const struct GNUNET_FS_Uri *chk_uri;

        } completed;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_PUBLISH_ERROR events.
         */
        struct
        {

          /**
           * Error message, never NULL.
           */
          const char *message;

        } error;

      } specifics;

    } publish;


    /**
     * Values for all "GNUNET_FS_STATUS_DOWNLOAD_*" events.
     */
    struct
    {

      /**
       * Context for controlling the download.
       */
      struct GNUNET_FS_DownloadContext *dc;

      /**
       * Client context pointer (set the last time
       * by the client for this operation; initially
       * NULL on START/RESUME events).
       */
      void *cctx;

      /**
       * Client context pointer for the parent operation
       * (if this is a file in a directory or a subdirectory).
       */
      void *pctx;

      /**
       * Client context pointer for the associated search operation
       * (specifically, context pointer for the specific search
       * result, not the overall search); only set if this
       * download was started from a search result.
       */
      void *sctx;

      /**
       * URI used for this download.
       */
      const struct GNUNET_FS_Uri *uri;

      /**
       * Name of the file that we are downloading.
       */
      const char *filename;

      /**
       * How large is the download overall?  This
       * is NOT necessarily the size from the
       * URI since we may be doing a partial download.
       */
      uint64_t size;

      /**
       * At what time do we expect to finish the download?
       * (will be a value in the past for completed
       * uploads).
       */
      struct GNUNET_TIME_Relative eta;

      /**
       * How long has this download been active?
       */
      struct GNUNET_TIME_Relative duration;

      /**
       * How many bytes have we completed?
       */
      uint64_t completed;

      /**
       * What anonymity level is used for this download?
       */
      uint32_t anonymity;

      /**
       * Is the download currently active.
       */
      int is_active;

      /**
       * Additional values for specific events.
       */
      union
      {

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_DOWNLOAD_PROGRESS events.
         */
        struct
        {

          /**
           * Data block we just obtained, can be NULL (even if
           * data_len > 0) if we found the entire block 'intact' on
           * disk.  In this case, it is also possible for 'data_len'
           * to be larger than an individual (32k) block.
           */
          const void *data;

          /**
           * At what offset in the file is "data"?
           */
          uint64_t offset;

          /**
           * Length of the data block.
           */
          uint64_t data_len;

          /**
           * How much time passed between us asking for this block and
           * actually getting it? GNUNET_TIME_UNIT_FOREVER_REL if unknown.
           */
          struct GNUNET_TIME_Relative block_download_duration;

          /**
           * Depth of the given block in the tree;
           * 0 would be the lowest level (DBLOCKS).
           */
          unsigned int depth;

          /**
           * How much respect did we offer for downloading this block? (estimate,
           * because we might have the same request pending for multiple clients,
           * and of course because a transmission may have failed at a lower
           * layer).
           */
          uint32_t respect_offered;

          /**
           * How often did we transmit the request? (estimate,
           * because we might have the same request pending for multiple clients,
           * and of course because a transmission may have failed at a lower
           * layer).
           */
          uint32_t num_transmissions;

        } progress;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_DOWNLOAD_START events.
         */
        struct
        {

          /**
           * Known metadata for the download.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

        } start;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_DOWNLOAD_RESUME events.
         */
        struct
        {

          /**
           * Known metadata for the download.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * Error message, NULL if we have not encountered any error yet.
           */
          const char *message;

        } resume;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_DOWNLOAD_ERROR events.
         */
        struct
        {

          /**
           * Error message.
           */
          const char *message;

        } error;

      } specifics;

    } download;

    /**
     * Values for all "GNUNET_FS_STATUS_SEARCH_*" events.
     */
    struct
    {

      /**
       * Context for controlling the search, NULL for
       * searches that were not explicitly triggered
       * by the client (i.e., searches for updates in
       * namespaces).
       */
      struct GNUNET_FS_SearchContext *sc;

      /**
       * Client context pointer (set the last time by the client for
       * this operation; initially NULL on START/RESUME events).  Note
       * that this value can only be set on START/RESUME; returning
       * non-NULL on RESULT/RESUME_RESULT will actually update the
       * private context for "UPDATE" events.
       */
      void *cctx;

      /**
       * Client parent-context pointer; NULL for top-level searches,
       * refers to the client context of the associated search result
       * for automatically triggered searches for updates in
       * namespaces.  In this case, 'presult' refers to that search
       * result.
       */
      void *pctx;

      /**
       * What query is used for this search
       * (list of keywords or SKS identifier).
       */
      const struct GNUNET_FS_Uri *query;

      /**
       * How long has this search been actively running
       * (excludes times where the search was paused or
       * suspended).
       */
      struct GNUNET_TIME_Relative duration;

      /**
       * What anonymity level is used for this search?
       */
      uint32_t anonymity;

      /**
       * Additional values for specific events.
       */
      union
      {

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_RESULT events.
         */
        struct
        {

          /**
           * Metadata for the search result.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * URI for the search result.
           */
          const struct GNUNET_FS_Uri *uri;

          /**
           * Handle to the result (for starting downloads).
           */
          struct GNUNET_FS_SearchResult *result;

          /**
           * Applicability rank (the larger, the better the result
           * fits the search criteria).
           */
          uint32_t applicability_rank;

        } result;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_RESUME_RESULT events.
         */
        struct
        {

          /**
           * Metadata for the search result.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * URI for the search result.
           */
          const struct GNUNET_FS_Uri *uri;

          /**
           * Handle to the result (for starting downloads).
           */
          struct GNUNET_FS_SearchResult *result;

          /**
           * Current availability rank (negative:
           * unavailable, positive: available)
           */
          int32_t availability_rank;

          /**
           * On how many total queries is the given
           * availability_rank based?
           */
          uint32_t availability_certainty;

          /**
           * Updated applicability rank (the larger,
           * the better the result fits the search
           * criteria).
           */
          uint32_t applicability_rank;

        } resume_result;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_UPDATE events.
         */
        struct
        {

          /**
           * Private context set for for this result
           * during the "RESULT" event.
           */
          void *cctx;

