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diff --git a/audio_codec/libflac/crc.c b/audio_codec/libflac/crc.c new file mode 100644 index 0000000..97221df --- a/dev/null +++ b/audio_codec/libflac/crc.c @@ -0,0 +1,146 @@ +/* + * 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 "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 + +/** + * Initializes a CRC table. + * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 + * @param cts_size size of ctx in bytes + * @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): + * bswap_32(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 + * @return <0 on failure + */ +int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size) +{ + int 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] = bswap_32(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; +} + +/** + * Gets 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]; +} + +/** + * Calculates 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 ^= le2me_32(*(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; +} |