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ucnv/googlitch_maps.user.js

Created August 10, 2009 11:42
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googlitch_maps.user.js
// ==UserScript==
// @name Googlitch Maps
// @namespace http://userscripts.org/users/ucnv
// @description crushes the Google Maps
// @include http://maps.google.tld/*
// ==/UserScript==
// This script is based on GlitchMonkey <http://github.com/youpy/glitchmonkey>
document.addEventListener('DOMAttrModified', glitch, false);
var Corruptions = {
'image/jpeg': function() {
return this.replace(/9/g, function(x) { return parseInt(x) + 1 });
},
'image/png': function() {
var dice = function() {
var x = ["\x99", "\xaa", "\xbb", "\xcc"];
return x[Math.floor(Math.random() * 4)] + x[Math.floor(Math.random() * 4)];
};
var png = new PNG(this);
png.decompressed = png.decompressed.replace(/[\x33\x55]/g, dice());
return png.output();
}
};
function glitch(e) {
if(e.target.tagName != 'IMG' || e.attrName != 'src' || e.newValue.length > 100) return;
var element = e.target;
var imgurl = e.newValue;
if(imgurl.indexOf('v=') + imgurl.indexOf('x=') + imgurl.indexOf('y=') < 0) return;
setTimeout(function() {
GM_xmlhttpRequest({
method: "GET",
overrideMimeType: "text/plain; charset=x-user-defined",
url: imgurl,
onload: function (res) {
for(var type in Corruptions) {
if(! new RegExp(type, 'm').test(res.responseHeaders)) continue;
element.src =
[
'data:',
type,
';base64,',
base64encode(Corruptions[type].apply(res.responseText)),
].join('');
}
}
});
}, 0);
}
function base64encode(data) {
return btoa(data.replace(/[\u0100-\uffff]/g, function(c) {
return String.fromCharCode(c.charCodeAt(0) & 0xff);
}));
}
function PNG() { this.initialize.apply(this, arguments); }
PNG.prototype = {
initialize: function(data) {
this.splitter = 'IDAT';
data = data.split(this.splitter);
this.idat = [];
for(var size, i = 0; i < data.length; i++) {
var d = data[i];
if(size) {
this.idat.push(d.slice(0, size));
if(i == data.length - 1)
this.tail = d.slice(size + 4); // without crc
} else {
this.head = d.slice(0, d.length - 4);
}
size = d.slice(d.length - 4);
size = parseInt(this._toHex(size), 16);
}
this.decompressed = this.inflate(this.idat.join(''));
},
output: function() {
var compressed = this.deflate(this.decompressed);
var size = this._toByte4(compressed.length);
var data = this.splitter + compressed;
data = size + data + this._toByte4(this._crc32(data));
return this.head
+ data
+ this.tail;
},
deflate: function(data) {
var self = this;
var wsize = 1024 * 32;
var cminfo = parseInt((Math.log(wsize) / Math.log(2)) - 8);
var cmf = (cminfo << 4) | 0x8;
var flg = 31 - ((cmf * 256 + 0) % 31); // fdict = 0, flevel = 0
var head = [cmf, flg];
var blocks = new Array(Math.ceil(data.length / wsize));
for(var i = 0; i < blocks.length; i++) {
var b = data.slice(i * wsize, (i + 1) * wsize);
var c = new Array(5);
c[0] = (i == blocks.length - 1) ? 1 : 0;
var blockLength = b.length;
var blockLengthComp = (~blockLength & 0xffff);
c[1] = blockLength & 0xff;
c[2] = (blockLength & 0xff00) >> 8;
c[3] = blockLengthComp & 0xff;
c[4] = (blockLengthComp & 0xff00) >> 8;
blocks[i] = self._packBytes(c) + b;
}
var checksum = this._adler32(data);
data = this._packBytes(head) + blocks.join('');
return data + this._toByte4(checksum);
},
inflate: function(data) {
var cmf = data.charCodeAt(0);
var flg = data.charCodeAt(1);
var b = data.slice(2, data.length - 4);
return Z.inflate(b);
},
_toHex: function(data) {
data = this._toByteArray(data);
data = data.map(function(e) {
return ((e < 16) ? '0' : '') + e.toString(16);
});
return data.join('');
},
_toByteArray: function(data) {
data = data.replace(/[\u0100-\uffff]/g, function(c) {
return String.fromCharCode(c.charCodeAt(0) & 0xff);
});
for(var bytes = new Array(data.length), i = 0; i < data.length; ++i) {
bytes[i] = data.charCodeAt(i);
}
return bytes;
},
_packBytes: function(bytes) {
for(var i = 0; i < bytes.length; i++) {
bytes[i] = String.fromCharCode(bytes[i]);
}
return bytes.join("");
},
_toByte4: function(data) {
return String.fromCharCode(
(data >> 24) & 255,
(data >> 16) & 255,
(data >> 8) & 255,
data & 255
);
},
_adler32: function(data) {
var adler = 1, base = 65521;
