mirror of
https://github.com/zen-browser/pdf.js.git
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370 lines
12 KiB
JavaScript
370 lines
12 KiB
JavaScript
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var Type1Parser = function(aAsciiStream, aBinaryStream) {
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var lexer = new Lexer(aAsciiStream);
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// Turn on this flag for additional debugging logs
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var debug = false;
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var dump = function(aData) {
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if (debug)
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log(aData);
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};
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/*
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* Decrypt a Sequence of Ciphertext Bytes to Produce the Original Sequence
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* of Plaintext Bytes. The function took a key as a parameter which can be
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* for decrypting the eexec block of for decoding charStrings.
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*/
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var kEexecEncryptionKey = 55665;
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var kCharStringsEncryptionKey = 4330;
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function decrypt(aStream, aKey, aDiscardNumber) {
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var r = aKey, c1 = 52845, c2 = 22719;
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var decryptedString = [];
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var value = "";
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var count = aStream.length;
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for (var i = 0; i < count; i++) {
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value = aStream.getByte();
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decryptedString[i] = String.fromCharCode(value ^ (r >> 8));
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r = ((value + r) * c1 + c2) & ((1 << 16) - 1);
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}
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return decryptedString.slice(aDiscardNumber);
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}
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/*
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* CharStrings are encoded following the the CharString Encoding sequence
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* describe in Chapter 6 of the "Adobe Type1 Font Format" specification.
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* The value in a byte indicates a command, a number, or subsequent bytes
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* that are to be interpreted in a special way.
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*
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* CharString Number Encoding:
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* A CharString byte containing the values from 32 through 255 inclusive
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* indicate an integer. These values are decoded in four ranges.
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*
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* 1. A CharString byte containing a value, v, between 32 and 246 inclusive,
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* indicate the integer v - 139. Thus, the integer values from -107 through
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* 107 inclusive may be encoded in single byte.
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*
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* 2. A CharString byte containing a value, v, between 247 and 250 inclusive,
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* indicates an integer involving the next byte, w, according to the formula:
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* [(v - 247) x 256] + w + 108
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*
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* 3. A CharString byte containing a value, v, between 251 and 254 inclusive,
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* indicates an integer involving the next byte, w, according to the formula:
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* -[(v - 251) * 256] - w - 108
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*
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* 4. A CharString containing the value 255 indicates that the next 4 bytes
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* are a two complement signed integer. The first of these bytes contains the
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* highest order bits, the second byte contains the next higher order bits
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* and the fourth byte contain the lowest order bits.
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*
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*
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* CharString Command Encoding:
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* CharStrings commands are encoded in 1 or 2 bytes.
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*
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* Single byte commands are encoded in 1 byte that contains a value between
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* 0 and 31 inclusive.
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* If a command byte contains the value 12, then the value in the next byte
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* indicates a command. This "escape" mechanism allows many extra commands
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* to be encoded and this encoding technique helps to minimize the length of
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* the charStrings.
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*/
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function decodeCharString(aStream) {
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var charString = [];
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var cmd = {
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"1": "hstem",
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"3": "vstem",
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"4": "vmoveto",
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"5": "rlineto",
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"6": "hlineto",
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"7": "vlineto",
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"8": "rrcurveto",
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"9": "closepath",
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"10": "callsubr",
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"11": "return",
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"12": {
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"0": "dotsection",
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"1": "vstem3",
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"3": "hstem3",
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"6": "seac",
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"7": "sbw",
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"12": "div",
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"16": "callothersubr",
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"17": "pop",
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"33": "setcurrentpoint"
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},
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"13": "hsbw",
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"14": "endchar",
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"21": "rmoveto",
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"22": "hmoveto",
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"30": "vhcurveto",
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"31": "hcurveto"
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}
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var value = "";
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var count = aStream.length;
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for (var i = 0; i < count; i++) {
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value = aStream.getByte();
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if (value < 0) {
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continue;
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} else if (value < 32) {
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if (value == 12) {
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value = cmd["12"][aStream.getByte()];
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count++;
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} else {
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value = cmd[value];
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}
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} else if (value <= 246) {
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value = parseInt(value) - 139;
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} else if (value <= 250) {
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value = ((value - 247) * 256) + parseInt(aStream.getByte()) + 108;
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count++;
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} else if (value <= 254) {
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value = -((value - 251) * 256) - parseInt(aStream.getByte()) - 108;
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count++;
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} else {
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error("Two complement signed integers are ignored for the moment");
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}
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charString.push(value);
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}
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return charString;
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}
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/*
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* The operand stack holds arbitrary PostScript objects that are the operands
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* and results of PostScript operators being executed. The interpreter pushes
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* objects on the operand stack when it encounters them as literal data in a
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* program being executed. When an operator requires one or more operands, it
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* obtains them by popping them off the top of the operand stack. When an
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* operator returns one or more results, it does so by pushing them on the
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* operand stack.
