198 lines
6.7 KiB
C++
198 lines
6.7 KiB
C++
/*
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* Copyright (C) 2010-2021 Apple Inc. All rights reserved.
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* Copyright (C) 2012 Google Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "config.h"
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#include <wtf/text/StringBuilder.h>
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#include <wtf/dtoa.h>
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#include <wtf/text/StringBuilderInternals.h>
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namespace WTF {
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static constexpr unsigned maxCapacity = String::MaxLength;
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unsigned StringBuilder::expandedCapacity(unsigned capacity, unsigned requiredCapacity)
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{
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static constexpr unsigned minimumCapacity = 16;
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return std::max(requiredCapacity, std::max(minimumCapacity, std::min(capacity * 2, maxCapacity)));
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}
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void StringBuilder::didOverflow()
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{
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if (m_shouldCrashOnOverflow)
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CRASH();
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m_length = std::numeric_limits<unsigned>::max();
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}
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void StringBuilder::reifyString() const
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{
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RELEASE_ASSERT(!hasOverflowed());
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// Check if the string already exists.
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if (!m_string.isNull()) {
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ASSERT(m_string.length() == m_length);
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return;
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}
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// Check for empty.
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if (!m_length) {
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m_string = StringImpl::empty();
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return;
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}
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// Must be valid in the buffer, take a substring (unless string fills the buffer).
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ASSERT(m_length <= m_buffer->length());
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if (m_length == m_buffer->length())
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m_string = m_buffer.get();
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else
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m_string = StringImpl::createSubstringSharingImpl(*m_buffer, 0, m_length);
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}
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void StringBuilder::shrink(unsigned newLength)
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{
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if (hasOverflowed())
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return;
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ASSERT(newLength <= m_length);
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if (newLength >= m_length) {
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if (newLength > m_length)
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didOverflow();
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return;
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}
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m_length = newLength;
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if (m_buffer) {
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m_string = { }; // Clear the string to remove the reference to m_buffer if any before checking the reference count of m_buffer.
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if (m_buffer->hasOneRef()) {
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// If the old buffer had only the one ref, we can just reduce the length and keep using the buffer.
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return;
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}
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// Allocate a fresh buffer, with a copy of the characters we are keeping.
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if (m_buffer->is8Bit())
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allocateBuffer<LChar>(m_buffer->characters<LChar>(), newLength);
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else
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allocateBuffer<UChar>(m_buffer->characters<UChar>(), newLength);
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return;
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}
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// Since the old length was not 0 and m_buffer is null, m_string is guaranteed to be non-null.
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m_string = StringImpl::createSubstringSharingImpl(*m_string.impl(), 0, newLength);
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}
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void StringBuilder::reallocateBuffer(unsigned requiredCapacity)
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{
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if (is8Bit())
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reallocateBuffer<LChar>(requiredCapacity);
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else
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reallocateBuffer<UChar>(requiredCapacity);
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}
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void StringBuilder::reserveCapacity(unsigned newCapacity)
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{
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if (hasOverflowed())
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return;
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if (m_buffer) {
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if (newCapacity > m_buffer->length())
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reallocateBuffer(newCapacity);
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} else {
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if (newCapacity > m_length) {
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if (!m_length)
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allocateBuffer<LChar>(static_cast<LChar*>(nullptr), newCapacity);
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else if (m_string.is8Bit())
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allocateBuffer<LChar>(m_string.characters8(), newCapacity);
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else
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allocateBuffer<UChar>(m_string.characters16(), newCapacity);
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}
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}
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ASSERT(hasOverflowed() || !newCapacity || m_buffer->length() >= newCapacity);
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}
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// Alterative extendBufferForAppending that can be called from the header without inlining.
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LChar* StringBuilder::extendBufferForAppendingLChar(unsigned requiredLength)
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{
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return extendBufferForAppending<LChar>(requiredLength);
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}
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UChar* StringBuilder::extendBufferForAppendingWithUpconvert(unsigned requiredLength)
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{
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if (is8Bit()) {
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allocateBuffer<UChar>(characters<LChar>(), expandedCapacity(capacity(), requiredLength));
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if (UNLIKELY(hasOverflowed()))
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return nullptr;
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return const_cast<UChar*>(m_buffer->characters<UChar>()) + std::exchange(m_length, requiredLength);
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}
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return extendBufferForAppending<UChar>(requiredLength);
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}
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void StringBuilder::appendCharacters(const UChar* characters, unsigned length)
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{
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if (!length || hasOverflowed())
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return;
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if (length == 1 && isLatin1(characters[0]) && is8Bit()) {
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append(static_cast<LChar>(characters[0]));
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return;
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}
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if (auto destination = extendBufferForAppendingWithUpconvert(saturatedSum<uint32_t>(m_length, length)))
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StringImpl::copyCharacters(destination, characters, length);
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}
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void StringBuilder::appendCharacters(const LChar* characters, unsigned length)
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{
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if (!length || hasOverflowed())
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return;
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if (is8Bit()) {
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if (auto destination = extendBufferForAppending<LChar>(saturatedSum<uint32_t>(m_length, length)))
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StringImpl::copyCharacters(destination, characters, length);
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} else {
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if (auto destination = extendBufferForAppending<UChar>(saturatedSum<uint32_t>(m_length, length)))
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StringImpl::copyCharacters(destination, characters, length);
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}
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}
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bool StringBuilder::shouldShrinkToFit() const
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{
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// Shrink the buffer if it's 80% full or less.
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static_assert(static_cast<size_t>(String::MaxLength) + (String::MaxLength >> 2) <= static_cast<size_t>(std::numeric_limits<unsigned>::max()));
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return !hasOverflowed() && m_buffer && m_buffer->length() > m_length + (m_length >> 2);
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}
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void StringBuilder::shrinkToFit()
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{
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if (shouldShrinkToFit()) {
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reallocateBuffer(m_length);
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m_string = std::exchange(m_buffer, nullptr);
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}
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}
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bool StringBuilder::isAllASCII() const
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{
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return StringView { *this }.isAllASCII();
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}
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} // namespace WTF
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