data = this._toByteArray(data);
var s1 = adler & 0xffff;
var s2 = (adler >> 16) & 0xffff;
for(var n = 0; n < data.length; n++) {
s1 = (s1 + data[n]) % base;
s2 = (s2 + s1) % base;
}
return ((s2>>>0) << 16) + (s1>>>0) >>> 0;
},
_crc32: function(data) {
var c = 0xffffffff;
for(var n = 0; n < data.length; n++) {
c = this._crc32table[(c ^ data.charCodeAt(n)) & 0xff] ^ (c >>> 8);
}
return c ^ 0xffffffff;
},
_crc32table: [
0x0, 0x77073096, 0xee0e612c, 0x990951ba, 0x76dc419, 0x706af48f,
0xe963a535, 0x9e6495a3, 0xedb8832, 0x79dcb8a4, 0xe0d5e91e,
0x97d2d988, 0x9b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d,
0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0,
0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63,
0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa,
0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75,
0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, 0xc8d75180,
0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87,
0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x1db7106,
0x98d220bc, 0xefd5102a, 0x71b18589, 0x6b6b51f, 0x9fbfe4a5,
0xe8b8d433, 0x7807c9a2, 0xf00f934, 0x9609a88e, 0xe10e9818,
0x7f6a0dbb, 0x86d3d2d, 0x91646c97, 0xe6635c01, 0x6b6b51f4,
0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b,
0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea,
0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541,
0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc,
0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f,
0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, 0x5edef90e,
0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x3b6e20c,
0x74b1d29a, 0xead54739, 0x9dd277af, 0x4db2615, 0x73dc1683,
0xe3630b12, 0x94643b84, 0xd6d6a3e, 0x7a6a5aa8, 0xe40ecf0b,
0x9309ff9d, 0xa00ae27, 0x7d079eb1, 0xf00f9344, 0x8708a3d2,
0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671,
0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8,
0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767,
0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, 0x36034af6,
0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795,
0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b,
0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x26d930a,
0x9c0906a9, 0xeb0e363f, 0x72076785, 0x5005713, 0x95bf4a82,
0xe2b87a14, 0x7bb12bae, 0xcb61b38, 0x92d28e9b, 0xe5d5be0d,
0x7cdcefb7, 0xbdbdf21, 0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8,
0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff,
0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee,
0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d,
0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c,
0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02,
0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
]
};
// following codes are based on http://www.onicos.com/staff/iz/amuse/javascript/expert/inflate.txt
var Z = {
DECODE_STORED_BLOCK : 0,
DECODE_STATIC_TREES : 1,
DECODE_DYN_TREES : 2,
// Tables for deflate from PKZIP's appnote.txt.
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. */
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
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],
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],
BL_ORDER: [ // 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],
inflate: function(data) {
return new Z.Inflater().inflate(data);
}
};
Z.IO = function() { this.initialize.apply(this, arguments); };
Z.IO.prototype = {
MASK_BITS: [
0x0000,
0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
],
initialize: function(data) {
this.input = {
data: data,
pos: 0,
length: 0, // bits in bit buffer
buffer: 0, // bit buffer
};
this.output = {
copyLen: 0,
copyDist: 0,
pos: 0,
data: ''
};
},
getByte: function() {
if(this.input.data.length == this.input.pos) return -1;
return this.input.data.charCodeAt(this.input.pos++) & 0xff;
},
needBits: function(n) {
while(this.input.length < n) {
this.input.buffer |= this.getByte() << this.input.length;
this.input.length += 8;
}
},
getBits: function(n) {
return this.input.buffer & this.MASK_BITS[n];
},
dumpBits: function(n) {
this.input.buffer >>= n;
this.input.length -= n;
},
writeStored: function(len) {
