/* This file is part of libmspack.
* (C) 2003-2004 Stuart Caie.
*
* The Quantum method was created by David Stafford, adapted by Microsoft
* Corporation.
*
* This decompressor is based on an implementation by Matthew Russotto, used
* with permission.
*
* libmspack is free software; you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License (LGPL) version 2.1
*
* For further details, see the file COPYING.LIB distributed with libmspack
*/
/* Quantum decompression implementation */
/* This decompressor was researched and implemented by Matthew Russotto. It
* has since been tidied up by Stuart Caie. More information can be found at
* http://www.speakeasy.org/~russotto/quantumcomp.html
*/
#include <system.h>
#include <qtm.h>
/* import bit-reading macros and code */
#define BITS_TYPE struct qtmd_stream
#define BITS_VAR qtm
#define BITS_ORDER_MSB
#define READ_BYTES do { \
unsigned char b0, b1; \
READ_IF_NEEDED; b0 = *i_ptr++; \
READ_IF_NEEDED; b1 = *i_ptr++; \
INJECT_BITS((b0 << 8) | b1, 16); \
} while (0)
#include <readbits.h>
/* Quantum static data tables:
*
* Quantum uses 'position slots' to represent match offsets. For every
* match, a small 'position slot' number and a small offset from that slot
* are encoded instead of one large offset.
*
* position_base[] is an index to the position slot bases
*
* extra_bits[] states how many bits of offset-from-base data is needed.
*
* length_base[] and length_extra[] are equivalent in function, but are
* used for encoding selector 6 (variable length match) match lengths,
* instead of match offsets.
*
* They are generated with the following code:
* unsigned int i, offset;
* for (i = 0, offset = 0; i < 42; i++) {
* position_base[i] = offset;
* extra_bits[i] = ((i < 2) ? 0 : (i - 2)) >> 1;
* offset += 1 << extra_bits[i];
* }
* for (i = 0, offset = 0; i < 26; i++) {
* length_base[i] = offset;
* length_extra[i] = (i < 2 ? 0 : i - 2) >> 2;
* offset += 1 << length_extra[i];
* }
* length_base[26] = 254; length_extra[26] = 0;
*/
static const unsigned int position_base[42] = {
0, 1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, 64, 96, 128, 192, 256, 384, 512, 768,
1024, 1536, 2048, 3072, 4096, 6144, 8192, 12288, 16384, 24576, 32768, 49152,
65536, 98304, 131072, 196608, 262144, 393216, 524288, 786432, 1048576, 1572864
};
static const unsigned char extra_bits[42] = {
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10,
11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19
};
static const unsigned char length_base[27] = {
0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 18, 22, 26,
30, 38, 46, 54, 62, 78, 94, 110, 126, 158, 190, 222, 254
};
static const unsigned char length_extra[27] = {
0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
};
/* Arithmetic decoder:
*
* GET_SYMBOL(model, var) fetches the next symbol from the stated model
* and puts it in var.
*
* If necessary, qtmd_update_model() is called.
