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      1 /*
      2  * Copyright (C) 2009 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
     14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
     15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
     17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
     23  * THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #include "config.h"
     27 #include "bindings/core/v8/V8StringResource.h"
     28 
     29 #include "bindings/core/v8/V8Binding.h"
     30 #include "core/inspector/BindingVisitors.h"
     31 #include "wtf/MainThread.h"
     32 
     33 namespace blink {
     34 
     35 template<class StringClass> struct StringTraits {
     36     static const StringClass& fromStringResource(WebCoreStringResourceBase*);
     37     template <typename V8StringTrait>
     38     static StringClass fromV8String(v8::Handle<v8::String>, int);
     39 };
     40 
     41 template<>
     42 struct StringTraits<String> {
     43     static const String& fromStringResource(WebCoreStringResourceBase* resource)
     44     {
     45         return resource->webcoreString();
     46     }
     47     template <typename V8StringTrait>
     48     static String fromV8String(v8::Handle<v8::String>, int);
     49 };
     50 
     51 template<>
     52 struct StringTraits<AtomicString> {
     53     static const AtomicString& fromStringResource(WebCoreStringResourceBase* resource)
     54     {
     55         return resource->atomicString();
     56     }
     57     template <typename V8StringTrait>
     58     static AtomicString fromV8String(v8::Handle<v8::String>, int);
     59 };
     60 
     61 struct V8StringTwoBytesTrait {
     62     typedef UChar CharType;
     63     ALWAYS_INLINE static void write(v8::Handle<v8::String> v8String, CharType* buffer, int length)
     64     {
     65         v8String->Write(reinterpret_cast<uint16_t*>(buffer), 0, length);
     66     }
     67 };
     68 
     69 struct V8StringOneByteTrait {
     70     typedef LChar CharType;
     71     ALWAYS_INLINE static void write(v8::Handle<v8::String> v8String, CharType* buffer, int length)
     72     {
     73         v8String->WriteOneByte(buffer, 0, length);
     74     }
     75 };
     76 
     77 template <typename V8StringTrait>
     78 String StringTraits<String>::fromV8String(v8::Handle<v8::String> v8String, int length)
     79 {
     80     ASSERT(v8String->Length() == length);
     81     typename V8StringTrait::CharType* buffer;
     82     String result = String::createUninitialized(length, buffer);
     83     V8StringTrait::write(v8String, buffer, length);
     84     return result;
     85 }
     86 
     87 template <typename V8StringTrait>
     88 AtomicString StringTraits<AtomicString>::fromV8String(v8::Handle<v8::String> v8String, int length)
     89 {
     90     ASSERT(v8String->Length() == length);
     91     static const int inlineBufferSize = 32 / sizeof(typename V8StringTrait::CharType);
     92     if (length <= inlineBufferSize) {
     93         typename V8StringTrait::CharType inlineBuffer[inlineBufferSize];
     94         V8StringTrait::write(v8String, inlineBuffer, length);
     95         return AtomicString(inlineBuffer, length);
     96     }
     97     typename V8StringTrait::CharType* buffer;
     98     String string = String::createUninitialized(length, buffer);
     99     V8StringTrait::write(v8String, buffer, length);
    100     return AtomicString(string);
    101 }
    102 
    103 template<typename StringType>
    104 StringType v8StringToWebCoreString(v8::Handle<v8::String> v8String, ExternalMode external)
    105 {
    106     {
    107         // This portion of this function is very hot in certain Dromeao benchmarks.
    108         v8::String::Encoding encoding;
    109         v8::String::ExternalStringResourceBase* resource = v8String->GetExternalStringResourceBase(&encoding);
    110         if (LIKELY(!!resource)) {
    111             WebCoreStringResourceBase* base;
    112             if (encoding == v8::String::ONE_BYTE_ENCODING)
    113                 base = static_cast<WebCoreStringResource8*>(resource);
    114             else
    115                 base = static_cast<WebCoreStringResource16*>(resource);
    116             return StringTraits<StringType>::fromStringResource(base);
    117         }
    118     }
    119 
    120     int length = v8String->Length();
    121     if (UNLIKELY(!length))
    122         return StringType("");
    123 
    124     bool oneByte = v8String->ContainsOnlyOneByte();
    125     StringType result(oneByte ? StringTraits<StringType>::template fromV8String<V8StringOneByteTrait>(v8String, length) : StringTraits<StringType>::template fromV8String<V8StringTwoBytesTrait>(v8String, length));
    126 
    127     if (external != Externalize || !v8String->CanMakeExternal())
    128         return result;
    129 
    130     if (result.is8Bit()) {
    131         WebCoreStringResource8* stringResource = new WebCoreStringResource8(result);
    132         if (UNLIKELY(!v8String->MakeExternal(stringResource)))
    133             delete stringResource;
    134     } else {
    135         WebCoreStringResource16* stringResource = new WebCoreStringResource16(result);
    136         if (UNLIKELY(!v8String->MakeExternal(stringResource)))
    137             delete stringResource;
    138     }
    139     return result;
    140 }
    141 
    142 // Explicitly instantiate the above template with the expected parameterizations,
    143 // to ensure the compiler generates the code; otherwise link errors can result in GCC 4.4.
    144 template String v8StringToWebCoreString<String>(v8::Handle<v8::String>, ExternalMode);
    145 template AtomicString v8StringToWebCoreString<AtomicString>(v8::Handle<v8::String>, ExternalMode);
    146 
    147 // Fast but non thread-safe version.
    148 String int32ToWebCoreStringFast(int value)
    149 {
    150     // Caching of small strings below is not thread safe: newly constructed AtomicString
    151     // are not safely published.
    152     ASSERT(isMainThread());
    153 
    154     // Most numbers used are <= 100. Even if they aren't used there's very little cost in using the space.
    155     const int kLowNumbers = 100;
    156     DEFINE_STATIC_LOCAL(Vector<AtomicString>, lowNumbers, (kLowNumbers + 1));
    157     String webCoreString;
    158     if (0 <= value && value <= kLowNumbers) {
    159         webCoreString = lowNumbers[value];
    160         if (!webCoreString) {
    161             AtomicString valueString = AtomicString::number(value);
    162             lowNumbers[value] = valueString;
    163             webCoreString = valueString;
    164         }
    165     } else {
    166         webCoreString = String::number(value);
    167     }
    168     return webCoreString;
    169 }
    170 
    171 String int32ToWebCoreString(int value)
    172 {
    173     // If we are on the main thread (this should always true for non-workers), call the faster one.
    174     if (isMainThread())
    175         return int32ToWebCoreStringFast(value);
    176     return String::number(value);
    177 }
    178 
    179 } // namespace blink
    180