GNUnet  0.10.x
crypto_crc.c
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1 /*
2  This file is part of GNUnet.
3  Copyright (C) 2001, 2002, 2003, 2004, 2006 GNUnet e.V.
4 
5  GNUnet is free software: you can redistribute it and/or modify it
6  under the terms of the GNU Affero General Public License as published
7  by the Free Software Foundation, either version 3 of the License,
8  or (at your option) any later version.
9 
10  GNUnet is distributed in the hope that it will be useful, but
11  WITHOUT ANY WARRANTY; without even the implied warranty of
12  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  Affero General Public License for more details.
14 
15  You should have received a copy of the GNU Affero General Public License
16  along with this program. If not, see <http://www.gnu.org/licenses/>.
17 
18  SPDX-License-Identifier: AGPL3.0-or-later
19 
20  For the actual CRC-32 code:
21  Copyright abandoned; this code is in the public domain.
22  Provided to GNUnet by peter@horizon.com
23  */
24 
30 #include "platform.h"
31 #include "gnunet_crypto_lib.h"
32 
33 #define LOG(kind, ...) GNUNET_log_from(kind, "util-crypto-crc", __VA_ARGS__)
34 
35 /* Avoid wasting space on 8-byte longs. */
36 #if UINT_MAX >= 0xffffffff
37 typedef unsigned int GNUNET_uLong;
38 #elif ULONG_MAX >= 0xffffffff
39 typedef unsigned long GNUNET_uLong;
40 #else
41 #error This compiler is not ANSI-compliant!
42 #endif
43 
44 #define Z_NULL 0
45 
46 
47 #define POLYNOMIAL (GNUNET_uLong)0xedb88320
48 static GNUNET_uLong crc_table[256];
49 
50 /*
51  * This routine writes each crc_table entry exactly once,
52  * with the correct final value. Thus, it is safe to call
53  * even on a table that someone else is using concurrently.
54  */
55 static void
57 {
58  static int once;
59  unsigned int i, j;
60  GNUNET_uLong h = 1;
61 
62  if (once)
63  return;
64  once = 1;
65  crc_table[0] = 0;
66  for (i = 128; i; i >>= 1)
67  {
68  h = (h >> 1) ^ ((h & 1) ? POLYNOMIAL : 0);
69  /* h is now crc_table[i] */
70  for (j = 0; j < 256; j += 2 * i)
71  crc_table[i + j] = crc_table[j] ^ h;
72  }
73 }
74 
75 /*
76  * This computes the standard preset and inverted CRC, as used
77  * by most networking standards. Start by passing in an initial
78  * chaining value of 0, and then pass in the return value from the
79  * previous crc32() call. The final return value is the CRC.
80  * Note that this is a little-endian CRC, which is best used with
81  * data transmitted lsbit-first, and it should, itself, be appended
82  * to data in little-endian byte and bit order to preserve the
83  * property of detecting all burst errors of length 32 bits or less.
84  */
85 static GNUNET_uLong
86 crc32(GNUNET_uLong crc, const char *buf, size_t len)
87 {
88  crc_init();
89  GNUNET_assert(crc_table[255] != 0);
90  crc ^= 0xffffffff;
91  while (len--)
92  crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
93  return crc ^ 0xffffffff;
94 }
95 
96 
104 int32_t
105 GNUNET_CRYPTO_crc32_n(const void *buf, size_t len)
106 {
107  GNUNET_uLong crc;
108 
109  crc = crc32(0L, Z_NULL, 0);
110  crc = crc32(crc, (char *)buf, len);
111  return crc;
112 }
113 
114 
123 uint32_t
124 GNUNET_CRYPTO_crc16_step(uint32_t sum, const void *buf, size_t len)
125 {
126  const uint16_t *hdr = buf;
127 
128  for (; len >= 2; len -= 2)
129  sum += *(hdr++);
130  if (len == 1)
131  sum += (*hdr) & ntohs(0xFF00);
132  return sum;
133 }
134 
135 
142 uint16_t
144 {
145  sum = (sum >> 16) + (sum & 0xFFFF);
146  sum += (sum >> 16);
147 
148  return ~sum;
149 }
150 
151 
159 uint16_t
160 GNUNET_CRYPTO_crc16_n(const void *buf, size_t len)
161 {
162  const uint16_t *hdr = buf;
163  uint32_t sum = GNUNET_CRYPTO_crc16_step(0, hdr, len);
164 
165  return GNUNET_CRYPTO_crc16_finish(sum);
166 }
167 
168 
177 uint8_t
179  size_t len)
180 {
181  const uint8_t *data = buf;
182  unsigned int crc = 0;
183  int i;
184  int j;
185 
186  for (j = len; 0 != j; j--)
187  {
188  crc ^= (*data++ << 8);
189  for (i = 8; 0 != i; i--)
190  {
191  if (0 != (crc & 0x8000))
192  crc ^= (0x1070 << 3);
193  crc <<= 1;
194  }
195  }
196  return (uint8_t)(crc >> 8);
197 }
198 
199 
200 /* end of crypto_crc.c */
uint16_t GNUNET_CRYPTO_crc16_n(const void *buf, size_t len)
Calculate the checksum of a buffer in one step.
Definition: crypto_crc.c:160
int32_t GNUNET_CRYPTO_crc32_n(const void *buf, size_t len)
Compute the CRC32 checksum for the first len bytes of the buffer.
Definition: crypto_crc.c:105
#define Z_NULL
Definition: crypto_crc.c:44
#define GNUNET_assert(cond)
Use this for fatal errors that cannot be handled.
static void crc_init()
Definition: crypto_crc.c:56
#define POLYNOMIAL
Definition: crypto_crc.c:47
static GNUNET_uLong crc_table[256]
Definition: crypto_crc.c:48
uint8_t GNUNET_CRYPTO_crc8_n(const void *buf, size_t len)
Calculate the checksum of a buffer in one step.
Definition: crypto_crc.c:178
static struct GNUNET_ARM_Handle * h
Connection with ARM.
Definition: gnunet-arm.c:94
cryptographic primitives for GNUnet
static int once
Global to mark if we&#39;ve run the initialization.
Definition: gnsrecord.c:67
static char buf[2048]
uint32_t GNUNET_CRYPTO_crc16_step(uint32_t sum, const void *buf, size_t len)
Perform an incremental step in a CRC16 (for TCP/IP) calculation.
Definition: crypto_crc.c:124
uint16_t GNUNET_CRYPTO_crc16_finish(uint32_t sum)
Convert results from GNUNET_CRYPTO_crc16_step() to final crc16.
Definition: crypto_crc.c:143
uint32_t data
The data value.
static GNUNET_uLong crc32(GNUNET_uLong crc, const char *buf, size_t len)
Definition: crypto_crc.c:86
uint16_t len
length of data (which is always a uint32_t, but presumably this can be used to specify that fewer byt...