          /**
           * Metadata for the search result.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * URI for the search result.
           */
          const struct GNUNET_FS_Uri *uri;

          /**
           * Current availability rank (negative:
           * unavailable, positive: available)
           */
          int32_t availability_rank;

          /**
           * On how many total queries is the given
           * availability_rank based?
           */
          uint32_t availability_certainty;

          /**
           * Updated applicability rank (the larger,
           * the better the result fits the search
           * criteria).
           */
          uint32_t applicability_rank;

          /**
           * How long has the current probe been active?
           */
          struct GNUNET_TIME_Relative current_probe_time;

        } update;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_RESULT_SUSPEND events.
         * These events are automatically triggered for
         * each search result before the
         * GNUNET_FS_STATUS_SEARCH_SUSPEND event.  This
         * happens primarily to give the client a chance
         * to clean up the "cctx" (if needed).
         */
        struct
        {

          /**
           * Private context set for for this result
           * during the "RESULT" event.
           */
          void *cctx;

          /**
           * Metadata for the search result.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * URI for the search result.
           */
          const struct GNUNET_FS_Uri *uri;

        } result_suspend;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_RESULT_STOPPED events.
         * These events are automatically triggered for
         * each search result before the
         * GNUNET_FS_STATUS_SEARCH_STOPPED event.  This
         * happens primarily to give the client a chance
         * to clean up the "cctx" (if needed).
         */
        struct
        {

          /**
           * Private context set for for this result
           * during the "RESULT" event.
           */
          void *cctx;

          /**
           * Metadata for the search result.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * URI for the search result.
           */
          const struct GNUNET_FS_Uri *uri;

        } result_stopped;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_RESUME events.
         */
        struct
        {

          /**
           * Error message, NULL if we have not encountered any error yet.
           */
          const char *message;

          /**
           * Is this search currently paused?
           */
          int is_paused;

        } resume;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_SEARCH_ERROR events.
         */
        struct
        {

          /**
           * Error message.
           */
          const char *message;

        } error;

        /**
         * Values for all "GNUNET_FS_STATUS_SEARCH_RESULT_NAMESPACE" events.
         */
        struct
        {

          /**
           * Handle to the namespace (NULL if it is not a local
           * namespace).
           */
          struct GNUNET_FS_Namespace *ns;

          /**
           * Short, human-readable name of the namespace.
           */
          const char *name;

          /**
           * Root identifier for the namespace, can be NULL.
           */
          const char *root;

          /**
           * Metadata for the namespace.
           */
          const struct GNUNET_CONTAINER_MetaData *meta;

          /**
           * Public key of the namespace.
           */
          struct GNUNET_PseudonymIdentifier pseudonym;

        } ns;

      } specifics;

    } search;

    /**
     * Values for all "GNUNET_FS_STATUS_UNINDEX_*" events.
     */
    struct
    {

      /**
       * Context for controlling the unindexing.
       */
      struct GNUNET_FS_UnindexContext *uc;

      /**
       * Client context pointer (set the last time
       * by the client for this operation; initially
       * NULL on START/RESUME events).
       */
      void *cctx;

      /**
       * Name of the file that is being unindexed.
       */
      const char *filename;

      /**
       * How large is the file overall?
       */
      uint64_t size;

      /**
       * At what time do we expect to finish unindexing?
       * (will be a value in the past for completed
       * unindexing opeations).
       */
      struct GNUNET_TIME_Relative eta;

      /**
       * How long has this upload been actively running
       * (excludes times where the upload was suspended).
       */
      struct GNUNET_TIME_Relative duration;

      /**
       * How many bytes have we completed?
       */
      uint64_t completed;

      /**
       * Additional values for specific events.
       */
      union
      {

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_UNINDEX_PROGRESS events.
         */
        struct
        {

          /**
           * Data block we just unindexed.
           */
          const void *data;

          /**
           * At what offset in the file is "data"?
           */
          uint64_t offset;

          /**
           * Length of the data block.
           */
          uint64_t data_len;

          /**
           * Depth of the given block in the tree;
           * 0 would be the lowest level (DBLOCKS).
           */
          unsigned int depth;

        } progress;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_UNINDEX_RESUME events.
         */
        struct
        {

          /**
           * Error message, NULL if we have not encountered any error yet.
           */
          const char *message;

        } resume;

        /**
         * These values are only valid for
         * GNUNET_FS_STATUS_UNINDEX_ERROR events.
         */
        struct
        {

          /**
           * Error message.
           */
          const char *message;

        } error;

      } specifics;

    } unindex;

  } value;

  /**
   * Specific status code (determines the event type).
   */
  enum GNUNET_FS_Status status;

};


/**
 * Notification of FS to a client about the progress of an
 * operation.  Callbacks of this type will be used for uploads,
 * downloads and searches.  Some of the arguments depend a bit
 * in their meaning on the context in which the callback is used.
 *
 * @param cls closure
 * @param info details about the event, specifying the event type
 *        and various bits about the event
 * @return client-context (for the next progress call
 *         for this operation; should be set to NULL for
 *         SUSPEND and STOPPED events).  The value returned
 *         will be passed to future callbacks in the respective
 *         field in the GNUNET_FS_ProgressInfo struct.
 */
typedef void *(*GNUNET_FS_ProgressCallback) (void *cls,
                                             const struct GNUNET_FS_ProgressInfo *info);


/**
 * General (global) option flags for file-sharing.
 */
enum GNUNET_FS_Flags
{
    /**
     * No special flags set.
     */
  GNUNET_FS_FLAGS_NONE = 0,

    /**
     * Is persistence of operations desired?
     * (will create SUSPEND/RESUME events).
     */
  GNUNET_FS_FLAGS_PERSISTENCE = 1,

    /**
     * Should we automatically trigger probes for search results
     * to determine availability?
     * (will create GNUNET_FS_STATUS_SEARCH_UPDATE events).
     */
  GNUNET_FS_FLAGS_DO_PROBES = 2
};


/**
 * Options specified in the VARARGs portion of GNUNET_FS_start.
 */
enum GNUNET_FS_OPTIONS
{