this.output.copyLen = len;
var s = this.input.data.substr(this.input.pos, len);
this.output.data += s;
this.needBits(8 * len);
this.dumpBits(8 * len);
while(this.output.copyLen > 0) {
this.output.copyLen--;
this.output.pos++;
}
return len;
},
write: function(b) {
this.output.pos++;
this.output.data += String.fromCharCode(b);
return 1;
},
repeat: function(len, dist) {
this.output.copyLen = len;
this.output.copyDist = dist;
var w = this.output.pos - this.output.copyDist;
var l = parseInt(this.output.copyLen / w);
var r = this.output.copyLen % w;
for(var i = 0; i < l; i++) {
var s = this.output.data.substr(this.output.copyDist, w);
this.output.copyDist += w;
this.output.data += s;
}
var s = this.output.data.substr(this.output.copyDist, r);
this.output.copyDist += r;
this.output.data += s;
this.output.pos += this.output.copyLen;
this.output.copyLen = 0;
return len;
},
close: function() {
this.input.data = null;
this.output.data = null;
}
};
Z.HuffmanTree = function() { this.initialize.apply(this, arguments); };
Z.HuffmanTree.prototype = {
initialize: function(
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; // 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; // (this.newNode) points to current table
var r = this.newNode(); // table entry for structure assignment
var u = new Array(this.BMAX); // this.newNode[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;
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] = this.newNode();
}
if(tail == null)
tail = this.root = this.newList();
else
tail = tail.next = this.newList();
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 */
},
newList: function() {
return {
next: null,
list: null
};
},
newNode: function() {
return {
e: 0, // number of extra bits or operation
b: 0, // number of bits in this code or subcode
// union
n: 0, // literal, length base, or distance base
t: null // (node) pointer to next level of table
};
}
};
Z.Inflater = function() { this.initialize.apply(this, arguments); };
Z.Inflater.prototype = {
initialize: function() {
this.method = -1;
this.eof = false;
this.tl = this.td = null; // literal/length and distance decoder tables
this.bl = this.bd = null; // number of bits decoded by tl and td
},
inflate: function(data) {
var io = new Z.IO(data);
try {
var i;
while((i = this._decode(io)) > 0) ;
return io.output.data;
} finally {
io.close();
}
},
_decode: function(io) {
// decompress an inflated entry
var size = io.input.data.length;
var i;
var n = 0;
while(n < size) {
if(this.eof && this.method == -1) return n;
if(io.output.copyLen > 0) {
if(this.method != Z.DECODE_STORED_BLOCK) {
// DECODE_STATIC_TREES or DECODE_DYN_TREES
n += io.repeat(io.output.copyLen, io.output.copyDist);
} else {
n += io.writeStored(io.output.copyLen);
if(this. io.output.copyLen == 0) this.method = -1; // done
}
if(n == size) return n;
}
if(this.method == -1) {
if(this.eof) break;
// read in last block bit
io.needBits(1);
if(io.getBits(1) != 0) this.eof = true;
io.dumpBits(1);
// read in block type
io.needBits(2);
this.method = io.getBits(2);
io.dumpBits(2);
this.tl = null;
io.output.copyLen = 0;
}
switch(this.method) {
case Z.DECODE_STORED_BLOCK:
i = this._decodeStored(io, n, size - n);
break;
case Z.DECODE_STATIC_TREES:
if(this.tl != null)
i = this._decodeCodes(io, n, size - n);
else
i = this._decodeFixed(io, n, size - n);
break;
case Z.DECODE_DYN_TREES:
if(this.tl != null)
i = this._decodeCodes(io, n, size - n);
else
i = this._decodeDynamic(io, n, size - n);
break;
default: // error
i = -1;
break;
}
if(i == -1) {
if(this.eof) return 0;
return -1;
}
n += i;
}
return n;
},
_decodeCodes: function(io, 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; // pointer to table entry
if(size == 0) return 0;
// inflate the coded data
var n = 0;
for(;;) { // do until end of block
io.needBits(this.bl);
t = this.tl.list[io.getBits(this.bl)];
e = t.e;
while(e > 16) {
if(e == 99) return -1;
io.dumpBits(t.b);
e -= 16;
io.needBits(e);
t = t.t[io.getBits(e)];
e = t.e;
}
io.dumpBits(t.b);
if(e == 16) { // then it's a literal
n += io.write(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
io.needBits(e);
io.output.copyLen = t.n + io.getBits(e);
io.dumpBits(e);
