309 lines
11 KiB
C
309 lines
11 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=4 sts=4 sw=4 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 1995-2017 Mark Adler │
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│ Use of this source code is governed by the BSD-style licenses that can │
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│ be found in the third_party/zlib/LICENSE file. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "third_party/zlib/inffast.h"
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#include "third_party/zlib/inflate.h"
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#include "third_party/zlib/inftrees.h"
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#include "third_party/zlib/zutil.h"
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asm(".ident\t\"\\n\\n\
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zlib (zlib License)\\n\
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Copyright 1995-2017 Jean-loup Gailly and Mark Adler\"");
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asm(".include \"libc/disclaimer.inc\"");
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/**
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* Decodes literal, length, and distance codes and write out the
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* resulting literal and match bytes until either not enough input or
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* output is available, an end-of-block is encountered, or a data error
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* is encountered. When large enough input and output buffers are
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* supplied to inflate(), for example, a 16K input buffer and a 64K
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* output buffer, more than 95% of the inflate() execution time is spent
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* in this routine.
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*
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* Entry assumptions:
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*
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* state->mode == LEN
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* strm->avail_in >= INFLATE_FAST_MIN_INPUT (6 bytes)
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* strm->avail_out >= INFLATE_FAST_MIN_OUTPUT (258 bytes)
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* start >= strm->avail_out
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* state->bits < 8
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*
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* On return, state->mode is one of:
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*
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* LEN -- ran out of enough output space or enough available input
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* TYPE -- reached end of block code, inflate() to interpret next block
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* BAD -- error in block data
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*
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* Some notes:
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*
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* INFLATE_FAST_MIN_INPUT: 6 bytes
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*
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* - The maximum input bits used by a length/distance pair is 15 bits
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* for the length code, 5 bits for the length extra, 15 bits for the
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* distance code, and 13 bits for the distance extra. This totals 48
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* bits, or six bytes. Therefore if strm->avail_in >= 6, then there
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* is enough input to avoid checking for available input while
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* decoding.
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*
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* INFLATE_FAST_MIN_OUTPUT: 258 bytes
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*
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* - The maximum bytes that a single length/distance pair can output is
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* 258 bytes, which is the maximum length that can be coded.
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* inflate_fast() requires strm->avail_out >= 258 for each loop to
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* avoid checking for available output space while decoding.
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*
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* @param start inflate() starting value for strm->avail_out
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*/
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void inflate_fast(z_streamp strm, unsigned start) {
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struct InflateState *state;
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const unsigned char *in; /* local strm->next_in */
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const unsigned char *last; /* have enough input while in < last */
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unsigned char *out; /* local strm->next_out */
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unsigned char *beg; /* inflate()'s initial strm->next_out */
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unsigned char *end; /* while out < end, enough space available */
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#ifdef INFLATE_STRICT
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unsigned dmax; /* maximum distance from zlib header */
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#endif
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unsigned wsize; /* window size or zero if not using window */
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unsigned whave; /* valid bytes in the window */
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unsigned wnext; /* window write index */
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unsigned char *window; /* allocated sliding window, if wsize != 0 */
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unsigned long hold; /* local strm->hold */
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unsigned bits; /* local strm->bits */
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const struct zcode *lcode; /* local strm->lencode */
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const struct zcode *dcode; /* local strm->distcode */
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unsigned lmask; /* mask for first level of length codes */
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unsigned dmask; /* mask for first level of distance codes */
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struct zcode here; /* retrieved table entry */
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unsigned op; /* code bits, operation, extra bits, or */
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/* window position, window bytes to copy */
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unsigned len; /* match length, unused bytes */
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unsigned dist; /* match distance */
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unsigned char *from; /* where to copy match from */
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/* copy state to local variables */
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state = (struct InflateState *)strm->state;
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in = strm->next_in;
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last = in + (strm->avail_in - (INFLATE_FAST_MIN_INPUT - 1));
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out = strm->next_out;
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beg = out - (start - strm->avail_out);
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end = out + (strm->avail_out - (INFLATE_FAST_MIN_OUTPUT - 1));
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#ifdef INFLATE_STRICT
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dmax = state->dmax;
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#endif
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wsize = state->wsize;
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whave = state->whave;
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wnext = state->wnext;
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window = state->window;
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hold = state->hold;
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bits = state->bits;
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lcode = state->lencode;
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dcode = state->distcode;
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lmask = (1U << state->lenbits) - 1;
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dmask = (1U << state->distbits) - 1;
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/* decode literals and length/distances until end-of-block or not enough
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input data or output space */
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do {
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if (bits < 15) {
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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}
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here = lcode[hold & lmask];
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dolen:
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op = (unsigned)(here.bits);
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hold >>= op;
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bits -= op;
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op = (unsigned)(here.op);
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if (op == 0) { /* literal */
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Tracevv((stderr,
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here.val >= 0x20 && here.val < 0x7f
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? "inflate: literal '%c'\n"
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: "inflate: literal 0x%02x\n",
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here.val));
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*out++ = (unsigned char)(here.val);
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} else if (op & 16) { /* length base */
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len = (unsigned)(here.val);
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op &= 15; /* number of extra bits */
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if (op) {
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if (bits < op) {
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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}
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len += (unsigned)hold & ((1U << op) - 1);
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hold >>= op;
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bits -= op;
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}
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Tracevv((stderr, "inflate: length %u\n", len));
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if (bits < 15) {
