| /** |
| ******************************************************************************* |
| * Copyright (C) 2005 - 2007, International Business Machines Corporation and * |
| * others. All Rights Reserved. * |
| ******************************************************************************* |
| */ |
| package com.ibm.icu.text; |
| |
| /** |
| * Charset recognizer for UTF-8 |
| * |
| * @internal |
| */ |
| class CharsetRecog_UTF8 extends CharsetRecognizer { |
| |
| String getName() { |
| return "UTF-8"; |
| } |
| |
| /* (non-Javadoc) |
| * @see com.ibm.icu.text.CharsetRecognizer#match(com.ibm.icu.text.CharsetDetector) |
| */ |
| int match(CharsetDetector det) { |
| boolean hasBOM = false; |
| int numValid = 0; |
| int numInvalid = 0; |
| byte input[] = det.fRawInput; |
| int i; |
| int trailBytes = 0; |
| int confidence; |
| |
| if (det.fRawLength >= 3 && |
| (input[0] & 0xFF) == 0xef && (input[1] & 0xFF) == 0xbb & (input[2] & 0xFF) == 0xbf) { |
| hasBOM = true; |
| } |
| |
| // Scan for multi-byte sequences |
| for (i=0; i<det.fRawLength; i++) { |
| int b = input[i]; |
| if ((b & 0x80) == 0) { |
| continue; // ASCII |
| } |
| |
| // Hi bit on char found. Figure out how long the sequence should be |
| if ((b & 0x0e0) == 0x0c0) { |
| trailBytes = 1; |
| } else if ((b & 0x0f0) == 0x0e0) { |
| trailBytes = 2; |
| } else if ((b & 0x0f8) == 0xf0) { |
| trailBytes = 3; |
| } else { |
| numInvalid++; |
| if (numInvalid > 5) { |
| break; |
| } |
| trailBytes = 0; |
| } |
| |
| // Verify that we've got the right number of trail bytes in the sequence |
| for (;;) { |
| i++; |
| if (i>=det.fRawLength) { |
| break; |
| } |
| b = input[i]; |
| if ((b & 0xc0) != 0x080) { |
| numInvalid++; |
| break; |
| } |
| if (--trailBytes == 0) { |
| numValid++; |
| break; |
| } |
| } |
| |
| } |
| |
| // Cook up some sort of confidence score, based on presense of a BOM |
| // and the existence of valid and/or invalid multi-byte sequences. |
| confidence = 0; |
| if (hasBOM && numInvalid==0) { |
| confidence = 100; |
| } else if (hasBOM && numValid > numInvalid*10) { |
| confidence = 80; |
| } else if (numValid > 3 && numInvalid == 0) { |
| confidence = 100; |
| } else if (numValid > 0 && numInvalid == 0) { |
| confidence = 80; |
| } else if (numValid == 0 && numInvalid == 0) { |
| // Plain ASCII. |
| confidence = 10; |
| } else if (numValid > numInvalid*10) { |
| // Probably corruput utf-8 data. Valid sequences aren't likely by chance. |
| confidence = 25; |
| } |
| return confidence; |
| } |
| |
| } |