1e3bccd496
There have been many reports of bugs in the assembler codes intended to speed up deflate and inflate. They are third-party contributions in contrib, and so are not supported by the zlib maintainers.
324 lines
13 KiB
C
324 lines
13 KiB
C
/* inffast.c -- fast decoding
|
|
* Copyright (C) 1995-2008, 2010, 2013, 2016 Mark Adler
|
|
* For conditions of distribution and use, see copyright notice in zlib.h
|
|
*/
|
|
|
|
#include "zutil.h"
|
|
#include "inftrees.h"
|
|
#include "inflate.h"
|
|
#include "inffast.h"
|
|
|
|
#ifdef ASMINF
|
|
# pragma message("Assembler code may have bugs -- use at your own risk")
|
|
#else
|
|
|
|
/*
|
|
Decode literal, length, and distance codes and write out the resulting
|
|
literal and match bytes until either not enough input or output is
|
|
available, an end-of-block is encountered, or a data error is encountered.
|
|
When large enough input and output buffers are supplied to inflate(), for
|
|
example, a 16K input buffer and a 64K output buffer, more than 95% of the
|
|
inflate execution time is spent in this routine.
|
|
|
|
Entry assumptions:
|
|
|
|
state->mode == LEN
|
|
strm->avail_in >= 6
|
|
strm->avail_out >= 258
|
|
start >= strm->avail_out
|
|
state->bits < 8
|
|
|
|
On return, state->mode is one of:
|
|
|
|
LEN -- ran out of enough output space or enough available input
|
|
TYPE -- reached end of block code, inflate() to interpret next block
|
|
BAD -- error in block data
|
|
|
|
Notes:
|
|
|
|
- The maximum input bits used by a length/distance pair is 15 bits for the
|
|
length code, 5 bits for the length extra, 15 bits for the distance code,
|
|
and 13 bits for the distance extra. This totals 48 bits, or six bytes.
|
|
Therefore if strm->avail_in >= 6, then there is enough input to avoid
|
|
checking for available input while decoding.
|
|
|
|
- The maximum bytes that a single length/distance pair can output is 258
|
|
bytes, which is the maximum length that can be coded. inflate_fast()
|
|
requires strm->avail_out >= 258 for each loop to avoid checking for
|
|
output space.
|
|
*/
|
|
void ZLIB_INTERNAL inflate_fast(strm, start)
|
|
z_streamp strm;
|
|
unsigned start; /* inflate()'s starting value for strm->avail_out */
|
|
{
|
|
struct inflate_state FAR *state;
|
|
z_const unsigned char FAR *in; /* local strm->next_in */
|
|
z_const unsigned char FAR *last; /* have enough input while in < last */
|
|
unsigned char FAR *out; /* local strm->next_out */
|
|
unsigned char FAR *beg; /* inflate()'s initial strm->next_out */
|
|
unsigned char FAR *end; /* while out < end, enough space available */
|
|
#ifdef INFLATE_STRICT
|
|
unsigned dmax; /* maximum distance from zlib header */
|
|
#endif
|
|
unsigned wsize; /* window size or zero if not using window */
|
|
unsigned whave; /* valid bytes in the window */
|
|
unsigned wnext; /* window write index */
|
|
unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */
|
|
unsigned long hold; /* local strm->hold */
|
|
unsigned bits; /* local strm->bits */
|
|
code const FAR *lcode; /* local strm->lencode */
|
|
code const FAR *dcode; /* local strm->distcode */
|
|
unsigned lmask; /* mask for first level of length codes */
|
|
unsigned dmask; /* mask for first level of distance codes */
|
|
