/*
This file is part of GNUnet.
- (C) 2001, 2002, 2003, 2004, 2006 Christian Grothoff (and other contributing authors)
+ Copyright (C) 2001, 2002, 2003, 2004, 2006 GNUnet e.V.
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
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.
+ Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ Boston, MA 02110-1301, 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"
+#define LOG(kind,...) GNUNET_log_from (kind, "util-crypto-crc", __VA_ARGS__)
+
/* Avoid wasting space on 8-byte longs. */
#if UINT_MAX >= 0xffffffff
-typedef unsigned int uLong;
+typedef unsigned int GNUNET_uLong;
#elif ULONG_MAX >= 0xffffffff
-typedef unsigned long uLong;
+typedef unsigned long GNUNET_uLong;
#else
#error This compiler is not ANSI-compliant!
#endif
#define Z_NULL 0
-#define POLYNOMIAL (uLong)0xedb88320
-static uLong crc_table[256];
+#define POLYNOMIAL (GNUNET_uLong)0xedb88320
+static GNUNET_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;
+ GNUNET_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;
+ }
}
/*
* to data in little-endian byte and bit order to preserve the
* property of detecting all burst errors of length 32 bits or less.
*/
-static uLong
-crc32 (uLong crc, const char *buf, size_t len)
+static GNUNET_uLong
+crc32 (GNUNET_uLong crc, const char *buf, size_t len)
{
+ crc_init ();
GNUNET_assert (crc_table[255] != 0);
crc ^= 0xffffffff;
while (len--)
int32_t
GNUNET_CRYPTO_crc32_n (const void *buf, size_t len)
{
- uLong crc;
+ GNUNET_uLong crc;
+
crc = crc32 (0L, Z_NULL, 0);
crc = crc32 (crc, (char *) buf, len);
return crc;
}
+
+/**
+ * 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);
+}
+
+
+/**
+ * @ingroup hash
+ * Calculate the checksum of a buffer in one step.
+ *
+ * @param buf buffer to calculate CRC over
+ * @param len number of bytes in @a buf
+ * @return crc8 value
+ */
+uint8_t
+GNUNET_CRYPTO_crc8_n (const void *buf,
+ size_t len)
+{
+ const uint8_t *data = buf;
+ unsigned int crc = 0;
+ int i;
+ int j;
+
+ for (j = len; 0 != j; j--)
+ {
+ crc ^= (*data++ << 8);
+ for (i = 8; 0 != i; i--)
+ {
+ if (0 != (crc & 0x8000))
+ crc ^= (0x1070 << 3);
+ crc <<= 1;
+ }
+ }
+ return (uint8_t) (crc >> 8);
+}
+
+
/* end of crypto_crc.c */
projects / oweals / gnunet.git / blobdiff