flutter_flutter/sky/engine/wtf/text/StringBuilder.cpp

/*
 * Copyright (C) 2010 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 "flutter/sky/engine/wtf/text/StringBuilder.h"

#include "flutter/sky/engine/wtf/dtoa.h"
#include "flutter/sky/engine/wtf/text/IntegerToStringConversion.h"
#include "flutter/sky/engine/wtf/text/WTFString.h"

namespace WTF {

static unsigned expandedCapacity(unsigned capacity, unsigned requiredLength) {
  static const unsigned minimumCapacity = 16;
  return std::max(requiredLength, std::max(minimumCapacity, capacity * 2));
}

void StringBuilder::reifyString() {
  if (!m_string.isNull()) {
    ASSERT(m_string.length() == m_length);
    return;
  }

  if (!m_length) {
    m_string = StringImpl::empty();
    return;
  }

  ASSERT(m_buffer && m_length <= m_buffer->length());
  if (m_length == m_buffer->length()) {
    m_string = m_buffer.release();
    return;
  }

  if (m_buffer->hasOneRef()) {
    m_buffer->truncateAssumingIsolated(m_length);
    m_string = m_buffer.release();
    return;
  }

  m_string = m_buffer->substring(0, m_length);
}

String StringBuilder::reifySubstring(unsigned position, unsigned length) const {
  ASSERT(m_string.isNull());
  ASSERT(m_buffer);
  unsigned substringLength = std::min(length, m_length - position);
  return m_buffer->substring(position, substringLength);
}

void StringBuilder::resize(unsigned newSize) {
  // Check newSize < m_length, hence m_length > 0.
  ASSERT(newSize <= m_length);
  if (newSize == m_length)
    return;
  ASSERT(m_length);

  // 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());
    }
    m_length = newSize;
    return;
  }

  // Since m_length && !m_buffer, the string must be valid in m_string, and
  // m_string.length() > 0.
  ASSERT(!m_string.isEmpty());
  ASSERT(m_length == m_string.length());
  ASSERT(newSize < m_string.length());
  m_length = newSize;
  RefPtr<StringImpl> string = m_string.releaseImpl();
  if (string->hasOneRef()) {
    // If we're the only ones with a reference to the string, we can
    // re-purpose the string as m_buffer and continue mutating it.
    m_buffer = string;
  } else {
    // Otherwise, we need to make a copy of the string so that we don't
    // mutate a String that's held elsewhere.
    m_buffer = string->substring(0, m_length);
  }
}

// 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(m_is8Bit);
  // Copy the existing data into a new buffer, set result to point to the end of
  // the existing data.
  RefPtr<StringImpl> buffer =
      StringImpl::createUninitialized(requiredLength, m_bufferCharacters8);
  memcpy(
      m_bufferCharacters8, currentCharacters,
      static_cast<size_t>(m_length) * sizeof(LChar));  // This can't overflow.

  // Update the builder state.
  m_buffer = buffer.release();
  m_string = String();
}

// 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(!m_is8Bit);
  // Copy the existing data into a new buffer, set result to point to the end of
  // the existing data.
  RefPtr<StringImpl> buffer =
      StringImpl::createUninitialized(requiredLength, m_bufferCharacters16);
  memcpy(
      m_bufferCharacters16, currentCharacters,
      static_cast<size_t>(m_length) * sizeof(UChar));  // This can't overflow.

  // Update the builder state.
  m_buffer = buffer.release();
  m_string = String();
}

// 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(m_is8Bit);
  // Copy the existing data into a new buffer, set result to point to the end of
  // the existing data.
  RefPtr<StringImpl> buffer =
      StringImpl::createUninitialized(requiredLength, m_bufferCharacters16);
  for (unsigned i = 0; i < m_length; ++i)
    m_bufferCharacters16[i] = currentCharacters[i];

  m_is8Bit = false;

  // Update the builder state.
  m_buffer = buffer.release();
  m_string = String();
}

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()) {
    m_buffer = StringImpl::reallocate(m_buffer.release(), requiredLength);
    m_bufferCharacters8 = const_cast<LChar*>(m_buffer->characters8());
  } else
    allocateBuffer(m_buffer->characters8(), 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()) {
    m_buffer = StringImpl::reallocate(m_buffer.release(), requiredLength);
    m_bufferCharacters16 = const_cast<UChar*>(m_buffer->characters16());
  } else
    allocateBuffer(m_buffer->characters16(), requiredLength);
}

void StringBuilder::reserveCapacity(unsigned newCapacity) {
  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.
    if (newCapacity > m_length) {
      if (!m_length) {
        LChar* nullPlaceholder = 0;
        allocateBuffer(nullPlaceholder, newCapacity);
      } else if (m_string.is8Bit())
        allocateBuffer(m_string.characters8(), newCapacity);
      else
        allocateBuffer(m_string.characters16(), newCapacity);
    }
  }
}