*/
#define GET_SYMBOL(model, var) do { \
range = ((H - L) & 0xFFFF) + 1; \
symf = ((((C - L + 1) * model.syms[0].cumfreq)-1) / range) & 0xFFFF; \
\
for (i = 1; i < model.entries; i++) { \
if (model.syms[i].cumfreq <= symf) break; \
} \
(var) = model.syms[i-1].sym; \
\
range = (H - L) + 1; \
symf = model.syms[0].cumfreq; \
H = L + ((model.syms[i-1].cumfreq * range) / symf) - 1; \
L = L + ((model.syms[i].cumfreq * range) / symf); \
\
do { model.syms[--i].cumfreq += 8; } while (i > 0); \
if (model.syms[0].cumfreq > 3800) qtmd_update_model(&model); \
\
while (1) { \
if ((L & 0x8000) != (H & 0x8000)) { \
if ((L & 0x4000) && !(H & 0x4000)) { \
/* underflow case */ \
C ^= 0x4000; L &= 0x3FFF; H |= 0x4000; \
} \
else break; \
} \
L <<= 1; H = (H << 1) | 1; \
ENSURE_BITS(1); \
C = (C << 1) | PEEK_BITS(1); \
REMOVE_BITS(1); \
} \
} while (0)
static void qtmd_update_model(struct qtmd_model *model) {
struct qtmd_modelsym tmp;
int i, j;
if (--model->shiftsleft) {
for (i = model->entries - 1; i >= 0; i--) {
/* -1, not -2; the 0 entry saves this */
model->syms[i].cumfreq >>= 1;
if (model->syms[i].cumfreq <= model->syms[i+1].cumfreq) {
model->syms[i].cumfreq = model->syms[i+1].cumfreq + 1;
}
}
}
else {
model->shiftsleft = 50;
for (i = 0; i < model->entries; i++) {
/* no -1, want to include the 0 entry */
/* this converts cumfreqs into frequencies, then shifts right */
model->syms[i].cumfreq -= model->syms[i+1].cumfreq;
model->syms[i].cumfreq++; /* avoid losing things entirely */
model->syms[i].cumfreq >>= 1;
}
/* now sort by frequencies, decreasing order -- this must be an
* inplace selection sort, or a sort with the same (in)stability
* characteristics */
for (i = 0; i < model->entries - 1; i++) {
for (j = i + 1; j < model->entries; j++) {
if (model->syms[i].cumfreq < model->syms[j].cumfreq) {
tmp = model->syms[i];
model->syms[i] = model->syms[j];
model->syms[j] = tmp;
}
}
}
/* then convert frequencies back to cumfreq */
for (i = model->entries - 1; i >= 0; i--) {
model->syms[i].cumfreq += model->syms[i+1].cumfreq;
}
}
}
/* Initialises a model to decode symbols from [start] to [start]+[len]-1 */
static void qtmd_init_model(struct qtmd_model *model,
struct qtmd_modelsym *syms, int start, int len)
{
int i;
model->shiftsleft = 4;
model->entries = len;
model->syms = syms;
for (i = 0; i <= len; i++) {
syms[i].sym = start + i; /* actual symbol */
syms[i].cumfreq = len - i; /* current frequency of that symbol */
}
}
/*-------- main Quantum code --------*/
struct qtmd_stream *qtmd_init(struct mspack_system *system,
struct mspack_file *input,
struct mspack_file *output,
int window_bits, int input_buffer_size)
{
unsigned int window_size = 1 << window_bits;
struct qtmd_stream *qtm;
int i;
if (!system) return NULL;
/* Quantum supports window sizes of 2^10 (1Kb) through 2^21 (2Mb) */
if (window_bits < 10 || window_bits > 21) return NULL;
/* round up input buffer size to multiple of two */
input_buffer_size = (input_buffer_size + 1) & -2;
if (input_buffer_size < 2) return NULL;
/* allocate decompression state */
if (!(qtm = (struct qtmd_stream *) system->alloc(system, sizeof(struct qtmd_stream)))) {
return NULL;
}
/* allocate decompression window and input buffer */
qtm->window = (unsigned char *) system->alloc(system, (size_t) window_size);
qtm->inbuf = (unsigned char *) system->alloc(system, (size_t) input_buffer_size);
if (!qtm->window || !qtm->inbuf) {
system->free(qtm->window);
system->free(qtm->inbuf);
system->free(qtm);
return NULL;
}
/* initialise decompression state */
qtm->sys = system;
qtm->input = input;
qtm->output = output;
qtm->inbuf_size = input_buffer_size;
qtm->window_size = window_size;
qtm->window_posn = 0;
qtm->frame_todo = QTM_FRAME_SIZE;
qtm->header_read = 0;
