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/*
* Copyright (C) 2010-2019 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/MathExtras.h>
namespace WTF {
static constexpr unsigned maxCapacity = String::MaxLength;
static unsigned expandedCapacity(unsigned capacity, unsigned requiredLength)
{
static constexpr unsigned minimumCapacity = 16;
return std::max(requiredLength, std::max(minimumCapacity, std::min(capacity * 2, maxCapacity)));
}
void StringBuilder::reifyString() const
{
ASSERT(!hasOverflowed());
// Check if the string already exists.
if (!m_string.isNull()) {
ASSERT(m_string.length() == m_length.unsafeGet<unsigned>());
return;
}
#if ASSERT_ENABLED
m_isReified = true;
#endif
// 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_buffer && m_length.unsafeGet<unsigned>() <= m_buffer->length());
if (m_length.unsafeGet<unsigned>() == m_buffer->length())
m_string = m_buffer.get();
else
m_string = StringImpl::createSubstringSharingImpl(*m_buffer, 0, m_length.unsafeGet());
}
void StringBuilder::resize(unsigned newSize)
{
if (hasOverflowed())
return;
// Check newSize < m_length, hence m_length > 0.
unsigned oldLength = m_length.unsafeGet();
ASSERT(newSize <= oldLength);
if (newSize == oldLength)
return;
ASSERT(oldLength);
m_length = newSize;
ASSERT(!hasOverflowed());
// If there is a buffer, we only need to duplicate it if it has more than one ref.
if (m_buffer) {
m_string = 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 (m_buffer->is8Bit())
allocateBuffer(m_buffer->characters8(), m_buffer->length());
else
allocateBuffer(m_buffer->characters16(), m_buffer->length());
}
ASSERT(hasOverflowed() || m_buffer->length() >= m_length.unsafeGet<unsigned>());
return;
}
// Since m_length && !m_buffer, the string must be valid in m_string, and m_string.length() > 0.
ASSERT(!m_string.isEmpty());
ASSERT(oldLength == m_string.length());
ASSERT(newSize < m_string.length());
m_string = StringImpl::createSubstringSharingImpl(*m_string.impl(), 0, newSize);
}
// Allocate a new 8 bit buffer, copying in currentCharacters (these may come from either m_string
// or m_buffer, neither will be reassigned until the copy has completed).
void StringBuilder::allocateBuffer(const LChar* currentCharacters, unsigned requiredLength)
{
ASSERT(!hasOverflowed());
ASSERT(m_is8Bit);
// Copy the existing data into a new buffer, set result to point to the end of the existing data.
auto buffer = StringImpl::tryCreateUninitialized(requiredLength, m_bufferCharacters8);
if (UNLIKELY(!buffer))
return didOverflow();
std::memcpy(m_bufferCharacters8, currentCharacters, m_length.unsafeGet());
// Update the builder state.
m_buffer = WTFMove(buffer);
m_string = String();
ASSERT(m_buffer->length() == requiredLength);
}
// Allocate a new 16 bit buffer, copying in currentCharacters (these may come from either m_string
// or m_buffer, neither will be reassigned until the copy has completed).
void StringBuilder::allocateBuffer(const UChar* currentCharacters, unsigned requiredLength)
{
ASSERT(!hasOverflowed());
ASSERT(!m_is8Bit);
// Copy the existing data into a new buffer, set result to point to the end of the existing data.
auto buffer = StringImpl::tryCreateUninitialized(requiredLength, m_bufferCharacters16);
if (UNLIKELY(!buffer))
return didOverflow();
std::memcpy(m_bufferCharacters16, currentCharacters, static_cast<size_t>(m_length.unsafeGet()) * sizeof(UChar)); // This can't overflow.
// Update the builder state.
m_buffer = WTFMove(buffer);
m_string = String();
ASSERT(m_buffer->length() == requiredLength);
}
// Allocate a new 16 bit buffer, copying in currentCharacters (which is 8 bit and may come
// from either m_string or m_buffer, neither will be reassigned until the copy has completed).
void StringBuilder::allocateBufferUpConvert(const LChar* currentCharacters, unsigned requiredLength)
{
ASSERT(!hasOverflowed());
ASSERT(m_is8Bit);
unsigned length = m_length.unsafeGet();
ASSERT(requiredLength <= maxCapacity && requiredLength >= length);
// Copy the existing data into a new buffer, set result to point to the end of the existing data.
auto buffer = StringImpl::tryCreateUninitialized(requiredLength, m_bufferCharacters16);
if (UNLIKELY(!buffer))
return didOverflow(); // Treat a failure to allcoate as an overflow.
for (unsigned i = 0; i < length; ++i)
m_bufferCharacters16[i] = currentCharacters[i];
m_is8Bit = false;
// Update the builder state.
m_buffer = WTFMove(buffer);
m_string = String();
ASSERT(m_buffer->length() == requiredLength);
}
template<>
void StringBuilder::reallocateBuffer<LChar>(unsigned requiredLength)
{
// If the buffer has only one ref (by this StringBuilder), reallocate it,
// otherwise fall back to "allocate and copy" method.