code here; /* retrieved table entry */
|
|
unsigned op; /* code bits, operation, extra bits, or */
|
|
/* window position, window bytes to copy */
|
|
unsigned len; /* match length, unused bytes */
|
|
unsigned dist; /* match distance */
|
|
unsigned char FAR *from; /* where to copy match from */
|
|
|
|
/* copy state to local variables */
|
|
state = (struct inflate_state FAR *)strm->state;
|
|
in = strm->next_in;
|
|
last = in + (strm->avail_in - 5);
|
|
out = strm->next_out;
|
|
beg = out - (start - strm->avail_out);
|
|
end = out + (strm->avail_out - 257);
|
|
#ifdef INFLATE_STRICT
|
|
dmax = state->dmax;
|
|
#endif
|
|
wsize = state->wsize;
|
|
whave = state->whave;
|
|
wnext = state->wnext;
|
|
window = state->window;
|
|
hold = state->hold;
|
|
bits = state->bits;
|
|
lcode = state->lencode;
|
|
dcode = state->distcode;
|
|
lmask = (1U << state->lenbits) - 1;
|
|
dmask = (1U << state->distbits) - 1;
|
|
|
|
/* decode literals and length/distances until end-of-block or not enough
|
|
input data or output space */
|
|
do {
|
|
if (bits < 15) {
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
}
|
|
here = lcode[hold & lmask];
|
|
dolen:
|
|
op = (unsigned)(here.bits);
|
|
hold >>= op;
|
|
bits -= op;
|
|
op = (unsigned)(here.op);
|
|
if (op == 0) { /* literal */
|
|
Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ?
|
|
"inflate: literal '%c'\n" :
|
|
"inflate: literal 0x%02x\n", here.val));
|
|
*out++ = (unsigned char)(here.val);
|
|
}
|
|
else if (op & 16) { /* length base */
|
|
len = (unsigned)(here.val);
|
|
op &= 15; /* number of extra bits */
|
|
if (op) {
|
|
if (bits < op) {
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
}
|
|
len += (unsigned)hold & ((1U << op) - 1);
|
|
hold >>= op;
|
|
bits -= op;
|
|
}
|
|
Tracevv((stderr, "inflate: length %u\n", len));
|
|
if (bits < 15) {
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
}
|
|
here = dcode[hold & dmask];
|
|
dodist:
|
|
op = (unsigned)(here.bits);
|
|
hold >>= op;
|
|
bits -= op;
|
|
op = (unsigned)(here.op);
|
|
if (op & 16) { /* distance base */
|
|
dist = (unsigned)(here.val);
|
|
op &= 15; /* number of extra bits */
|
|
if (bits < op) {
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
if (bits < op) {
|
|
hold += (unsigned long)(*in++) << bits;
|
|
bits += 8;
|
|
}
|
|
}
|
|
dist += (unsigned)hold & ((1U << op) - 1);
|
|
#ifdef INFLATE_STRICT
|
|
if (dist > dmax) {
|
|
strm->msg = (char *)"invalid distance too far back";
|
|
state->mode = BAD;
|
|
break;
|
|
}
|
|
#endif
|
|
hold >>= op;
|
|
bits -= op;
|
|
Tracevv((stderr, "inflate: distance %u\n", dist));
|
|
op = (unsigned)(out - beg); /* max distance in output */
|
|
if (dist > op) { /* see if copy from window */
|
|
op = dist - op; /* distance back in window */
|
|
if (op > whave) {
|
|
if (state->sane) {
|
|
strm->msg =
|
|
(char *)"invalid distance too far back";
|
|
state->mode = BAD;
|
|
break;
|
|
}
|
|
#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
|
|
if (len <= op - whave) {
|
|
do {
|
|
*out++ = 0;
|
|
} while (--len);
|
|
continue;
|
|
}
|
|
len -= op - whave;
|
|
do {
|
|
*out++ = 0;
|
|
} while (--op > whave);
|
|
if (op == 0) {
|
|
from = out - dist;
|
|
do {
|
|
*out++ = *from++;
|
|
} while (--len);
|
|
continue;
|
|