  /**
   * Last option in the VARARG list.
   */
  GNUNET_FS_OPTIONS_END = 0,

  /**
   * Select the desired amount of parallelism (this option should be
   * followed by an "unsigned int" giving the desired maximum number
   * of parallel downloads).
   */
  GNUNET_FS_OPTIONS_DOWNLOAD_PARALLELISM = 1,

  /**
   * Maximum number of requests that should be pending at a given
   * point in time (invidivual downloads may go above this, but
   * if we are above this threshold, we should not activate any
   * additional downloads.
   */
  GNUNET_FS_OPTIONS_REQUEST_PARALLELISM = 2
};


/**
 * Settings for publishing a block (which may of course also
 * apply to an entire directory or file).
 */
struct GNUNET_FS_BlockOptions
{

  /**
   * At what time should the block expire?  Data blocks (DBLOCKS and
   * IBLOCKS) may still be used even if they are expired (however,
   * they'd be removed quickly from the datastore if we are short on
   * space), all other types of blocks will no longer be returned
   * after they expire.
   */
  struct GNUNET_TIME_Absolute expiration_time;

  /**
   * At which anonymity level should the block be shared?
   * (0: no anonymity, 1: normal GAP, >1: with cover traffic).
   */
  uint32_t anonymity_level;

  /**
   * How important is it for us to store the block?  If we run
   * out of space, the highest-priority, non-expired blocks will
   * be kept.
   */
  uint32_t content_priority;

  /**
   * How often should we try to migrate the block to other peers?
   * Only used if "CONTENT_PUSHING" is set to YES, in which case we
   * first push each block to other peers according to their
   * replication levels.  Once each block has been pushed that many
   * times to other peers, blocks are chosen for migration at random.
   * Naturally, there is no guarantee that the other peers will keep
   * these blocks for any period of time (since they won't have any
   * priority or might be too busy to even store the block in the
   * first place).
   */
  uint32_t replication_level;

};


/**
 * Return the current year (i.e. '2011').
 */
unsigned int
GNUNET_FS_get_current_year (void);


/**
 * Convert a year to an expiration time of January 1st of that year.
 *
 * @param year a year (after 1970, please ;-)).
 * @return absolute time for January 1st of that year.
 */
struct GNUNET_TIME_Absolute
GNUNET_FS_year_to_time (unsigned int year);


/**
 * Convert an expiration time to the respective year (rounds)
 *
 * @param at absolute time 
 * @return year a year (after 1970), 0 on error
 */
unsigned int 
GNUNET_FS_time_to_year (struct GNUNET_TIME_Absolute at);


/**
 * Handle to the file-sharing service.
 */
struct GNUNET_FS_Handle;


/**
 * Setup a connection to the file-sharing service.
 *
 * @param cfg configuration to use
 * @param client_name unique identifier for this client
 * @param upcb function to call to notify about FS actions
 * @param upcb_cls closure for upcb
 * @param flags specific attributes for fs-operations
 * @param ... list of optional options, terminated with GNUNET_FS_OPTIONS_END
 * @return NULL on error
 */
struct GNUNET_FS_Handle *
GNUNET_FS_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
                 const char *client_name, GNUNET_FS_ProgressCallback upcb,
                 void *upcb_cls, enum GNUNET_FS_Flags flags, ...);


/**
 * Close our connection with the file-sharing service.
 * The callback given to GNUNET_FS_start will no longer be
 * called after this function returns.
 *
 * @param h handle that was returned from GNUNET_FS_start
 */
void
GNUNET_FS_stop (struct GNUNET_FS_Handle *h);


/**
 * Function called on entries in a GNUNET_FS_FileInformation publish-structure.
 *
 * @param cls closure
 * @param fi the entry in the publish-structure
 * @param length length of the file or directory
 * @param meta metadata for the file or directory (can be modified)
 * @param uri pointer to the keywords that will be used for this entry (can be modified)
 * @param bo block options (can be modified)
 * @param do_index should we index (can be modified)
 * @param client_info pointer to client context set upon creation (can be modified)
 * @return GNUNET_OK to continue, GNUNET_NO to remove
 *         this entry from the directory, GNUNET_SYSERR
 *         to abort the iteration
 */
typedef int (*GNUNET_FS_FileInformationProcessor) (void *cls,
                                                   struct
                                                   GNUNET_FS_FileInformation *
                                                   fi, uint64_t length,
                                                   struct
                                                   GNUNET_CONTAINER_MetaData *
                                                   meta,
                                                   struct GNUNET_FS_Uri ** uri,
                                                   struct GNUNET_FS_BlockOptions
                                                   * bo, int *do_index,
                                                   void **client_info);


/**
 * Obtain the name under which this file information
 * structure is stored on disk.  Only works for top-level
 * file information structures.
 *
 * @param s structure to get the filename for
 * @return NULL on error, otherwise filename that
 *         can be passed to "GNUNET_FS_file_information_recover"
 *         to read this fi-struct from disk.
 */
const char *
GNUNET_FS_file_information_get_id (struct GNUNET_FS_FileInformation *s);


/**
 * Obtain the filename from the file information structure.
 *
 * @param s structure to get the filename for
 * @return "filename" field of the structure (can be NULL)
 */
const char *
GNUNET_FS_file_information_get_filename (struct GNUNET_FS_FileInformation *s);


/**
 * Set the filename in the file information structure.
 * If filename was already set, frees it before setting the new one.
 * Makes a copy of the argument.
 *
 * @param s structure to get the filename for
 * @param filename filename to set
 */
void
GNUNET_FS_file_information_set_filename (struct GNUNET_FS_FileInformation *s,
                                         const char *filename);


/**
 * Create an entry for a file in a publish-structure.
 *
 * @param h handle to the file sharing subsystem
 * @param client_info initial client-info value for this entry
 * @param filename name of the file or directory to publish
 * @param keywords under which keywords should this file be available
 *         directly; can be NULL
 * @param meta metadata for the file
 * @param do_index GNUNET_YES for index, GNUNET_NO for insertion,
 *                GNUNET_SYSERR for simulation
 * @param bo block options
 * @return publish structure entry for the file
 */
struct GNUNET_FS_FileInformation *
GNUNET_FS_file_information_create_from_file (struct GNUNET_FS_Handle *h,
                                             void *client_info,
                                             const char *filename,
                                             const struct GNUNET_FS_Uri
                                             *keywords,
                                             const struct
                                             GNUNET_CONTAINER_MetaData *meta,
                                             int do_index,
                                             const struct GNUNET_FS_BlockOptions
                                             *bo);