qtm->error = MSPACK_ERR_OK;
qtm->i_ptr = qtm->i_end = &qtm->inbuf[0];
qtm->o_ptr = qtm->o_end = &qtm->window[0];
qtm->input_end = 0;
qtm->bits_left = 0;
qtm->bit_buffer = 0;
/* initialise arithmetic coding models
* - model 4 depends on window size, ranges from 20 to 24
* - model 5 depends on window size, ranges from 20 to 36
* - model 6pos depends on window size, ranges from 20 to 42
*/
i = window_bits * 2;
qtmd_init_model(&qtm->model0, &qtm->m0sym[0], 0, 64);
qtmd_init_model(&qtm->model1, &qtm->m1sym[0], 64, 64);
qtmd_init_model(&qtm->model2, &qtm->m2sym[0], 128, 64);
qtmd_init_model(&qtm->model3, &qtm->m3sym[0], 192, 64);
qtmd_init_model(&qtm->model4, &qtm->m4sym[0], 0, (i > 24) ? 24 : i);
qtmd_init_model(&qtm->model5, &qtm->m5sym[0], 0, (i > 36) ? 36 : i);
qtmd_init_model(&qtm->model6, &qtm->m6sym[0], 0, i);
qtmd_init_model(&qtm->model6len, &qtm->m6lsym[0], 0, 27);
qtmd_init_model(&qtm->model7, &qtm->m7sym[0], 0, 7);
/* all ok */
return qtm;
}
int qtmd_decompress(struct qtmd_stream *qtm, off_t out_bytes) {
unsigned int frame_todo, frame_end, window_posn, match_offset, range;
unsigned char *window, *i_ptr, *i_end, *runsrc, *rundest;
int i, j, selector, extra, sym, match_length;
unsigned short H, L, C, symf;
register unsigned int bit_buffer;
register unsigned char bits_left;
/* easy answers */
if (!qtm || (out_bytes < 0)) return MSPACK_ERR_ARGS;
if (qtm->error) return qtm->error;
/* flush out any stored-up bytes before we begin */
i = qtm->o_end - qtm->o_ptr;
if ((off_t) i > out_bytes) i = (int) out_bytes;
if (i) {
if (qtm->sys->write(qtm->output, qtm->o_ptr, i) != i) {
return qtm->error = MSPACK_ERR_WRITE;
}
qtm->o_ptr += i;
out_bytes -= i;
}
if (out_bytes == 0) return MSPACK_ERR_OK;
/* restore local state */
RESTORE_BITS;
window = qtm->window;
window_posn = qtm->window_posn;
frame_todo = qtm->frame_todo;
H = qtm->H;
L = qtm->L;
C = qtm->C;
/* while we do not have enough decoded bytes in reserve: */
while ((qtm->o_end - qtm->o_ptr) < out_bytes) {
/* read header if necessary. Initialises H, L and C */
if (!qtm->header_read) {
H = 0xFFFF; L = 0; READ_BITS(C, 16);
qtm->header_read = 1;
}
/* decode more, up to the number of bytes needed, the frame boundary,
* or the window boundary, whichever comes first */
frame_end = window_posn + (out_bytes - (qtm->o_end - qtm->o_ptr));
if ((window_posn + frame_todo) < frame_end) {
frame_end = window_posn + frame_todo;
}
if (frame_end > qtm->window_size) {
frame_end = qtm->window_size;
}
while (window_posn < frame_end) {
GET_SYMBOL(qtm->model7, selector);
if (selector < 4) {
/* literal byte */
struct qtmd_model *mdl = (selector == 0) ? &qtm->model0 :
((selector == 1) ? &qtm->model1 :
((selector == 2) ? &qtm->model2 :
&qtm->model3));
GET_SYMBOL((*mdl), sym);
window[window_posn++] = sym;
frame_todo--;
}
else {
/* match repeated string */
switch (selector) {
case 4: /* selector 4 = fixed length match (3 bytes) */
GET_SYMBOL(qtm->model4, sym);
READ_MANY_BITS(extra, extra_bits[sym]);
match_offset = position_base[sym] + extra + 1;
match_length = 3;
break;
case 5: /* selector 5 = fixed length match (4 bytes) */
GET_SYMBOL(qtm->model5, sym);
READ_MANY_BITS(extra, extra_bits[sym]);
match_offset = position_base[sym] + extra + 1;
match_length = 4;
break;
case 6: /* selector 6 = variable length match */
GET_SYMBOL(qtm->model6len, sym);
READ_MANY_BITS(extra, length_extra[sym]);
match_length = length_base[sym] + extra + 5;
GET_SYMBOL(qtm->model6, sym);
READ_MANY_BITS(extra, extra_bits[sym]);
match_offset = position_base[sym] + extra + 1;
break;
default:
/* should be impossible, model7 can only return 0-6 */
D(("got %d from selector", selector))
return qtm->error = MSPACK_ERR_DECRUNCH;
}
rundest = &window[window_posn];
frame_todo -= match_length;
