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/*
* Copyright (C) 2010-2023 Apple Inc. All rights reserved.
* Copyright (C) 2012 Google 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. ``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
* 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.
*/
#pragma once
#include <wtf/text/StringBuilder.h>
namespace WTF {
// Allocate a new buffer, copying in currentCharacters (these may come from either m_string or m_buffer.
template<typename AllocationCharacterType, typename CurrentCharacterType> void StringBuilder::allocateBuffer(std::span<const CurrentCharacterType> currentCharactersToCopy, unsigned requiredCapacity)
{
std::span<AllocationCharacterType> newBufferCharacters;
auto buffer = StringImpl::tryCreateUninitialized(requiredCapacity, newBufferCharacters);
if (UNLIKELY(!buffer)) {
didOverflow();
return;
}
ASSERT(!hasOverflowed());
StringImpl::copyCharacters(newBufferCharacters, currentCharactersToCopy);
m_buffer = WTFMove(buffer);
m_string = { };
}
template<typename CharacterType> void StringBuilder::reallocateBuffer(unsigned requiredCapacity)
{
// If the buffer has only one ref (by this StringBuilder), reallocate it.
if (m_buffer) {
m_string = { }; // Clear the string to remove the reference to m_buffer if any before checking the reference count of m_buffer.
if (m_buffer->hasOneRef()) {
CharacterType* bufferCharacters;
auto buffer = StringImpl::tryReallocate(m_buffer.releaseNonNull(), requiredCapacity, bufferCharacters);
if (UNLIKELY(!buffer)) {
didOverflow();
return;
}
m_buffer = WTFMove(*buffer);
return;
}
}
allocateBuffer<CharacterType>(span<CharacterType>(), requiredCapacity);
}
// Make 'additionalLength' additional capacity be available in m_buffer, update m_string & m_length to use,
// that capacity and return a pointer to the newly allocated storage so the caller can write characters there.
// Returns nullptr if allocation fails, length overflows, or if total capacity is 0 so no buffer is needed.
// The caller has the responsibility for checking that CharacterType is the type of the existing buffer.
template<typename CharacterType> std::span<CharacterType> StringBuilder::extendBufferForAppending(unsigned requiredLength)
{
if (m_buffer && requiredLength <= m_buffer->length()) {
m_string = { };
return spanConstCast<CharacterType>(m_buffer->span<CharacterType>().subspan(std::exchange(m_length, requiredLength)));
}
return extendBufferForAppendingSlowCase<CharacterType>(requiredLength);
}
// Shared by the other extendBuffer functions.
template<typename CharacterType> std::span<CharacterType> StringBuilder::extendBufferForAppendingSlowCase(unsigned requiredLength)
{
if (!requiredLength || hasOverflowed())
return { };
reallocateBuffer(expandedCapacity(capacity(), requiredLength));
if (UNLIKELY(hasOverflowed()))
return { };
return spanConstCast<CharacterType>(m_buffer->span<CharacterType>().subspan(std::exchange(m_length, requiredLength)));
}
} // namespace WTF
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