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/* inffast.c -- fast decoding
* Copyright (C) 1995-2004 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*/
#include <linux/zutil.h>
#include "inftrees.h"
#include "inflate.h"
#include "inffast.h"
#ifndef ASMINF
/* Allow machine dependent optimization for post-increment or pre-increment.
Based on testing to date,
Pre-increment preferred for:
- PowerPC G3 (Adler)
- MIPS R5000 (Randers-Pehrson)
Post-increment preferred for:
- none
No measurable difference:
- Pentium III (Anderson)
- M68060 (Nikl)
*/
#ifdef POSTINC
# define OFF 0
# define PUP(a) *(a)++
#else
# define OFF 1
# define PUP(a) *++(a)
#endif
/*
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.
- @start: inflate()'s starting value for strm->avail_out
*/
void inflate_fast(z_streamp strm, unsigned start)
{
struct inflate_state *state;
const unsigned char *in; /* local strm->next_in */
const unsigned char *last; /* while in < last, enough input available */
unsigned char *out; /* local strm->next_out */
unsigned char *beg; /* inflate()'s initial strm->next_out */
unsigned char *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 write; /* window write index */
unsigned char *window; /* allocated sliding window, if wsize != 0 */
unsigned long hold; /* local strm->hold */
unsigned bits; /* local strm->bits */
code const *lcode; /* local strm->lencode */
code const *dcode; /* local strm->distcode */
unsigned lmask; /* mask for first level of length codes */
unsigned dmask; /* mask for first level of distance codes */
code this; /* 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 *from; /* where to copy match from */
/* copy state to local variables */
state = (struct inflate_state *)strm->state;
in = strm->next_in - OFF;
last = in + (strm->avail_in - 5);
out = strm->next_out - OFF;
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;
write = state->write;
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)(PUP(in)) << bits;
bits += 8;
hold += (unsigned long)(PUP(in)) << bits;
bits += 8;
}
this = lcode[hold & lmask];
dolen:
op = (unsigned)(this.bits);
hold >>= op;
bits -= op;
op = (unsigned)(this.op);
if (op == 0) { /* literal */
PUP(out) = (unsigned char)(this.val);
}
else if (op & 16) { /* length base */
len = (unsigned)(this.val);
op &= 15; /* number of extra bits */
if (op) {
if (bits < op) {
hold += (unsigned long)(PUP(in)) << bits;
bits += 8;
}
len += (unsigned)hold & ((1U << op) - 1);
hold >>= op;
bits -= op;
}
if (bits < 15) {
hold += (unsigned long)(PUP(in)) << bits;
bits += 8;
hold += (unsigned long)(PUP(in)) << bits;
bits += 8;
}
this = dcode[hold & dmask];
dodist:
op = (unsigned)(this.bits);
hold >>= op;
bits -= op;
op = (unsigned)(this.op);
if (op & 16) { /* distance base */
dist = (unsigned)(this.val);
op &= 15; /* number of extra bits */
if (bits < op) {
hold += (unsigned long)(PUP(in)) << bits;
bits += 8;
if (bits < op) {
hold += (unsigned long)(PUP(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;
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) {
strm->msg = (char *)"invalid distance too far back";
state->mode = BAD;
break;
}
from = window - OFF;
if (write == 0) { /* very common case */
from += wsize - op;
if (op < len) { /* some from window */
len -= op;
do {
PUP(out) = PUP(from);
} while (--op);
from = out - dist; /* rest from output */
}
}
else if (write < op) { /* wrap around window */
from += wsize + write - op;
op -= write;
if (op < len) { /* some from end of window */
len -= op;
do {
PUP(out) = PUP(from);
} while (--op);
from = window - OFF;
if (write < len) { /* some from start of window */
op = write;
len -= op;
do {
PUP(out) = PUP(from);
} while (--op);
from = out - dist; /* rest from output */
}
}
}
else { /* contiguous in window */
from += write - op;
if (op < len) { /* some from window */
len -= op;
do {
PUP(out) = PUP(from);
} while (--op);
from = out - dist; /* rest from output */
}
}
while (len > 2) {
PUP(out) = PUP(from);
PUP(out) = PUP(from);
PUP(out) = PUP(from);
len -= 3;
}
if (len) {
PUP(out)
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