/* does match destination wrap the window? This situation is possible
* where the window size is less than the 32k frame size, but matches
* must not go beyond a frame boundary */
if ((window_posn + match_length) > qtm->window_size) {
/* copy first part of match, before window end */
i = qtm->window_size - window_posn;
j = window_posn - match_offset;
while (i--) *rundest++ = window[j++ & (qtm->window_size - 1)];
/* flush currently stored data */
i = (&window[qtm->window_size] - qtm->o_ptr);
/* this should not happen, but if it does then this code
* can't handle the situation (can't flush up to the end of
* the window, but can't break out either because we haven't
* finished writing the match). bail out in this case */
if (i > out_bytes) {
D(("during window-wrap match; %d bytes to flush but only need %d",
i, (int) out_bytes))
return qtm->error = MSPACK_ERR_DECRUNCH;
}
if (qtm->sys->write(qtm->output, qtm->o_ptr, i) != i) {
return qtm->error = MSPACK_ERR_WRITE;
}
out_bytes -= i;
qtm->o_ptr = &window[0];
qtm->o_end = &window[0];
/* copy second part of match, after window wrap */
rundest = &window[0];
i = match_length - (qtm->window_size - window_posn);
while (i--) *rundest++ = window[j++ & (qtm->window_size - 1)];
window_posn = window_posn + match_length - qtm->window_size;
break; /* because "window_posn < frame_end" has now failed */
}
else {
/* normal match - output won't wrap window or frame end */
i = match_length;
/* does match _offset_ wrap the window? */
if (match_offset > window_posn) {
/* j = length from match offset to end of window */
j = match_offset - window_posn;
if (j > (int) qtm->window_size) {
D(("match offset beyond window boundaries"))
return qtm->error = MSPACK_ERR_DECRUNCH;
}
runsrc = &window[qtm->window_size - j];
if (j < i) {
/* if match goes over the window edge, do two copy runs */
i -= j; while (j-- > 0) *rundest++ = *runsrc++;
runsrc = window;
}
while (i-- > 0) *rundest++ = *runsrc++;
}
else {
runsrc = rundest - match_offset;
while (i-- > 0) *rundest++ = *runsrc++;
}
window_posn += match_length;
}
} /* if (window_posn+match_length > frame_end) */
} /* while (window_posn < frame_end) */
qtm->o_end = &window[window_posn];
/* if we subtracted too much from frame_todo, it will
* wrap around past zero and go above its max value */
if (frame_todo > QTM_FRAME_SIZE) {
D(("overshot frame alignment"))
return qtm->error = MSPACK_ERR_DECRUNCH;
}
/* another frame completed? */
if (frame_todo == 0) {
/* re-align input */
if (bits_left & 7) REMOVE_BITS(bits_left & 7);
/* special Quantum hack -- cabd.c injects a trailer byte to allow the
* decompressor to realign itself. CAB Quantum blocks, unlike LZX
* blocks, can have anything from 0 to 4 trailing null bytes. */
do { READ_BITS(i, 8); } while (i != 0xFF);
qtm->header_read = 0;
frame_todo = QTM_FRAME_SIZE;
}
/* window wrap? */
if (window_posn == qtm->window_size) {
/* flush all currently stored data */
i = (qtm->o_end - qtm->o_ptr);
/* break out if we have more than enough to finish this request */
if (i >= out_bytes) break;
if (qtm->sys->write(qtm->output, qtm->o_ptr, i) != i) {
return qtm->error = MSPACK_ERR_WRITE;
}
out_bytes -= i;
qtm->o_ptr = &window[0];
qtm->o_end = &window[0];
window_posn = 0;
}
} /* while (more bytes needed) */
if (out_bytes) {
i = (int) out_bytes;
if (qtm->sys->write(qtm->output, qtm->o_ptr, i) != i) {
return qtm->error = MSPACK_ERR_WRITE;
}
qtm->o_ptr += i;
}
/* store local state */
STORE_BITS;
qtm->window_posn = window_posn;
qtm->frame_todo = frame_todo;
qtm->H = H;
qtm->L = L;
qtm->C = C;
return MSPACK_ERR_OK;
}
void qtmd_free(struct qtmd_stream *qtm) {
struct mspack_system *sys;
if (qtm) {
sys = qtm->sys;
sys->free(qtm->window);
sys->free(qtm->inbuf);
sys->free(qtm);
}
}