/**
 * Create an entry for a file in a publish-structure.
 *
 * @param h handle to the file sharing subsystem
 * @param client_info initial client-info value for this entry
 * @param length length of the file
 * @param data data for the file (should not be used afterwards by
 *        the caller; callee will "free")
 * @param keywords under which keywords should this file be available
 *         directly; can be NULL
 * @param meta metadata for the file
 * @param do_index GNUNET_YES for index, GNUNET_NO for insertion,
 *                GNUNET_SYSERR for simulation
 * @param bo block options
 * @return publish structure entry for the file
 */
struct GNUNET_FS_FileInformation *
GNUNET_FS_file_information_create_from_data (struct GNUNET_FS_Handle *h,
                                             void *client_info, uint64_t length,
                                             void *data,
                                             const struct GNUNET_FS_Uri
                                             *keywords,
                                             const struct
                                             GNUNET_CONTAINER_MetaData *meta,
                                             int do_index,
                                             const struct GNUNET_FS_BlockOptions
                                             *bo);


/**
 * Function that provides data.
 *
 * @param cls closure
 * @param offset offset to read from; it is possible
 *            that the caller might need to go backwards
 *            a bit at times; set to UINT64_MAX to tell
 *            the reader that we won't be reading for a while
 *            (used to close the file descriptor but NOT fully
 *             clean up the reader's state); in this case,
 *            a value of '0' for max should be ignored
 * @param max maximum number of bytes that should be
 *            copied to buf; readers are not allowed
 *            to provide less data unless there is an error;
 *            a value of "0" will be used at the end to allow
 *            the reader to clean up its internal state
 * @param buf where the reader should write the data
 * @param emsg location for the reader to store an error message
 * @return number of bytes written, usually "max", 0 on error
 */
typedef size_t (*GNUNET_FS_DataReader) (void *cls, uint64_t offset, size_t max,
                                        void *buf, char **emsg);


/**
 * Create an entry for a file in a publish-structure.
 *
 * @param h handle to the file sharing subsystem
 * @param client_info initial client-info value for this entry
 * @param length length of the file
 * @param reader function that can be used to obtain the data for the file
 * @param reader_cls closure for "reader"
 * @param keywords under which keywords should this file be available
 *         directly; can be NULL
 * @param meta metadata for the file
 * @param do_index GNUNET_YES for index, GNUNET_NO for insertion,
 *                GNUNET_SYSERR for simulation
 * @param bo block options
 * @return publish structure entry for the file
 */
struct GNUNET_FS_FileInformation *
GNUNET_FS_file_information_create_from_reader (struct GNUNET_FS_Handle *h,
                                               void *client_info,
                                               uint64_t length,
                                               GNUNET_FS_DataReader reader,
                                               void *reader_cls,
                                               const struct GNUNET_FS_Uri
                                               *keywords,
                                               const struct
                                               GNUNET_CONTAINER_MetaData *meta,
                                               int do_index,
                                               const struct
                                               GNUNET_FS_BlockOptions *bo);


/**
 * Create an entry for an empty directory in a publish-structure.
 * This function should be used by applications for which the
 * use of "GNUNET_FS_file_information_create_from_directory"
 * is not appropriate.
 *
 * @param h handle to the file sharing subsystem
 * @param client_info initial client-info value for this entry
 * @param keywords under which keywords should this directory be available
 *         directly; can be NULL
 * @param meta metadata for the directory
 * @param bo block options
 * @param filename name of the directory; can be NULL
 * @return publish structure entry for the directory , NULL on error
 */
struct GNUNET_FS_FileInformation *
GNUNET_FS_file_information_create_empty_directory (struct GNUNET_FS_Handle *h,
                                                   void *client_info,
                                                   const struct GNUNET_FS_Uri
                                                   *keywords,
                                                   const struct
                                                   GNUNET_CONTAINER_MetaData
                                                   *meta,
                                                   const struct
                                                   GNUNET_FS_BlockOptions *bo,
                                                   const char *filename);


/**
 * Test if a given entry represents a directory.
 *
 * @param ent check if this FI represents a directory
 * @return GNUNET_YES if so, GNUNET_NO if not
 */
int
GNUNET_FS_file_information_is_directory (const struct GNUNET_FS_FileInformation
                                         *ent);


/**
 * Add an entry to a directory in a publish-structure.  Clients
 * should never modify publish structures that were passed to
 * "GNUNET_FS_publish_start" already.
 *
 * @param dir the directory
 * @param ent the entry to add; the entry must not have been
 *            added to any other directory at this point and
 *            must not include "dir" in its structure
 * @return GNUNET_OK on success, GNUNET_SYSERR on error
 */
int
GNUNET_FS_file_information_add (struct GNUNET_FS_FileInformation *dir,
                                struct GNUNET_FS_FileInformation *ent);


/**
 * Inspect a file or directory in a publish-structure.  Clients
 * should never modify publish structures that were passed to
 * "GNUNET_FS_publish_start" already.  When called on a directory,
 * this function will FIRST call "proc" with information about
 * the directory itself and then for each of the files in the
 * directory (but not for files in subdirectories).  When called
 * on a file, "proc" will be called exactly once (with information
 * about the specific file).
 *
 * @param dir the directory
 * @param proc function to call on each entry
 * @param proc_cls closure for proc
 */
void
GNUNET_FS_file_information_inspect (struct GNUNET_FS_FileInformation *dir,
                                    GNUNET_FS_FileInformationProcessor proc,
                                    void *proc_cls);


