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Switch to a single "code stack".

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This commit is contained in:
Brendan Dahl 2011-12-29 13:41:54 -08:00
parent 2e82588145
commit 20dace0513
2 changed files with 34 additions and 49 deletions
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54
src/function.js
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@ -360,7 +360,7 @@ var PDFFunction = (function PDFFunctionClosure() {
var range = IR[2];
var code = IR[3];
var numOutputs = range.length / 2;
var evaluator = new PostScriptEvaluator(code[0], code[1]);
var evaluator = new PostScriptEvaluator(code);
// Cache the values for a big speed up, the cache size is limited though
// since the number of possible values can be huge from a PS function.
var cache = new FunctionCache();
@ -393,6 +393,8 @@ var PDFFunction = (function PDFFunctionClosure() {
})();
var FunctionCache = (function FunctionCache() {
// Of 10 PDF's with type4 functions the maxium number of distinct values seen
// was 256. This still may need some tweaking in the future though.
var MAX_CACHE_SIZE = 1024;
function FunctionCache() {
this.cache = {};
@ -441,8 +443,8 @@ var PostScriptStack = (function PostScriptStack() {
index: function index(n) {
this.push(this.stack[this.stack.length - n - 1]);
},
// rotate the last n stack elements p times
roll: function roll(n, p) {
// rotate the last n stack elements p times
var a = this.stack.splice(this.stack.length - n, n);
// algorithm from http://jsfromhell.com/array/rotate
var l = a.length, p = (Math.abs(p) >= l && (p %= l),
@ -464,27 +466,26 @@ var PostScriptEvaluator = (function PostScriptEvaluator() {
var stack = new PostScriptStack(initialStack);
var counter = 0;
var operators = this.operators;
var operands = this.operands;
var length = operators.length;
var a, b, operand;
var operator, a, b;
while (counter < length) {
var operator = operators[counter];
++counter;
operator = operators[counter++];
if (typeof operator == 'number') {
// Operator is really an operand and should be pushed to the stack.
stack.push(operator);
continue;
}
switch (operator) {
// non standard ps operators
case 'push':
operand = operands[counter - 1];
stack.push(operand);
break;
case 'jz': // jump if false
operand = operands[counter - 1];
b = stack.pop();
a = stack.pop();
if (!a)
counter = operand;
counter = b;
break;
case 'j': // jump
operand = operands[counter - 1];
counter = operand;
a = stack.pop();
counter = a;
break;
// all ps operators in alphabetical order (excluding if/ifelse)
@ -696,7 +697,6 @@ var PostScriptParser = (function PostScriptParser() {
function PostScriptParser(lexer) {
this.lexer = lexer;
this.operators = [];
this.operands = [];
this.token;
this.prev;
}
@ -723,16 +723,14 @@ var PostScriptParser = (function PostScriptParser() {
this.expect(PostScriptTokenTypes.LBRACE);
this.parseBlock();
this.expect(PostScriptTokenTypes.RBRACE);
return [this.operators, this.operands];
return this.operators;
},
parseBlock: function parseBlock() {
while (true) {
if (this.accept(PostScriptTokenTypes.NUMBER)) {
this.operators.push('push');
this.operands.push(this.prev.value);
this.operators.push(this.prev.value);
} else if (this.accept(PostScriptTokenTypes.OPERATOR)) {
this.operators.push(this.prev.value);
this.operands.push(null);
} else if (this.accept(PostScriptTokenTypes.LBRACE)) {
this.parseCondition();
} else {
@ -743,31 +741,29 @@ var PostScriptParser = (function PostScriptParser() {
parseCondition: function parseCondition() {
// Add two place holders that will be updated later
var conditionLocation = this.operators.length;
this.operators.push(null);
this.operands.push(null);
this.operators.push(null, null);
this.parseBlock();
this.expect(PostScriptTokenTypes.RBRACE);
if (this.accept(PostScriptTokenTypes.IF)) {
// The true block is right after the 'if' so it just falls through on
// true else it jumps and skips the true block.
this.operators[conditionLocation] = 'jz';
this.operands[conditionLocation] = this.operators.length;
this.operators[conditionLocation] = this.operators.length;
this.operators[conditionLocation + 1] = 'jz';
} else if (this.accept(PostScriptTokenTypes.LBRACE)) {
var jumpLocation = this.operators.length;
this.operators.push(null);
this.operands.push(null);
this.operators.push(null, null);
var endOfTrue = this.operators.length;
this.parseBlock();
this.expect(PostScriptTokenTypes.RBRACE);
this.expect(PostScriptTokenTypes.IFELSE);
// The jump is added at the end of the true block to skip the false
// block.
this.operators[jumpLocation] = 'j';
this.operands[jumpLocation] = this.operands.length;
this.operators[jumpLocation] = this.operators.length;
this.operators[jumpLocation + 1] = 'j';
this.operators[conditionLocation] = 'jz';
this.operands[conditionLocation] = endOfTrue;
this.operators[conditionLocation] = endOfTrue;
this.operators[conditionLocation + 1] = 'jz';
} else {
error('PS Function: error parsing conditional.');
}