CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. All rights reserved.

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * 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.

//     * Neither the name of Google Inc. nor the names of its

//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "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 THE COPYRIGHT

// OWNER 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.

#ifndef V8_UTILS_H_

#define V8_UTILS_H_

#include <stdlib.h>

#include <string.h>

#include <algorithm>

#include <climits>

#include "allocation.h"

#include "checks.h"

#include "globals.h"

namespace v8 {

namespace internal {

// ----------------------------------------------------------------------------

// General helper functions

#define IS_POWER_OF_TWO(x) (((x) & ((x) - 1)) == 0)

// Returns true iff x is a power of 2 (or zero). Cannot be used with the

// maximally negative value of the type T (the -1 overflows).

template <typename T>

inline bool IsPowerOf2(T x) {

  return IS_POWER_OF_TWO(x);

}

// X must be a power of 2.  Returns the number of trailing zeros.

inline int WhichPowerOf2(uint32_t x) {

  ASSERT(IsPowerOf2(x));

  ASSERT(x != 0);

  int bits = 0;

#ifdef DEBUG

  int original_x = x;

#endif

  if (x >= 0x10000) {

    bits += 16;

    x >>= 16;

  }

  if (x >= 0x100) {

    bits += 8;

    x >>= 8;

  }

  if (x >= 0x10) {

    bits += 4;

    x >>= 4;

  }

  switch (x) {

    default: UNREACHABLE();

    case 8: bits++;  // Fall through.

    case 4: bits++;  // Fall through.

    case 2: bits++;  // Fall through.

    case 1: break;

  }

  ASSERT_EQ(1 << bits, original_x);

  return bits;

  return 0;

}

inline int MostSignificantBit(uint32_t x) {

  static const int msb4[] = {0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4};

  int nibble = 0;

  if (x & 0xffff0000) {

    nibble += 16;

    x >>= 16;

  }

  if (x & 0xff00) {

    nibble += 8;

    x >>= 8;

  }

  if (x & 0xf0) {

    nibble += 4;

    x >>= 4;

  }

  return nibble + msb4[x];

}

// Magic numbers for integer division.

// These are kind of 2's complement reciprocal of the divisors.

// Details and proofs can be found in:

// - Hacker's Delight, Henry S. Warren, Jr.

// - The PowerPC Compiler Writer’s Guide

// and probably many others.

// See details in the implementation of the algorithm in

// lithium-codegen-arm.cc : LCodeGen::TryEmitSignedIntegerDivisionByConstant().

struct DivMagicNumbers {

  unsigned M;

  unsigned s;

};

const DivMagicNumbers InvalidDivMagicNumber= {0, 0};

const DivMagicNumbers DivMagicNumberFor3   = {0x55555556, 0};

const DivMagicNumbers DivMagicNumberFor5   = {0x66666667, 1};

const DivMagicNumbers DivMagicNumberFor7   = {0x92492493, 2};

const DivMagicNumbers DivMagicNumberFor9   = {0x38e38e39, 1};

const DivMagicNumbers DivMagicNumberFor11  = {0x2e8ba2e9, 1};

const DivMagicNumbers DivMagicNumberFor25  = {0x51eb851f, 3};

const DivMagicNumbers DivMagicNumberFor125 = {0x10624dd3, 3};

const DivMagicNumbers DivMagicNumberFor625 = {0x68db8bad, 8};

const DivMagicNumbers DivMagicNumberFor(int32_t divisor);

// The C++ standard leaves the semantics of '>>' undefined for

// negative signed operands. Most implementations do the right thing,

// though.

inline int ArithmeticShiftRight(int x, int s) {

  return x >> s;

}

// Compute the 0-relative offset of some absolute value x of type T.

// This allows conversion of Addresses and integral types into

// 0-relative int offsets.

template <typename T>

inline intptr_t OffsetFrom(T x) {

  return x - static_cast<T>(0);

}

// Compute the absolute value of type T for some 0-relative offset x.

