| /* |
| * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> |
| * |
| * This file is part of FFmpeg. |
| * |
| * FFmpeg is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * FFmpeg 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 |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with FFmpeg; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include "config.h" |
| #include "common.h" |
| #include "bswap.h" |
| #include "crc.h" |
| |
| #if CONFIG_HARDCODED_TABLES |
| #include "crc_data.h" |
| #else |
| static struct { |
| uint8_t le; |
| uint8_t bits; |
| uint32_t poly; |
| } av_crc_table_params[AV_CRC_MAX] = { |
| [AV_CRC_8_ATM] = { 0, 8, 0x07 }, |
| [AV_CRC_16_ANSI] = { 0, 16, 0x8005 }, |
| [AV_CRC_16_CCITT] = { 0, 16, 0x1021 }, |
| [AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 }, |
| [AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 }, |
| }; |
| static AVCRC av_crc_table[AV_CRC_MAX][257]; |
| #endif |
| |
| /** |
| * Initialize a CRC table. |
| * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 |
| * @param le If 1, the lowest bit represents the coefficient for the highest |
| * exponent of the corresponding polynomial (both for poly and |
| * actual CRC). |
| * If 0, you must swap the CRC parameter and the result of av_crc |
| * if you need the standard representation (can be simplified in |
| * most cases to e.g. bswap16): |
| * av_bswap32(crc << (32-bits)) |
| * @param bits number of bits for the CRC |
| * @param poly generator polynomial without the x**bits coefficient, in the |
| * representation as specified by le |
| * @param ctx_size size of ctx in bytes |
| * @return <0 on failure |
| */ |
| int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size) |
| { |
| unsigned i, j; |
| uint32_t c; |
| |
| if (bits < 8 || bits > 32 || poly >= (1LL << bits)) |
| return -1; |
| if (ctx_size != sizeof(AVCRC) * 257 && ctx_size != sizeof(AVCRC) * 1024) |
| return -1; |
| |
| for (i = 0; i < 256; i++) { |
| if (le) { |
| for (c = i, j = 0; j < 8; j++) |
| c = (c >> 1) ^ (poly & (-(c & 1))); |
| ctx[i] = c; |
| } else { |
| for (c = i << 24, j = 0; j < 8; j++) |
| c = (c << 1) ^ ((poly << (32 - bits)) & (((int32_t) c) >> 31)); |
| ctx[i] = av_bswap32(c); |
| } |
| } |
| ctx[256] = 1; |
| #if !CONFIG_SMALL |
| if (ctx_size >= sizeof(AVCRC) * 1024) |
| for (i = 0; i < 256; i++) |
| for (j = 0; j < 3; j++) |
| ctx[256 *(j + 1) + i] = |
| (ctx[256 * j + i] >> 8) ^ ctx[ctx[256 * j + i] & 0xFF]; |
| #endif |
| |
| return 0; |
| } |
| |
| /** |
| * Get an initialized standard CRC table. |
| * @param crc_id ID of a standard CRC |
| * @return a pointer to the CRC table or NULL on failure |
| */ |
| const AVCRC *av_crc_get_table(AVCRCId crc_id) |
| { |
| #if !CONFIG_HARDCODED_TABLES |
| if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id]) - 1]) |
| if (av_crc_init(av_crc_table[crc_id], |
| av_crc_table_params[crc_id].le, |
| av_crc_table_params[crc_id].bits, |
| av_crc_table_params[crc_id].poly, |
| sizeof(av_crc_table[crc_id])) < 0) |
| return NULL; |
| #endif |
| return av_crc_table[crc_id]; |
| } |
| |
| /** |
| * Calculate the CRC of a block. |
| * @param crc CRC of previous blocks if any or initial value for CRC |
| * @return CRC updated with the data from the given block |
| * |
| * @see av_crc_init() "le" parameter |
| */ |
| uint32_t av_crc(const AVCRC *ctx, uint32_t crc, |
| const uint8_t *buffer, size_t length) |
| { |
| const uint8_t *end = buffer + length; |
| |
| #if !CONFIG_SMALL |
| if (!ctx[256]) { |
| while (((intptr_t) buffer & 3) && buffer < end) |
| crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8); |
| |
| while (buffer < end - 3) { |
| crc ^= av_le2ne32(*(const uint32_t *) buffer); buffer += 4; |
| crc = ctx[3 * 256 + ( crc & 0xFF)] ^ |
| ctx[2 * 256 + ((crc >> 8 ) & 0xFF)] ^ |
| ctx[1 * 256 + ((crc >> 16) & 0xFF)] ^ |
| ctx[0 * 256 + ((crc >> 24) )]; |
| } |
| } |
| #endif |
| while (buffer < end) |
| crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8); |
| |
| return crc; |
| } |
| |
| #ifdef TEST |
| #undef printf |
| int main(void) |
| { |
| uint8_t buf[1999]; |
| int i; |
| int p[4][3] = { { AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04 }, |
| { AV_CRC_32_IEEE , 0x04C11DB7, 0xC0F5BAE0 }, |
| { AV_CRC_16_ANSI , 0x8005 , 0x1FBB }, |
| { AV_CRC_8_ATM , 0x07 , 0xE3 } |
| }; |
| const AVCRC *ctx; |
| |
| for (i = 0; i < sizeof(buf); i++) |
| buf[i] = i + i * i; |
| |
| for (i = 0; i < 4; i++) { |
| ctx = av_crc_get_table(p[i][0]); |
| printf("crc %08X = %X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf))); |
| } |
| return 0; |
| } |
| #endif |