X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Futil%2Fcrypto_crc.c;h=cda6243bee2723d88494dba18397cd187aba4efc;hb=71c8f1cd446bbd38e2e5ffda87355c10d28bb873;hp=35d1e257689dc6b698bdc32a32d0a9c505aa3704;hpb=0a217a8df1657b4334b55b0e4a6c7837a8dbcfd9;p=oweals%2Fgnunet.git

diff --git a/src/util/crypto_crc.c b/src/util/crypto_crc.c
index 35d1e2576..cda6243be 100644
--- a/src/util/crypto_crc.c
+++ b/src/util/crypto_crc.c
@@ -4,7 +4,7 @@
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 2, or (at your
+     by the Free Software Foundation; either version 3, or (at your
      option) any later version.
 
      GNUnet is distributed in the hope that it will be useful, but
@@ -17,20 +17,20 @@
      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
      Boston, MA 02111-1307, USA.
 
-     For the actual CRC code:
+     For the actual CRC-32 code:
      Copyright abandoned; this code is in the public domain.
      Provided to GNUnet by peter@horizon.com
 */
 
 /**
  * @file util/crypto_crc.c
- * @brief implementation of CRC32
+ * @brief implementation of CRC16 and CRC32
  * @author Christian Grothoff
  */
-
 #include "platform.h"
-#include "gnunet_common.h"
-#include "gnunet_crypto_lib.h"
+#include "gnunet_util_lib.h"
+
+#define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__)
 
 /* Avoid wasting space on 8-byte longs. */
 #if UINT_MAX >= 0xffffffff
@@ -49,21 +49,27 @@ static uLong crc_table[256];
 
 /*
  * This routine writes each crc_table entry exactly once,
- * with the ccorrect final value.  Thus, it is safe to call
+ * with the correct final value.  Thus, it is safe to call
  * even on a table that someone else is using concurrently.
  */
-void __attribute__ ((constructor)) GNUNET_CRYPTO_crc_init ()
+static void
+crc_init ()
 {
+  static int once;
   unsigned int i, j;
   uLong h = 1;
+
+  if (once)
+    return;
+  once = 1;
   crc_table[0] = 0;
   for (i = 128; i; i >>= 1)
-    {
-      h = (h >> 1) ^ ((h & 1) ? POLYNOMIAL : 0);
-      /* h is now crc_table[i] */
-      for (j = 0; j < 256; j += 2 * i)
-        crc_table[i + j] = crc_table[j] ^ h;
-    }
+  {
+    h = (h >> 1) ^ ((h & 1) ? POLYNOMIAL : 0);
+    /* h is now crc_table[i] */
+    for (j = 0; j < 256; j += 2 * i)
+      crc_table[i + j] = crc_table[j] ^ h;
+  }
 }
 
 /*
@@ -79,6 +85,7 @@ void __attribute__ ((constructor)) GNUNET_CRYPTO_crc_init ()
 static uLong
 crc32 (uLong crc, const char *buf, size_t len)
 {
+  crc_init ();
   GNUNET_assert (crc_table[255] != 0);
   crc ^= 0xffffffff;
   while (len--)
@@ -94,13 +101,69 @@ crc32 (uLong crc, const char *buf, size_t len)
  * @param len the length of the buffer
  * @return the resulting CRC32 checksum
  */
-int
-GNUNET_CRYPTO_crc32_n (const void *buf, unsigned int len)
+int32_t
+GNUNET_CRYPTO_crc32_n (const void *buf, size_t len)
 {
   uLong crc;
+
   crc = crc32 (0L, Z_NULL, 0);
   crc = crc32 (crc, (char *) buf, len);
   return crc;
 }
 
-/* end of crc32.c */
+
+/**
+ * Perform an incremental step in a CRC16 (for TCP/IP) calculation.
+ *
+ * @param sum current sum, initially 0
+ * @param buf buffer to calculate CRC over (must be 16-bit aligned)
+ * @param len number of bytes in hdr, must be multiple of 2
+ * @return updated crc sum (must be subjected to GNUNET_CRYPTO_crc16_finish to get actual crc16)
+ */
+uint32_t
+GNUNET_CRYPTO_crc16_step (uint32_t sum, const void *buf, size_t len)
+{
+  const uint16_t *hdr = buf;
+  for (; len >= 2; len -= 2)
+    sum += *(hdr++);
+  if (len == 1)
+    sum += (*hdr) & ntohs(0xFF00);
+  return sum;
+}
+
+
+/**
+ * Convert results from GNUNET_CRYPTO_crc16_step to final crc16.
+ *
+ * @param sum cummulative sum
+ * @return crc16 value
+ */
+uint16_t
+GNUNET_CRYPTO_crc16_finish (uint32_t sum)
+{
+  sum = (sum >> 16) + (sum & 0xFFFF);
+  sum += (sum >> 16);
+
+  return ~sum;
+}
+
+
+/**
+ * Calculate the checksum of a buffer in one step.
+ *
+ * @param buf buffer to  calculate CRC over (must be 16-bit aligned)
+ * @param len number of bytes in hdr, must be multiple of 2
+ * @return crc16 value
+ */
+uint16_t
+GNUNET_CRYPTO_crc16_n (const void *buf, size_t len)
+{
+  const uint16_t *hdr = buf;
+  uint32_t sum = GNUNET_CRYPTO_crc16_step (0, hdr, len);
+
+  return GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+
+/* end of crypto_crc.c */