// This allows conversion of 0-relative int offsets into Addresses and

// integral types.

template <typename T>

inline T AddressFrom(intptr_t x) {

  return static_cast<T>(static_cast<T>(0) + x);

}

// Return the largest multiple of m which is <= x.

template <typename T>

inline T RoundDown(T x, intptr_t m) {

  ASSERT(IsPowerOf2(m));

  return AddressFrom<T>(OffsetFrom(x) & -m);

}

// Return the smallest multiple of m which is >= x.

template <typename T>

inline T RoundUp(T x, intptr_t m) {

  return RoundDown<T>(static_cast<T>(x + m - 1), m);

}

template <typename T>

int Compare(const T& a, const T& b) {

  if (a == b)

    return 0;

  else if (a < b)

    return -1;

  else

    return 1;

}

template <typename T>

int PointerValueCompare(const T* a, const T* b) {

  return Compare<T>(*a, *b);

}

// Compare function to compare the object pointer value of two

// handlified objects. The handles are passed as pointers to the

// handles.

template<typename T> class Handle;  // Forward declaration.

template <typename T>

int HandleObjectPointerCompare(const Handle<T>* a, const Handle<T>* b) {

  return Compare<T*>(*(*a), *(*b));

}

// Returns the smallest power of two which is >= x. If you pass in a

// number that is already a power of two, it is returned as is.

// Implementation is from "Hacker's Delight" by Henry S. Warren, Jr.,

// figure 3-3, page 48, where the function is called clp2.

inline uint32_t RoundUpToPowerOf2(uint32_t x) {

  ASSERT(x <= 0x80000000u);

  x = x - 1;

  x = x | (x >> 1);

  x = x | (x >> 2);

  x = x | (x >> 4);

  x = x | (x >> 8);

  x = x | (x >> 16);

  return x + 1;

}

inline uint32_t RoundDownToPowerOf2(uint32_t x) {

  uint32_t rounded_up = RoundUpToPowerOf2(x);

  if (rounded_up > x) return rounded_up >> 1;

  return rounded_up;

}

template <typename T, typename U>

inline bool IsAligned(T value, U alignment) {

  return (value & (alignment - 1)) == 0;

}

// Returns true if (addr + offset) is aligned.

inline bool IsAddressAligned(Address addr,

                             intptr_t alignment,

                             int offset = 0) {

  intptr_t offs = OffsetFrom(addr + offset);

  return IsAligned(offs, alignment);

}

// Returns the maximum of the two parameters.

template <typename T>

T Max(T a, T b) {

  return a < b ? b : a;

}

// Returns the minimum of the two parameters.

template <typename T>

T Min(T a, T b) {

  return a < b ? a : b;

}

// Returns the absolute value of its argument.

template <typename T>

T Abs(T a) {

  return a < 0 ? -a : a;

}

// Returns the negative absolute value of its argument.

template <typename T>

T NegAbs(T a) {

  return a < 0 ? a : -a;

}

inline int StrLength(const char* string) {

  size_t length = strlen(string);

  ASSERT(length == static_cast<size_t>(static_cast<int>(length)));

  return static_cast<int>(length);

}

// ----------------------------------------------------------------------------

// BitField is a help template for encoding and decode bitfield with

// unsigned content.

template<class T, int shift, int size, class U>

class BitFieldBase {

 public:

  // A type U mask of bit field.  To use all bits of a type U of x bits

  // in a bitfield without compiler warnings we have to compute 2^x

  // without using a shift count of x in the computation.

  static const U kOne = static_cast<U>(1U);

  static const U kMask = ((kOne << shift) << size) - (kOne << shift);

  static const U kShift = shift;

  static const U kSize = size;

  // Value for the field with all bits set.

  static const T kMax = static_cast<T>((1U << size) - 1);

  // Tells whether the provided value fits into the bit field.

  static bool is_valid(T value) {

    return (static_cast<U>(value) & ~static_cast<U>(kMax)) == 0;

  }

  // Returns a type U with the bit field value encoded.

  static U encode(T value) {

    ASSERT(is_valid(value));

    return static_cast<U>(value) << shift;

  }

  // Returns a type U with the bit field value updated.

  static U update(U previous, T value) {

    return (previous & ~kMask) | encode(value);

  }

  // Extracts the bit field from the value.

  static T decode(U value) {

    return static_cast<T>((value & kMask) >> shift);

  }

};

template<class T, int shift, int size>

class BitField : public BitFieldBase<T, shift, size, uint32_t> { };

template<class T, int shift, int size>

class BitField64 : public BitFieldBase<T, shift, size, uint64_t> { };

// ----------------------------------------------------------------------------

// Hash function.

static const uint32_t kZeroHashSeed = 0;

// Thomas Wang, Integer Hash Functions.

