var util = require('util'),
Match = require ('../match');
/**
* Binary search implementation (recursive)
*/
function binarySearch(arr, searchValue) {
function find(arr, searchValue, left, right) {
if (right < left)
return -1;
/*
int mid = mid = (left + right) / 2;
There is a bug in the above line;
Joshua Bloch suggests the following replacement:
*/
var mid = Math.floor((left + right) >>> 1);
if (searchValue > arr[mid])
return find(arr, searchValue, mid + 1, right);
if (searchValue < arr[mid])
return find(arr, searchValue, left, mid - 1);
return mid;
};
return find(arr, searchValue, 0, arr.length - 1);
};
// 'Character' iterated character class.
// Recognizers for specific mbcs encodings make their 'characters' available
// by providing a nextChar() function that fills in an instance of iteratedChar
// with the next char from the input.
// The returned characters are not converted to Unicode, but remain as the raw
// bytes (concatenated into an int) from the codepage data.
//
// For Asian charsets, use the raw input rather than the input that has been
// stripped of markup. Detection only considers multi-byte chars, effectively
// stripping markup anyway, and double byte chars do occur in markup too.
//
function IteratedChar() {
this.charValue = 0; // 1-4 bytes from the raw input data
this.index = 0;
this.nextIndex = 0;
this.error = false;
this.done = false;
this.reset = function() {
this.charValue = 0;
this.index = -1;
this.nextIndex = 0;
this.error = false;
this.done = false;
};
this.nextByte = function(det) {
if (this.nextIndex >= det.fRawLength) {
this.done = true;
return -1;
}
var byteValue = det.fRawInput[this.nextIndex++] & 0x00ff;
return byteValue;
};
};
/**
* Asian double or multi-byte - charsets.
* Match is determined mostly by the input data adhering to the
* encoding scheme for the charset, and, optionally,
* frequency-of-occurence of characters.
*/
function mbcs() {};
/**
* Test the match of this charset with the input text data
* which is obtained via the CharsetDetector object.
*
* @param det The CharsetDetector, which contains the input text
* to be checked for being in this charset.
* @return Two values packed into one int (Damn java, anyhow)
* bits 0-7: the match confidence, ranging from 0-100
* bits 8-15: The match reason, an enum-like value.
*/
mbcs.prototype.match = function(det) {
var singleByteCharCount = 0, //TODO Do we really need this?
doubleByteCharCount = 0,
commonCharCount = 0,
badCharCount = 0,
totalCharCount = 0,
confidence = 0;
var iter = new IteratedChar();
detectBlock: {
for (iter.reset(); this.nextChar(iter, det);) {
totalCharCount++;
if (iter.error) {
badCharCount++;
} else {
var cv = iter.charValue & 0xFFFFFFFF;
if (cv <= 0xff) {
singleByteCharCount++;
} else {
doubleByteCharCount++;
if (this.commonChars != null) {
// NOTE: This assumes that there are no 4-byte common chars.
if (binarySearch(this.commonChars, cv) >= 0) {
commonCharCount++;
}
}
}
}
if (badCharCount >= 2 && badCharCount * 5 >= doubleByteCharCount) {
// console.log('its here!')
// Bail out early if the byte data is not matching the encoding scheme.
break detectBlock;
}
}
if (doubleByteCharCount <= 10 && badCharCount== 0) {
// Not many multi-byte chars.
if (doubleByteCharCount == 0 && totalCharCount < 10) {
// There weren't any multibyte sequences, and there was a low density of non-ASCII single bytes.
// We don't have enough data to have any confidence.
// Statistical analysis of single byte non-ASCII charcters would probably help here.
confidence = 0;
}
else {
// ASCII or ISO file? It's probably not our encoding,
// but is not incompatible with our encoding, so don't give it a zero.
confidence = 10;
}
break detectBlock;
}
//
// No match if there are too many characters that don't fit the encoding scheme.
// (should we have zero tolerance for these?)
//
if (doubleByteCharCount < 20 * badCharCount) {
confidence = 0;
break detectBlock;
}
if (this.commonChars == null) {
// We have no statistics on frequently occuring characters.
