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An implementation of unzip for JavaScript
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JavaScript
/* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
* Version: 1.0.0.1
* LastModified: Dec 25 1999
*
* Ported to CommonJS by Tom Robinson, 2010
*/
var BufferIO = require("./buffer-io").BufferIO;
var bops = require("bops");
exports.inflate = function (input) {
// all of these variables must be reset between runs otherwise we get very strange bugs
// so we've wrapped the whole thing in a closure which is also the CommonJS API.
/* constant parameters */
var WSIZE = 32768; // Sliding Window size
var STORED_BLOCK = 0;
var STATIC_TREES = 1;
var DYN_TREES = 2;
/* for inflate */
var lbits = 9; // bits in base literal/length lookup table
var dbits = 6; // bits in base distance lookup table
var INBUFSIZ = 32768; // Input buffer size
var INBUF_EXTRA = 64; // Extra buffer
/* variables (inflate) */
var slide;
var wp; // current position in slide
var fixed_tl = null; // inflate static
var fixed_td; // inflate static
var fixed_bl, fixed_bd; // inflate static
var bit_buf; // bit buffer
var bit_len; // bits in bit buffer
var method;
var eof;
var copy_leng;
var copy_dist;
var tl, td; // literal/length and distance decoder tables
var bl, bd; // number of bits decoded by tl and td
var inflate_data;
var inflate_pos;
/* constant tables (inflate) */
var MASK_BITS = [
0x0000,
0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
];
// Tables for deflate from PKZIP's appnote.txt.
var cplens = [ // Copy lengths for literal codes 257..285
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0
];
/* note: see note #13 above about the 258 in this list. */
var cplext = [ // Extra bits for literal codes 257..285
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99
]; // 99==invalid
var cpdist = [ // Copy offsets for distance codes 0..29
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
8193, 12289, 16385, 24577
];
var cpdext = [ // Extra bits for distance codes
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 13, 13
];
var border = [ // Order of the bit length code lengths
16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
];
/* objects (inflate) */
function HuftList() {
this.next = null;
this.list = null;
}
function HuftNode() {
this.e = 0; // number of extra bits or operation
this.b = 0; // number of bits in this code or subcode
// union
this.n = 0; // literal, length base, or distance base
this.t = null; // (HuftNode) pointer to next level of table
}
function HuftBuild(b, // code lengths in bits (all assumed <= BMAX)
n, // number of codes (assumed <= N_MAX)
s, // number of simple-valued codes (0..s-1)
d, // list of base values for non-simple codes
e, // list of extra bits for non-simple codes
mm // maximum lookup bits
) {
this.BMAX = 16; // maximum bit length of any code
this.N_MAX = 288; // maximum number of codes in any set
this.status = 0; // 0: success, 1: incomplete table, 2: bad input
this.root = null; // (HuftList) starting table
this.m = 0; // maximum lookup bits, returns actual
/* Given a list of code lengths and a maximum table size, make a set of
tables to decode that set of codes. Return zero on success, one if
the given code set is incomplete (the tables are still built in this
case), two if the input is invalid (all zero length codes or an
oversubscribed set of lengths), and three if not enough memory.