// http://www.concentric.net/~Ttwang/tech/inthash.htm

inline uint32_t ComputeIntegerHash(uint32_t key, uint32_t seed) {

  uint32_t hash = key;

  hash = hash ^ seed;

  hash = ~hash + (hash << 15);  // hash = (hash << 15) - hash - 1;

  hash = hash ^ (hash >> 12);

  hash = hash + (hash << 2);

  hash = hash ^ (hash >> 4);

  hash = hash * 2057;  // hash = (hash + (hash << 3)) + (hash << 11);

  hash = hash ^ (hash >> 16);

  return hash;

}

inline uint32_t ComputeLongHash(uint64_t key) {

  uint64_t hash = key;

  hash = ~hash + (hash << 18);  // hash = (hash << 18) - hash - 1;

  hash = hash ^ (hash >> 31);

  hash = hash * 21;  // hash = (hash + (hash << 2)) + (hash << 4);

  hash = hash ^ (hash >> 11);

  hash = hash + (hash << 6);

  hash = hash ^ (hash >> 22);

  return static_cast<uint32_t>(hash);

}

inline uint32_t ComputePointerHash(void* ptr) {

  return ComputeIntegerHash(

      static_cast<uint32_t>(reinterpret_cast<intptr_t>(ptr)),

      v8::internal::kZeroHashSeed);

}

// ----------------------------------------------------------------------------

// Miscellaneous

// A static resource holds a static instance that can be reserved in

// a local scope using an instance of Access.  Attempts to re-reserve

// the instance will cause an error.

template <typename T>

class StaticResource {

 public:

  StaticResource() : is_reserved_(false)  {}

 private:

  template <typename S> friend class Access;

  T instance_;

  bool is_reserved_;

};

// Locally scoped access to a static resource.

template <typename T>

class Access {

 public:

  explicit Access(StaticResource<T>* resource)

    : resource_(resource)

    , instance_(&resource->instance_) {

    ASSERT(!resource->is_reserved_);

    resource->is_reserved_ = true;

  }

  ~Access() {

    resource_->is_reserved_ = false;

    resource_ = NULL;

    instance_ = NULL;

  }

  T* value()  { return instance_; }

  T* operator -> ()  { return instance_; }

 private:

  StaticResource<T>* resource_;

  T* instance_;

};

template <typename T>

class Vector {

 public:

  Vector() : start_(NULL), length_(0) {}

  Vector(T* data, int length) : start_(data), length_(length) {

    ASSERT(length == 0 || (length > 0 && data != NULL));

  }

  static Vector<T> New(int length) {

    return Vector<T>(NewArray<T>(length), length);

  }

  // Returns a vector using the same backing storage as this one,

  // spanning from and including 'from', to but not including 'to'.

  Vector<T> SubVector(int from, int to) {

    SLOW_ASSERT(to <= length_);

    SLOW_ASSERT(from < to);

    ASSERT(0 <= from);

    return Vector<T>(start() + from, to - from);

  }

  // Returns the length of the vector.

  int length() const { return length_; }

  // Returns whether or not the vector is empty.

  bool is_empty() const { return length_ == 0; }

  // Returns the pointer to the start of the data in the vector.

  T* start() const { return start_; }

  // Access individual vector elements - checks bounds in debug mode.

  T& operator[](int index) const {

    ASSERT(0 <= index && index < length_);

    return start_[index];

  }

  const T& at(int index) const { return operator[](index); }

  T& first() { return start_[0]; }

  T& last() { return start_[length_ - 1]; }

  // Returns a clone of this vector with a new backing store.

