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C++ port of r2157

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git-svn-id: https://zxing.googlecode.com/svn/trunk@2202 59b500cc-1b3d-0410-9834-0bbf25fbcc57
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smparkes@smparkes.net 2012-02-17 20:52:49 +00:00
parent e57ed43976
commit 8fde7556cf
1 changed files with 121 additions and 98 deletions
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219
cpp/core/src/zxing/common/StringUtils.cpp
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@ -35,34 +35,40 @@ char const* const StringUtils::ISO88591 = "ISO8859-1";
const bool StringUtils::ASSUME_SHIFT_JIS = false; const bool StringUtils::ASSUME_SHIFT_JIS = false;
string string
StringUtils::guessEncoding(unsigned char* bytes, int length, Hashtable const& hints) { StringUtils::guessEncoding(unsigned char* bytes, int length,
Hashtable const& hints) {
Hashtable::const_iterator i = hints.find(DecodeHints::CHARACTER_SET); Hashtable::const_iterator i = hints.find(DecodeHints::CHARACTER_SET);
if (i != hints.end()) { if (i != hints.end()) {
return i->second; return i->second;
} }
// Does it start with the UTF-8 byte order mark? then guess it's UTF-8 typedef bool boolean;
if (length > 3 &&
bytes[0] == (unsigned char) 0xEF &&
bytes[1] == (unsigned char) 0xBB &&
bytes[2] == (unsigned char) 0xBF) {
return UTF8;
}
// For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS, // For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS,
// which should be by far the most common encodings. ISO-8859-1 // which should be by far the most common encodings.
// should not have bytes in the 0x80 - 0x9F range, while Shift_JIS boolean canBeISO88591 = true;
// uses this as a first byte of a two-byte character. If we see this boolean canBeShiftJIS = true;
// followed by a valid second byte in Shift_JIS, assume it is Shift_JIS. boolean canBeUTF8 = true;
// If we see something else in that second byte, we'll make the risky guess
// that it's UTF-8.
bool canBeISO88591 = true;
bool canBeShiftJIS = true;
bool canBeUTF8 = true;
int utf8BytesLeft = 0; int utf8BytesLeft = 0;
int maybeDoubleByteCount = 0; //int utf8LowChars = 0;
int maybeSingleByteKatakanaCount = 0; int utf2BytesChars = 0;
bool sawLatin1Supplement = false; int utf3BytesChars = 0;
bool sawUTF8Start = false; int utf4BytesChars = 0;
bool lastWasPossibleDoubleByteStart = false; int sjisBytesLeft = 0;
//int sjisLowChars = 0;
int sjisKatakanaChars = 0;
//int sjisDoubleBytesChars = 0;
int sjisCurKatakanaWordLength = 0;
int sjisCurDoubleBytesWordLength = 0;
int sjisMaxKatakanaWordLength = 0;
int sjisMaxDoubleBytesWordLength = 0;
//int isoLowChars = 0;
//int isoHighChars = 0;
int isoHighOther = 0;
typedef unsigned char byte;
boolean utf8bom = length > 3 &&
bytes[0] == (byte) 0xEF &&
bytes[1] == (byte) 0xBB &&
bytes[2] == (byte) 0xBF;
for (int i = 0; for (int i = 0;
i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8); i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8);
@ -71,105 +77,122 @@ StringUtils::guessEncoding(unsigned char* bytes, int length, Hashtable const& hi
int value = bytes[i] & 0xFF; int value = bytes[i] & 0xFF;
// UTF-8 stuff // UTF-8 stuff
if (value >= 0x80 && value <= 0xBF) { if (canBeUTF8) {
if (utf8BytesLeft > 0) { if (utf8BytesLeft > 0) {
utf8BytesLeft--; if ((value & 0x80) == 0) {
} canBeUTF8 = false;
} else { } else {
if (utf8BytesLeft > 0) { utf8BytesLeft--;
canBeUTF8 = false;
}
if (value >= 0xC0 && value <= 0xFD) {
sawUTF8Start = true;
int valueCopy = value;
while ((valueCopy & 0x40) != 0) {
utf8BytesLeft++;
valueCopy <<= 1;
} }
} } else if ((value & 0x80) != 0) {
if ((value & 0x40) == 0) {
canBeUTF8 = false;
} else {
utf8BytesLeft++;
if ((value & 0x20) == 0) {
utf2BytesChars++;
} else {
utf8BytesLeft++;
if ((value & 0x10) == 0) {
utf3BytesChars++;
} else {
utf8BytesLeft++;
if ((value & 0x08) == 0) {
utf4BytesChars++;
} else {
canBeUTF8 = false;
}
}
}
}
} //else {
//utf8LowChars++;
//}
} }
// ISO-8859-1 stuff // ISO-8859-1 stuff
if (canBeISO88591) {
if ((value == 0xC2 || value == 0xC3) && i < length - 1) { if (value > 0x7F && value < 0xA0) {
// This is really a poor hack. The slightly more exotic characters people might want to put in canBeISO88591 = false;
// a QR Code, by which I mean the Latin-1 supplement characters (e.g. u-umlaut) have encodings } else if (value > 0x9F) {
// that start with 0xC2 followed by [0xA0,0xBF], or start with 0xC3 followed by [0x80,0xBF]. if (value < 0xC0 || value == 0xD7 || value == 0xF7) {
int nextValue = bytes[i + 1] & 0xFF; isoHighOther++;
if (nextValue <= 0xBF && } //else {
((value == 0xC2 && nextValue >= 0xA0) || (value == 0xC3 && nextValue >= 0x80))) { //isoHighChars++;
sawLatin1Supplement = true; //}
} } //else {
} //isoLowChars++;
if (value >= 0x7F && value <= 0x9F) { //}
canBeISO88591 = false;
} }
// Shift_JIS stuff // Shift_JIS stuff
if (canBeShiftJIS) {
if (value >= 0xA1 && value <= 0xDF) { if (sjisBytesLeft > 0) {
// count the number of characters that might be a Shift_JIS single-byte Katakana character if (value < 0x40 || value == 0x7F || value > 0xFC) {
if (!lastWasPossibleDoubleByteStart) {
maybeSingleByteKatakanaCount++;
}
}
if (!lastWasPossibleDoubleByteStart &&
((value >= 0xF0 && value <= 0xFF) || value == 0x80 || value == 0xA0)) {
canBeShiftJIS = false;
}
if ((value >= 0x81 && value <= 0x9F) || (value >= 0xE0 && value <= 0xEF)) {
// These start double-byte characters in Shift_JIS. Let's see if it's followed by a valid
// second byte.
