166 lines
5.4 KiB
C
166 lines
5.4 KiB
C
/*
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* Copyright (C) 2017 Amlogic, Inc. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Description:
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*/
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/*
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* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "bswap.h"
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#include "crc.h"
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#if CONFIG_HARDCODED_TABLES
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#include "crc_data.h"
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#else
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static struct {
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uint8_t le;
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uint8_t bits;
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uint32_t poly;
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} av_crc_table_params[AV_CRC_MAX] = {
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[AV_CRC_8_ATM] = { 0, 8, 0x07 },
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[AV_CRC_16_ANSI] = { 0, 16, 0x8005 },
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[AV_CRC_16_CCITT] = { 0, 16, 0x1021 },
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[AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 },
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[AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
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};
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static AVCRC av_crc_table[AV_CRC_MAX][257];
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#endif
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/**
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* Initializes a CRC table.
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* @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
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* @param cts_size size of ctx in bytes
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* @param le If 1, the lowest bit represents the coefficient for the highest
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* exponent of the corresponding polynomial (both for poly and
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* actual CRC).
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* If 0, you must swap the CRC parameter and the result of av_crc
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* if you need the standard representation (can be simplified in
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* most cases to e.g. bswap16):
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* bswap_32(crc << (32-bits))
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* @param bits number of bits for the CRC
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* @param poly generator polynomial without the x**bits coefficient, in the
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* representation as specified by le
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* @return <0 on failure
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*/
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int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
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{
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int i, j;
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uint32_t c;
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if (bits < 8 || bits > 32 || poly >= (1LL << bits)) {
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return -1;
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}
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if (ctx_size != sizeof(AVCRC) * 257 && ctx_size != sizeof(AVCRC) * 1024) {
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return -1;
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}
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for (i = 0; i < 256; i++) {
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if (le) {
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for (c = i, j = 0; j < 8; j++) {
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c = (c >> 1) ^(poly & (-(c & 1)));
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}
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ctx[i] = c;
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} else {
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for (c = i << 24, j = 0; j < 8; j++) {
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c = (c << 1) ^((poly << (32 - bits)) & (((int32_t)c) >> 31));
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}
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ctx[i] = bswap_32(c);
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}
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}
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ctx[256] = 1;
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//#if !CONFIG_SMALL
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if (ctx_size >= sizeof(AVCRC) * 1024)
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for (i = 0; i < 256; i++)
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for (j = 0; j < 3; j++) {
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ctx[256 * (j + 1) + i] = (ctx[256 * j + i] >> 8) ^ ctx[ ctx[256 * j + i] & 0xFF ];
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}
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//#endif
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return 0;
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}
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/**
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* Gets an initialized standard CRC table.
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* @param crc_id ID of a standard CRC
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* @return a pointer to the CRC table or NULL on failure
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*/
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const AVCRC *av_crc_get_table(AVCRCId crc_id)
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{
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//#if !CONFIG_HARDCODED_TABLES
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if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id]) - 1])
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if (av_crc_init(av_crc_table[crc_id],
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av_crc_table_params[crc_id].le,
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av_crc_table_params[crc_id].bits,
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av_crc_table_params[crc_id].poly,
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sizeof(av_crc_table[crc_id])) < 0) {
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return NULL;
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}
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//#endif
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return av_crc_table[crc_id];
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}
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/**
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* Calculates the CRC of a block.
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* @param crc CRC of previous blocks if any or initial value for CRC
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* @return CRC updated with the data from the given block
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*
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* @see av_crc_init() "le" parameter
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*/
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uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length)
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{
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const uint8_t *end = buffer + length;
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//#if !CONFIG_SMALL
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if (!ctx[256]) {
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while (((intptr_t) buffer & 3) && buffer < end) {
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crc = ctx[((uint8_t)crc) ^ *buffer++] ^(crc >> 8);
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}
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while (buffer < end - 3) {
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crc ^= le2me_32(*(const uint32_t*)buffer);
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buffer += 4;
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crc = ctx[3 * 256 + (crc & 0xFF)]
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^ ctx[2 * 256 + ((crc >> 8) & 0xFF)]
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^ ctx[1 * 256 + ((crc >> 16) & 0xFF)]
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^ ctx[0 * 256 + ((crc >> 24))];
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}
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}
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//#endif
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while (buffer < end) {
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crc = ctx[((uint8_t)crc) ^ *buffer++] ^(crc >> 8);
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}
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return crc;
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}
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