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Selective node splitting. #4

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Selective node splitting. #4

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25 changes: 21 additions & 4 deletions libs/lz-string.js
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ var LZString = (function () {
streamDataPosition,
streamBitsPerChar,
streamGetCharFromInt,
breakCode=44,
reverseDict = {},
base = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+",
Base64CharArray = (base + "/=").split(''),
Expand Down Expand Up @@ -61,7 +62,8 @@ var LZString = (function () {
node = _node(3), // first node will always be initialised like this.
nextNode,
dictSize = 3,
numBitsMask = 0b100;
numBitsMask = 0b100,
forceBreak=true;

if (uncompressed.length) {
// If there is a string, the first charCode is guaranteed to
Expand All @@ -87,8 +89,16 @@ var LZString = (function () {

for (j = 1; j < uncompressed.length; j++) {
c = uncompressed.charCodeAt(j);
// does the new charCode match an existing prefix?
nextNode = node.d[c];

// split Node at defined split symbol (do not split if the node starts with the symbol)
if (c===breakCode && forceBreak) {
nextNode=false;
forceBreak=false;
} else {
// does the new charCode match an existing prefix?
nextNode = node.d[c];
}

if (nextNode) {
// continue with next prefix
node = nextNode;
Expand All @@ -100,6 +110,11 @@ var LZString = (function () {
// Then we set node to the root node matching
// the charCode.

// mark the node if it starts not with the split symbol
if (c!==breakCode) {
forceBreak=true;
}

if (freshNode) {
// Prefix is a freshly added character token,
// which was already written to the bitstream
Expand Down Expand Up @@ -369,7 +384,9 @@ var LZString = (function () {
return _decompress(compressed.length, 16, function (index) { return compressed.charCodeAt(index); });
},

decompressFromArray: _decompressFromArray
decompressFromArray: _decompressFromArray,
setBreakCode: function (a) { breakCode=a; },
getBreakCode: function () { return breakCode; }
};
})();

Expand Down