forked from KolibriOS/kolibrios
184 lines
4.2 KiB
C
184 lines
4.2 KiB
C
/*
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* Snappy decompression algorithm
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* Copyright (c) 2015 Luca Barbato
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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 "libavutil/mem.h"
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#include "bytestream.h"
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#include "snappy.h"
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enum {
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SNAPPY_LITERAL,
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SNAPPY_COPY_1,
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SNAPPY_COPY_2,
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SNAPPY_COPY_4,
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};
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static int64_t bytestream2_get_levarint(GetByteContext *gb)
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{
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uint64_t val = 0;
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int shift = 0;
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int tmp;
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do {
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tmp = bytestream2_get_byte(gb);
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val |= (tmp & 127) << shift;
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shift += 7;
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} while (tmp & 128);
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return val;
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}
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static int snappy_literal(GetByteContext *gb, uint8_t *p, int size, int val)
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{
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unsigned int len = 1;
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switch (val) {
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case 63:
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len += bytestream2_get_le32(gb);
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break;
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case 62:
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len += bytestream2_get_le24(gb);
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break;
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case 61:
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len += bytestream2_get_le16(gb);
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break;
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case 60:
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len += bytestream2_get_byte(gb);
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break;
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default: // val < 60
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len += val;
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}
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if (size < len)
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return AVERROR_INVALIDDATA;
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bytestream2_get_buffer(gb, p, len);
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return len;
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}
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static int snappy_copy(uint8_t *start, uint8_t *p, int size,
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unsigned int off, int len)
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{
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uint8_t *q;
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int i;
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if (off > p - start || size < len)
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return AVERROR_INVALIDDATA;
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q = p - off;
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for (i = 0; i < len; i++)
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p[i] = q[i];
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return len;
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}
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static int snappy_copy1(GetByteContext *gb, uint8_t *start, uint8_t *p,
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int size, int val)
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{
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int len = 4 + (val & 0x7);
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unsigned int off = bytestream2_get_byte(gb) | (val & 0x38) << 5;
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return snappy_copy(start, p, size, off, len);
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}
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static int snappy_copy2(GetByteContext *gb, uint8_t *start, uint8_t *p,
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int size, int val)
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{
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int len = 1 + val;
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unsigned int off = bytestream2_get_le16(gb);
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return snappy_copy(start, p, size, off, len);
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}
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static int snappy_copy4(GetByteContext *gb, uint8_t *start, uint8_t *p,
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int size, int val)
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{
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int len = 1 + val;
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unsigned int off = bytestream2_get_le32(gb);
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return snappy_copy(start, p, size, off, len);
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}
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static int64_t decode_len(GetByteContext *gb)
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{
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int64_t len = bytestream2_get_levarint(gb);
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if (len < 0 || len > UINT_MAX)
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return AVERROR_INVALIDDATA;
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return len;
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}
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int64_t ff_snappy_peek_uncompressed_length(GetByteContext *gb)
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{
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int pos = bytestream2_get_bytes_left(gb);
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int64_t len = decode_len(gb);
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bytestream2_seek(gb, -pos, SEEK_END);
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return len;
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}
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int ff_snappy_uncompress(GetByteContext *gb, uint8_t *buf, int64_t *size)
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{
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int64_t len = decode_len(gb);
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int ret = 0;
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uint8_t *p;
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if (len < 0)
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return len;
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if (len > *size)
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return AVERROR_BUFFER_TOO_SMALL;
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*size = len;
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p = buf;
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while (bytestream2_get_bytes_left(gb) > 0) {
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uint8_t s = bytestream2_get_byte(gb);
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int val = s >> 2;
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switch (s & 0x03) {
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case SNAPPY_LITERAL:
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ret = snappy_literal(gb, p, len, val);
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break;
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case SNAPPY_COPY_1:
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ret = snappy_copy1(gb, buf, p, len, val);
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break;
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case SNAPPY_COPY_2:
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ret = snappy_copy2(gb, buf, p, len, val);
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break;
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case SNAPPY_COPY_4:
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ret = snappy_copy4(gb, buf, p, len, val);
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break;
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}
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if (ret < 0)
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return ret;
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p += ret;
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len -= ret;
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}
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return 0;
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}
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