  Vector<T> Clone() const {

    T* result = NewArray<T>(length_);

    for (int i = 0; i < length_; i++) result[i] = start_[i];

    return Vector<T>(result, length_);

  }

  void Sort(int (*cmp)(const T*, const T*)) {

    std::sort(start(), start() + length(), RawComparer(cmp));

  }

  void Sort() {

    std::sort(start(), start() + length());

  }

  void Truncate(int length) {

    ASSERT(length <= length_);

    length_ = length;

  }

  // Releases the array underlying this vector. Once disposed the

  // vector is empty.

  void Dispose() {

    DeleteArray(start_);

    start_ = NULL;

    length_ = 0;

  }

  inline Vector<T> operator+(int offset) {

    ASSERT(offset < length_);

    return Vector<T>(start_ + offset, length_ - offset);

  }

  // Factory method for creating empty vectors.

  static Vector<T> empty() { return Vector<T>(NULL, 0); }

  template<typename S>

  static Vector<T> cast(Vector<S> input) {

    return Vector<T>(reinterpret_cast<T*>(input.start()),

                     input.length() * sizeof(S) / sizeof(T));

  }

 protected:

  void set_start(T* start) { start_ = start; }

 private:

  T* start_;

  int length_;

  class RawComparer {

   public:

    explicit RawComparer(int (*cmp)(const T*, const T*)) : cmp_(cmp) {}

    bool operator()(const T& a, const T& b) {

      return cmp_(&a, &b) < 0;

    }

   private:

    int (*cmp_)(const T*, const T*);

  };

};

// A pointer that can only be set once and doesn't allow NULL values.

template<typename T>

class SetOncePointer {

 public:

  SetOncePointer() : pointer_(NULL) { }

  bool is_set() const { return pointer_ != NULL; }

  T* get() const {

    ASSERT(pointer_ != NULL);

    return pointer_;

  }

  void set(T* value) {

    ASSERT(pointer_ == NULL && value != NULL);

    pointer_ = value;

  }

 private:

  T* pointer_;

};

template <typename T, int kSize>

class EmbeddedVector : public Vector<T> {

 public:

  EmbeddedVector() : Vector<T>(buffer_, kSize) { }

  explicit EmbeddedVector(T initial_value) : Vector<T>(buffer_, kSize) {

    for (int i = 0; i < kSize; ++i) {

      buffer_[i] = initial_value;

    }

  }

  // When copying, make underlying Vector to reference our buffer.

  EmbeddedVector(const EmbeddedVector& rhs)

      : Vector<T>(rhs) {

    // TODO(jkummerow): Refactor #includes and use OS::MemCopy() instead.

    memcpy(buffer_, rhs.buffer_, sizeof(T) * kSize);

    set_start(buffer_);

  }

  EmbeddedVector& operator=(const EmbeddedVector& rhs) {

    if (this == &rhs) return *this;

    Vector<T>::operator=(rhs);

    // TODO(jkummerow): Refactor #includes and use OS::MemCopy() instead.

    memcpy(buffer_, rhs.buffer_, sizeof(T) * kSize);

    this->set_start(buffer_);

    return *this;

  }

 private:

  T buffer_[kSize];

};

template <typename T>

class ScopedVector : public Vector<T> {

 public:

  explicit ScopedVector(int length) : Vector<T>(NewArray<T>(length), length) { }

  ~ScopedVector() {

    DeleteArray(this->start());

  }

 private:

  DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedVector);

};

#define STATIC_ASCII_VECTOR(x)                        \

  v8::internal::Vector<const uint8_t>(reinterpret_cast<const uint8_t*>(x), \

                                      ARRAY_SIZE(x)-1)

inline Vector<const char> CStrVector(const char* data) {

  return Vector<const char>(data, StrLength(data));

}

inline Vector<const uint8_t> OneByteVector(const char* data, int length) {

  return Vector<const uint8_t>(reinterpret_cast<const uint8_t*>(data), length);

}

inline Vector<const uint8_t> OneByteVector(const char* data) {

  return OneByteVector(data, StrLength(data));

}

inline Vector<char> MutableCStrVector(char* data) {

  return Vector<char>(data, StrLength(data));

}

inline Vector<char> MutableCStrVector(char* data, int max) {

  int length = StrLength(data);

  return Vector<char>(data, (length < max) ? length : max);

}

/*

 * A class that collects values into a backing store.

