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