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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/lazy_instance.h"
     11 #include "base/logging.h"
     12 #include "third_party/icu/source/common/unicode/ucnv.h"
     13 #include "third_party/icu/source/common/unicode/ucnv_cb.h"
     14 #include "third_party/icu/source/common/unicode/uidna.h"
     15 #include "url/url_canon_icu.h"
     16 #include "url/url_canon_internal.h"  // for _itoa_s
     17 
     18 namespace url {
     19 
     20 namespace {
     21 
     22 // Called when converting a character that can not be represented, this will
     23 // append an escaped version of the numerical character reference for that code
     24 // point. It is of the form "&#1234;" and we will escape the non-digits to
     25 // "%26%231234%3B". Why? This is what Netscape did back in the olden days.
     26 void appendURLEscapedChar(const void* context,
     27                           UConverterFromUnicodeArgs* from_args,
     28                           const UChar* code_units,
     29                           int32_t length,
     30                           UChar32 code_point,
     31                           UConverterCallbackReason reason,
     32                           UErrorCode* err) {
     33   if (reason == UCNV_UNASSIGNED) {
     34     *err = U_ZERO_ERROR;
     35 
     36     const static int prefix_len = 6;
     37     const static char prefix[prefix_len + 1] = "%26%23";  // "&#" percent-escaped
     38     ucnv_cbFromUWriteBytes(from_args, prefix, prefix_len, 0, err);
     39 
     40     DCHECK(code_point < 0x110000);
     41     char number[8];  // Max Unicode code point is 7 digits.
     42     _itoa_s(code_point, number, 10);
     43     int number_len = static_cast<int>(strlen(number));
     44     ucnv_cbFromUWriteBytes(from_args, number, number_len, 0, err);
     45 
     46     const static int postfix_len = 3;
     47     const static char postfix[postfix_len + 1] = "%3B";   // ";" percent-escaped
     48     ucnv_cbFromUWriteBytes(from_args, postfix, postfix_len, 0, err);
     49   }
     50 }
     51 
     52 // A class for scoping the installation of the invalid character callback.
     53 class AppendHandlerInstaller {
     54  public:
     55   // The owner of this object must ensure that the converter is alive for the
     56   // duration of this object's lifetime.
     57   AppendHandlerInstaller(UConverter* converter) : converter_(converter) {
     58     UErrorCode err = U_ZERO_ERROR;
     59     ucnv_setFromUCallBack(converter_, appendURLEscapedChar, 0,
     60                           &old_callback_, &old_context_, &err);
     61   }
     62 
     63   ~AppendHandlerInstaller() {
     64     UErrorCode err = U_ZERO_ERROR;
     65     ucnv_setFromUCallBack(converter_, old_callback_, old_context_, 0, 0, &err);
     66   }
     67 
     68  private:
     69   UConverter* converter_;
     70 
     71   UConverterFromUCallback old_callback_;
     72   const void* old_context_;
     73 };
     74 
     75 // A wrapper to use LazyInstance<>::Leaky with ICU's UIDNA, a C pointer to
     76 // a UTS46/IDNA 2008 handling object opened with uidna_openUTS46().
     77 //
     78 // We use UTS46 with BiDiCheck to migrate from IDNA 2003 (with unassigned
     79 // code points allowed) to IDNA 2008 with
     80 // the backward compatibility in mind. What it does:
     81 //
     82 // 1. Use the up-to-date Unicode data.
     83 // 2. Define a case folding/mapping with the up-to-date Unicode data as
     84 //    in IDNA 2003.
     85 // 3. Use transitional mechanism for 4 deviation characters (sharp-s,
     86 //    final sigma, ZWJ and ZWNJ) for now.
     87 // 4. Continue to allow symbols and punctuations.
     88 // 5. Apply new BiDi check rules more permissive than the IDNA 2003 BiDI rules.
     89 // 6. Do not apply STD3 rules
     90 // 7. Do not allow unassigned code points.
     91 //
     92 // It also closely matches what IE 10 does except for the BiDi check (
     93 // http://goo.gl/3XBhqw ).