}
|
|
#endif
|
|
}
|
|
from = window;
|
|
if (wnext == 0) { /* very common case */
|
|
from += wsize - op;
|
|
if (op < len) { /* some from window */
|
|
len -= op;
|
|
do {
|
|
*out++ = *from++;
|
|
} while (--op);
|
|
from = out - dist; /* rest from output */
|
|
}
|
|
}
|
|
else if (wnext < op) { /* wrap around window */
|
|
from += wsize + wnext - op;
|
|
op -= wnext;
|
|
if (op < len) { /* some from end of window */
|
|
len -= op;
|
|
do {
|
|
*out++ = *from++;
|
|
} while (--op);
|
|
from = window;
|
|
if (wnext < len) { /* some from start of window */
|
|
op = wnext;
|
|
len -= op;
|
|
do {
|
|
*out++ = *from++;
|
|
} while (--op);
|
|
from = out - dist; /* rest from output */
|
|
}
|
|
}
|
|
}
|
|
else { /* contiguous in window */
|
|
from += wnext - op;
|
|
if (op < len) { /* some from window */
|
|
len -= op;
|
|
do {
|
|
*out++ = *from++;
|
|
} while (--op);
|
|
from = out - dist; /* rest from output */
|
|
}
|
|
}
|
|
while (len > 2) {
|
|
*out++ = *from++;
|
|
*out++ = *from++;
|
|
*out++ = *from++;
|
|
len -= 3;
|
|
}
|
|
if (len) {
|
|
*out++ = *from++;
|
|
if (len > 1)
|
|
*out++ = *from++;
|
|
}
|
|
}
|
|
else {
|
|
from = out - dist; /* copy direct from output */
|
|
do { /* minimum length is three */
|
|
*out++ = *from++;
|
|
*out++ = *from++;
|
|
*out++ = *from++;
|
|
len -= 3;
|
|
} while (len > 2);
|
|
if (len) {
|
|
*out++ = *from++;
|
|
if (len > 1)
|
|
*out++ = *from++;
|
|
}
|
|
}
|
|
}
|
|
else if ((op & 64) == 0) { /* 2nd level distance code */
|
|
here = dcode[here.val + (hold & ((1U << op) - 1))];
|
|
goto dodist;
|
|
}
|
|
else {
|
|
strm->msg = (char *)"invalid distance code";
|
|
state->mode = BAD;
|
|
break;
|
|
}
|
|
}
|
|
else if ((op & 64) == 0) { /* 2nd level length code */
|
|
here = lcode[here.val + (hold & ((1U << op) - 1))];
|
|
goto dolen;
|
|
}
|
|
else if (op & 32) { /* end-of-block */
|
|
Tracevv((stderr, "inflate: end of block\n"));
|
|
state->mode = TYPE;
|
|
break;
|
|
}
|
|
else {
|
|
strm->msg = (char *)"invalid literal/length code";
|
|
state->mode = BAD;
|
|
break;
|
|
}
|
|
} while (in < last && out < end);
|
|
|
|
/* return unused bytes (on entry, bits < 8, so in won't go too far back) */
|
|
len = bits >> 3;
|
|
in -= len;
|
|
bits -= len << 3;
|
|
hold &= (1U << bits) - 1;
|
|
|
|
/* update state and return */
|
|
strm->next_in = in;
|
|
strm->next_out = out;
|
|
strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
|
|
strm->avail_out = (unsigned)(out < end ?
|
|
257 + (end - out) : 257 - (out - end));
|
|
state->hold = hold;
|
|
state->bits = bits;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
|
|
- Using bit fields for code structure
|
|
- Different op definition to avoid & for extra bits (do & for table bits)
|
|
- Three separate decoding do-loops for direct, window, and wnext == 0
|
|
- Special case for distance > 1 copies to do overlapped load and store copy
|
|
- Explicit branch predictions (based on measured branch probabilities)
|
|
- Deferring match copy and interspersed it with decoding subsequent codes
|
|
- Swapping literal/length else
|
|
- Swapping window/direct else
|
|
- Larger unrolled copy loops (three is about right)
|
|
- Moving len -= 3 statement into middle of loop
|
|
*/
|
|
|
|
#endif /* !ASMINF */
|