| /* |
| ********************************************************************** |
| * Copyright (C) 2005-2012, International Business Machines |
| * Corporation and others. All Rights Reserved. |
| ********************************************************************** |
| */ |
| |
| #include "unicode/utypes.h" |
| |
| #if !UCONFIG_NO_CONVERSION |
| |
| #include "csrutf8.h" |
| #include "csmatch.h" |
| |
| U_NAMESPACE_BEGIN |
| |
| CharsetRecog_UTF8::~CharsetRecog_UTF8() |
| { |
| // nothing to do |
| } |
| |
| const char *CharsetRecog_UTF8::getName() const |
| { |
| return "UTF-8"; |
| } |
| |
| UBool CharsetRecog_UTF8::match(InputText* input, CharsetMatch *results) const { |
| bool hasBOM = FALSE; |
| int32_t numValid = 0; |
| int32_t numInvalid = 0; |
| const uint8_t *inputBytes = input->fRawInput; |
| int32_t i; |
| int32_t trailBytes = 0; |
| int32_t confidence; |
| |
| if (input->fRawLength >= 3 && |
| inputBytes[0] == 0xEF && inputBytes[1] == 0xBB && inputBytes[2] == 0xBF) { |
| hasBOM = TRUE; |
| } |
| |
| // Scan for multi-byte sequences |
| for (i=0; i < input->fRawLength; i += 1) { |
| int32_t b = inputBytes[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 += 1; |
| |
| if (numInvalid > 5) { |
| break; |
| } |
| |
| trailBytes = 0; |
| } |
| |
| // Verify that we've got the right number of trail bytes in the sequence |
| for (;;) { |
| i += 1; |
| |
| if (i >= input->fRawLength) { |
| break; |
| } |
| |
| b = inputBytes[i]; |
| |
| if ((b & 0xC0) != 0x080) { |
| numInvalid += 1; |
| break; |
| } |
| |
| if (--trailBytes == 0) { |
| numValid += 1; |
| 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; |
| } |
| |
| results->set(input, this, confidence); |
| return (confidence > 0); |
| } |
| |
| U_NAMESPACE_END |
| #endif |