The code with value 256 is special, and the tables are constructed
so that no bits beyond that code are fetched when that code is
decoded. */
{
var a; // counter for codes of length k
var c = new Array(this.BMAX+1); // bit length count table
var el; // length of EOB code (value 256)
var f; // i repeats in table every f entries
var g; // maximum code length
var h; // table level
var i; // counter, current code
var j; // counter
var k; // number of bits in current code
var lx = new Array(this.BMAX+1); // stack of bits per table
var p; // pointer into c[], b[], or v[]
var pidx; // index of p
var q; // (HuftNode) points to current table
var r = new HuftNode(); // table entry for structure assignment
var u = new Array(this.BMAX); // HuftNode[BMAX][] table stack
var v = new Array(this.N_MAX); // values in order of bit length
var w;
var x = new Array(this.BMAX+1);// bit offsets, then code stack
var xp; // pointer into x or c
var y; // number of dummy codes added
var z; // number of entries in current table
var o;
var tail; // (HuftList)
tail = this.root = null;
for(i = 0; i < c.length; i++)
c[i] = 0;
for(i = 0; i < lx.length; i++)
lx[i] = 0;
for(i = 0; i < u.length; i++)
u[i] = null;
for(i = 0; i < v.length; i++)
v[i] = 0;
for(i = 0; i < x.length; i++)
x[i] = 0;
// Generate counts for each bit length
el = n > 256 ? b[256] : this.BMAX; // set length of EOB code, if any
p = b; pidx = 0;
i = n;
do {
c[p[pidx]]++; // assume all entries <= BMAX
pidx++;
} while(--i > 0);
if(c[0] == n) { // null input--all zero length codes
this.root = null;
this.m = 0;
this.status = 0;
return;
}
// Find minimum and maximum length, bound *m by those
for(j = 1; j <= this.BMAX; j++)
if(c[j] != 0)
break;
k = j; // minimum code length
if(mm < j)
mm = j;
for(i = this.BMAX; i != 0; i--)
if(c[i] != 0)
break;
g = i; // maximum code length
if(mm > i)
mm = i;
// Adjust last length count to fill out codes, if needed
for(y = 1 << j; j < i; j++, y <<= 1)
if((y -= c[j]) < 0) {
this.status = 2; // bad input: more codes than bits
this.m = mm;
return;
}
if((y -= c[i]) < 0) {
this.status = 2;
this.m = mm;
return;
}
c[i] += y;
// Generate starting offsets into the value table for each length
x[1] = j = 0;
p = c;
pidx = 1;
xp = 2;
while(--i > 0) // note that i == g from above
x[xp++] = (j += p[pidx++]);
// Make a table of values in order of bit lengths
p = b; pidx = 0;
i = 0;
do {
if((j = p[pidx++]) != 0)
v[x[j]++] = i;
} while(++i < n);
n = x[g]; // set n to length of v
// Generate the Huffman codes and for each, make the table entries
x[0] = i = 0; // first Huffman code is zero
p = v; pidx = 0; // grab values in bit order
h = -1; // no tables yet--level -1
w = lx[0] = 0; // no bits decoded yet
q = null; // ditto
z = 0; // ditto
// go through the bit lengths (k already is bits in shortest code)
for(; k <= g; k++) {
a = c[k];
while(a-- > 0) {
// here i is the Huffman code of length k bits for value p[pidx]
// make tables up to required level
while(k > w + lx[1 + h]) {
w += lx[1 + h]; // add bits already decoded
h++;
// compute minimum size table less than or equal to *m bits
z = (z = g - w) > mm ? mm : z; // upper limit
if((f = 1 << (j = k - w)) > a + 1) { // try a k-w bit table
