📄 lzx.cpp
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/* it's possible to have a file where the next run is less than
* 16 bits in size. In this case, the READ_HUFFSYM() macro used
* in building the tables will exhaust the buffer, so we should
* allow for this, but not allow those accidentally read bits to
* be used (so we check that there are at least 16 bits
* remaining - in this boundary case they aren't really part of
* the compressed data)
*/
if (inpos > (endinp+2) || bitsleft < 16) return DECR_ILLEGALDATA;
}
while ((this_run = pState->block_remaining) > 0 && togo > 0) {
if (this_run > togo) this_run = togo;
togo -= this_run;
pState->block_remaining -= this_run;
/* apply 2^x-1 mask */
window_posn &= window_size - 1;
/* runs can't straddle the window wraparound */
if ((window_posn + this_run) > window_size)
return DECR_DATAFORMAT;
switch (pState->block_type) {
case LZX_BLOCKTYPE_VERBATIM:
while (this_run > 0) {
READ_HUFFSYM(MAINTREE, main_element);
if (main_element < LZX_NUM_CHARS) {
/* literal: 0 to LZX_NUM_CHARS-1 */
window[window_posn++] = main_element;
this_run--;
}
else {
/* match: LZX_NUM_CHARS + ((slot<<3) | length_header (3 bits)) */
main_element -= LZX_NUM_CHARS;
match_length = main_element & LZX_NUM_PRIMARY_LENGTHS;
if (match_length == LZX_NUM_PRIMARY_LENGTHS) {
READ_HUFFSYM(LENGTH, length_footer);
match_length += length_footer;
}
match_length += LZX_MIN_MATCH;
match_offset = main_element >> 3;
if (match_offset > 2) {
/* not repeated offset */
if (match_offset != 3) {
extra = extra_bits[match_offset];
READ_BITS(verbatim_bits, extra);
match_offset = position_base[match_offset] - 2 + verbatim_bits;
}
else {
match_offset = 1;
}
/* update repeated offset LRU queue */
R2 = R1; R1 = R0; R0 = match_offset;
}
else if (match_offset == 0) {
match_offset = R0;
}
else if (match_offset == 1) {
match_offset = R1;
R1 = R0; R0 = match_offset;
}
else /* match_offset == 2 */ {
match_offset = R2;
R2 = R0; R0 = match_offset;
}
rundest = window + window_posn;
runsrc = rundest - match_offset;
window_posn += match_length;
this_run -= match_length;
/* copy any wrapped around source data */
while ((runsrc < window) && (match_length-- > 0)) {
*rundest++ = *(runsrc + window_size); runsrc++;
}
/* copy match data - no worries about destination wraps */
while (match_length-- > 0) *rundest++ = *runsrc++;
}
}
break;
case LZX_BLOCKTYPE_ALIGNED:
while (this_run > 0) {
READ_HUFFSYM(MAINTREE, main_element);
if (main_element < LZX_NUM_CHARS) {
/* literal: 0 to LZX_NUM_CHARS-1 */
window[window_posn++] = main_element;
this_run--;
}
else {
/* match: LZX_NUM_CHARS + ((slot<<3) | length_header (3 bits)) */
main_element -= LZX_NUM_CHARS;
match_length = main_element & LZX_NUM_PRIMARY_LENGTHS;
if (match_length == LZX_NUM_PRIMARY_LENGTHS) {
READ_HUFFSYM(LENGTH, length_footer);
match_length += length_footer;
}
match_length += LZX_MIN_MATCH;
match_offset = main_element >> 3;
if (match_offset > 2) {
/* not repeated offset */
extra = extra_bits[match_offset];
match_offset = position_base[match_offset] - 2;
if (extra > 3) {
/* verbatim and aligned bits */
extra -= 3;
READ_BITS(verbatim_bits, extra);
match_offset += (verbatim_bits << 3);