 * Specialized versions of the class can allow access to the backing store

 * in different ways.

 * There is no guarantee that the backing store is contiguous (and, as a

 * consequence, no guarantees that consecutively added elements are adjacent

 * in memory). The collector may move elements unless it has guaranteed not

 * to.

 */

template <typename T, int growth_factor = 2, int max_growth = 1 * MB>

class Collector {

 public:

  explicit Collector(int initial_capacity = kMinCapacity)

      : index_(0), size_(0) {

    current_chunk_ = Vector<T>::New(initial_capacity);

  }

  virtual ~Collector() {

    // Free backing store (in reverse allocation order).

    current_chunk_.Dispose();

    for (int i = chunks_.length() - 1; i >= 0; i--) {

      chunks_.at(i).Dispose();

    }

  }

  // Add a single element.

  inline void Add(T value) {

    if (index_ >= current_chunk_.length()) {

      Grow(1);

    }

    current_chunk_[index_] = value;

    index_++;

    size_++;

  }

  // Add a block of contiguous elements and return a Vector backed by the

  // memory area.

  // A basic Collector will keep this vector valid as long as the Collector

  // is alive.

  inline Vector<T> AddBlock(int size, T initial_value) {

    ASSERT(size > 0);

    if (size > current_chunk_.length() - index_) {

      Grow(size);

    }

    T* position = current_chunk_.start() + index_;

    index_ += size;

    size_ += size;

    for (int i = 0; i < size; i++) {

      position[i] = initial_value;

    }

    return Vector<T>(position, size);

  }

  // Add a contiguous block of elements and return a vector backed

  // by the added block.

  // A basic Collector will keep this vector valid as long as the Collector

  // is alive.

  inline Vector<T> AddBlock(Vector<const T> source) {

    if (source.length() > current_chunk_.length() - index_) {

      Grow(source.length());

    }

    T* position = current_chunk_.start() + index_;

    index_ += source.length();

    size_ += source.length();

    for (int i = 0; i < source.length(); i++) {

      position[i] = source[i];

    }

    return Vector<T>(position, source.length());

  }

  // Write the contents of the collector into the provided vector.

  void WriteTo(Vector<T> destination) {

    ASSERT(size_ <= destination.length());

    int position = 0;

    for (int i = 0; i < chunks_.length(); i++) {

      Vector<T> chunk = chunks_.at(i);

      for (int j = 0; j < chunk.length(); j++) {

        destination[position] = chunk[j];

        position++;

      }

    }

    for (int i = 0; i < index_; i++) {

      destination[position] = current_chunk_[i];

      position++;

    }

  }

  // Allocate a single contiguous vector, copy all the collected

  // elements to the vector, and return it.

  // The caller is responsible for freeing the memory of the returned

  // vector (e.g., using Vector::Dispose).

  Vector<T> ToVector() {

    Vector<T> new_store = Vector<T>::New(size_);

    WriteTo(new_store);

    return new_store;

  }

  // Resets the collector to be empty.

  virtual void Reset();

  // Total number of elements added to collector so far.

  inline int size() { return size_; }

 protected:

  static const int kMinCapacity = 16;

  List<Vector<T> > chunks_;

  Vector<T> current_chunk_;  // Block of memory currently being written into.

  int index_;  // Current index in current chunk.

  int size_;  // Total number of elements in collector.

  // Creates a new current chunk, and stores the old chunk in the chunks_ list.

  void Grow(int min_capacity) {

    ASSERT(growth_factor > 1);

    int new_capacity;

    int current_length = current_chunk_.length();

    if (current_length < kMinCapacity) {

      // The collector started out as empty.

      new_capacity = min_capacity * growth_factor;

      if (new_capacity < kMinCapacity) new_capacity = kMinCapacity;

    } else {

      int growth = current_length * (growth_factor - 1);

      if (growth > max_growth) {

        growth = max_growth;

      }

      new_capacity = current_length + growth;

      if (new_capacity < min_capacity) {

        new_capacity = min_capacity + growth;

      }

    }

    NewChunk(new_capacity);

    ASSERT(index_ + min_capacity <= current_chunk_.length());

  }

  // Before replacing the current chunk, give a subclass the option to move

  // some of the current data into the new chunk. The function may update

  // the current index_ value to represent data no longer in the current chunk.