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*/
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var operandStack = {
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__innerStack__: [],
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push: function(aOperand) {
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this.__innerStack__.push(aOperand);
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},
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pop: function() {
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return this.__innerStack__.pop();
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},
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peek: function() {
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return this.__innerStack__[this.__innerStack__.length - 1];
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},
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get length() {
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return this.__innerStack__.length;
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}
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};
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// Flag indicating if the topmost operand of the operandStack is an array
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var operandIsArray = 0;
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/*
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* The dictionary stack holds only dictionary objects. The current set of
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* dictionaries on the dictionary stack defines the environment for all
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* implicit name searches, such as those that occur when the interpreter
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* encounters an executable name. The role of the dictionary stack is
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* introduced in Section 3.3, “Data Types and Objects,” and is further
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* explained in Section 3.5, “Execution.” of the PostScript Language
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* Reference.
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*/
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var systemDict = new Dict(),
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globalDict = new Dict(),
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userDict = new Dict();
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var dictionaryStack = {
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__innerStack__: [systemDict, globalDict],
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push: function(aDictionary) {
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this.__innerStack__.push(aDictionary);
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},
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pop: function() {
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if (this.__innerStack__.length == 2)
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return null;
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return this.__innerStack__.pop();
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},
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peek: function() {
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return this.__innerStack__[this.__innerStack__.length - 1];
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},
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get length() {
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return this.__innerStack__.length;
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}
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}
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/*
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* The execution stack holds executable objects (mainly procedures and files)
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* that are in intermediate stages of execution. At any point in the
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* execution of a PostScript program, this stack represents the program’s
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* call stack. Whenever the interpreter suspends execution of an object to
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* execute some other object, it pushes the new object on the execution
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* stack. When the interpreter finishes executing an object, it pops that
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* object off the execution stack and resumes executing the suspended object
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* beneath it.
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*/
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var executionStack = [];
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/*
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* Parse a font file from the first segment to the last assuming the eexec
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* block is binary data.
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*
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* The method thrown an error if it encounters an unknown token.
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*/
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this.getObj = function() {
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var obj = lexer.getObj();
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if (operandIsArray && !IsCmd(obj, "{") && !IsCmd(obj, "[") &&
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!IsCmd(obj, "}") && !IsCmd(obj, "]")) {
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operandStack.peek().push(obj);
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this.getObj();
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} else if (IsCmd(obj, "{") || IsCmd(obj, "[")) {
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dump("Start Array: " + obj);
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operandStack.push([]);
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operandIsArray++;
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this.getObj();
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} else if (IsCmd(obj, "}") || IsCmd(obj, "]")) {
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dump("End Array: " + obj);
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operandIsArray--;
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this.getObj();
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} else if (IsBool(obj) || IsInt(obj) || IsNum(obj) || IsString(obj)) {
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//dump("Value: " + obj);
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operandStack.push(obj);
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this.getObj();
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} else if (IsCmd(obj, "dup")) {
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dump("Duplicate");
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operandStack.push(operandStack.peek());
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this.getObj();
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} else if (IsCmd(obj, "currentdict")) {
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dump("currentdict");
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operandStack.push(dictionaryStack.peek());
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this.getObj();
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} else if (IsCmd(obj, "systemdict")) {
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dump("systemdict");
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operandStack.push(systemDict);
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this.getObj();
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} else if (IsCmd(obj, "readonly") || IsCmd(obj, "executeonly") ||
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IsCmd(obj, "currentfile") || IsCmd(obj, "NP")) {