m_string = String();
ASSERT(m_is8Bit);
ASSERT(m_buffer->is8Bit());
if (m_buffer->hasOneRef()) {
auto expectedStringImpl = StringImpl::tryReallocate(m_buffer.releaseNonNull(), requiredLength, m_bufferCharacters8);
if (UNLIKELY(!expectedStringImpl))
return didOverflow();
m_buffer = WTFMove(expectedStringImpl.value());
} else
allocateBuffer(m_buffer->characters8(), requiredLength);
ASSERT(hasOverflowed() || m_buffer->length() == requiredLength);
}
template<>
void StringBuilder::reallocateBuffer<UChar>(unsigned requiredLength)
{
// If the buffer has only one ref (by this StringBuilder), reallocate it,
// otherwise fall back to "allocate and copy" method.
m_string = String();
if (m_buffer->is8Bit())
allocateBufferUpConvert(m_buffer->characters8(), requiredLength);
else if (m_buffer->hasOneRef()) {
auto expectedStringImpl = StringImpl::tryReallocate(m_buffer.releaseNonNull(), requiredLength, m_bufferCharacters16);
if (UNLIKELY(!expectedStringImpl))
return didOverflow();
m_buffer = WTFMove(expectedStringImpl.value());
} else
allocateBuffer(m_buffer->characters16(), requiredLength);
ASSERT(hasOverflowed() || m_buffer->length() == requiredLength);
}
void StringBuilder::reserveCapacity(unsigned newCapacity)
{
if (hasOverflowed())
return;
ASSERT(newCapacity <= String::MaxLength);
if (m_buffer) {
// If there is already a buffer, then grow if necessary.
if (newCapacity > m_buffer->length()) {
if (m_buffer->is8Bit())
reallocateBuffer<LChar>(newCapacity);
else
reallocateBuffer<UChar>(newCapacity);
}
} else {
// Grow the string, if necessary.
unsigned length = m_length.unsafeGet();
if (newCapacity > length) {
if (!length) {
LChar* nullPlaceholder = nullptr;
allocateBuffer(nullPlaceholder, newCapacity);
} else if (m_string.is8Bit())
allocateBuffer(m_string.characters8(), newCapacity);
else
allocateBuffer(m_string.characters16(), newCapacity);
}
}
ASSERT(hasOverflowed() || !newCapacity || m_buffer->length() >= newCapacity);
}
// Make 'additionalLength' additional capacity be available in m_buffer, update m_string & m_length,
// return a pointer to the newly allocated storage.
// Returns nullptr if the size of the new builder would have overflowed
template<typename CharacterType> ALWAYS_INLINE CharacterType* StringBuilder::extendBufferForAppending(unsigned additionalLength)
{
ASSERT(additionalLength);
// Calculate the new size of the builder after appending.
CheckedInt32 requiredLength = m_length + additionalLength;
if (requiredLength.hasOverflowed()) {
didOverflow();
return nullptr;
}
return extendBufferForAppendingWithoutOverflowCheck<CharacterType>(requiredLength);
}
template<typename CharacterType> ALWAYS_INLINE CharacterType* StringBuilder::extendBufferForAppendingWithoutOverflowCheck(CheckedInt32 requiredLength)
{
ASSERT(!requiredLength.hasOverflowed());
if (m_buffer && (requiredLength.unsafeGet<unsigned>() <= m_buffer->length())) {
// If the buffer is valid it must be at least as long as the current builder contents!
ASSERT(m_buffer->length() >= m_length.unsafeGet<unsigned>());
unsigned currentLength = m_length.unsafeGet();
m_string = String();
m_length = requiredLength;
return getBufferCharacters<CharacterType>() + currentLength;
}
return extendBufferForAppendingSlowCase<CharacterType>(requiredLength.unsafeGet());
}
LChar* StringBuilder::extendBufferForAppending8(CheckedInt32 requiredLength)
{
if (UNLIKELY(requiredLength.hasOverflowed())) {
didOverflow();
return nullptr;
}
return extendBufferForAppendingWithoutOverflowCheck<LChar>(requiredLength);
}
UChar* StringBuilder::extendBufferForAppending16(CheckedInt32 requiredLength)
{
if (UNLIKELY(requiredLength.hasOverflowed())) {
didOverflow();
return nullptr;
}
if (m_is8Bit) {
const LChar* characters;
if (m_buffer) {
ASSERT(m_buffer->length() >= m_length.unsafeGet<unsigned>());
characters = m_buffer->characters8();
} else {
ASSERT(m_string.length() == m_length.unsafeGet<unsigned>());
characters = m_string.isNull() ? nullptr : m_string.characters8();
}
allocateBufferUpConvert(characters, expandedCapacity(capacity(), requiredLength.unsafeGet()));
if (UNLIKELY(hasOverflowed()))
return nullptr;
unsigned oldLength = m_length.unsafeGet();
m_length = requiredLength.unsafeGet();
return m_bufferCharacters16 + oldLength;
}
return extendBufferForAppendingWithoutOverflowCheck<UChar>(requiredLength);
}
// Make 'requiredLength' capacity be available in m_buffer, update m_string & m_length,
// return a pointer to the newly allocated storage.
template<typename CharacterType> CharacterType* StringBuilder::extendBufferForAppendingSlowCase(unsigned requiredLength)
{
ASSERT(!hasOverflowed());
ASSERT(requiredLength);
if (m_buffer) {
// If the buffer is valid it must be at least as long as the current builder contents!