// Assess confidence purely on having a reasonable number of
// multi-byte characters (the more the better
confidence = 30 + doubleByteCharCount - 20 * badCharCount;
if (confidence > 100) {
confidence = 100;
}
} else {
//
// Frequency of occurence statistics exist.
//
var maxVal = Math.log(parseFloat(doubleByteCharCount) / 4);
var scaleFactor = 90.0 / maxVal;
confidence = Math.floor(Math.log(commonCharCount + 1) * scaleFactor + 10);
confidence = Math.min(confidence, 100);
}
} // end of detectBlock:
return confidence == 0 ? null : new Match(det, this, confidence);
};
/**
* Get the next character (however many bytes it is) from the input data
* Subclasses for specific charset encodings must implement this function
* to get characters according to the rules of their encoding scheme.
*
* This function is not a method of class iteratedChar only because
* that would require a lot of extra derived classes, which is awkward.
* @param it The iteratedChar 'struct' into which the returned char is placed.
* @param det The charset detector, which is needed to get at the input byte data
* being iterated over.
* @return True if a character was returned, false at end of input.
*/
mbcs.prototype.nextChar = function(iter, det) {};
/**
* Shift-JIS charset recognizer.
*/
module.exports.sjis = function() {
this.name = function() {
return 'Shift-JIS';
};
this.language = function() {
return 'ja';
};
// TODO: This set of data comes from the character frequency-
// of-occurence analysis tool. The data needs to be moved
// into a resource and loaded from there.
this.commonChars = [
0x8140, 0x8141, 0x8142, 0x8145, 0x815b, 0x8169, 0x816a, 0x8175, 0x8176, 0x82a0,
0x82a2, 0x82a4, 0x82a9, 0x82aa, 0x82ab, 0x82ad, 0x82af, 0x82b1, 0x82b3, 0x82b5,
0x82b7, 0x82bd, 0x82be, 0x82c1, 0x82c4, 0x82c5, 0x82c6, 0x82c8, 0x82c9, 0x82cc,
0x82cd, 0x82dc, 0x82e0, 0x82e7, 0x82e8, 0x82e9, 0x82ea, 0x82f0, 0x82f1, 0x8341,
0x8343, 0x834e, 0x834f, 0x8358, 0x835e, 0x8362, 0x8367, 0x8375, 0x8376, 0x8389,
0x838a, 0x838b, 0x838d, 0x8393, 0x8e96, 0x93fa, 0x95aa
];
this.nextChar = function(iter, det) {
iter.index = iter.nextIndex;
iter.error = false;
var firstByte;
firstByte = iter.charValue = iter.nextByte(det);
if (firstByte < 0)
return false;
if (firstByte <= 0x7f || (firstByte > 0xa0 && firstByte <= 0xdf))
return true;
var secondByte = iter.nextByte(det);
if (secondByte < 0)
return false;
iter.charValue = (firstByte << 8) | secondByte;
if (! ((secondByte >= 0x40 && secondByte <= 0x7f) || (secondByte >= 0x80 && secondByte <= 0xff))) {
// Illegal second byte value.
iter.error = true;
}
return true;
};
};
util.inherits(module.exports.sjis, mbcs);
/**
* Big5 charset recognizer.
*/
module.exports.big5 = function() {
this.name = function() {
return 'Big5';
};
this.language = function() {
return 'zh';
};
// TODO: This set of data comes from the character frequency-
// of-occurence analysis tool. The data needs to be moved
// into a resource and loaded from there.