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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}
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here = dcode[hold & dmask];
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dodist:
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op = (unsigned)(here.bits);
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hold >>= op;
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bits -= op;
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op = (unsigned)(here.op);
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if (op & 16) { /* distance base */
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dist = (unsigned)(here.val);
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op &= 15; /* number of extra bits */
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if (bits < op) {
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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if (bits < op) {
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hold += (unsigned long)(*in++) << bits;
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bits += 8;
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}
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}
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dist += (unsigned)hold & ((1U << op) - 1);
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#ifdef INFLATE_STRICT
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if (dist > dmax) {
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strm->msg = (char *)"invalid distance too far back";
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state->mode = BAD;
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break;
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}
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#endif
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hold >>= op;
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bits -= op;
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Tracevv((stderr, "inflate: distance %u\n", dist));
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op = (unsigned)(out - beg); /* max distance in output */
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if (dist > op) { /* see if copy from window */
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op = dist - op; /* distance back in window */
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if (op > whave) {
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if (state->sane) {
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strm->msg = (char *)"invalid distance too far back";
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state->mode = BAD;
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break;
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}
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#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
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if (len <= op - whave) {
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do {
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*out++ = 0;
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} while (--len);
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continue;
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}
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len -= op - whave;
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do {
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*out++ = 0;
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} while (--op > whave);
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if (op == 0) {
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from = out - dist;
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do {
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*out++ = *from++;
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} while (--len);
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continue;
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}
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#endif
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}
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from = window;
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if (wnext == 0) { /* very common case */
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from += wsize - op;
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if (op < len) { /* some from window */
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len -= op;
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do {
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*out++ = *from++;
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} while (--op);
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from = out - dist; /* rest from output */
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}
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} else if (wnext < op) { /* wrap around window */
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from += wsize + wnext - op;
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op -= wnext;
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if (op < len) { /* some from end of window */
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len -= op;
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do {
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*out++ = *from++;
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} while (--op);
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from = window;
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if (wnext < len) { /* some from start of window */
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op = wnext;
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len -= op;
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do {
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*out++ = *from++;
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} while (--op);
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from = out - dist; /* rest from output */
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}
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}
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} else { /* contiguous in window */
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from += wnext - op;
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if (op < len) { /* some from window */
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len -= op;
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do {
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*out++ = *from++;
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} while (--op);
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from = out - dist; /* rest from output */
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}
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}
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while (len > 2) {
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*out++ = *from++;
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*out++ = *from++;
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*out++ = *from++;
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len -= 3;
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}
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if (len) {
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*out++ = *from++;
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if (len > 1) *out++ = *from++;
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}
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} else {
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from = out - dist; /* copy direct from output */
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do { /* minimum length is three */
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*out++ = *from++;
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*out++ = *from++;
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*out++ = *from++;
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len -= 3;
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} while (len > 2);
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if (len) {
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*out++ = *from++;
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if (len > 1) *out++ = *from++;
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}
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}
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} else if ((op & 64) == 0) { /* 2nd level distance code */
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here = dcode[here.val + (hold & ((1U << op) - 1))];
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goto dodist;
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} else {
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strm->msg = (char *)"invalid distance code";
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state->mode = BAD;
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break;
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}
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} else if ((op & 64) == 0) { /* 2nd level length code */
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here = lcode[here.val + (hold & ((1U << op) - 1))];
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goto dolen;
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} else if (op & 32) { /* end-of-block */
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Tracevv((stderr, "inflate: end of block\n"));
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state->mode = TYPE;
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break;
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} else {
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strm->msg = (char *)"invalid literal/length code";
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state->mode = BAD;
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break;
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}
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} while (in < last && out < end);
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/* return unused bytes (on entry, bits < 8, so in won't go too far back) */
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len = bits >> 3;
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in -= len;
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bits -= len << 3;
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hold &= (1U << bits) - 1;
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/* update state and return */
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strm->next_in = in;
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strm->next_out = out;
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strm->avail_in =
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(unsigned)(in < last ? (INFLATE_FAST_MIN_INPUT - 1) + (last - in)
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: (INFLATE_FAST_MIN_INPUT - 1) - (in - last));
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strm->avail_out =
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(unsigned)(out < end ? (INFLATE_FAST_MIN_OUTPUT - 1) + (end - out)
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: (INFLATE_FAST_MIN_OUTPUT - 1) - (out - end));
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state->hold = hold;
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state->bits = bits;
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return;
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}
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