text: /*
   * Copyright (C) 2012-2016 Apple 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 "ExceptionHelpers.h"
  #include "JSCJSValue.h"
  
  namespace JSC {
  
  class JSStringJoiner {
  public:
      JSStringJoiner(ExecState&, LChar separator, unsigned stringCount);
      JSStringJoiner(ExecState&, StringView separator, unsigned stringCount);
      ~JSStringJoiner();
  
      void append(ExecState&, JSValue);
      bool appendWithoutSideEffects(ExecState&, JSValue);
      void appendEmptyString();
  
      JSValue join(ExecState&);
  
  private:
      void append(StringViewWithUnderlyingString&&);
      void append8Bit(const String&);
      void appendLiteral(const Identifier&);
      unsigned joinedLength(ExecState&) const;
  
      LChar m_singleCharacterSeparator;
      StringView m_separator;
      Vector<StringViewWithUnderlyingString> m_strings;
      Checked<unsigned, RecordOverflow> m_accumulatedStringsLength;
      bool m_isAll8Bit { true };
  };
  
  inline JSStringJoiner::JSStringJoiner(ExecState& state, StringView separator, unsigned stringCount)
      : m_separator(separator)
      , m_isAll8Bit(m_separator.is8Bit())
  {
      VM& vm = state.vm();
      auto scope = DECLARE_THROW_SCOPE(vm);
      if (UNLIKELY(!m_strings.tryReserveCapacity(stringCount)))
          throwOutOfMemoryError(&state, scope);
  }
  
  inline JSStringJoiner::JSStringJoiner(ExecState& state, LChar separator, unsigned stringCount)
      : m_singleCharacterSeparator(separator)
      , m_separator { &m_singleCharacterSeparator, 1 }
  {
      VM& vm = state.vm();
      auto scope = DECLARE_THROW_SCOPE(vm);
      if (UNLIKELY(!m_strings.tryReserveCapacity(stringCount)))
          throwOutOfMemoryError(&state, scope);
  }
  
  ALWAYS_INLINE void JSStringJoiner::append(StringViewWithUnderlyingString&& string)
  {
      m_accumulatedStringsLength += string.view.length();
      m_isAll8Bit = m_isAll8Bit && string.view.is8Bit();
      m_strings.uncheckedAppend(WTFMove(string));
  }
  
  ALWAYS_INLINE void JSStringJoiner::append8Bit(const String& string)
  {
      ASSERT(string.is8Bit());
      m_accumulatedStringsLength += string.length();
      m_strings.uncheckedAppend({ string, string });
  }
  
  ALWAYS_INLINE void JSStringJoiner::appendLiteral(const Identifier& literal)
  {
      m_accumulatedStringsLength += literal.length();
      ASSERT(literal.string().is8Bit());
      m_strings.uncheckedAppend({ literal.string(), { } });
  }
  
  ALWAYS_INLINE void JSStringJoiner::appendEmptyString()
  {
      m_strings.uncheckedAppend({ { }, { } });
  }
  
  ALWAYS_INLINE bool JSStringJoiner::appendWithoutSideEffects(ExecState& state, JSValue value)
  {
      // The following code differs from using the result of JSValue::toString in the following ways:
      // 1) It's inlined more than JSValue::toString is.
      // 2) It includes conversion to WTF::String in a way that avoids allocating copies of substrings.
      // 3) It doesn't create a JSString for numbers, true, or false.
      // 4) It turns undefined and null into the empty string instead of "undefined" and "null".
      // 5) It uses optimized code paths for all the cases known to be 8-bit and for the empty string.
      // If we might make an effectful calls, return false. Otherwise return true.
  
      if (value.isCell()) {
          JSString* jsString;
          if (!value.asCell()->isString())
              return false;
          jsString = asString(value);
          append(jsString->viewWithUnderlyingString(state));
          return true;
      }
  
      if (value.isInt32()) {
          append8Bit(state.vm().numericStrings.add(value.asInt32()));
          return true;
      }
      if (value.isDouble()) {
          append8Bit(state.vm().numericStrings.add(value.asDouble()));
          return true;
      }
      if (value.isTrue()) {
          append8Bit(state.vm().propertyNames->trueKeyword.string());
          return true;
      }
      if (value.isFalse()) {
          append8Bit(state.vm().propertyNames->falseKeyword.string());
          return true;
      }
      ASSERT(value.isUndefinedOrNull());
      appendEmptyString();
      return true;
  }
  
  ALWAYS_INLINE void JSStringJoiner::append(ExecState& state, JSValue value)
  {
      if (!appendWithoutSideEffects(state, value)) {
          JSString* jsString = value.toString(&state);
          append(jsString->viewWithUnderlyingString(state));
      }
  }
  
  } // namespace JSC
  