/**
 * Destroy publish-structure.  Clients should never destroy publish
 * structures that were passed to "GNUNET_FS_publish_start" already.
 *
 * @param fi structure to destroy
 * @param cleaner function to call on each entry in the structure
 *        (useful to clean up client_info); can be NULL; return
 *        values are ignored
 * @param cleaner_cls closure for cleaner
 */
void
GNUNET_FS_file_information_destroy (struct GNUNET_FS_FileInformation *fi,
                                    GNUNET_FS_FileInformationProcessor cleaner,
                                    void *cleaner_cls);


/**
 * Options for publishing.  Compatible options
 * can be OR'ed together.
 */
enum GNUNET_FS_PublishOptions
{
    /**
     * No options (use defaults for everything).
     */
  GNUNET_FS_PUBLISH_OPTION_NONE = 0,

    /**
     * Simulate publishing.  With this option, no data will be stored
     * in the datastore.  Useful for computing URIs from files.
     */
  GNUNET_FS_PUBLISH_OPTION_SIMULATE_ONLY = 1
};

/**
 * Publish a file or directory.
 *
 * @param h handle to the file sharing subsystem
 * @param fi information about the file or directory structure to publish
 * @param ns namespace to publish the file in, NULL for no namespace
 * @param nid identifier to use for the publishd content in the namespace
 *        (can be NULL, must be NULL if namespace is NULL)
 * @param nuid update-identifier that will be used for future updates
 *        (can be NULL, must be NULL if namespace or nid is NULL)
 * @param options options for the publication
 * @return context that can be used to control the publish operation
 */
struct GNUNET_FS_PublishContext *
GNUNET_FS_publish_start (struct GNUNET_FS_Handle *h,
                         struct GNUNET_FS_FileInformation *fi,
                         struct GNUNET_FS_Namespace *ns, const char *nid,
                         const char *nuid,
                         enum GNUNET_FS_PublishOptions options);


/**
 * Stop a publication.  Will abort incomplete publications (but
 * not remove blocks that have already been published) or
 * simply clean up the state for completed publications.
 * Must NOT be called from within the event callback!
 *
 * @param pc context for the publication to stop
 */
void
GNUNET_FS_publish_stop (struct GNUNET_FS_PublishContext *pc);


/**
 * Signature of a function called as the continuation of a KBlock or
 * SBlock publication.
 *
 * @param cls closure
 * @param uri URI under which the block is now available, NULL on error
 * @param emsg error message, NULL on success
 */
typedef void (*GNUNET_FS_PublishContinuation) (void *cls,
                                               const struct GNUNET_FS_Uri * uri,
                                               const char *emsg);


/**
 * Handle to cancel publish KSK operation.
 */
struct GNUNET_FS_PublishKskContext;


/**
 * Publish a KBlock on GNUnet.
 *
 * @param h handle to the file sharing subsystem
 * @param ksk_uri keywords to use
 * @param meta metadata to use
 * @param uri URI to refer to in the KBlock
 * @param bo block options
 * @param options publication options
 * @param cont continuation
 * @param cont_cls closure for cont
 * @return NULL on error ('cont' will still be called)
 */
struct GNUNET_FS_PublishKskContext *
GNUNET_FS_publish_ksk (struct GNUNET_FS_Handle *h,
                       const struct GNUNET_FS_Uri *ksk_uri,
                       const struct GNUNET_CONTAINER_MetaData *meta,
                       const struct GNUNET_FS_Uri *uri,
                       const struct GNUNET_FS_BlockOptions *bo,
                       enum GNUNET_FS_PublishOptions options,
                       GNUNET_FS_PublishContinuation cont, void *cont_cls);


/**
 * Abort the KSK publishing operation.
 *
 * @param pkc context of the operation to abort.
 */
void
GNUNET_FS_publish_ksk_cancel (struct GNUNET_FS_PublishKskContext *pkc);


/**
 * Handle to cancel publish SKS operation.
 */
struct GNUNET_FS_PublishSksContext;


/**
 * Publish an SBlock on GNUnet.
 *
 * @param h handle to the file sharing subsystem
 * @param ns namespace to publish in
 * @param identifier identifier to use
 * @param update update identifier to use
 * @param meta metadata to use
 * @param uri URI to refer to in the SBlock
 * @param bo block options
 * @param options publication options
 * @param cont continuation
 * @param cont_cls closure for cont
 * @return NULL on error ('cont' will still be called)
 */
struct GNUNET_FS_PublishSksContext *
GNUNET_FS_publish_sks (struct GNUNET_FS_Handle *h,
                       struct GNUNET_FS_Namespace *ns,
                       const char *identifier, const char *update,
                       const struct GNUNET_CONTAINER_MetaData *meta,
                       const struct GNUNET_FS_Uri *uri,
                       const struct GNUNET_FS_BlockOptions *bo,
                       enum GNUNET_FS_PublishOptions options,
                       GNUNET_FS_PublishContinuation cont, void *cont_cls);


/**
 * Abort the SKS publishing operation.
 *
 * @param psc context of the operation to abort.
 */
void
GNUNET_FS_publish_sks_cancel (struct GNUNET_FS_PublishSksContext *psc);


/**
 * Type of a function called by "GNUNET_FS_get_indexed_files".
 *
 * @param cls closure
 * @param filename the name of the file, NULL for end of list
 * @param file_id hash of the contents of the indexed file
 * @return GNUNET_OK to continue iteration, GNUNET_SYSERR to abort
 */
typedef int (*GNUNET_FS_IndexedFileProcessor) (void *cls, const char *filename,
                                               const struct GNUNET_HashCode * file_id);


/**
 * Handle to cancel 'GNUNET_FS_get_indexed_files'.
 */
struct GNUNET_FS_GetIndexedContext;


/**
 * Iterate over all indexed files.
 *
 * @param h handle to the file sharing subsystem
 * @param iterator function to call on each indexed file
 * @param iterator_cls closure for iterator
 * @return NULL on error ('iter' is not called)
 */
struct GNUNET_FS_GetIndexedContext *
GNUNET_FS_get_indexed_files (struct GNUNET_FS_Handle *h,
                             GNUNET_FS_IndexedFileProcessor iterator,
                             void *iterator_cls);


