tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
Log | Files | Refs | README | LICENSE

csrutf8.cpp (3021B)

      1 // © 2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html
      3 /*
      4 **********************************************************************
      5 *   Copyright (C) 2005-2014, International Business Machines
      6 *   Corporation and others.  All Rights Reserved.
      7 **********************************************************************
      8 */
      9 
     10 #include "unicode/utypes.h"
     11 
     12 #if !UCONFIG_NO_CONVERSION
     13 
     14 #include "csrutf8.h"
     15 #include "csmatch.h"
     16 
     17 U_NAMESPACE_BEGIN
     18 
     19 CharsetRecog_UTF8::~CharsetRecog_UTF8()
     20 {
     21    // nothing to do
     22 }
     23 
     24 const char *CharsetRecog_UTF8::getName() const
     25 {
     26    return "UTF-8";
     27 }
     28 
     29 UBool CharsetRecog_UTF8::match(InputText* input, CharsetMatch *results) const {
     30    bool hasBOM = false;
     31    int32_t numValid = 0;
     32    int32_t numInvalid = 0;
     33    const uint8_t *inputBytes = input->fRawInput;
     34    int32_t i;
     35    int32_t trailBytes = 0;
     36    int32_t confidence;
     37 
     38    if (input->fRawLength >= 3 && 
     39        inputBytes[0] == 0xEF && inputBytes[1] == 0xBB && inputBytes[2] == 0xBF) {
     40            hasBOM = true;
     41    }
     42 
     43    // Scan for multi-byte sequences
     44    for (i=0; i < input->fRawLength; i += 1) {
     45        int32_t b = inputBytes[i];
     46 
     47        if ((b & 0x80) == 0) {
     48            continue;   // ASCII
     49        }
     50 
     51        // Hi bit on char found.  Figure out how long the sequence should be
     52        if ((b & 0x0E0) == 0x0C0) {
     53            trailBytes = 1;
     54        } else if ((b & 0x0F0) == 0x0E0) {
     55            trailBytes = 2;
     56        } else if ((b & 0x0F8) == 0xF0) {
     57            trailBytes = 3;
     58        } else {
     59            numInvalid += 1;
     60            continue;
     61        }
     62 
     63        // Verify that we've got the right number of trail bytes in the sequence
     64        for (;;) {
     65            i += 1;
     66 
     67            if (i >= input->fRawLength) {
     68                break;
     69            }
     70 
     71            b = inputBytes[i];
     72 
     73            if ((b & 0xC0) != 0x080) {
     74                numInvalid += 1;
     75                break;
     76            }
     77 
     78            if (--trailBytes == 0) {
     79                numValid += 1;
     80                break;
     81            }
     82        }
     83 
     84    }
     85 
     86    // Cook up some sort of confidence score, based on presence of a BOM
     87    //    and the existence of valid and/or invalid multi-byte sequences.
     88    confidence = 0;
     89    if (hasBOM && numInvalid == 0) {
     90        confidence = 100;
     91    } else if (hasBOM && numValid > numInvalid*10) {
     92        confidence = 80;
     93    } else if (numValid > 3 && numInvalid == 0) {
     94        confidence = 100;
     95    } else if (numValid > 0 && numInvalid == 0) {
     96        confidence = 80;
     97    } else if (numValid == 0 && numInvalid == 0) {
     98        // Plain ASCII. Confidence must be > 10, it's more likely than UTF-16, which
     99        //              accepts ASCII with confidence = 10.
    100        confidence = 15;
    101    } else if (numValid > numInvalid*10) {
    102        // Probably corrupt utf-8 data.  Valid sequences aren't likely by chance.
    103        confidence = 25;
    104    }
    105 
    106    results->set(input, this, confidence);
    107    return (confidence > 0);
    108 }
    109 
    110 U_NAMESPACE_END
    111 #endif