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// Do nothing for the moment
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this.getObj();
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} else if (IsName(obj)) {
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//dump("Name: " + obj.name);
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operandStack.push(obj.name);
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this.getObj();
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} else if (IsCmd(obj, "dict")) {
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dump("Dict: " + obj);
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var size = operandStack.pop();
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var dict = new Dict(size);
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operandStack.push(dict);
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this.getObj();
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} else if (IsCmd(obj, "begin")) {
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dump("begin a dictionary");
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dictionaryStack.push(operandStack.pop());
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this.getObj();
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} else if (IsCmd(obj, "end")) {
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dump("Ending a dictionary");
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dictionaryStack.pop();
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this.getObj();
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} else if (IsCmd(obj, "def")) {
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var value = operandStack.pop();
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var key = operandStack.pop();
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dump("def: " + key + " = " + value);
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dictionaryStack.peek().set(key, value);
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this.getObj();
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} else if (IsCmd(obj, "eexec")) {
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// All the first segment data has been read, decrypt the second segment
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// and start interpreting it in order to decode it
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var eexecString = decrypt(aBinaryStream, kEexecEncryptionKey, 4).join("");
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lexer = new Lexer(new StringStream(eexecString));
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this.getObj();
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} else if (IsCmd(obj, "known")) {
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dump("known");
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var name = operandStack.pop();
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var dict = operandStack.pop();
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// returns dict.hasKey(name);
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this.getObj();
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} else if (IsCmd(obj, "RD")) {
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dump("RD");
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var size = operandStack.pop();
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var key = operandStack.pop();
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// Add '1' because of the space separator, this is dirty
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var stream = lexer.stream.makeSubStream(lexer.stream.pos + 1, size);
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lexer.stream.skip(size + 1);
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var charString = decrypt(stream, kCharStringsEncryptionKey, 4).join("");
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var charStream = new StringStream(charString);
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// XXX do we want to store that on the top dictionary or somewhere else
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dictionaryStack.peek().set(key, charStream);
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var decodedCharString = decodeCharString(charStream);
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log(decodedCharString);
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this.getObj();
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} else if (IsCmd(obj, "LenIV")) {
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error("LenIV: argh! we need to modify the length of discard characters for charStrings");
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} else if (IsCmd(obj, "closefile")) {
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// End of binary data;
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} else if (IsCmd(obj, "StandardEncoding")) {
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// For some reason the value is considered as a command, maybe it is
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// because of the uppercae 'S'
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operandStack.push(obj.cmd);
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this.getObj();
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} else {
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dump(obj);
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error("Unknow token while parsing font");
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}
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return operandStack.peek();
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}
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};
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var hack = false;
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var Type1Font = function(aFontName, aFontFile) {
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// All Type1 font program should begin with the comment %!
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if (aFontFile.getByte() != 0x25 || aFontFile.getByte() != 0x21)
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error("Invalid file header");
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if (!hack) {
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log(aFontName);
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var ASCIIStream = aFontFile.makeSubStream(0, aFontFile.dict.get("Length1"), aFontFile.dict);
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var binaryStream = aFontFile.makeSubStream(aFontFile.dict.get("Length1"), aFontFile.dict.get("Length2"), aFontFile.dict);
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this.parser = new Type1Parser(ASCIIStream, binaryStream);
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var fontDictionary = this.parser.getObj();
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log(fontDictionary + "\t" + "fontInfo: " + fontDictionary.get("FontInfo"));
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hack = true;
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}
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this.info = {};
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this.name = aFontName;
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this.encoding = [];
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this.paintType = 0;
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this.fontType = 0;
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this.fontMatrix = [];
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this.fontBBox = [];
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this.uniqueID = 0;
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this.metrics = {};
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this.strokeWidth = 0.0;
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this.private = {};
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this.charStrings = {}
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this.FID = 0;
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};
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