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/*
* Copyright (C) 2010-2021 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.
*/
#include "config.h"
#include <wtf/text/StringBuilder.h>
#include <wtf/dtoa.h>
#include <wtf/text/StringBuilderInternals.h>
namespace WTF {
static constexpr unsigned maxCapacity = String::MaxLength;
unsigned StringBuilder::expandedCapacity(unsigned capacity, unsigned requiredCapacity)
{
static constexpr unsigned minimumCapacity = 16;
return std::max(requiredCapacity, std::max(minimumCapacity, std::min(capacity * 2, maxCapacity)));
}
void StringBuilder::didOverflow()
{
if (m_shouldCrashOnOverflow)
CRASH();
m_length = std::numeric_limits<unsigned>::max();
}
void StringBuilder::reifyString() const
{
RELEASE_ASSERT(!hasOverflowed());
// Check if the string already exists.
if (!m_string.isNull()) {
ASSERT(m_string.length() == m_length);
return;
}
// Check for empty.
if (!m_length) {
m_string = StringImpl::empty();
return;
}
// Must be valid in the buffer, take a substring (unless string fills the buffer).
ASSERT(m_length <= m_buffer->length());
if (m_length == m_buffer->length())
m_string = m_buffer.get();
else
m_string = StringImpl::createSubstringSharingImpl(Ref { *m_buffer }, 0, m_length);
}
void StringBuilder::shrink(unsigned newLength)
{
if (hasOverflowed())
return;
ASSERT(newLength <= m_length);
if (newLength >= m_length) {
if (newLength > m_length)
didOverflow();
return;
}
m_length = newLength;
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()) {
// If the old buffer had only the one ref, we can just reduce the length and keep using the buffer.
return;
}
// Allocate a fresh buffer, with a copy of the characters we are keeping.
if (m_buffer->is8Bit())
allocateBuffer<LChar>(m_buffer->span8().first(m_length), newLength);
else
allocateBuffer<UChar>(m_buffer->span16().first(m_length), newLength);
return;
}
// Since the old length was not 0 and m_buffer is null, m_string is guaranteed to be non-null.
m_string = StringImpl::createSubstringSharingImpl(*m_string.impl(), 0, newLength);
}
void StringBuilder::reallocateBuffer(unsigned requiredCapacity)
{
if (is8Bit())
reallocateBuffer<LChar>(requiredCapacity);
else
reallocateBuffer<UChar>(requiredCapacity);
}
void StringBuilder::reserveCapacity(unsigned newCapacity)
{
if (hasOverflowed())
return;
if (m_buffer) {
if (newCapacity > m_buffer->length())
reallocateBuffer(newCapacity);
} else {
if (newCapacity > m_length) {
if (!m_length)
allocateBuffer<LChar>(std::span<const LChar> { }, newCapacity);
else if (m_string.is8Bit())
allocateBuffer<LChar>(m_string.span8(), newCapacity);
else
allocateBuffer<UChar>(m_string.span16(), newCapacity);
}
}
ASSERT(hasOverflowed() || !newCapacity || m_buffer->length() >= newCapacity);
}
// Alterative extendBufferForAppending that can be called from the header without inlining.
std::span<LChar> StringBuilder::extendBufferForAppendingLChar(unsigned requiredLength)
{
return extendBufferForAppending<LChar>(requiredLength);
}
std::span<UChar> StringBuilder::extendBufferForAppendingWithUpconvert(unsigned requiredLength)
{
if (is8Bit()) {
allocateBuffer<UChar>(span8(), expandedCapacity(capacity(), requiredLength));
if (UNLIKELY(hasOverflowed()))
return { };
return spanConstCast<UChar>(m_buffer->span16().subspan(std::exchange(m_length, requiredLength)));
}
return extendBufferForAppending<UChar>(requiredLength);
}
void StringBuilder::append(std::span<const UChar> characters)
{
if (characters.empty() || hasOverflowed())
return;
if (characters.size() == 1 && isLatin1(characters[0]) && is8Bit()) {
append(static_cast<LChar>(characters[0]));
return;
}
RELEASE_ASSERT(characters.size() < std::numeric_limits<uint32_t>::max());
if (auto destination = extendBufferForAppendingWithUpconvert(saturatedSum<uint32_t>(m_length, static_cast<uint32_t>(characters.size()))); destination.data())
StringImpl::copyCharacters(destination, characters);
}
void StringBuilder::append(std::span<const LChar> characters)
{
if (characters.empty() || hasOverflowed())
return;
RELEASE_ASSERT(characters.size() < std::numeric_limits<uint32_t>::max());
if (is8Bit()) {
if (auto destination = extendBufferForAppending<LChar>(saturatedSum<uint32_t>(m_length, static_cast<uint32_t>(characters.size()))); destination.data())
StringImpl::copyCharacters(destination, characters);
} else {
if (auto destination = extendBufferForAppending<UChar>(saturatedSum<uint32_t>(m_length, static_cast<uint32_t>(characters.size()))); destination.data())
StringImpl::copyCharacters(destination, characters);
}
}
bool StringBuilder::shouldShrinkToFit() const
{
// Shrink the buffer if it's 80% full or less.
static_assert(static_cast<size_t>(String::MaxLength) + (String::MaxLength >> 2) <= static_cast<size_t>(std::numeric_limits<unsigned>::max()));
return !hasOverflowed() && m_buffer && m_buffer->length() > m_length + (m_length >> 2);
}
void StringBuilder::shrinkToFit()
{
if (shouldShrinkToFit()) {
reallocateBuffer(m_length);
m_string = std::exchange(m_buffer, nullptr);
}
}
bool StringBuilder::containsOnlyASCII() const
{
return StringView { *this }.containsOnlyASCII();
}
} // namespace WTF
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