+++ /dev/null
-/* inffast.c -- fast decoding
- * Copyright (C) 1995-2008, 2010, 2013 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"
-
-#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.
- */
-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 - 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;
- 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)(PUP(in)) << bits;
- bits += 8;
- hold += (unsigned long)(PUP(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));
- PUP(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)(PUP(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)(PUP(in)) << bits;
- bits += 8;
- hold += (unsigned long)(PUP(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)(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;
- 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 {
- PUP(out) = 0;
- } while (--len);
- continue;
- }
- len -= op - whave;
- do {
- PUP(out) = 0;
- } while (--op > whave);
- if (op == 0) {
- from = out - dist;
- do {
- PUP(out) = PUP(from);
- } while (--len);
- continue;
- }
-#endif
- }
- from = window - OFF;
- if (wnext == 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 (wnext < op) { /* wrap around window */
- from += wsize + wnext - op;
- op -= wnext;
- if (op < len) { /* some from end of window */
- len -= op;
- do {
- PUP(out) = PUP(from);
- } while (--op);
- from = window - OFF;
- if (wnext < len) { /* some from start of window */
- op = wnext;
- len -= op;
- do {
- PUP(out) = PUP(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 {
- 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) = PUP(from);
- if (len > 1)
- PUP(out) = PUP(from);
- }
- }
- else {
- from = out - dist; /* copy direct from output */
- do { /* minimum length is three */
- PUP(out) = PUP(from);
- PUP(out) = PUP(from);
- PUP(out) = PUP(from);
- len -= 3;
- } while (len > 2);
- if (len) {
- PUP(out) = PUP(from);
- if (len > 1)
- PUP(out) = PUP(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 + OFF;
- strm->next_out = out + OFF;
- 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 */
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