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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/v8/V8StringResource.h"
     28 
     29 #include "bindings/v8/V8Binding.h"
     30 #include "core/inspector/BindingVisitors.h"
     31 #include "wtf/MainThread.h"
     32 
     33 namespace WebCore {
     34 
     35 WebCoreStringResourceBase* WebCoreStringResourceBase::toWebCoreStringResourceBase(v8::Handle<v8::String> string)
     36 {
     37     v8::String::Encoding encoding;
     38     v8::String::ExternalStringResourceBase* resource = string->GetExternalStringResourceBase(&encoding);
     39     if (!resource)
     40         return 0;
     41     if (encoding == v8::String::ONE_BYTE_ENCODING)
     42         return static_cast<WebCoreStringResource8*>(resource);
     43     return static_cast<WebCoreStringResource16*>(resource);
     44 }
     45 
     46 void WebCoreStringResourceBase::visitStrings(ExternalStringVisitor* visitor)
     47 {
     48     visitor->visitJSExternalString(m_plainString.impl());
     49     if (m_plainString.impl() != m_atomicString.impl() && !m_atomicString.isNull())
     50         visitor->visitJSExternalString(m_atomicString.impl());
     51 }
     52 
     53 template<class StringClass> struct StringTraits {
     54     static const StringClass& fromStringResource(WebCoreStringResourceBase*);
     55     template<bool oneByte>
     56     static StringClass fromV8String(v8::Handle<v8::String>, int);
     57 };
     58 
     59 template<>
     60 struct StringTraits<String> {
     61     static const String& fromStringResource(WebCoreStringResourceBase* resource)
     62     {
     63         return resource->webcoreString();
     64     }
     65     template<bool oneByte>
     66     static String fromV8String(v8::Handle<v8::String>, int);
     67 };
     68 
     69 template<>
     70 struct StringTraits<AtomicString> {
     71     static const AtomicString& fromStringResource(WebCoreStringResourceBase* resource)
     72     {
     73         return resource->atomicString();
     74     }
     75     template<bool oneByte>
     76     static AtomicString fromV8String(v8::Handle<v8::String>, int);
     77 };
     78 
     79 template<>
     80 String StringTraits<String>::fromV8String<false>(v8::Handle<v8::String> v8String, int length)
     81 {
     82     ASSERT(v8String->Length() == length);
     83     UChar* buffer;
     84     String result = String::createUninitialized(length, buffer);
     85     v8String->Write(reinterpret_cast<uint16_t*>(buffer), 0, length);
     86     return result;
     87 }
     88 
     89 template<>
     90 AtomicString StringTraits<AtomicString>::fromV8String<false>(v8::Handle<v8::String> v8String, int length)
     91 {
     92     ASSERT(v8String->Length() == length);
     93     static const int inlineBufferSize = 16;
     94     if (length <= inlineBufferSize) {
     95         UChar inlineBuffer[inlineBufferSize];
     96         v8String->Write(reinterpret_cast<uint16_t*>(inlineBuffer), 0, length);
     97         return AtomicString(inlineBuffer, length);
     98     }
     99     UChar* buffer;
    100     String result = String::createUninitialized(length, buffer);
    101     v8String->Write(reinterpret_cast<uint16_t*>(buffer), 0, length);
    102     return AtomicString(result);
    103 }
    104 
    105 template<>
    106 String StringTraits<String>::fromV8String<true>(v8::Handle<v8::String> v8String, int length)
    107 {
    108     ASSERT(v8String->Length() == length);
    109     LChar* buffer;
    110     String result = String::createUninitialized(length, buffer);
    111     v8String->WriteOneByte(buffer, 0, length);
    112     return result;
    113 }
    114 
    115 template<>
    116 AtomicString StringTraits<AtomicString>::fromV8String<true>(v8::Handle<v8::String> v8String, int length)
    117 {
    118     ASSERT(v8String->Length() == length);
    119     static const int inlineBufferSize = 32;
    120     if (length <= inlineBufferSize) {
    121         LChar inlineBuffer[inlineBufferSize];
    122         v8String->WriteOneByte(inlineBuffer, 0, length);
    123         return AtomicString(inlineBuffer, length);
    124     }
    125     LChar* buffer;
    126     String string = String::createUninitialized(length, buffer);
    127     v8String->WriteOneByte(buffer, 0, length);
    128     return AtomicString(string);
    129 }
    130 
    131 template<typename StringType>
    132 StringType v8StringToWebCoreString(v8::Handle<v8::String> v8String, ExternalMode external)
    133 {
    134     {
    135         // A lot of WebCoreStringResourceBase::toWebCoreStringResourceBase is copied here by hand for performance reasons.