  // Returns the initial index of the new chunk (after copied data).

  virtual void NewChunk(int new_capacity)  {

    Vector<T> new_chunk = Vector<T>::New(new_capacity);

    if (index_ > 0) {

      chunks_.Add(current_chunk_.SubVector(0, index_));

    } else {

      current_chunk_.Dispose();

    }

    current_chunk_ = new_chunk;

    index_ = 0;

  }

};

/*

 * A collector that allows sequences of values to be guaranteed to

 * stay consecutive.

 * If the backing store grows while a sequence is active, the current

 * sequence might be moved, but after the sequence is ended, it will

 * not move again.

 * NOTICE: Blocks allocated using Collector::AddBlock(int) can move

 * as well, if inside an active sequence where another element is added.

 */

template <typename T, int growth_factor = 2, int max_growth = 1 * MB>

class SequenceCollector : public Collector<T, growth_factor, max_growth> {

 public:

  explicit SequenceCollector(int initial_capacity)

      : Collector<T, growth_factor, max_growth>(initial_capacity),

        sequence_start_(kNoSequence) { }

  virtual ~SequenceCollector() {}

  void StartSequence() {

    ASSERT(sequence_start_ == kNoSequence);

    sequence_start_ = this->index_;

  }

  Vector<T> EndSequence() {

    ASSERT(sequence_start_ != kNoSequence);

    int sequence_start = sequence_start_;

    sequence_start_ = kNoSequence;

    if (sequence_start == this->index_) return Vector<T>();

    return this->current_chunk_.SubVector(sequence_start, this->index_);

  }

  // Drops the currently added sequence, and all collected elements in it.

  void DropSequence() {

    ASSERT(sequence_start_ != kNoSequence);

    int sequence_length = this->index_ - sequence_start_;

    this->index_ = sequence_start_;

    this->size_ -= sequence_length;

    sequence_start_ = kNoSequence;

  }

  virtual void Reset() {

    sequence_start_ = kNoSequence;

    this->Collector<T, growth_factor, max_growth>::Reset();

  }

 private:

  static const int kNoSequence = -1;

  int sequence_start_;

  // Move the currently active sequence to the new chunk.

  virtual void NewChunk(int new_capacity) {

    if (sequence_start_ == kNoSequence) {

      // Fall back on default behavior if no sequence has been started.

      this->Collector<T, growth_factor, max_growth>::NewChunk(new_capacity);

      return;

    }

    int sequence_length = this->index_ - sequence_start_;

    Vector<T> new_chunk = Vector<T>::New(sequence_length + new_capacity);

    ASSERT(sequence_length < new_chunk.length());

    for (int i = 0; i < sequence_length; i++) {

      new_chunk[i] = this->current_chunk_[sequence_start_ + i];

    }

    if (sequence_start_ > 0) {

      this->chunks_.Add(this->current_chunk_.SubVector(0, sequence_start_));

    } else {

      this->current_chunk_.Dispose();

    }

    this->current_chunk_ = new_chunk;

    this->index_ = sequence_length;

    sequence_start_ = 0;

  }

};

// Compare ASCII/16bit chars to ASCII/16bit chars.

template <typename lchar, typename rchar>

inline int CompareCharsUnsigned(const lchar* lhs,

                                const rchar* rhs,

                                int chars) {

  const lchar* limit = lhs + chars;

#ifdef V8_HOST_CAN_READ_UNALIGNED

  if (sizeof(*lhs) == sizeof(*rhs)) {

    // Number of characters in a uintptr_t.