     94 // See http://http://unicode.org/reports/tr46/ and references therein
     95 // for more details.
     96 struct UIDNAWrapper {
     97   UIDNAWrapper() {
     98     UErrorCode err = U_ZERO_ERROR;
     99     // TODO(jungshik): Change options as different parties (browsers,
    100     // registrars, search engines) converge toward a consensus.
    101     value = uidna_openUTS46(UIDNA_CHECK_BIDI, &err);
    102     if (U_FAILURE(err))
    103       value = NULL;
    104   }
    105 
    106   UIDNA* value;
    107 };
    108 
    109 }  // namespace
    110 
    111 ICUCharsetConverter::ICUCharsetConverter(UConverter* converter)
    112     : converter_(converter) {
    113 }
    114 
    115 ICUCharsetConverter::~ICUCharsetConverter() {
    116 }
    117 
    118 void ICUCharsetConverter::ConvertFromUTF16(const base::char16* input,
    119                                            int input_len,
    120                                            CanonOutput* output) {
    121   // Install our error handler. It will be called for character that can not
    122   // be represented in the destination character set.
    123   AppendHandlerInstaller handler(converter_);
    124 
    125   int begin_offset = output->length();
    126   int dest_capacity = output->capacity() - begin_offset;
    127   output->set_length(output->length());
    128 
    129   do {
    130     UErrorCode err = U_ZERO_ERROR;
    131     char* dest = &output->data()[begin_offset];
    132     int required_capacity = ucnv_fromUChars(converter_, dest, dest_capacity,
    133                                             input, input_len, &err);
    134     if (err != U_BUFFER_OVERFLOW_ERROR) {
    135       output->set_length(begin_offset + required_capacity);
    136       return;
    137     }
    138 
    139     // Output didn't fit, expand
    140     dest_capacity = required_capacity;
    141     output->Resize(begin_offset + dest_capacity);
    142   } while (true);
    143 }
    144 
    145 static base::LazyInstance<UIDNAWrapper>::Leaky
    146     g_uidna = LAZY_INSTANCE_INITIALIZER;
    147 
    148 // Converts the Unicode input representing a hostname to ASCII using IDN rules.
    149 // The output must be ASCII, but is represented as wide characters.
    150 //
    151 // On success, the output will be filled with the ASCII host name and it will
    152 // return true. Unlike most other canonicalization functions, this assumes that
    153 // the output is empty. The beginning of the host will be at offset 0, and
    154 // the length of the output will be set to the length of the new host name.
    155 //
    156 // On error, this will return false. The output in this case is undefined.
    157 // TODO(jungshik): use UTF-8/ASCII version of nameToASCII.
    158 // Change the function signature and callers accordingly to avoid unnecessary
    159 // conversions in our code. In addition, consider using icu::IDNA's UTF-8/ASCII
    160 // version with StringByteSink. That way, we can avoid C wrappers and additional
    161 // string conversion.
    162 bool IDNToASCII(const base::char16* src, int src_len, CanonOutputW* output) {
    163   DCHECK(output->length() == 0);  // Output buffer is assumed empty.
    164 
    165   UIDNA* uidna = g_uidna.Get().value;
    166   DCHECK(uidna != NULL);
    167   while (true) {
    168     UErrorCode err = U_ZERO_ERROR;
    169     UIDNAInfo info = UIDNA_INFO_INITIALIZER;
    170     int output_length = uidna_nameToASCII(uidna, src, src_len, output->data(),
    171                                           output->capacity(), &info, &err);
    172     if (U_SUCCESS(err) && info.errors == 0) {
    173       output->set_length(output_length);
    174       return true;
    175     }
    176 
    177     // TODO(jungshik): Look at info.errors to handle them case-by-case basis
    178     // if necessary.
    179     if (err != U_BUFFER_OVERFLOW_ERROR || info.errors != 0)
    180       return false;  // Unknown error, give up.
    181 
    182     // Not enough room in our buffer, expand.
    183     output->Resize(output_length);
    184   }
    185 }
    186 
    187 }  // namespace url
    188