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/*
* Copyright (C) 2014 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef StringView_h
#define StringView_h
#include <wtf/text/WTFString.h>
namespace WTF {
// StringView is a non-owning reference to a string, similar to the proposed std::string_view.
// Whether the string is 8-bit or 16-bit is encoded in the upper bit of the length member.
// This means that strings longer than 2 Gigabytes can not be represented. If that turns out to be
// a problem we can investigate alternative solutions.
class StringView {
public:
StringView()
: m_characters(nullptr)
, m_length(0)
{
}
StringView(const LChar* characters, unsigned length)
{
initialize(characters, length);
}
StringView(const UChar* characters, unsigned length)
{
initialize(characters, length);
}
StringView(const String& string)
: m_characters(nullptr)
, m_length(0)
{
if (!string.impl())
return;
if (string.is8Bit())
initialize(string.characters8(), string.length());
else
initialize(string.characters16(), string.length());
}
static StringView empty()
{
return StringView(reinterpret_cast<const LChar*>(""), 0);
}
const LChar* characters8() const
{
ASSERT(is8Bit());
return static_cast<const LChar*>(m_characters);
}
const UChar* characters16() const
{
ASSERT(!is8Bit());
return static_cast<const UChar*>(m_characters);
}
bool isNull() const { return !m_characters; }
bool isEmpty() const { return !length(); }
unsigned length() const { return m_length & ~is16BitStringFlag; }
explicit operator bool() const { return !isNull(); }
bool is8Bit() const { return !(m_length & is16BitStringFlag); }
StringView substring(unsigned start, unsigned length = std::numeric_limits<unsigned>::max()) const
{
if (start >= this->length())
return empty();
unsigned maxLength = this->length() - start;
if (length >= maxLength) {
if (!start)
return *this;
length = maxLength;
}
if (is8Bit())
return StringView(characters8() + start, length);
return StringView(characters16() + start, length);
}
String toString() const
{
if (is8Bit())
return String(characters8(), length());
return String(characters16(), length());
}
String toStringWithoutCopying() const
{
if (is8Bit())
return StringImpl::createWithoutCopying(characters8(), length());
return StringImpl::createWithoutCopying(characters16(), length());
}
private:
void initialize(const LChar* characters, unsigned length)
{
ASSERT(!(length & is16BitStringFlag));
m_characters = characters;
m_length = length;
}
void initialize(const UChar* characters, unsigned length)
{
ASSERT(!(length & is16BitStringFlag));
m_characters = characters;
m_length = is16BitStringFlag | length;
}
static const unsigned is16BitStringFlag = 1u << 31;
const void* m_characters;
unsigned m_length;
};
} // namespace WTF
using WTF::StringView;
#endif // StringView_h
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