READ_HUFFSYM(ALIGNED, aligned_bits);
match_offset += aligned_bits;
}
else if (extra == 3) {
/* aligned bits only */
READ_HUFFSYM(ALIGNED, aligned_bits);
match_offset += aligned_bits;
}
else if (extra > 0) { /* extra==1, extra==2 */
/* verbatim bits only */
READ_BITS(verbatim_bits, extra);
match_offset += verbatim_bits;
}
else /* extra == 0 */ {
/* ??? */
match_offset = 1;
}
/* update repeated offset LRU queue */
R2 = R1; R1 = R0; R0 = match_offset;
}
else if (match_offset == 0) {
match_offset = R0;
}
else if (match_offset == 1) {
match_offset = R1;
R1 = R0; R0 = match_offset;
}
else /* match_offset == 2 */ {
match_offset = R2;
R2 = R0; R0 = match_offset;
}
rundest = window + window_posn;
runsrc = rundest - match_offset;
window_posn += match_length;
this_run -= match_length;
/* copy any wrapped around source data */
while ((runsrc < window) && (match_length-- > 0)) {
*rundest++ = *(runsrc + window_size); runsrc++;
}
/* copy match data - no worries about destination wraps */
while (match_length-- > 0) *rundest++ = *runsrc++;
}
}
break;
case LZX_BLOCKTYPE_UNCOMPRESSED:
if ((inpos + this_run) > endinp) return DECR_ILLEGALDATA;
memcpy(window + window_posn, inpos, (size_t) this_run);
inpos += this_run; window_posn += this_run;
break;
default:
return DECR_ILLEGALDATA; /* might as well */
}
}
}
if (togo != 0) return DECR_ILLEGALDATA;
memcpy(outpos, window + ((!window_posn) ? window_size : window_posn) - outlen, (size_t) outlen);
pState->window_posn = window_posn;
pState->R0 = R0;
pState->R1 = R1;
pState->R2 = R2;
/* intel E8 decoding */
if ((pState->frames_read++ < 32768) && pState->intel_filesize != 0) {
if (outlen <= 6 || !pState->intel_started) {
pState->intel_curpos += outlen;
}
else {
UBYTE *data = outpos;
UBYTE *dataend = data + outlen - 10;
LONG curpos = pState->intel_curpos;
LONG filesize = pState->intel_filesize;
LONG abs_off, rel_off;
pState->intel_curpos = curpos + outlen;
while (data < dataend) {
if (*data++ != 0xE8) { curpos++; continue; }
abs_off = data[0] | (data[1]<<8) | (data[2]<<16) | (data[3]<<24);
if ((abs_off >= -curpos) && (abs_off < filesize)) {
rel_off = (abs_off >= 0) ? abs_off - curpos : abs_off + filesize;
data[0] = (UBYTE) rel_off;
data[1] = (UBYTE) (rel_off >> 8);
data[2] = (UBYTE) (rel_off >> 16);
data[3] = (UBYTE) (rel_off >> 24);
}
data += 4;
curpos += 5;
}
}
}
return DECR_OK;
}
#ifdef LZX_CHM_TESTDRIVER
int main(int c, char **v)
{
FILE *fin, *fout;
struct LZXstate state;
UBYTE ibuf[16384];
UBYTE obuf[32768];
int ilen, olen;
int status;
int i;
int count=0;
int w = atoi(v[1]);
LZXinit(&state, w);
fout = fopen(v[2], "wb");
for (i=3; i<c; i++)
{
fin = fopen(v[i], "rb");
ilen = fread(ibuf, 1, 16384, fin);
status = LZXdecompress(&state, ibuf, obuf, ilen, 32768);
switch (status)
{
case DECR_OK:
printf("ok\n");
fwrite(obuf, 1, 32768, fout);
break;
case DECR_DATAFORMAT:
printf("bad format\n");
break;
case DECR_ILLEGALDATA:
printf("illegal data\n");
break;
case DECR_NOMEMORY:
printf("no memory\n");
break;
default:
break;
}
fclose(fin);
if (++count == 2)
{
count = 0;
LZXreset(&state);
}
}
fclose(fout);
}
#endif
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