/* 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
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <mspack.h>
#include <system.h>
#include <qtm.h>
/* Quantum decompressor bitstream reading macros
*
* STORE_BITS stores bitstream state in qtmd_stream structure
* RESTORE_BITS restores bitstream state from qtmd_stream structure
* READ_BITS(var,n) takes N bits from the buffer and puts them in var
* FILL_BUFFER if there is room for another 16 bits, reads another
* 16 bits from the input stream.
* PEEK_BITS(n) extracts without removing N bits from the bit buffer
* REMOVE_BITS(n) removes N bits from the bit buffer
*
* These bit access routines work by using the area beyond the MSB and the
* LSB as a free source of zeroes. This avoids having to mask any bits.
* So we have to know the bit width of the bitbuffer variable.
*/
#ifdef HAVE_LIMITS_H
# include <limits.h>
#endif
#ifndef CHAR_BIT
# define CHAR_BIT (8)
#endif
#define BITBUF_WIDTH (sizeof(unsigned int) * CHAR_BIT)
#define STORE_BITS do { \
qtm->i_ptr = i_ptr; \
qtm->i_end = i_end; \
qtm->bit_buffer = bit_buffer; \
qtm->bits_left = bits_left; \
} while (0)
#define RESTORE_BITS do { \
i_ptr = qtm->i_ptr; \
i_end = qtm->i_end; \
bit_buffer = qtm->bit_buffer; \
bits_left = qtm->bits_left; \
} while (0)
/* adds 16 bits to bit buffer, if there's space for the new bits */
#define FILL_BUFFER do { \
if (bits_left <= (BITBUF_WIDTH - 16)) { \
if (i_ptr >= i_end) { \
if (qtmd_read_input(qtm)) return qtm->error; \
i_ptr = qtm->i_ptr; \
i_end = qtm->i_end; \
} \
bit_buffer |= ((i_ptr[0] << 8) | i_ptr[1]) \
<< (BITBUF_WIDTH - 16 - bits_left); \
bits_left += 16; \
i_ptr += 2; \
} \
} while (0)
#define PEEK_BITS(n) (bit_buffer >> (BITBUF_WIDTH - (n)))
#define REMOVE_BITS(n) ((bit_buffer <<= (n)), (bits_left -= (n)))
#define READ_BITS(val, bits) do { \
(val) = 0; \
for (bits_needed = (bits); bits_needed > 0; bits_needed -= bit_run) { \
FILL_BUFFER; \
bit_run = (bits_left < bits_needed) ? bits_left : bits_needed; \
(val) = ((val) << bit_run) | PEEK_BITS(bit_run); \
REMOVE_BITS(bit_run); \
} \
} while (0)
static int qtmd_read_input(struct qtmd_stream *qtm) {
int read = qtm->sys->read(qtm->input, &qtm->inbuf[0], (int)qtm->inbuf_size);
if (read < 0) return qtm->error = MSPACK_ERR_READ;
qtm->i_ptr = &qtm->inbuf[0];
qtm->i_end = &qtm->inbuf[read];
return MSPACK_ERR_OK;
}
/* 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.
*/
static unsigned int position_base[42];
static unsigned char extra_bits[42], length_base[27], length_extra[27];
static void qtmd_static_init() {
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;
}
/* 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; \
FILL_BUFFER; \
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) */
/* tk: temporary fix: only process 32KB+ window sizes */
if (window_bits < 15 || window_bits > 21) return NULL;
input_buffer_size = (input_buffer_size + 1) & -2;
if (input_buffer_size < 2) return NULL;
/* initialise static data */
qtmd_static_init();
/* allocate decompression state */
if (!(qtm = system->alloc(system, sizeof(struct qtmd_stream)))) {
return NULL;
}
/* allocate decompression window and input buffer */
qtm->window = system->alloc(system, (size_t) window_size);
qtm->inbuf = 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_start = 0;
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->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_start, 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;
unsigned char bits_needed, bit_run;
/* 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_start = qtm->frame_start;
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, at most up to to frame boundary */
frame_end = window_posn + (out_bytes - (qtm->o_end - qtm->o_ptr));
if ((frame_start + QTM_FRAME_SIZE) < frame_end) {
frame_end = frame_start + QTM_FRAME_SIZE;
}
while (window_posn < frame_end) {
GET_SYMBOL(qtm->model7, selector);
if (selector < 4) {
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;
}
else {
switch (selector) {
case 4: /* selector 4 = fixed length match (3 bytes) */
GET_SYMBOL(qtm->model4, sym);
READ_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_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_BITS(extra, length_extra[sym]);
match_length = length_base[sym] + extra + 5;
GET_SYMBOL(qtm->model6, sym);
READ_BITS(extra, extra_bits[sym]);
match_offset = position_base[sym] + extra + 1;
break;
default:
/* should be impossible, model7 can only return 0-6 */
return qtm->error = MSPACK_ERR_DECRUNCH;
}
rundest = &window[window_posn];
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;
}
} /* while (window_posn < frame_end) */
qtm->o_end = &window[window_posn];
/* another frame completed? */
if ((window_posn - frame_start) >= QTM_FRAME_SIZE) {
if ((window_posn - frame_start) != QTM_FRAME_SIZE) {
D(("overshot frame alignment"))
return qtm->error = MSPACK_ERR_DECRUNCH;
}
/* re-align input */
if (bits_left & 7) REMOVE_BITS(bits_left & 7);
do { READ_BITS(i, 8); } while (i != 0xFF);
qtm->header_read = 0;
/* window wrap? */
if (window_posn == qtm->window_size) {
/* flush all currently stored data */
i = (qtm->o_end - qtm->o_ptr);
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;
}
frame_start = window_posn;
}
} /* 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_start = frame_start;
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);
}
}