this.commonChars = [
0xa140, 0xa141, 0xa142, 0xa143, 0xa147, 0xa149, 0xa175, 0xa176, 0xa440, 0xa446,
0xa447, 0xa448, 0xa451, 0xa454, 0xa457, 0xa464, 0xa46a, 0xa46c, 0xa477, 0xa4a3,
0xa4a4, 0xa4a7, 0xa4c1, 0xa4ce, 0xa4d1, 0xa4df, 0xa4e8, 0xa4fd, 0xa540, 0xa548,
0xa558, 0xa569, 0xa5cd, 0xa5e7, 0xa657, 0xa661, 0xa662, 0xa668, 0xa670, 0xa6a8,
0xa6b3, 0xa6b9, 0xa6d3, 0xa6db, 0xa6e6, 0xa6f2, 0xa740, 0xa751, 0xa759, 0xa7da,
0xa8a3, 0xa8a5, 0xa8ad, 0xa8d1, 0xa8d3, 0xa8e4, 0xa8fc, 0xa9c0, 0xa9d2, 0xa9f3,
0xaa6b, 0xaaba, 0xaabe, 0xaacc, 0xaafc, 0xac47, 0xac4f, 0xacb0, 0xacd2, 0xad59,
0xaec9, 0xafe0, 0xb0ea, 0xb16f, 0xb2b3, 0xb2c4, 0xb36f, 0xb44c, 0xb44e, 0xb54c,
0xb5a5, 0xb5bd, 0xb5d0, 0xb5d8, 0xb671, 0xb7ed, 0xb867, 0xb944, 0xbad8, 0xbb44,
0xbba1, 0xbdd1, 0xc2c4, 0xc3b9, 0xc440, 0xc45f
];
this.nextChar = function(iter, det) {
iter.index = iter.nextIndex;
iter.error = false;
var firstByte = iter.charValue = iter.nextByte(det);
if (firstByte < 0)
return false;
// single byte character.
if (firstByte <= 0x7f || firstByte == 0xff)
return true;
var secondByte = iter.nextByte(det);
if (secondByte < 0)
return false;
iter.charValue = (iter.charValue << 8) | secondByte;
if (secondByte < 0x40 || secondByte == 0x7f || secondByte == 0xff)
iter.error = true;
return true;
};
};
util.inherits(module.exports.big5, mbcs);
/**
* EUC charset recognizers. One abstract class that provides the common function
* for getting the next character according to the EUC encoding scheme,
* and nested derived classes for EUC_KR, EUC_JP, EUC_CN.
*
* Get the next character value for EUC based encodings.
* Character 'value' is simply the raw bytes that make up the character
* packed into an int.
*/
function eucNextChar(iter, det) {
iter.index = iter.nextIndex;
iter.error = false;
var firstByte = 0;
var secondByte = 0;
var thirdByte = 0;
//int fourthByte = 0;
buildChar: {
firstByte = iter.charValue = iter.nextByte(det);
if (firstByte < 0) {
// Ran off the end of the input data
iter.done = true;
break buildChar;
}
if (firstByte <= 0x8d) {
// single byte char
break buildChar;
}
secondByte = iter.nextByte(det);
iter.charValue = (iter.charValue << 8) | secondByte;
if (firstByte >= 0xA1 && firstByte <= 0xfe) {
// Two byte Char
if (secondByte < 0xa1) {
iter.error = true;
}
break buildChar;
}
if (firstByte == 0x8e) {
// Code Set 2.
// In EUC-JP, total char size is 2 bytes, only one byte of actual char value.
// In EUC-TW, total char size is 4 bytes, three bytes contribute to char value.
// We don't know which we've got.
// Treat it like EUC-JP. If the data really was EUC-TW, the following two
// bytes will look like a well formed 2 byte char.
if (secondByte < 0xa1) {
iter.error = true;
}
break buildChar;
}
if (firstByte == 0x8f) {
// Code set 3.
// Three byte total char size, two bytes of actual char value.
thirdByte = iter.nextByte(det);
iter.charValue = (iter.charValue << 8) | thirdByte;
if (thirdByte < 0xa1) {
iter.error = true;
}
}
}
return iter.done == false;
};
/**
* The charset recognize for EUC-JP. A singleton instance of this class
* is created and kept by the public CharsetDetector class
*/
module.exports.euc_jp = function() {
this.name = function() {
return 'EUC-JP';
};
this.language = function() {
return 'ja';
};
// TODO: This set of data comes from the character frequency-
// of-occurence analysis tool. The data needs to be moved
// into a resource and loaded from there.