    static const int kStepSize = sizeof(uintptr_t) / sizeof(*lhs);  // NOLINT

    while (lhs <= limit - kStepSize) {

      if (*reinterpret_cast<const uintptr_t*>(lhs) !=

          *reinterpret_cast<const uintptr_t*>(rhs)) {

        break;

      }

      lhs += kStepSize;

      rhs += kStepSize;

    }

  }

#endif

  while (lhs < limit) {

    int r = static_cast<int>(*lhs) - static_cast<int>(*rhs);

    if (r != 0) return r;

    ++lhs;

    ++rhs;

  }

  return 0;

}

template<typename lchar, typename rchar>

inline int CompareChars(const lchar* lhs, const rchar* rhs, int chars) {

  ASSERT(sizeof(lchar) <= 2);

  ASSERT(sizeof(rchar) <= 2);

  if (sizeof(lchar) == 1) {

    if (sizeof(rchar) == 1) {

      return CompareCharsUnsigned(reinterpret_cast<const uint8_t*>(lhs),

                                  reinterpret_cast<const uint8_t*>(rhs),

                                  chars);

    } else {

      return CompareCharsUnsigned(reinterpret_cast<const uint8_t*>(lhs),

                                  reinterpret_cast<const uint16_t*>(rhs),

                                  chars);

    }

  } else {

    if (sizeof(rchar) == 1) {

      return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(lhs),

                                  reinterpret_cast<const uint8_t*>(rhs),

                                  chars);

    } else {

      return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(lhs),

                                  reinterpret_cast<const uint16_t*>(rhs),

                                  chars);

    }

  }

}

// Calculate 10^exponent.

inline int TenToThe(int exponent) {

  ASSERT(exponent <= 9);

  ASSERT(exponent >= 1);

  int answer = 10;

  for (int i = 1; i < exponent; i++) answer *= 10;

  return answer;

}

// The type-based aliasing rule allows the compiler to assume that pointers of

// different types (for some definition of different) never alias each other.

// Thus the following code does not work:

//

// float f = foo();

// int fbits = *(int*)(&f);

//

// The compiler 'knows' that the int pointer can't refer to f since the types

// don't match, so the compiler may cache f in a register, leaving random data

// in fbits.  Using C++ style casts makes no difference, however a pointer to

// char data is assumed to alias any other pointer.  This is the 'memcpy

// exception'.

//

// Bit_cast uses the memcpy exception to move the bits from a variable of one

// type of a variable of another type.  Of course the end result is likely to

// be implementation dependent.  Most compilers (gcc-4.2 and MSVC 2005)

// will completely optimize BitCast away.

//

// There is an additional use for BitCast.

// Recent gccs will warn when they see casts that may result in breakage due to

// the type-based aliasing rule.  If you have checked that there is no breakage

// you can use BitCast to cast one pointer type to another.  This confuses gcc

// enough that it can no longer see that you have cast one pointer type to

// another thus avoiding the warning.

// We need different implementations of BitCast for pointer and non-pointer

// values. We use partial specialization of auxiliary struct to work around

// issues with template functions overloading.

template <class Dest, class Source>

struct BitCastHelper {

  STATIC_ASSERT(sizeof(Dest) == sizeof(Source));

  INLINE(static Dest cast(const Source& source)) {

    Dest dest;

    // TODO(jkummerow): Refactor #includes and use OS::MemCopy() instead.

    memcpy(&dest, &source, sizeof(dest));

    return dest;

  }

};

template <class Dest, class Source>

struct BitCastHelper<Dest, Source*> {

  INLINE(static Dest cast(Source* source)) {

    return BitCastHelper<Dest, uintptr_t>::

        cast(reinterpret_cast<uintptr_t>(source));

  }

};

template <class Dest, class Source>

INLINE(Dest BitCast(const Source& source));

template <class Dest, class Source>

inline Dest BitCast(const Source& source) {

  return BitCastHelper<Dest, Source>::cast(source);

}

template<typename ElementType, int NumElements>

class EmbeddedContainer {

 public:

  EmbeddedContainer() : elems_() { }

  int length() const { return NumElements; }

  const ElementType& operator[](int i) const {

    ASSERT(i < length());

    return elems_[i];

