50 lines
910 B
JavaScript
50 lines
910 B
JavaScript
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function Decoder(input) {
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this.input = atob(input);
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this.cache = 0;
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this.size = 0;
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}
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Decoder.prototype.pop = function() {
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if(this.size < 1) {
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if(this.input.length < 1) {
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return null;
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} else {
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this.cache = this.input.charCodeAt(0);
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this.size = 8;
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this.input = this.input.slice(1);
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}
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}
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this.size--;
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var wasFirstBitOne = this.cache > 0x7f;
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this.cache = (2*this.cache) & 0xff;
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return wasFirstBitOne ? 1 : 0;
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};
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Decoder.prototype.variableLength3 = function() {
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if(this.pop() == 1) {
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return this.pop() + 1;
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} else {
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return 0;
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}
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};
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Decoder.prototype.variableLength6 = function() {
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if(this.pop() == 1) {
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return 2 + this.int(2);
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} else {
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return this.pop();
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}
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};
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Decoder.prototype.int = function(size) {
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var result = 0;
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for(var i = 0; i < size; i++) {
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result = 2*result + this.pop();
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}
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return result;
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};
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return {
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make: function(input) {return new Decoder(input);}
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};
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