// Make 'length' additional capacity be available in m_buffer, update m_string &
// m_length, return a pointer to the newly allocated storage.
template <typename CharType>
ALWAYS_INLINE CharType* StringBuilder::appendUninitialized(unsigned length) {
  ASSERT(length);

  // Calculate the new size of the builder after appending.
  unsigned requiredLength = length + m_length;
  RELEASE_ASSERT(requiredLength >= length);

  if ((m_buffer) && (requiredLength <= 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);
    unsigned currentLength = m_length;
    m_string = String();
    m_length = requiredLength;
    return getBufferCharacters<CharType>() + currentLength;
  }

  return appendUninitializedSlow<CharType>(requiredLength);
}

// Make 'length' additional capacity be available in m_buffer, update m_string &
// m_length, return a pointer to the newly allocated storage.
template <typename CharType>
CharType* StringBuilder::appendUninitializedSlow(unsigned requiredLength) {
  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);

    reallocateBuffer<CharType>(expandedCapacity(capacity(), requiredLength));
  } else {
    ASSERT(m_string.length() == m_length);
    allocateBuffer(m_length ? m_string.getCharacters<CharType>() : 0,
                   expandedCapacity(capacity(), requiredLength));
  }

  CharType* result = getBufferCharacters<CharType>() + m_length;
  m_length = requiredLength;
  return result;
}

void StringBuilder::append(const UChar* characters, unsigned length) {
  if (!length)
    return;

  ASSERT(characters);

  if (m_is8Bit) {
    if (length == 1 && !(*characters & ~0xff)) {
      // Append as 8 bit character
      LChar lChar = static_cast<LChar>(*characters);
      append(&lChar, 1);
      return;
    }

    // Calculate the new size of the builder after appending.
    unsigned requiredLength = length + m_length;
    RELEASE_ASSERT(requiredLength >= length);

    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);

      allocateBufferUpConvert(m_buffer->characters8(),
                              expandedCapacity(capacity(), requiredLength));
    } else {
      ASSERT(m_string.length() == m_length);
      allocateBufferUpConvert(m_string.isNull() ? 0 : m_string.characters8(),
                              expandedCapacity(capacity(), requiredLength));
    }

    memcpy(m_bufferCharacters16 + m_length, characters,
           static_cast<size_t>(length) * sizeof(UChar));
    m_length = requiredLength;
  } else
    memcpy(appendUninitialized<UChar>(length), characters,
           static_cast<size_t>(length) * sizeof(UChar));
}

void StringBuilder::append(const LChar* characters, unsigned length) {
  if (!length)
    return;
  ASSERT(characters);

  if (m_is8Bit) {
    LChar* dest = appendUninitialized<LChar>(length);
    if (length > 8)
      memcpy(dest, characters, static_cast<size_t>(length) * sizeof(LChar));
    else {
      const LChar* end = characters + length;
      while (characters < end)
        *(dest++) = *(characters++);
    }
  } else {
    UChar* dest = appendUninitialized<UChar>(length);
    const LChar* end = characters + length;
    while (characters < end)
      *(dest++) = *(characters++);
  }
}

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);
}

static void expandLCharToUCharInplace(UChar* buffer, size_t length) {
  const LChar* sourceEnd = reinterpret_cast<LChar*>(buffer) + length;
  UChar* current = buffer + length;
  while (current != buffer)
    *--current = *--sourceEnd;
}

void StringBuilder::appendNumber(
    double number,
    unsigned precision,
    TrailingZerosTruncatingPolicy trailingZerosTruncatingPolicy) {
  bool truncateTrailingZeros =
      trailingZerosTruncatingPolicy == TruncateTrailingZeros;
  size_t numberLength;
  if (m_is8Bit) {
    LChar* dest = appendUninitialized<LChar>(NumberToStringBufferLength);
    const char* result = numberToFixedPrecisionString(
        number, precision, reinterpret_cast<char*>(dest),
        truncateTrailingZeros);
    numberLength = strlen(result);
  } else {
    UChar* dest = appendUninitialized<UChar>(NumberToStringBufferLength);
    const char* result = numberToFixedPrecisionString(
        number, precision, reinterpret_cast<char*>(dest),
        truncateTrailingZeros);
    numberLength = strlen(result);
    expandLCharToUCharInplace(dest, numberLength);
  }
  ASSERT(m_length >= NumberToStringBufferLength);
  // Remove what appendUninitialized added.
  m_length -= NumberToStringBufferLength;
  ASSERT(numberLength <= NumberToStringBufferLength);
  m_length += numberLength;
}

bool StringBuilder::canShrink() const {
  // Only shrink the buffer if it's less than 80% full. Need to tune this
  // heuristic!
  return m_buffer && m_buffer->length() > (m_length + (m_length >> 2));
}

void StringBuilder::shrinkToFit() {
  if (!canShrink())
    return;
  if (m_is8Bit)
    reallocateBuffer<LChar>(m_length);
  else
    reallocateBuffer<UChar>(m_length);
  m_string = m_buffer.release();
}

}  // namespace WTF