// too few codes for k-w bit table
f -= a + 1; // deduct codes from patterns left
xp = k;
while(++j < z) { // try smaller tables up to z bits
if((f <<= 1) <= c[++xp])
break; // enough codes to use up j bits
f -= c[xp]; // else deduct codes from patterns
}
}
if(w + j > el && w < el)
j = el - w; // make EOB code end at table
z = 1 << j; // table entries for j-bit table
lx[1 + h] = j; // set table size in stack
// allocate and link in new table
q = new Array(z);
for(o = 0; o < z; o++) {
q[o] = new HuftNode();
}
if(tail == null)
tail = this.root = new HuftList();
else
tail = tail.next = new HuftList();
tail.next = null;
tail.list = q;
u[h] = q; // table starts after link
/* connect to last table, if there is one */
if(h > 0) {
x[h] = i; // save pattern for backing up
r.b = lx[h]; // bits to dump before this table
r.e = 16 + j; // bits in this table
r.t = q; // pointer to this table
j = (i & ((1 << w) - 1)) >> (w - lx[h]);
u[h-1][j].e = r.e;
u[h-1][j].b = r.b;
u[h-1][j].n = r.n;
u[h-1][j].t = r.t;
}
}
// set up table entry in r
r.b = k - w;
if(pidx >= n)
r.e = 99; // out of values--invalid code
else if(p[pidx] < s) {
r.e = (p[pidx] < 256 ? 16 : 15); // 256 is end-of-block code
r.n = p[pidx++]; // simple code is just the value
} else {
r.e = e[p[pidx] - s]; // non-simple--look up in lists
r.n = d[p[pidx++] - s];
}
// fill code-like entries with r //
f = 1 << (k - w);
for(j = i >> w; j < z; j += f) {
q[j].e = r.e;
q[j].b = r.b;
q[j].n = r.n;
q[j].t = r.t;
}
// backwards increment the k-bit code i
for(j = 1 << (k - 1); (i & j) != 0; j >>= 1)
i ^= j;
i ^= j;
// backup over finished tables
while((i & ((1 << w) - 1)) != x[h]) {
w -= lx[h]; // don't need to update q
h--;
}
}
}
/* return actual size of base table */
this.m = lx[1];
/* Return true (1) if we were given an incomplete table */
this.status = ((y != 0 && g != 1) ? 1 : 0);
} /* end of constructor */
}
/* routines (inflate) */
function GET_BYTE() {
if(inflate_data.length == inflate_pos)
return -1;
return bops.readUInt8(inflate_data, inflate_pos++);
}
function NEEDBITS(n) {
while(bit_len < n) {
bit_buf |= GET_BYTE() << bit_len;
bit_len += 8;
}
}
function GETBITS(n) {
return bit_buf & MASK_BITS[n];
}
function DUMPBITS(n) {
bit_buf >>= n;
bit_len -= n;
}
function inflate_codes(buff, off, size) {
/* inflate (decompress) the codes in a deflated (compressed) block.
Return an error code or zero if it all goes ok. */
var e; // table entry flag/number of extra bits
var t; // (HuftNode) pointer to table entry
var n;
if(size == 0)
return 0;
// inflate the coded data
n = 0;
for(;;) { // do until end of block
NEEDBITS(bl);
t = tl.list[GETBITS(bl)];
e = t.e;
while(e > 16) {
if(e == 99)
return -1;
DUMPBITS(t.b);
e -= 16;
NEEDBITS(e);
t = t.t[GETBITS(e)];
e = t.e;
}
DUMPBITS(t.b);
if(e == 16) { // then it's a literal
wp &= WSIZE - 1;
buff[off + n++] = slide[wp++] = t.n;
if(n == size)
return size;
continue;
}
// exit if end of block
if(e == 15)
break;
// it's an EOB or a length
// get length of block to copy
NEEDBITS(e);
copy_leng = t.n + GETBITS(e);
DUMPBITS(e);
// decode distance of block to copy
NEEDBITS(bd);
t = td.list[GETBITS(bd)];
e = t.e;
while(e > 16) {
if(e == 99)
return -1;
DUMPBITS(t.b);
e -= 16;
NEEDBITS(e);
