1 /* 2 ********************************************************************** 3 * Copyright (C) 2005-2014, International Business Machines 4 * Corporation and others. All Rights Reserved. 5 ********************************************************************** 6 */ 7 8 #include "unicode/utypes.h" 9 10 #if !UCONFIG_NO_CONVERSION 11 12 #include "csrutf8.h" 13 #include "csmatch.h" 14 15 U_NAMESPACE_BEGIN 16 ~CharsetRecog_UTF8()17CharsetRecog_UTF8::~CharsetRecog_UTF8() 18 { 19 // nothing to do 20 } 21 getName() const22const char *CharsetRecog_UTF8::getName() const 23 { 24 return "UTF-8"; 25 } 26 match(InputText * input,CharsetMatch * results) const27UBool CharsetRecog_UTF8::match(InputText* input, CharsetMatch *results) const { 28 bool hasBOM = FALSE; 29 int32_t numValid = 0; 30 int32_t numInvalid = 0; 31 const uint8_t *inputBytes = input->fRawInput; 32 int32_t i; 33 int32_t trailBytes = 0; 34 int32_t confidence; 35 36 if (input->fRawLength >= 3 && 37 inputBytes[0] == 0xEF && inputBytes[1] == 0xBB && inputBytes[2] == 0xBF) { 38 hasBOM = TRUE; 39 } 40 41 // Scan for multi-byte sequences 42 for (i=0; i < input->fRawLength; i += 1) { 43 int32_t b = inputBytes[i]; 44 45 if ((b & 0x80) == 0) { 46 continue; // ASCII 47 } 48 49 // Hi bit on char found. Figure out how long the sequence should be 50 if ((b & 0x0E0) == 0x0C0) { 51 trailBytes = 1; 52 } else if ((b & 0x0F0) == 0x0E0) { 53 trailBytes = 2; 54 } else if ((b & 0x0F8) == 0xF0) { 55 trailBytes = 3; 56 } else { 57 numInvalid += 1; 58 continue; 59 } 60 61 // Verify that we've got the right number of trail bytes in the sequence 62 for (;;) { 63 i += 1; 64 65 if (i >= input->fRawLength) { 66 break; 67 } 68 69 b = inputBytes[i]; 70 71 if ((b & 0xC0) != 0x080) { 72 numInvalid += 1; 73 break; 74 } 75 76 if (--trailBytes == 0) { 77 numValid += 1; 78 break; 79 } 80 } 81 82 } 83 84 // Cook up some sort of confidence score, based on presence of a BOM 85 // and the existence of valid and/or invalid multi-byte sequences. 86 confidence = 0; 87 if (hasBOM && numInvalid == 0) { 88 confidence = 100; 89 } else if (hasBOM && numValid > numInvalid*10) { 90 confidence = 80; 91 } else if (numValid > 3 && numInvalid == 0) { 92 confidence = 100; 93 } else if (numValid > 0 && numInvalid == 0) { 94 confidence = 80; 95 } else if (numValid == 0 && numInvalid == 0) { 96 // Plain ASCII. Confidence must be > 10, it's more likely than UTF-16, which 97 // accepts ASCII with confidence = 10. 98 confidence = 15; 99 } else if (numValid > numInvalid*10) { 100 // Probably corruput utf-8 data. Valid sequences aren't likely by chance. 101 confidence = 25; 102 } 103 104 results->set(input, this, confidence); 105 return (confidence > 0); 106 } 107 108 U_NAMESPACE_END 109 #endif 110