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'use strict';
// See state defs from inflate.js
var BAD = 30; /* got a data error -- remain here until reset */
var TYPE = 12; /* i: waiting for type bits, including last-flag bit */
/*
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.
*/
module.exports = function inflate_fast(strm, start) {
var state;
var _in; /* local strm.input */
var last; /* have enough input while in < last */
var _out; /* local strm.output */
var beg; /* inflate()'s initial strm.output */
var end; /* while out < end, enough space available */
//#ifdef INFLATE_STRICT
var dmax; /* maximum distance from zlib header */
//#endif
var wsize; /* window size or zero if not using window */
var whave; /* valid bytes in the window */
var wnext; /* window write index */
// Use `s_window` instead `window`, avoid conflict with instrumentation tools
var s_window; /* allocated sliding window, if wsize != 0 */
var hold; /* local strm.hold */
var bits; /* local strm.bits */
var lcode; /* local strm.lencode */
var dcode; /* local strm.distcode */
var lmask; /* mask for first level of length codes */
var dmask; /* mask for first level of distance codes */
var here; /* retrieved table entry */
var op; /* code bits, operation, extra bits, or */
/* window position, window bytes to copy */
var len; /* match length, unused bytes */
var dist; /* match distance */
var from; /* where to copy match from */
var from_source;
var input, output; // JS specific, because we have no pointers
/* copy state to local variables */
state = strm.state;
//here = state.here;
_in = strm.next_in;
input = strm.input;
last = _in + (strm.avail_in - 5);
_out = strm.next_out;
output = strm.output;
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;
s_window = state.window;
hold = state.hold;
bits = state.bits;
lcode = state.lencode;
dcode = state.distcode;
lmask = (1 << state.lenbits) - 1;
dmask = (1 << state.distbits) - 1;
/* decode literals and length/distances until end-of-block or not enough
input data or output space */
top:
do {
if (bits < 15) {
hold += input[_in++] << bits;
bits += 8;
hold += input[_in++] << bits;
bits += 8;
}
here = lcode[hold & lmask];
dolen:
for (;;) { // Goto emulation
op = here >>> 24/*here.bits*/;
hold >>>= op;
bits -= op;
op = (here >>> 16) & 0xff/*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));
output[_out++] = here & 0xffff/*here.val*/;
}
else if (op & 16) { /* length base */
len = here & 0xffff/*here.val*/;
op &= 15; /* number of extra bits */
if (op) {
if (bits < op) {
hold += input[_in++] << bits;
bits += 8;
}
len += hold & ((1 << op) - 1);
hold >>>= op;
bits -= op;
}
//Tracevv((stderr, "inflate: length %u\n", len));
if (bits < 15) {
hold += input[_in++] << bits;
bits += 8;
hold += input[_in++] << bits;
bits += 8;
}
here = dcode[hold & dmask];
dodist:
for (;;) { // goto emulation
op = here >>> 24/*here.bits*/;
hold >>>= op;
bits -= op;
op = (here >>> 16) & 0xff/*here.op*/;
if (op & 16) { /* distance base */
dist = here & 0xffff/*here.val*/;
op &= 15; /* number of extra bits */
if (bits < op) {
hold += input[_in++] << bits;
bits += 8;
if (bits < op) {
hold += input[_in++] << bits;
bits += 8;
}
}
dist += hold & ((1 << op) - 1);
//#ifdef INFLATE_STRICT
if (dist > dmax) {
strm.msg = 'invalid distance too far back';
state.mode = BAD;
break top;
}
//#endif
hold >>>= op;
bits -= op;
//Tracevv((stderr, "inflate: distance %u\n", dist));
op = _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 = 'invalid distance too far back';
state.mode = BAD;
break top;
}
// (!) This block is disabled in zlib defailts,
// don't enable it for binary compatibility
//#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
// if (len <= op - whave) {
// do {
// output[_out++] = 0;
// } while (--len);
// continue top;
// }
// len -= op - whave;
// do {
// output[_out++] = 0;
// } while (--op > whave);
// if (op === 0) {
// from = _out - dist;
// do {
// output[_out++] = output[from++];
// } while (--len);
// continue top;
// }
//#endif
}
from = 0; // window index
from_source = s_window;
if (wnext === 0) { /* very common case */
from += wsize - op;
if (op < len) { /* some from window */
len -= op;
do {
output[_out++] = s_window[from++];
} while (--op);
from = _out - dist; /* rest from output */
from_source = 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 {
output[_out++] = s_window[from++];
} while (--op);
from = 0;
if (wnext < len) { /* some from start of window */
op = wnext;
len -= op;
do {
output[_out++] = s_window[from++];
} while (--op);
from = _out - dist; /* rest from output */
from_source = output;
}
}
}
else { /* contiguous in window */
from += wnext - op;
if (op < len) { /* some from window */
len -= op;
do {
output[_out++] = s_window[from++];
} while (--op);
from = _out - dist; /* rest from output */
from_source = output;
}
}
while (len > 2) {
output[_out++] = from_source[from++];
output[_out++] = from_source[from++];
output[_out++] = from_source[from++];
len -= 3;
}
if (len) {
output[_out++] = from_source[from++];
if (len > 1) {
output[_out++] = from_source[from++];
}
}
}
else {
from = _out - dist; /* copy direct from output */
do { /* minimum length is three */
output[_out++] = output[from++];
output[_out++] = output[from++];
output[_out++] = output[from++];
len -= 3;
} while (len > 2);
if (len) {
output[_out++] = output[from++];
if (len > 1) {
output[_out++] = output[from++];
}
}
}
}
else if ((op & 64) === 0) { /* 2nd level distance code */
here = dcode[(here & 0xffff)/*here.val*/ + (hold & ((1 << op) - 1))];
continue dodist;
}
else {
strm.msg = 'invalid distance code';
state.mode = BAD;
break top;
}
break; // need to emulate goto via "continue"
}
}
else if ((op & 64) === 0) { /* 2nd level length code */
here = lcode[(here & 0xffff)/*here.val*/ + (hold & ((1 << op) - 1))];
continue dolen;
}
else if (op & 32) { /* end-of-block */
//Tracevv((stderr, "inflate: end of block\n"));
state.mode = TYPE;
break top;
}
else {
strm.msg = 'invalid literal/length code';
state.mode = BAD;
break top;
}
break; // need to emulate goto via "continue"
}
} 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 &= (1 << bits) - 1;
/* update state and return */
strm.next_in = _in;
strm.next_out = _out;
strm.avail_in = (_in < last ? 5 + (last - _in) : 5 - (_in - last));
strm.avail_out = (_out < end ? 257 + (end - _out) : 257 - (_out - end));
state.hold = hold;
state.bits = bits;
return;
};