t = t.t[GETBITS(e)];
e = t.e;
}
DUMPBITS(t.b);
NEEDBITS(e);
copy_dist = wp - t.n - GETBITS(e);
DUMPBITS(e);
// do the copy
while(copy_leng > 0 && n < size) {
copy_leng--;
copy_dist &= WSIZE - 1;
wp &= WSIZE - 1;
buff[off + n++] = slide[wp++]
= slide[copy_dist++];
}
if(n == size)
return size;
}
method = -1; // done
return n;
}
function inflate_stored(buff, off, size) {
/* "decompress" an inflated type 0 (stored) block. */
var n;
// go to byte boundary
n = bit_len & 7;
DUMPBITS(n);
// get the length and its complement
NEEDBITS(16);
n = GETBITS(16);
DUMPBITS(16);
NEEDBITS(16);
if(n != ((~bit_buf) & 0xffff))
return -1; // error in compressed data
DUMPBITS(16);
// read and output the compressed data
copy_leng = n;
n = 0;
while(copy_leng > 0 && n < size) {
copy_leng--;
wp &= WSIZE - 1;
NEEDBITS(8);
buff[off + n++] = slide[wp++] =
GETBITS(8);
DUMPBITS(8);
}
if(copy_leng == 0)
method = -1; // done
return n;
}
function inflate_fixed(buff, off, size) {
/* decompress an inflated type 1 (fixed Huffman codes) block. We should
either replace this with a custom decoder, or at least precompute the
Huffman tables. */
// if first time, set up tables for fixed blocks
if(fixed_tl == null) {
var i; // temporary variable
var l = new Array(288); // length list for huft_build
var h; // HuftBuild
// literal table
for(i = 0; i < 144; i++)
l[i] = 8;
for(; i < 256; i++)
l[i] = 9;
for(; i < 280; i++)
l[i] = 7;
for(; i < 288; i++) // make a complete, but wrong code set
l[i] = 8;
fixed_bl = 7;
h = new HuftBuild(l, 288, 257, cplens, cplext,
fixed_bl);
if(h.status != 0) {
alert("HufBuild error: "+h.status);
return -1;
}
fixed_tl = h.root;
fixed_bl = h.m;
// distance table
for(i = 0; i < 30; i++) // make an incomplete code set
l[i] = 5;
var fixed_bd = 5;
h = new HuftBuild(l, 30, 0, cpdist, cpdext, fixed_bd);
if(h.status > 1) {
fixed_tl = null;
alert("HufBuild error: "+h.status);
return -1;
}
fixed_td = h.root;
fixed_bd = h.m;
}
tl = fixed_tl;
td = fixed_td;
bl = fixed_bl;
bd = fixed_bd;
return inflate_codes(buff, off, size);
}
function inflate_dynamic(buff, off, size) {
// decompress an inflated type 2 (dynamic Huffman codes) block.
var i; // temporary variables
var j;
var l; // last length
var n; // number of lengths to get
var t; // (HuftNode) literal/length code table
var nb; // number of bit length codes
var nl; // number of literal/length codes
var nd; // number of distance codes
var ll = new Array(286+30); // literal/length and distance code lengths
var h; // (HuftBuild)
for(i = 0; i < ll.length; i++)
ll[i] = 0;
// read in table lengths
NEEDBITS(5);
nl = 257 + GETBITS(5); // number of literal/length codes
DUMPBITS(5);
NEEDBITS(5);
nd = 1 + GETBITS(5); // number of distance codes
DUMPBITS(5);
NEEDBITS(4);
nb = 4 + GETBITS(4); // number of bit length codes
DUMPBITS(4);
if(nl > 286 || nd > 30)
return -1; // bad lengths
// read in bit-length-code lengths
for(j = 0; j < nb; j++)
{
NEEDBITS(3);
ll[border[j]] = GETBITS(3);
DUMPBITS(3);
}
for(; j < 19; j++)
ll[border[j]] = 0;
// build decoding table for trees--single level, 7 bit lookup
bl = 7;
h = new HuftBuild(ll, 19, 19, null, null, bl);
if(h.status != 0)
return -1; // incomplete code set
tl = h.root;
bl = h.m;