this.commonChars = [
0xa1a1, 0xa1a2, 0xa1a3, 0xa1a6, 0xa1bc, 0xa1ca, 0xa1cb, 0xa1d6, 0xa1d7, 0xa4a2,
0xa4a4, 0xa4a6, 0xa4a8, 0xa4aa, 0xa4ab, 0xa4ac, 0xa4ad, 0xa4af, 0xa4b1, 0xa4b3,
0xa4b5, 0xa4b7, 0xa4b9, 0xa4bb, 0xa4bd, 0xa4bf, 0xa4c0, 0xa4c1, 0xa4c3, 0xa4c4,
0xa4c6, 0xa4c7, 0xa4c8, 0xa4c9, 0xa4ca, 0xa4cb, 0xa4ce, 0xa4cf, 0xa4d0, 0xa4de,
0xa4df, 0xa4e1, 0xa4e2, 0xa4e4, 0xa4e8, 0xa4e9, 0xa4ea, 0xa4eb, 0xa4ec, 0xa4ef,
0xa4f2, 0xa4f3, 0xa5a2, 0xa5a3, 0xa5a4, 0xa5a6, 0xa5a7, 0xa5aa, 0xa5ad, 0xa5af,
0xa5b0, 0xa5b3, 0xa5b5, 0xa5b7, 0xa5b8, 0xa5b9, 0xa5bf, 0xa5c3, 0xa5c6, 0xa5c7,
0xa5c8, 0xa5c9, 0xa5cb, 0xa5d0, 0xa5d5, 0xa5d6, 0xa5d7, 0xa5de, 0xa5e0, 0xa5e1,
0xa5e5, 0xa5e9, 0xa5ea, 0xa5eb, 0xa5ec, 0xa5ed, 0xa5f3, 0xb8a9, 0xb9d4, 0xbaee,
0xbbc8, 0xbef0, 0xbfb7, 0xc4ea, 0xc6fc, 0xc7bd, 0xcab8, 0xcaf3, 0xcbdc, 0xcdd1
];
this.nextChar = eucNextChar;
};
util.inherits(module.exports.euc_jp, mbcs);
/**
* The charset recognize for EUC-KR. A singleton instance of this class
* is created and kept by the public CharsetDetector class
*/
module.exports.euc_kr = function() {
this.name = function() {
return 'EUC-KR';
};
this.language = function() {
return 'ko';
};
// TODO: This set of data comes from the character frequency-
// of-occurence analysis tool. The data needs to be moved
// into a resource and loaded from there.
this.commonChars = [
0xb0a1, 0xb0b3, 0xb0c5, 0xb0cd, 0xb0d4, 0xb0e6, 0xb0ed, 0xb0f8, 0xb0fa, 0xb0fc,
0xb1b8, 0xb1b9, 0xb1c7, 0xb1d7, 0xb1e2, 0xb3aa, 0xb3bb, 0xb4c2, 0xb4cf, 0xb4d9,
0xb4eb, 0xb5a5, 0xb5b5, 0xb5bf, 0xb5c7, 0xb5e9, 0xb6f3, 0xb7af, 0xb7c2, 0xb7ce,
0xb8a6, 0xb8ae, 0xb8b6, 0xb8b8, 0xb8bb, 0xb8e9, 0xb9ab, 0xb9ae, 0xb9cc, 0xb9ce,
0xb9fd, 0xbab8, 0xbace, 0xbad0, 0xbaf1, 0xbbe7, 0xbbf3, 0xbbfd, 0xbcad, 0xbcba,
0xbcd2, 0xbcf6, 0xbdba, 0xbdc0, 0xbdc3, 0xbdc5, 0xbec6, 0xbec8, 0xbedf, 0xbeee,
0xbef8, 0xbefa, 0xbfa1, 0xbfa9, 0xbfc0, 0xbfe4, 0xbfeb, 0xbfec, 0xbff8, 0xc0a7,
0xc0af, 0xc0b8, 0xc0ba, 0xc0bb, 0xc0bd, 0xc0c7, 0xc0cc, 0xc0ce, 0xc0cf, 0xc0d6,
0xc0da, 0xc0e5, 0xc0fb, 0xc0fc, 0xc1a4, 0xc1a6, 0xc1b6, 0xc1d6, 0xc1df, 0xc1f6,
0xc1f8, 0xc4a1, 0xc5cd, 0xc6ae, 0xc7cf, 0xc7d1, 0xc7d2, 0xc7d8, 0xc7e5, 0xc8ad
];
this.nextChar = eucNextChar;
};
util.inherits(module.exports.euc_kr, mbcs);
/**
* GB-18030 recognizer. Uses simplified Chinese statistics.
