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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 // ICU integration functions.
      6 
      7 #include <stdlib.h>
      8 #include <string.h>
      9 
     10 #include "base/logging.h"
     11 #include "third_party/icu/source/common/unicode/ucnv.h"
     12 #include "third_party/icu/source/common/unicode/ucnv_cb.h"
     13 #include "third_party/icu/source/common/unicode/uidna.h"
     14 #include "url/url_canon_icu.h"
     15 #include "url/url_canon_internal.h"  // for _itoa_s
     16 
     17 namespace url_canon {
     18 
     19 namespace {
     20 
     21 // Called when converting a character that can not be represented, this will
     22 // append an escaped version of the numerical character reference for that code
     23 // point. It is of the form "&#1234;" and we will escape the non-digits to
     24 // "%26%231234%3B". Why? This is what Netscape did back in the olden days.
     25 void appendURLEscapedChar(const void* context,
     26                           UConverterFromUnicodeArgs* from_args,
     27                           const UChar* code_units,
     28                           int32_t length,
     29                           UChar32 code_point,
     30                           UConverterCallbackReason reason,
     31                           UErrorCode* err) {
     32   if (reason == UCNV_UNASSIGNED) {
     33     *err = U_ZERO_ERROR;
     34 
     35     const static int prefix_len = 6;
     36     const static char prefix[prefix_len + 1] = "%26%23";  // "&#" percent-escaped
     37     ucnv_cbFromUWriteBytes(from_args, prefix, prefix_len, 0, err);
     38 
     39     DCHECK(code_point < 0x110000);
     40     char number[8];  // Max Unicode code point is 7 digits.
     41     _itoa_s(code_point, number, 10);
     42     int number_len = static_cast<int>(strlen(number));
     43     ucnv_cbFromUWriteBytes(from_args, number, number_len, 0, err);
     44 
     45     const static int postfix_len = 3;
     46     const static char postfix[postfix_len + 1] = "%3B";   // ";" percent-escaped
     47     ucnv_cbFromUWriteBytes(from_args, postfix, postfix_len, 0, err);
     48   }
     49 }
     50 
     51 // A class for scoping the installation of the invalid character callback.
     52 class AppendHandlerInstaller {
     53  public:
     54   // The owner of this object must ensure that the converter is alive for the
     55   // duration of this object's lifetime.
     56   AppendHandlerInstaller(UConverter* converter) : converter_(converter) {
     57     UErrorCode err = U_ZERO_ERROR;
     58     ucnv_setFromUCallBack(converter_, appendURLEscapedChar, 0,
     59                           &old_callback_, &old_context_, &err);
     60   }
     61 
     62   ~AppendHandlerInstaller() {
     63     UErrorCode err = U_ZERO_ERROR;
     64     ucnv_setFromUCallBack(converter_, old_callback_, old_context_, 0, 0, &err);
     65   }
     66 
     67  private:
     68   UConverter* converter_;
     69 
     70   UConverterFromUCallback old_callback_;
     71   const void* old_context_;
     72 };
     73 
     74 }  // namespace
     75 
     76 ICUCharsetConverter::ICUCharsetConverter(UConverter* converter)
     77     : converter_(converter) {
     78 }
     79 
     80 ICUCharsetConverter::~ICUCharsetConverter() {
     81 }
     82 
     83 void ICUCharsetConverter::ConvertFromUTF16(const base::char16* input,
     84                                            int input_len,
     85                                            CanonOutput* output) {
     86   // Install our error handler. It will be called for character that can not
     87   // be represented in the destination character set.
     88   AppendHandlerInstaller handler(converter_);
     89 
     90   int begin_offset = output->length();
     91   int dest_capacity = output->capacity() - begin_offset;
     92   output->set_length(output->length());
     93 
     94   do {
     95     UErrorCode err = U_ZERO_ERROR;
     96     char* dest = &output->data()[begin_offset];
     97     int required_capacity = ucnv_fromUChars(converter_, dest, dest_capacity,
     98                                             input, input_len, &err);
     99     if (err != U_BUFFER_OVERFLOW_ERROR) {
    100       output->set_length(begin_offset + required_capacity);
    101       return;
    102     }
    103 
    104     // Output didn't fit, expand
    105     dest_capacity = required_capacity;
    106     output->Resize(begin_offset + dest_capacity);
    107   } while (true);
    108 }
    109 
    110 // Converts the Unicode input representing a hostname to ASCII using IDN rules.
    111 // The output must be ASCII, but is represented as wide characters.
    112 //
    113 // On success, the output will be filled with the ASCII host name and it will
    114 // return true. Unlike most other canonicalization functions, this assumes that
    115 // the output is empty. The beginning of the host will be at offset 0, and
    116 // the length of the output will be set to the length of the new host name.
    117 //
    118 // On error, this will return false. The output in this case is undefined.
    119 bool IDNToASCII(const base::char16* src, int src_len, CanonOutputW* output) {
    120   DCHECK(output->length() == 0);  // Output buffer is assumed empty.
    121   while (true) {
    122     // Use ALLOW_UNASSIGNED to be more tolerant of hostnames that violate
    123     // the spec (which do exist). This does not present any risk and is a
    124     // little more future proof.
    125     UErrorCode err = U_ZERO_ERROR;
    126     int num_converted = uidna_IDNToASCII(src, src_len, output->data(),
    127                                          output->capacity(),
    128                                          UIDNA_ALLOW_UNASSIGNED, NULL, &err);
    129     if (err == U_ZERO_ERROR) {
    130       output->set_length(num_converted);
    131       return true;
    132     }
    133     if (err != U_BUFFER_OVERFLOW_ERROR)
    134       return false;  // Unknown error, give up.
    135 
    136     // Not enough room in our buffer, expand.
    137     output->Resize(output->capacity() * 2);
    138   }
    139 }
    140 
    141 bool ReadUTFChar(const char* str, int* begin, int length,
    142                  unsigned* code_point_out) {
    143   int code_point;  // Avoids warning when U8_NEXT writes -1 to it.
    144   U8_NEXT(str, *begin, length, code_point);
    145   *code_point_out = static_cast<unsigned>(code_point);
    146 
    147   // The ICU macro above moves to the next char, we want to point to the last
    148   // char consumed.
    149   (*begin)--;
    150 
    151   // Validate the decoded value.
    152   if (U_IS_UNICODE_CHAR(code_point))
    153     return true;
    154   *code_point_out = kUnicodeReplacementCharacter;
    155   return false;
    156 }
    157 
    158 bool ReadUTFChar(const base::char16* str, int* begin, int length,
    159                  unsigned* code_point) {
    160   if (U16_IS_SURROGATE(str[*begin])) {
    161     if (!U16_IS_SURROGATE_LEAD(str[*begin]) || *begin + 1 >= length ||
    162         !U16_IS_TRAIL(str[*begin + 1])) {
    163       // Invalid surrogate pair.
    164       *code_point = kUnicodeReplacementCharacter;
    165       return false;
    166     } else {
    167       // Valid surrogate pair.
    168       *code_point = U16_GET_SUPPLEMENTARY(str[*begin], str[*begin + 1]);
    169       (*begin)++;
    170     }
    171   } else {
    172     // Not a surrogate, just one 16-bit word.
    173     *code_point = str[*begin];
    174   }
    175 
    176   if (U_IS_UNICODE_CHAR(*code_point))
    177     return true;
    178 
    179   // Invalid code point.
    180   *code_point = kUnicodeReplacementCharacter;
    181   return false;
    182 }
    183 
    184 }  // namespace url_canon
    185