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1 files changed, 106 insertions, 0 deletions

diff --git a/src/util/crypto_crc.c b/src/util/crypto_crc.c
new file mode 100644
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+++ b/src/util/crypto_crc.c
@@ -0,0 +1,106 @@
+/*
+     This file is part of GNUnet.
+     (C) 2001, 2002, 2003, 2004, 2006 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 2, or (at your
+     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.
+
+     For the actual CRC 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
+ * @author Christian Grothoff
+ */
+
+#include "platform.h"
+#include "gnunet_common.h"
+#include "gnunet_crypto_lib.h"
+
+/* Avoid wasting space on 8-byte longs. */
+#if UINT_MAX >= 0xffffffff
+typedef unsigned int uLong;
+#elif ULONG_MAX >= 0xffffffff
+typedef unsigned long uLong;
+#else
+#error This compiler is not ANSI-compliant!
+#endif
+
+#define Z_NULL  0
+
+
+#define POLYNOMIAL (uLong)0xedb88320
+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
+ * even on a table that someone else is using concurrently.
+ */
+void __attribute__ ((constructor)) GNUNET_CRYPTO_crc_init ()
+{
+  unsigned int i, j;
+  uLong h = 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;
+    }
+}
+
+/*
+ * This computes the standard preset and inverted CRC, as used
+ * by most networking standards.  Start by passing in an initial
+ * chaining value of 0, and then pass in the return value from the
+ * previous crc32() call.  The final return value is the CRC.
+ * Note that this is a little-endian CRC, which is best used with
+ * data transmitted lsbit-first, and it should, itself, be appended
+ * 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)
+{
+  GNUNET_assert (crc_table[255] != 0);
+  crc ^= 0xffffffff;
+  while (len--)
+    crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
+  return crc ^ 0xffffffff;
+}
+
+
+/**
+ * Compute the CRC32 checksum for the first len bytes of the buffer.
+ *
+ * @param buf the data over which we're taking the CRC
+ * @param len the length of the buffer
+ * @return the resulting CRC32 checksum
+ */
+int
+GNUNET_CRYPTO_crc32_n (const void *buf, unsigned int len)
+{
+  uLong crc;
+  crc = crc32 (0L, Z_NULL, 0);
+  crc = crc32 (crc, (char *) buf, len);
+  return crc;
+}
+
+/* end of crc32.c */