// read in literal and distance code lengths
n = nl + nd;
i = l = 0;
while(i < n) {
NEEDBITS(bl);
t = tl.list[GETBITS(bl)];
j = t.b;
DUMPBITS(j);
j = t.n;
if(j < 16) // length of code in bits (0..15)
ll[i++] = l = j; // save last length in l
else if(j == 16) { // repeat last length 3 to 6 times
NEEDBITS(2);
j = 3 + GETBITS(2);
DUMPBITS(2);
if(i + j > n)
return -1;
while(j-- > 0)
ll[i++] = l;
} else if(j == 17) { // 3 to 10 zero length codes
NEEDBITS(3);
j = 3 + GETBITS(3);
DUMPBITS(3);
if(i + j > n)
return -1;
while(j-- > 0)
ll[i++] = 0;
l = 0;
} else { // j == 18: 11 to 138 zero length codes
NEEDBITS(7);
j = 11 + GETBITS(7);
DUMPBITS(7);
if(i + j > n)
return -1;
while(j-- > 0)
ll[i++] = 0;
l = 0;
}
}
// build the decoding tables for literal/length and distance codes
bl = lbits;
h = new HuftBuild(ll, nl, 257, cplens, cplext, bl);
if(bl == 0) // no literals or lengths
h.status = 1;
if(h.status != 0) {
if(h.status == 1)
;// **incomplete literal tree**
return -1; // incomplete code set
}
tl = h.root;
bl = h.m;
for(i = 0; i < nd; i++)
ll[i] = ll[i + nl];
bd = dbits;
h = new HuftBuild(ll, nd, 0, cpdist, cpdext, bd);
td = h.root;
bd = h.m;
if(bd == 0 && nl > 257) { // lengths but no distances
// **incomplete distance tree**
return -1;
}
if(h.status == 1) {
;// **incomplete distance tree**
}
if(h.status != 0)
return -1;
// decompress until an end-of-block code
return inflate_codes(buff, off, size);
}
function inflate_start() {
var i;
if(slide == null)
slide = new Array(2 * WSIZE);
wp = 0;
bit_buf = 0;
bit_len = 0;
method = -1;
eof = false;
copy_leng = copy_dist = 0;
tl = null;
}
function inflate_internal(buff, off, size) {
// decompress an inflated entry
var n, i;
n = 0;
while(n < size) {
if(eof && method == -1)
return n;
if(copy_leng > 0) {
if(method != STORED_BLOCK) {
// STATIC_TREES or DYN_TREES
while(copy_leng > 0 && n < size) {
copy_leng--;
copy_dist &= WSIZE - 1;
wp &= WSIZE - 1;
buff[off + n++] = slide[wp++] =
slide[copy_dist++];
}
} else {
while(copy_leng > 0 && n < size) {
copy_leng--;
wp &= WSIZE - 1;
NEEDBITS(8);
buff[off + n++] = slide[wp++] = GETBITS(8);
DUMPBITS(8);
}
if(copy_leng == 0)
method = -1; // done
}
if(n == size)
return n;
}
if(method == -1) {
if(eof)
break;
// read in last block bit
NEEDBITS(1);
if(GETBITS(1) != 0)
eof = true;
DUMPBITS(1);
// read in block type
NEEDBITS(2);
method = GETBITS(2);
DUMPBITS(2);
tl = null;
copy_leng = 0;
}
switch(method) {
case 0: // STORED_BLOCK
i = inflate_stored(buff, off + n, size - n);
break;
case 1: // STATIC_TREES
if(tl != null)
i = inflate_codes(buff, off + n, size - n);
else
i = inflate_fixed(buff, off + n, size - n);
break;
case 2: // DYN_TREES
if(tl != null)
i = inflate_codes(buff, off + n, size - n);
else
i = inflate_dynamic(buff, off + n, size - n);
break;
default: // error
i = -1;
break;
}
if(i == -1) {
if(eof)
return 0;
return -1;
}
n += i;
}
return n;
}
var inflate = function (bytes) {
var out, buff;
var i, j;
inflate_start();
inflate_data = bytes;
inflate_pos = 0;
buff = new Array(1024);
out = new BufferIO(); // XXX TODO
while((i = inflate_internal(buff, 0, buff.length)) > 0) {
out.write(buff.slice(0, i)); // XXX TODO
}
inflate_data = undefined; // G.C.
return out.toBuffer();
}
return inflate(input);
};