if (lastWasPossibleDoubleByteStart) {
// If we just checked this and the last byte for being a valid double-byte
// char, don't check starting on this byte. If this and the last byte
// formed a valid pair, then this shouldn't be checked to see if it starts
// a double byte pair of course.
lastWasPossibleDoubleByteStart = false;
} else {
// ... otherwise do check to see if this plus the next byte form a valid
// double byte pair encoding a character.
lastWasPossibleDoubleByteStart = true;
if (i >= length - 1) {
canBeShiftJIS = false; canBeShiftJIS = false;
} else { } else {
int nextValue = bytes[i + 1] & 0xFF; sjisBytesLeft--;
if (nextValue < 0x40 || nextValue > 0xFC) {
canBeShiftJIS = false;
} else {
maybeDoubleByteCount++;
}
// There is some conflicting information out there about which bytes can follow which in
// double-byte Shift_JIS characters. The rule above seems to be the one that matches practice.
} }
} else if (value == 0x80 || value == 0xA0 || value > 0xEF) {
canBeShiftJIS = false;
} else if (value > 0xA0 && value < 0xE0) {
sjisKatakanaChars++;
sjisCurDoubleBytesWordLength = 0;
sjisCurKatakanaWordLength++;
if (sjisCurKatakanaWordLength > sjisMaxKatakanaWordLength) {
sjisMaxKatakanaWordLength = sjisCurKatakanaWordLength;
}
} else if (value > 0x7F) {
sjisBytesLeft++;
//sjisDoubleBytesChars++;
sjisCurKatakanaWordLength = 0;
sjisCurDoubleBytesWordLength++;
if (sjisCurDoubleBytesWordLength > sjisMaxDoubleBytesWordLength) {
sjisMaxDoubleBytesWordLength = sjisCurDoubleBytesWordLength;
}
} else {
//sjisLowChars++;
sjisCurKatakanaWordLength = 0;
sjisCurDoubleBytesWordLength = 0;
} }
} else {
lastWasPossibleDoubleByteStart = false;
} }
} }
if (utf8BytesLeft > 0) {
if (canBeUTF8 && utf8BytesLeft > 0) {
canBeUTF8 = false; canBeUTF8 = false;
} }
if (canBeShiftJIS && sjisBytesLeft > 0) {
// Easy -- if assuming Shift_JIS and no evidence it can't be, done canBeShiftJIS = false;
if (canBeShiftJIS && ASSUME_SHIFT_JIS) {
return SHIFT_JIS;
} }
if (canBeUTF8 && sawUTF8Start) {
// Easy -- if there is BOM or at least 1 valid not-single byte character (and no evidence it can't be UTF-8), done
if (canBeUTF8 && (utf8bom || utf2BytesChars + utf3BytesChars + utf4BytesChars > 0)) {
return UTF8; return UTF8;
} }
// Distinguishing Shift_JIS and ISO-8859-1 can be a little tough. The crude heuristic is: // Easy -- if assuming Shift_JIS or at least 3 valid consecutive not-ascii characters (and no evidence it can't be), done
// - If we saw if (canBeShiftJIS && (ASSUME_SHIFT_JIS || sjisMaxKatakanaWordLength >= 3 || sjisMaxDoubleBytesWordLength >= 3)) {
// - at least 3 bytes that starts a double-byte value (bytes that are rare in ISO-8859-1), or
// - over 5% of bytes could be single-byte Katakana (also rare in ISO-8859-1),
// - and, saw no sequences that are invalid in Shift_JIS, then we conclude Shift_JIS
if (canBeShiftJIS && (maybeDoubleByteCount >= 3 || 20 * maybeSingleByteKatakanaCount > length)) {
return SHIFT_JIS; return SHIFT_JIS;
} }
// Otherwise, we default to ISO-8859-1 unless we know it can't be // Distinguishing Shift_JIS and ISO-8859-1 can be a little tough for short words. The crude heuristic is:
if (!sawLatin1Supplement && canBeISO88591) { // - If we saw
// - only two consecutive katakana chars in the whole text, or
// - at least 10% of bytes that could be "upper" not-alphanumeric Latin1,
// - then we conclude Shift_JIS, else ISO-8859-1
if (canBeISO88591 && canBeShiftJIS) {
return (sjisMaxKatakanaWordLength == 2 && sjisKatakanaChars == 2) || isoHighOther * 10 >= length
? SHIFT_JIS : ISO88591;
}
// Otherwise, try in order ISO-8859-1, Shift JIS, UTF-8 and fall back to default platform encoding
if (canBeISO88591) {
return ISO88591; return ISO88591;
} }
if (canBeShiftJIS) {
return SHIFT_JIS;
}
if (canBeUTF8) {
return UTF8;
}
// Otherwise, we take a wild guess with platform encoding // Otherwise, we take a wild guess with platform encoding
return PLATFORM_DEFAULT_ENCODING; return PLATFORM_DEFAULT_ENCODING;
} }