ASSERT(m_buffer->length() >= m_length.unsafeGet<unsigned>());
reallocateBuffer<CharacterType>(expandedCapacity(capacity(), requiredLength));
} else {
ASSERT(m_string.length() == m_length.unsafeGet<unsigned>());
allocateBuffer(m_length ? m_string.characters<CharacterType>() : nullptr, expandedCapacity(capacity(), requiredLength));
}
if (UNLIKELY(hasOverflowed()))
return nullptr;
CharacterType* result = getBufferCharacters<CharacterType>() + m_length.unsafeGet();
m_length = requiredLength;
ASSERT(!hasOverflowed());
ASSERT(m_buffer->length() >= m_length.unsafeGet<unsigned>());
return result;
}
void StringBuilder::appendCharacters(const UChar* characters, unsigned length)
{
if (!length || hasOverflowed())
return;
ASSERT(characters);
if (m_is8Bit && length == 1 && isLatin1(characters[0])) {
append(static_cast<LChar>(characters[0]));
return;
}
// FIXME: Should we optimize memory by keeping the string 8-bit when all the characters are Latin-1?
UChar* destination = extendBufferForAppending16(m_length + length);
if (UNLIKELY(!destination))
return;
std::memcpy(destination, characters, static_cast<size_t>(length) * sizeof(UChar));
ASSERT(!hasOverflowed());
ASSERT(m_buffer->length() >= m_length.unsafeGet<unsigned>());
}
void StringBuilder::appendCharacters(const LChar* characters, unsigned length)
{
if (!length || hasOverflowed())
return;
ASSERT(characters);
if (m_is8Bit) {
LChar* destination = extendBufferForAppending<LChar>(length);
if (!destination) {
ASSERT(hasOverflowed());
return;
}
if (length > 8)
std::memcpy(destination, characters, length);
else {
// FIXME: How strong is our evidence that this is faster than memcpy? What platforms is this true for?
const LChar* end = characters + length;
while (characters < end)
*destination++ = *characters++;
}
} else {
UChar* destination = extendBufferForAppending<UChar>(length);
if (!destination) {
ASSERT(hasOverflowed());
return;
}
const LChar* end = characters + length;
while (characters < end)
*destination++ = *characters++;
}
}
#if USE(CF)
void StringBuilder::append(CFStringRef string)
{
// Fast path: avoid constructing a temporary String when possible.
if (auto* characters = CFStringGetCStringPtr(string, kCFStringEncodingISOLatin1)) {
appendCharacters(reinterpret_cast<const LChar*>(characters), CFStringGetLength(string));
return;
}
append(String(string));
}
#endif
void StringBuilder::appendNumber(int number)
{
numberToStringSigned<StringBuilder>(number, this);
}
void StringBuilder::appendNumber(unsigned number)
{
numberToStringUnsigned<StringBuilder>(number, this);
}
void StringBuilder::appendNumber(long number)
{
numberToStringSigned<StringBuilder>(number, this);
}
void StringBuilder::appendNumber(unsigned long number)
{
numberToStringUnsigned<StringBuilder>(number, this);
}
void StringBuilder::appendNumber(long long number)
{
numberToStringSigned<StringBuilder>(number, this);
}
void StringBuilder::appendNumber(unsigned long long number)
{
numberToStringUnsigned<StringBuilder>(number, this);
}
void StringBuilder::appendNumber(float number)
{
NumberToStringBuffer buffer;
append(numberToString(number, buffer));
}
void StringBuilder::appendNumber(double number)
{
NumberToStringBuffer buffer;
append(numberToString(number, buffer));
}
bool StringBuilder::canShrink() const
{
if (hasOverflowed())
return false;
// Only shrink the buffer if it's less than 80% full.
// FIXME: We should tune this heuristic based some actual test case measurements.
unsigned length = m_length.unsafeGet();
return m_buffer && m_buffer->length() > (length + (length >> 2));
}
void StringBuilder::shrinkToFit()
{
if (canShrink()) {
if (m_is8Bit)
reallocateBuffer<LChar>(m_length.unsafeGet());
else
reallocateBuffer<UChar>(m_length.unsafeGet());
ASSERT(!hasOverflowed());
m_string = WTFMove(m_buffer);
}
}
} // namespace WTF