/* crc32.c -- calculate POSIX CRC32 checksums
Copyright (C) 2009, R.N. Bokhorst, reinoud.bokhorst@bmtargoss.com
This program 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 of the License, or
(at your option) any later version.
This program 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 this program. If not, see .
*/
/*
The checksum algorithm and calculation of crctab was originally written
by Q. Frank Xia for the cksum utility, part of the GNU coreutils package
(v7.4). It was modified by R.N. Bokhorst for use in wgrib2.
The code calculates the crctab when the cksum function is called for the
first time. The calculated crctab should be identical to the one given in
the code segment between "#ifdef STATIC_CRCTAB" and "#else". It was done
this way to limit the number of 'static' bytes in the final binary. The
static table can be used instead by defining STATIC_CRCTAB.
This software is NOT compatible with either the System V or the BSD
`sum' program. Nor will it produce the same result as most typical CRC32
implementations that use the reverse representation of the polynomial
(0xEDB88320 ). It is supposed to conform to POSIX, except perhaps
for foreign language support.
*/
#include
#include /* C99 portable types */
#include "wgrib2.h"
//#define STATIC_CRCTAB
#ifdef STATIC_CRCTAB
static uint32_t crctab[256] = {
0x00000000,
0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b,
0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6,
0x2b4bcb61, 0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9, 0x5f15adac,
0x5bd4b01b, 0x569796c2, 0x52568b75, 0x6a1936c8, 0x6ed82b7f,
0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3, 0x709f7b7a,
0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58,
0xbaea46ef, 0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033,
0xa4ad16ea, 0xa06c0b5d, 0xd4326d90, 0xd0f37027, 0xddb056fe,
0xd9714b49, 0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, 0xe13ef6f4,
0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0,
0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5,
0x2ac12072, 0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca, 0x7897ab07,
0x7c56b6b0, 0x71159069, 0x75d48dde, 0x6b93dddb, 0x6f52c06c,
0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1,
0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b,
0xbb60adfc, 0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698,
0x832f1041, 0x87ee0df6, 0x99a95df3, 0x9d684044, 0x902b669d,
0x94ea7b2a, 0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2, 0xc6bcf05f,
0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34,
0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80,
0x644fc637, 0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f, 0x5c007b8a,
0x58c1663d, 0x558240e4, 0x51435d53, 0x251d3b9e, 0x21dc2629,
0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5, 0x3f9b762c,
0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e,
0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65,
0xeba91bbc, 0xef68060b, 0xd727bbb6, 0xd3e6a601, 0xdea580d8,
0xda649d6f, 0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, 0xae3afba2,
0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71,
0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74,
0x857130c3, 0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c, 0x7b827d21,
0x7f436096, 0x7200464f, 0x76c15bf8, 0x68860bfd, 0x6c47164a,
0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e, 0x18197087,
0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d,
0x2056cd3a, 0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce,
0xcc2b1d17, 0xc8ea00a0, 0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb,
0xdbee767c, 0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4, 0x89b8fd09,
0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662,
0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf,
0xa2f33668, 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
};
#else
/*
Calculate the crctab once on init.
The generating polynomial is
32 26 23 22 16 12 11 10 8 7 5 4 2 1
G(X)=X + X + X + X + X + X + X + X + X + X + X + X + X + X + 1
The i bit in GEN is set if X^i is a summand of G(X) except X^32.
#define GEN (BIT (26) | BIT (23) | BIT (22) | BIT (16) | BIT (12) \
| BIT (11) | BIT (10) | BIT (8) | BIT (7) | BIT (5) \
| BIT (4) | BIT (2) | BIT (1) | BIT (0))
which produces 0x04c11db7
*/
#define BIT(x) ((uint32_t) 1 << (x))
#define SBIT BIT(31)
#define GEN (uint32_t)0x04C11DB7
static uint32_t crctab[256];
static uint32_t crc_remainder(int m, uint32_t *r)
{
uint32_t rem = 0;
int i;
for (i = 0; i < 8; i++) {
if (BIT (i) & m) {
rem ^= r[i];
}
}
return rem & 0xFFFFFFFF; /* Make it run on 64-bit machine */
}
static int init_crctab(void)
{
int i;
uint32_t r[8];
/* Fill r */
r[0] = GEN;
for (i = 1; i < 8; i++) {
r[i] = (r[i - 1] << 1) ^ ((r[i - 1] & SBIT) ? GEN : 0);
}
crctab[0] = 0x00000000;
for (i = 1; i < 256; i++) {
crctab[i] = crc_remainder(i, r);
}
return 1;
}
#endif /* ! STATIC_CRCTAB */
/*
Calculate and return the CRC32 checksum of buffer with length in bytes
Note: cksum needs to be 32-bit+ unsigned integer
*/
unsigned int cksum(unsigned char const *buf, size_t length)
{
uint32_t crc = 0;
size_t bytes = length;
#ifndef STATIC_CRCTAB
static short inited = 0;
if (!inited) inited = init_crctab();
#endif
while (bytes--) {
crc = (crc << 8) ^ crctab[((crc >> 24) ^ *buf++) & 0xFF];
}
for (; length; length >>= 8) {
crc = (crc << 8) ^ crctab[((crc >> 24) ^ length) & 0xFF];
}
crc = ~crc & 0xFFFFFFFF;
return crc;
}