    136         // This portion of this function is very hot in certain Dromeao benchmarks.
    137         v8::String::Encoding encoding;
    138         v8::String::ExternalStringResourceBase* resource = v8String->GetExternalStringResourceBase(&encoding);
    139         if (LIKELY(!!resource)) {
    140             WebCoreStringResourceBase* base;
    141             if (encoding == v8::String::ONE_BYTE_ENCODING)
    142                 base = static_cast<WebCoreStringResource8*>(resource);
    143             else
    144                 base = static_cast<WebCoreStringResource16*>(resource);
    145             return StringTraits<StringType>::fromStringResource(base);
    146         }
    147     }
    148 
    149     int length = v8String->Length();
    150     if (UNLIKELY(!length))
    151         return String("");
    152 
    153     bool oneByte = v8String->ContainsOnlyOneByte();
    154     StringType result(oneByte ? StringTraits<StringType>::template fromV8String<true>(v8String, length) : StringTraits<StringType>::template fromV8String<false>(v8String, length));
    155 
    156     if (external != Externalize || !v8String->CanMakeExternal())
    157         return result;
    158 
    159     if (result.is8Bit()) {
    160         WebCoreStringResource8* stringResource = new WebCoreStringResource8(result);
    161         if (UNLIKELY(!v8String->MakeExternal(stringResource)))
    162             delete stringResource;
    163     } else {
    164         WebCoreStringResource16* stringResource = new WebCoreStringResource16(result);
    165         if (UNLIKELY(!v8String->MakeExternal(stringResource)))
    166             delete stringResource;
    167     }
    168     return result;
    169 }
    170 
    171 // Explicitly instantiate the above template with the expected parameterizations,
    172 // to ensure the compiler generates the code; otherwise link errors can result in GCC 4.4.
    173 template String v8StringToWebCoreString<String>(v8::Handle<v8::String>, ExternalMode);
    174 template AtomicString v8StringToWebCoreString<AtomicString>(v8::Handle<v8::String>, ExternalMode);
    175 
    176 // Fast but non thread-safe version.
    177 String int32ToWebCoreStringFast(int value)
    178 {
    179     // Caching of small strings below is not thread safe: newly constructed AtomicString
    180     // are not safely published.
    181     ASSERT(isMainThread());
    182 
    183     // Most numbers used are <= 100. Even if they aren't used there's very little cost in using the space.
    184     const int kLowNumbers = 100;
    185     DEFINE_STATIC_LOCAL(Vector<AtomicString>, lowNumbers, (kLowNumbers + 1));
    186     String webCoreString;
    187     if (0 <= value && value <= kLowNumbers) {
    188         webCoreString = lowNumbers[value];
    189         if (!webCoreString) {
    190             AtomicString valueString = AtomicString(String::number(value));
    191             lowNumbers[value] = valueString;
    192             webCoreString = valueString;
    193         }
    194     } else
    195         webCoreString = String::number(value);
    196     return webCoreString;
    197 }
    198 
    199 String int32ToWebCoreString(int value)
    200 {
    201     // If we are on the main thread (this should always true for non-workers), call the faster one.
    202     if (isMainThread())
    203         return int32ToWebCoreStringFast(value);
    204     return String::number(value);
    205 }
    206 
    207 } // namespace WebCore
    208