/**
 * Cancel iteration over all indexed files.
 *
 * @param gic operation to cancel
 */
void
GNUNET_FS_get_indexed_files_cancel (struct GNUNET_FS_GetIndexedContext *gic);


/**
 * Unindex a file.
 *
 * @param h handle to the file sharing subsystem
 * @param filename file to unindex
 * @param cctx initial value for the client context
 * @return NULL on error, otherwise handle
 */
struct GNUNET_FS_UnindexContext *
GNUNET_FS_unindex_start (struct GNUNET_FS_Handle *h, const char *filename,
                         void *cctx);


/**
 * Clean up after completion of an unindex operation.
 *
 * @param uc handle
 */
void
GNUNET_FS_unindex_stop (struct GNUNET_FS_UnindexContext *uc);


/**
 * Create a namespace with the given name; if one already
 * exists, return a handle to the existing namespace.
 *
 * @param h handle to the file sharing subsystem
 * @param name name to use for the namespace
 * @return handle to the namespace, NULL on error (i.e. invalid filename)
 */
struct GNUNET_FS_Namespace *
GNUNET_FS_namespace_create (struct GNUNET_FS_Handle *h, const char *name);


/**
 * Open the namespace with the given name; if it does not exist,
 * or the key file is corrupted, the function fails.
 *
 * @param h handle to the file sharing subsystem
 * @param name name of the namespace
 * @return handle to the namespace,
 *         NULL on error (i.e. invalid filename, non-existent filename)
 */
struct GNUNET_FS_Namespace *
GNUNET_FS_namespace_open_existing (struct GNUNET_FS_Handle *h, const char *name);


/**
 * Rename a local namespace.
 *
 * @param h handle to the file sharing subsystem
 * @param old_name old name of the namespace
 * @param new_name new name of the namespace
 * @return GNUNET_OK on success, GNUNET_SYSERR on error (see errno for details)
 */
int
GNUNET_FS_namespace_rename (struct GNUNET_FS_Handle *h, const char *old_name,
    const char *new_name);


/**
 * Duplicate a namespace handle.
 *
 * @param ns namespace handle
 * @return duplicated handle to the namespace
 */
struct GNUNET_FS_Namespace *
GNUNET_FS_namespace_dup (struct GNUNET_FS_Namespace *ns);


/**
 * Get hash of the public key of a namespace.
 *
 * @param ns namespace
 * @param id buffer to store the key in
 * @return GNUNET_OK on success
 *         GNUNET_SYSERR on failure (contents of id remain intact)
 */
int
GNUNET_FS_namespace_get_public_identifier (struct GNUNET_FS_Namespace *ns,
                                           struct GNUNET_PseudonymIdentifier *id);


/**
 * Delete a namespace handle.  Can be used for a clean shutdown (free
 * memory) or also to freeze the namespace to prevent further
 * insertions by anyone.
 *
 * @param ns handle to the namespace that should be deleted / freed
 * @param freeze prevents future insertions; creating a namespace
 *        with the same name again will create a fresh namespace instead
 *
 * @return GNUNET_OK on success, GNUNET_SYSERR on error
 */
int
GNUNET_FS_namespace_delete (struct GNUNET_FS_Namespace *ns, int freeze);


/**
 * Callback with information about local (!) namespaces.
 * Contains the names of the local namespace and the global
 * ID.
 *
 * @param cls closure
 * @param name human-readable identifier of the namespace
 * @param id identifier for the namespace
 */
typedef void (*GNUNET_FS_NamespaceInfoProcessor) (void *cls, const char *name,
                                                  const struct GNUNET_PseudonymIdentifier *id);


/**
 * Build a list of all available local (!) namespaces The returned
 * names are only the nicknames since we only iterate over the local
 * namespaces.
 *
 * @param h handle to the file sharing subsystem
 * @param cb function to call on each known namespace
 * @param cb_cls closure for cb
 */
void
GNUNET_FS_namespace_list (struct GNUNET_FS_Handle *h,
                          GNUNET_FS_NamespaceInfoProcessor cb, void *cb_cls);


/**
 * Function called on updateable identifiers.
 *
 * @param cls closure
 * @param last_id last identifier
 * @param last_uri uri used for the content published under the last_id
 * @param last_meta metadata associated with last_uri
 * @param next_id identifier that should be used for updates
 */
typedef void (*GNUNET_FS_IdentifierProcessor) (void *cls, const char *last_id,
                                               const struct GNUNET_FS_Uri *
                                               last_uri,
                                               const struct
                                               GNUNET_CONTAINER_MetaData *
                                               last_meta, const char *next_id);


/**
 * List all of the identifiers in the namespace for which we could
 * produce an update.  Namespace updates form a graph where each node
 * has a name.  Each node can have any number of URI/meta-data entries
 * which can each be linked to other nodes.  Cycles are possible.
 *
 * Calling this function with "next_id" NULL will cause the library to
 * call "ip" with a root for each strongly connected component of the
 * graph (a root being a node from which all other nodes in the Scc
 * are reachable).
 *
 * Calling this function with "next_id" being the name of a node will
 * cause the library to call "ip" with all children of the node.  Note
 * that cycles within an SCC are possible (including self-loops).
 *
 * @param ns namespace to inspect for updateable content
 * @param next_id ID to look for; use NULL to look for SCC roots
 * @param ip function to call on each updateable identifier
 * @param ip_cls closure for ip
 */
void
GNUNET_FS_namespace_list_updateable (struct GNUNET_FS_Namespace *ns,
                                     const char *next_id,
                                     GNUNET_FS_IdentifierProcessor ip,
                                     void *ip_cls);


/**
 * Options for searching.  Compatible options
 * can be OR'ed together.
 */
enum GNUNET_FS_SearchOptions
{
    /**
     * No options (use defaults for everything).
     */
  GNUNET_FS_SEARCH_OPTION_NONE = 0,

    /**
     * Only search the local host, do not search remote systems (no P2P)
     */
  GNUNET_FS_SEARCH_OPTION_LOOPBACK_ONLY = 1
};


