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// SPDX-License-Identifier: MIT OR MPL-2.0 OR LGPL-2.1-or-later OR GPL-2.0-or-later
// Copyright 2015, SIL International, All rights reserved.
#include <cassert>
#include "inc/Decompressor.h"
#include "inc/Compression.h"
using namespace lz4;
namespace {
inline
u32 read_literal(u8 const * &s, u8 const * const e, u32 l) {
if (l == 15 && s != e)
{
u8 b = 0;
do { l += b = *s++; } while(b==0xff && s != e);
}
return l;
}
bool read_sequence(u8 const * &src, u8 const * const end, u8 const * &literal,
u32 & literal_len, u32 & match_len, u32 & match_dist)
{
u8 const token = *src++;
literal_len = read_literal(src, end, token >> 4);
literal = src;
src += literal_len;
// Normal exit for end of stream, wrap arround check and parital match check.
if (src > end - sizeof(u16) || src < literal)
return false;
match_dist = *src++;
match_dist |= *src++ << 8;
match_len = read_literal(src, end, token & 0xf) + MINMATCH;
// Malformed stream check.
return src <= end-MINCODA;
}
}
int lz4::decompress(void const *in, size_t in_size, void *out, size_t out_size)
{
if (out_size <= in_size || in_size < MINSRCSIZE)
return -1;
u8 const * src = static_cast<u8 const *>(in),
* literal = 0,
* const src_end = src + in_size;
u8 * dst = static_cast<u8*>(out),
* const dst_end = dst + out_size;
// Check the in and out size hasn't wrapped around.
if (src >= src_end || dst >= dst_end)
return -1;
u32 literal_len = 0,
match_len = 0,
match_dist = 0;
while (read_sequence(src, src_end, literal, literal_len, match_len,
match_dist))
{
if (literal_len != 0)
{
// Copy in literal. At this point the a minimal literal + minminal
// match plus the coda (1 + 2 + 5) must be 8 bytes or more allowing
// us to remain within the src buffer for an overrun_copy on
// machines upto 64 bits.
if (align(literal_len) > out_size)
return -1;
dst = overrun_copy(dst, literal, literal_len);
out_size -= literal_len;
}
// Copy, possibly repeating, match from earlier in the
// decoded output.
u8 const * const pcpy = dst - match_dist;
if (pcpy < static_cast<u8*>(out)
|| match_len > unsigned(out_size - LASTLITERALS)
// Wrap around checks:
|| out_size < LASTLITERALS || pcpy >= dst)
return -1;
if (dst > pcpy+sizeof(unsigned long)
&& align(match_len) <= out_size)
dst = overrun_copy(dst, pcpy, match_len);
else
dst = safe_copy(dst, pcpy, match_len);
out_size -= match_len;
}
if (literal > src_end - literal_len || literal_len > out_size)
return -1;
dst = fast_copy(dst, literal, literal_len);
return int(dst - (u8*)out);
}
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