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/*
* LZO 1x decompression
* Copyright (c) 2006 Reimar Doeffinger
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "common.h"
#include "lzo.h"
typedef struct LZOContext {
uint8_t *in, *in_end;
uint8_t *out, *out_end;
int out_size;
int error;
} LZOContext;
/**
* \brief read one byte from input buffer, avoiding overrun
* \return byte read
*/
static inline int get_byte(LZOContext *c) {
if (c->in < c->in_end)
return *c->in++;
c->error |= LZO_INPUT_DEPLETED;
return -1;
}
/**
* \brief decode a length value in the coding used by lzo
* \param x previous byte value
* \param mask bits used from x
* \return decoded length value
*/
static inline int get_len(LZOContext *c, int x, int mask) {
int cnt = x & mask;
if (!cnt) {
while (!(x = get_byte(c))) cnt += 255;
cnt += mask + x;
}
return cnt;
}
/**
* \brief copy bytes from input to output buffer with checking
* \param cnt number of bytes to copy, must be > 0
*/
static inline void copy(LZOContext *c, int cnt) {
if (c->in + cnt > c->in_end) {
cnt = c->in_end - c->in;
c->error |= LZO_INPUT_DEPLETED;
}
if (c->out + cnt > c->out_end) {
cnt = c->out_end - c->out;
c->error |= LZO_OUTPUT_FULL;
}
do {
*c->out++ = *c->in++;
} while (--cnt);
}
/**
* \brief copy previously decoded bytes to current position
* \param back how many bytes back we start
* \param cnt number of bytes to copy, must be > 0
*
* cnt > back is valid, this will copy the bytes we just copied.
*/
static inline void copy_backptr(LZOContext *c, int back, int cnt) {
if (c->out - back < c->out_end - c->out_size) {
c->error |= LZO_INVALID_BACKPTR;
return;
}
if (c->out + cnt > c->out_end) {
cnt = c->out_end - c->out;
c->error |= LZO_OUTPUT_FULL;
}
do {
*c->out++ = c->out[-back];
} while (--cnt);
}
/**
* \brief decode LZO 1x compressed data
* \param out output buffer
* \param outlen size of output buffer, number of bytes left are returned here
* \param in input buffer
* \param inlen size of input buffer, number of bytes left are returned here
* \return 0 on success, otherwise error flags, see lzo.h
*/
int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
enum {COPY, BACKPTR} state = COPY;
int x;
LZOContext c;
c.in = in;
c.in_end = in + *inlen;
c.out = out;
c.out_end = out + * outlen;
c.out_size = *outlen;
c.error = 0;
x = get_byte(&c);
if (x > 17) {
copy(&c, x - 17);
x = get_byte(&c);
if (x < 16) c.error |= LZO_ERROR;
}
while (!c.error) {
int cnt, back;
if (x >> 4) {
state = BACKPTR;
if (x >> 6) {
cnt = (x >> 5) - 1;
back = (get_byte(&c) << 3) + ((x >> 2) & 7) + 1;
} else if (x >> 5) {
cnt = get_len(&c, x, 31);
x = get_byte(&c);
back = (get_byte(&c) << 6) + (x >> 2) + 1;
} else {
cnt = get_len(&c, x, 7);
back = (1 << 14) + ((x & 8) << 11);
x = get_byte(&c);
back += (get_byte(&c) << 6) + (x >> 2);
if (back == (1 << 14)) {
if (cnt != 1)
c.error |= LZO_ERROR;
break;
}
}
} else
switch (state) {
case COPY:
cnt = get_len(&c, x, 15);
copy(&c, cnt + 3);
x = get_byte(&c);
if (x >> 4)
continue;
cnt = 1;
back = (1 << 11) + (get_byte(&c) << 2) + (x >> 2) + 1;
break;
case BACKPTR:
cnt = 0;
back = (get_byte(&c) << 2) + (x >> 2) + 1;
break;
}
copy_backptr(&c, back, cnt + 2);
cnt = x & 3;
if (cnt)
copy(&c, cnt);
else
state = (state == COPY) ? BACKPTR : COPY;
x = get_byte(&c);
}
*inlen = c.in_end - c.in;
*outlen = c.out_end - c.out;
return c.error;
}
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