// decode distance of block to copy
io.needBits(this.bd);
t = this.td.list[io.getBits(this.bd)];
e = t.e;
while(e > 16) {
if(e == 99) return -1;
io.dumpBits(t.b);
e -= 16;
io.needBits(e);
t = t.t[io.getBits(e)];
e = t.e;
}
io.dumpBits(t.b);
io.needBits(e);
io.output.copyDist = io.output.pos - t.n - io.getBits(e);
io.dumpBits(e);
// do the copy
n += io.repeat(io.output.copyLen, io.output.copyDist);
if(n == size) return size;
}
this.method = -1; // done
return n;
},
_decodeStored: function(io, off, size) {
/* "decompress" an inflated type 0 (stored) block. */
// go to byte boundary
var n = io.input.length & 7;
io.dumpBits(n);
// get the length and its complement
io.needBits(16);
n = io.getBits(16);
io.dumpBits(16);
io.needBits(16);
if(n != ((~(io.input.buffer)) & 0xffff)) return -1; // error in compressed data
io.dumpBits(16);
// read and output the compressed data
var len = n;
n = 0;
n += io.writeStored(len);
if(io.output.copyLen == 0) this.method = -1; // done
return n;
},
_decodeFixed: function(io, 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. */
var tlFixed = null;
var tdFixed;
var blFixed, bdFixed;
// if first time, set up tables for fixed blocks
if(tlFixed == null) {
// literal table
var i = 0;
for(; i < 144; i++) l[i] = 8;
for(; i < 256; i++) l[i] = 9;
for(; i < 280; i++) l[i] = 7;
for(; i < 288; i++) l[i] = 8; // make a complete, but wrong code set
blFixed = 7;
var h = new Z.HuffmanTree(new Array(288), 288, 257, Z.CPLENS, Z.CPLEXT, blFixed);
if(h.status != 0) {
alert("HuffmanTree error: "+h.status);
return -1;
}
tlFixed = h.root;
blFixed = h.m;
// distance table
for(i = 0; i < 30; i++) // make an incomplete code set
l[i] = 5;
bdFixed = 5;
h = new Z.HuffmanTree(l, 30, 0, Z.CPDIST, Z.CPDEXT, bdFixed);
if(h.status > 1) {
tlFixed = null;
alert("HuffmanTree error: "+h.status);
return -1;
}
tdFixed = h.root;
bdFixed = h.m;
}
this.tl = tlFixed;
this.td = tdFixed;
this.bl = blFixed;
this.bd = bdFixed;
return this._decodeCodes(io, off, size);
},
_decodeDynamic: function(io, 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; // 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; // (Z.HuffmanTree)
var lbits = 9; // bits in base literal/length lookup table
var dbits = 6; // bits in base distance lookup table
for(i = 0; i < ll.length; i++) ll[i] = 0;
// read in table lengths
io.needBits(5);
nl = 257 + io.getBits(5); // number of literal/length codes
io.dumpBits(5);
io.needBits(5);
nd = 1 + io.getBits(5); // number of distance codes
io.dumpBits(5);
io.needBits(4);
nb = 4 + io.getBits(4); // number of bit length codes
io.dumpBits(4);
if(nl > 286 || nd > 30) return -1; // bad lengths
// read in bit-length-code lengths
for(j = 0; j < nb; j++) {
io.needBits(3);
ll[Z.BL_ORDER[j]] = io.getBits(3);
io.dumpBits(3);
}
for(; j < 19; j++) ll[Z.BL_ORDER[j]] = 0;
// build decoding table for trees--single level, 7 bit lookup
this.bl = 7;
h = new Z.HuffmanTree(ll, 19, 19, null, null, this.bl);
if(h.status != 0) return -1; // incomplete code set
this.tl = h.root;
this.bl = h.m;
// read in literal and distance code lengths
n = nl + nd;
i = l = 0;
while(i < n) {
io.needBits(this.bl);
t = this.tl.list[io.getBits(this.bl)];
j = t.b;
io.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
io.needBits(2);
j = 3 + io.getBits(2);
io.dumpBits(2);
if(i + j > n)
return -1;
while(j-- > 0)
ll[i++] = l;
} else if(j == 17) { // 3 to 10 zero length codes
io.needBits(3);
j = 3 + io.getBits(3);
io.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
io.needBits(7);
j = 11 + io.getBits(7);
io.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
this.bl = lbits;
h = new Z.HuffmanTree(ll, nl, 257, Z.CPLENS, Z.CPLEXT, this.bl);
if(this.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
}
this.tl = h.root;
this.bl = h.m;
for(i = 0; i < nd; i++) ll[i] = ll[i + nl];
this.bd = dbits;
h = new Z.HuffmanTree(ll, nd, 0, Z.CPDIST, Z.CPDEXT, this.bd);
this.td = h.root;
this.bd = h.m;
if(this.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 this._decodeCodes(io, off, size);
}
};
@Korb
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Korb commented Apr 10, 2021

What exactly does this script do?

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