/**
 * Start search for content.
 *
 * @param h handle to the file sharing subsystem
 * @param uri specifies the search parameters; can be
 *        a KSK URI or an SKS URI.
 * @param anonymity desired level of anonymity
 * @param options options for the search
 * @param cctx initial value for the client context
 * @return context that can be used to control the search
 */
struct GNUNET_FS_SearchContext *
GNUNET_FS_search_start (struct GNUNET_FS_Handle *h,
                        const struct GNUNET_FS_Uri *uri, uint32_t anonymity,
                        enum GNUNET_FS_SearchOptions options, void *cctx);


/**
 * Pause search.
 *
 * @param sc context for the search that should be paused
 */
void
GNUNET_FS_search_pause (struct GNUNET_FS_SearchContext *sc);


/**
 * Continue paused search.
 *
 * @param sc context for the search that should be resumed
 */
void
GNUNET_FS_search_continue (struct GNUNET_FS_SearchContext *sc);


/**
 * Stop search for content.
 *
 * @param sc context for the search that should be stopped
 */
void
GNUNET_FS_search_stop (struct GNUNET_FS_SearchContext *sc);




/**
 * Options for downloading.  Compatible options
 * can be OR'ed together.
 */
enum GNUNET_FS_DownloadOptions
{
    /**
     * No options (use defaults for everything).
     */
  GNUNET_FS_DOWNLOAD_OPTION_NONE = 0,

    /**
     * Only download from the local host, do not access remote systems (no P2P)
     */
  GNUNET_FS_DOWNLOAD_OPTION_LOOPBACK_ONLY = 1,

    /**
     * Do a recursive download (that is, automatically trigger the
     * download of files in directories).
     */
  GNUNET_FS_DOWNLOAD_OPTION_RECURSIVE = 2,

    /**
     * Do not append temporary data to
     * the target file (for the IBlocks).
     */
  GNUNET_FS_DOWNLOAD_NO_TEMPORARIES = 4,

    /**
     * Internal option used to flag this download as a 'probe' for a
     * search result.  Impacts the priority with which the download is
     * run and causes signalling callbacks to be done differently.
     * Also, probe downloads are not serialized on suspension.  Normal
     * clients should not use this!
     */
  GNUNET_FS_DOWNLOAD_IS_PROBE = (1 << 31)
};



/**
 * Download parts of a file.  Note that 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 uri the URI of the file (determines what to download); CHK or LOC URI
 * @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
 * @param options various download options
 * @param cctx initial value for the client context for this download
 * @param parent parent download to associate this download with (use NULL
 *        for top-level downloads; useful for manually-triggered recursive downloads)
 * @return context that can be used to control this download
 */
struct GNUNET_FS_DownloadContext *
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,
                          enum GNUNET_FS_DownloadOptions options, void *cctx,
                          struct GNUNET_FS_DownloadContext *parent);


/**
 * 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.
 *
 * 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
 */
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);


/**
 * Stop a download (aborts if download is incomplete).
 *
 * @param dc handle for the download
 * @param do_delete delete files of incomplete downloads
 */
void
GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc, int do_delete);



/* ******************** Directory API *********************** */


#define GNUNET_FS_DIRECTORY_MIME  "application/gnunet-directory"
#define GNUNET_FS_DIRECTORY_MAGIC "\211GND\r\n\032\n"
#define GNUNET_FS_DIRECTORY_EXT   ".gnd"

/**
 * Does the meta-data claim that this is a directory?
 * Checks if the mime-type is that of a GNUnet directory.
 *
 * @return GNUNET_YES if it is, GNUNET_NO if it is not, GNUNET_SYSERR if
 *  we have no mime-type information (treat as 'GNUNET_NO')
 */
int
GNUNET_FS_meta_data_test_for_directory (const struct GNUNET_CONTAINER_MetaData
                                        *md);


/**
 * Set the MIMETYPE information for the given
 * metadata to "application/gnunet-directory".
 *
 * @param md metadata to add mimetype to
 */
void
GNUNET_FS_meta_data_make_directory (struct GNUNET_CONTAINER_MetaData *md);


/**
 * Suggest a filename based on given metadata.
 *
 * @param md given meta data
 * @return NULL if meta data is useless for suggesting a filename
 */
char *
GNUNET_FS_meta_data_suggest_filename (const struct GNUNET_CONTAINER_MetaData
                                      *md);


/**
 * Function used to process entries in a directory.
 *
 * @param cls closure
 * @param filename name of the file in the directory
 * @param uri URI of the file
 * @param metadata metadata for the file; metadata for
 *        the directory if everything else is NULL/zero
 * @param length length of the available data for the file
 *           (of type size_t since data must certainly fit
 *            into memory; if files are larger than size_t
 *            permits, then they will certainly not be
 *            embedded with the directory itself).
 * @param data data available for the file (length bytes)
 */
typedef void (*GNUNET_FS_DirectoryEntryProcessor) (void *cls,
                                                   const char *filename,
                                                   const struct GNUNET_FS_Uri *
                                                   uri,
                                                   const struct
                                                   GNUNET_CONTAINER_MetaData *
                                                   meta, size_t length,
                                                   const void *data);


/**
 * Iterate over all entries in a directory.  Note that directories
 * are structured such that it is possible to iterate over the
 * individual blocks as well as over the entire directory.  Thus
 * a client can call this function on the buffer in the
 * GNUNET_FS_ProgressCallback.  Also, directories can optionally
 * include the contents of (small) files embedded in the directory
 * itself; for those files, the processor may be given the
 * contents of the file directly by this function.
 *
 * @param size number of bytes in data
 * @param data pointer to the beginning of the directory
 * @param offset offset of data in the directory
 * @param dep function to call on each entry
 * @param dep_cls closure for dep
 * @return GNUNET_OK if this could be a block in a directory,
 *         GNUNET_NO if this could be part of a directory (but not 100% OK)
 *         GNUNET_SYSERR if 'data' does not represent a directory
 */
int
GNUNET_FS_directory_list_contents (size_t size, const void *data,
                                   uint64_t offset,
                                   GNUNET_FS_DirectoryEntryProcessor dep,
                                   void *dep_cls);


/**
 * Opaque handle to a directory builder.
 */
struct GNUNET_FS_DirectoryBuilder;