*/
module.exports.gb_18030 = function() {
this.name = function() {
return 'GB18030';
};
this.language = function() {
return 'zh';
};
/*
* Get the next character value for EUC based encodings.
* Character 'value' is simply the raw bytes that make up the character
* packed into an int.
*/
this.nextChar = function(iter, det) {
iter.index = iter.nextIndex;
iter.error = false;
var firstByte = 0;
var secondByte = 0;
var thirdByte = 0;
var fourthByte = 0;
buildChar: {
firstByte = iter.charValue = iter.nextByte(det);
if (firstByte < 0) {
// Ran off the end of the input data
iter.done = true;
break buildChar;
}
if (firstByte <= 0x80) {
// single byte char
break buildChar;
}
secondByte = iter.nextByte(det);
iter.charValue = (iter.charValue << 8) | secondByte;
if (firstByte >= 0x81 && firstByte <= 0xFE) {
// Two byte Char
if ((secondByte >= 0x40 && secondByte <= 0x7E) || (secondByte >=80 && secondByte <= 0xFE)) {
break buildChar;
}
// Four byte char
if (secondByte >= 0x30 && secondByte <= 0x39) {
thirdByte = iter.nextByte(det);
if (thirdByte >= 0x81 && thirdByte <= 0xFE) {
fourthByte = iter.nextByte(det);
if (fourthByte >= 0x30 && fourthByte <= 0x39) {
iter.charValue = (iter.charValue << 16) | (thirdByte << 8) | fourthByte;
break buildChar;
}
}
}
iter.error = true;
break buildChar;
}
}
return iter.done == false;
};
// TODO: This set of data comes from the character frequency-
// of-occurence analysis tool. The data needs to be moved
// into a resource and loaded from there.
this.commonChars = [
0xa1a1, 0xa1a2, 0xa1a3, 0xa1a4, 0xa1b0, 0xa1b1, 0xa1f1, 0xa1f3, 0xa3a1, 0xa3ac,
0xa3ba, 0xb1a8, 0xb1b8, 0xb1be, 0xb2bb, 0xb3c9, 0xb3f6, 0xb4f3, 0xb5bd, 0xb5c4,
0xb5e3, 0xb6af, 0xb6d4, 0xb6e0, 0xb7a2, 0xb7a8, 0xb7bd, 0xb7d6, 0xb7dd, 0xb8b4,
0xb8df, 0xb8f6, 0xb9ab, 0xb9c9, 0xb9d8, 0xb9fa, 0xb9fd, 0xbacd, 0xbba7, 0xbbd6,
0xbbe1, 0xbbfa, 0xbcbc, 0xbcdb, 0xbcfe, 0xbdcc, 0xbecd, 0xbedd, 0xbfb4, 0xbfc6,
0xbfc9, 0xc0b4, 0xc0ed, 0xc1cb, 0xc2db, 0xc3c7, 0xc4dc, 0xc4ea, 0xc5cc, 0xc6f7,
0xc7f8, 0xc8ab, 0xc8cb, 0xc8d5, 0xc8e7, 0xc9cf, 0xc9fa, 0xcab1, 0xcab5, 0xcac7,
0xcad0, 0xcad6, 0xcaf5, 0xcafd, 0xccec, 0xcdf8, 0xceaa, 0xcec4, 0xced2, 0xcee5,
0xcfb5, 0xcfc2, 0xcfd6, 0xd0c2, 0xd0c5, 0xd0d0, 0xd0d4, 0xd1a7, 0xd2aa, 0xd2b2,
0xd2b5, 0xd2bb, 0xd2d4, 0xd3c3, 0xd3d0, 0xd3fd, 0xd4c2, 0xd4da, 0xd5e2, 0xd6d0
];
};
util.inherits(module.exports.gb_18030, mbcs);