/**
 * Create a directory builder.
 *
 * @param mdir metadata for the directory
 */
struct GNUNET_FS_DirectoryBuilder *
GNUNET_FS_directory_builder_create (const struct GNUNET_CONTAINER_MetaData
                                    *mdir);


/**
 * Add an entry to a directory.
 *
 * @param bld directory to extend
 * @param uri uri of the entry (must not be a KSK)
 * @param md metadata of the entry
 * @param data raw data of the entry, can be NULL, otherwise
 *        data must point to exactly the number of bytes specified
 *        by the uri
 */
void
GNUNET_FS_directory_builder_add (struct GNUNET_FS_DirectoryBuilder *bld,
                                 const struct GNUNET_FS_Uri *uri,
                                 const struct GNUNET_CONTAINER_MetaData *md,
                                 const void *data);


/**
 * Finish building the directory.  Frees the
 * builder context and returns the directory
 * in-memory.
 *
 * @param bld directory to finish
 * @param rsize set to the number of bytes needed
 * @param rdata set to the encoded directory
 * @return GNUNET_OK on success
 */
int
GNUNET_FS_directory_builder_finish (struct GNUNET_FS_DirectoryBuilder *bld,
                                    size_t * rsize, void **rdata);


/* ******************** DirScanner API *********************** */

/**
 * Progress reasons of the directory scanner.
 */
enum GNUNET_FS_DirScannerProgressUpdateReason
{

  /**
   * We've started processing a file or directory.
   */
  GNUNET_FS_DIRSCANNER_FILE_START = 0,

  /**
   * We're having trouble accessing a file (soft-error); it will
   * be ignored.
   */
  GNUNET_FS_DIRSCANNER_FILE_IGNORED,

  /**
   * We've found all files (in the pre-pass).
   */
  GNUNET_FS_DIRSCANNER_ALL_COUNTED,

  /**
   * We've finished extracting meta data from a file.
   */
  GNUNET_FS_DIRSCANNER_EXTRACT_FINISHED,

  /**
   * Last call to the progress function: we have finished scanning
   * the directory.
   */
  GNUNET_FS_DIRSCANNER_FINISHED,

  /**
   * There was an internal error.  Application should abort the scan.
   */
  GNUNET_FS_DIRSCANNER_INTERNAL_ERROR

};


/**
 * Function called over time as the directory scanner makes
 * progress on the job at hand.
 *
 * @param cls closure
 * @param filename which file we are making progress on
 * @param is_directory GNUNET_YES if this is a directory,
 *                     GNUNET_NO if this is a file
 *                     GNUNET_SYSERR if it is neither (or unknown)
 * @param reason kind of progress we are making
 */
typedef void (*GNUNET_FS_DirScannerProgressCallback) (void *cls, 
                                                      const char *filename,
                                                      int is_directory, 
                                                      enum GNUNET_FS_DirScannerProgressUpdateReason reason);


/**
 * A node of a directory tree (produced by dirscanner)
 */
struct GNUNET_FS_ShareTreeItem
{
  /**
   * This is a doubly-linked list
   */
  struct GNUNET_FS_ShareTreeItem *prev;

  /**
   * This is a doubly-linked list
   */
  struct GNUNET_FS_ShareTreeItem *next;

  /**
   * This is a doubly-linked tree
   * NULL for top-level entries.
   */
  struct GNUNET_FS_ShareTreeItem *parent;

  /**
   * This is a doubly-linked tree
   * NULL for files and empty directories
   */
  struct GNUNET_FS_ShareTreeItem *children_head;

  /**
   * This is a doubly-linked tree
   * NULL for files and empty directories
   */
  struct GNUNET_FS_ShareTreeItem *children_tail;

  /**
   * Metadata for this file or directory
   */
  struct GNUNET_CONTAINER_MetaData *meta;

  /**
   * Keywords for this file or directory (derived from metadata).
   */
  struct GNUNET_FS_Uri *ksk_uri;

  /**
   * Name of the file/directory
   */
  char *filename;

  /**
   * Base name of the file/directory.
   */
  char *short_filename;

  /**
   * GNUNET_YES if this is a directory
   */
  int is_directory;

};


/**
 * Opaqe handle to an asynchronous directory scanning activity.
 */
struct GNUNET_FS_DirScanner;


/**
 * Start a directory scanner.
 *
 * @param filename name of the directory to scan
 * @param disable_extractor GNUNET_YES to not to run libextractor on files (only build a tree)
 * @param ex if not NULL, must be a list of extra plugins for extractor
 * @param cb the callback to call when there are scanning progress messages
 * @param cb_cls closure for 'cb'
 * @return directory scanner object to be used for controlling the scanner
 */
struct GNUNET_FS_DirScanner *
GNUNET_FS_directory_scan_start (const char *filename,
                                int disable_extractor, 
                                const char *ex,
                                GNUNET_FS_DirScannerProgressCallback cb, 
                                void *cb_cls);


/**
 * Abort the scan.    Must not be called from within the progress_callback
 * function.
 *
 * @param ds directory scanner structure
 */
void
GNUNET_FS_directory_scan_abort (struct GNUNET_FS_DirScanner *ds);


/**
 * Obtain the result of the scan after the scan has signalled
 * completion.  Must not be called prior to completion.  The 'ds' is
 * freed as part of this call.
 *
 * @param ds directory scanner structure
 * @return the results of the scan (a directory tree)
 */
struct GNUNET_FS_ShareTreeItem *
GNUNET_FS_directory_scan_get_result (struct GNUNET_FS_DirScanner *ds);


/**
 * Process a share item tree, moving frequent keywords up and
 * copying frequent metadata up.
 *
 * @param toplevel toplevel directory in the tree, returned by the scanner
 */
void
GNUNET_FS_share_tree_trim (struct GNUNET_FS_ShareTreeItem *toplevel);


/**
 * Release memory of a share item tree.
 *
 * @param toplevel toplevel of the tree to be freed
 */
void
GNUNET_FS_share_tree_free (struct GNUNET_FS_ShareTreeItem *toplevel);


#if 0                           /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif


#endif