  }

  ElementType& operator[](int i) {

    ASSERT(i < length());

    return elems_[i];

  }

 private:

  ElementType elems_[NumElements];

};

template<typename ElementType>

class EmbeddedContainer<ElementType, 0> {

 public:

  int length() const { return 0; }

  const ElementType& operator[](int i) const {

    UNREACHABLE();

    static ElementType t = 0;

    return t;

  }

  ElementType& operator[](int i) {

    UNREACHABLE();

    static ElementType t = 0;

    return t;

  }

};

// Helper class for building result strings in a character buffer. The

// purpose of the class is to use safe operations that checks the

// buffer bounds on all operations in debug mode.

// This simple base class does not allow formatted output.

class SimpleStringBuilder {

 public:

  // Create a string builder with a buffer of the given size. The

  // buffer is allocated through NewArray<char> and must be

  // deallocated by the caller of Finalize().

  explicit SimpleStringBuilder(int size);

  SimpleStringBuilder(char* buffer, int size)

      : buffer_(buffer, size), position_(0) { }

  ~SimpleStringBuilder() { if (!is_finalized()) Finalize(); }

  int size() const { return buffer_.length(); }

  // Get the current position in the builder.

  int position() const {

    ASSERT(!is_finalized());

    return position_;

  }

  // Reset the position.

  void Reset() { position_ = 0; }

  // Add a single character to the builder. It is not allowed to add

  // 0-characters; use the Finalize() method to terminate the string

  // instead.

  void AddCharacter(char c) {

    ASSERT(c != '\0');

    ASSERT(!is_finalized() && position_ < buffer_.length());

    buffer_[position_++] = c;

  }

  // Add an entire string to the builder. Uses strlen() internally to

  // compute the length of the input string.

  void AddString(const char* s);

  // Add the first 'n' characters of the given string 's' to the

  // builder. The input string must have enough characters.

  void AddSubstring(const char* s, int n);

  // Add character padding to the builder. If count is non-positive,

  // nothing is added to the builder.

  void AddPadding(char c, int count);

  // Add the decimal representation of the value.

  void AddDecimalInteger(int value);

  // Finalize the string by 0-terminating it and returning the buffer.

  char* Finalize();

 protected:

  Vector<char> buffer_;

  int position_;

  bool is_finalized() const { return position_ < 0; }

 private:

  DISALLOW_IMPLICIT_CONSTRUCTORS(SimpleStringBuilder);

};

// A poor man's version of STL's bitset: A bit set of enums E (without explicit

// values), fitting into an integral type T.

template <class E, class T = int>

class EnumSet {

 public:

  explicit EnumSet(T bits = 0) : bits_(bits) {}

  bool IsEmpty() const { return bits_ == 0; }

  bool Contains(E element) const { return (bits_ & Mask(element)) != 0; }

  bool ContainsAnyOf(const EnumSet& set) const {

    return (bits_ & set.bits_) != 0;

  }

  void Add(E element) { bits_ |= Mask(element); }

  void Add(const EnumSet& set) { bits_ |= set.bits_; }

  void Remove(E element) { bits_ &= ~Mask(element); }

  void Remove(const EnumSet& set) { bits_ &= ~set.bits_; }

  void RemoveAll() { bits_ = 0; }

  void Intersect(const EnumSet& set) { bits_ &= set.bits_; }

  T ToIntegral() const { return bits_; }

  bool operator==(const EnumSet& set) { return bits_ == set.bits_; }

  bool operator!=(const EnumSet& set) { return bits_ != set.bits_; }

  EnumSet<E, T> operator|(const EnumSet& set) const {

    return EnumSet<E, T>(bits_ | set.bits_);

  }

 private:

  T Mask(E element) const {

    // The strange typing in ASSERT is necessary to avoid stupid warnings, see:

    // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43680

    ASSERT(static_cast<int>(element) < static_cast<int>(sizeof(T) * CHAR_BIT));

    return 1 << element;

  }

  T bits_;

};

class TypeFeedbackId {

 public:

  explicit TypeFeedbackId(int id) : id_(id) { }

  int ToInt() const { return id_; }

  static TypeFeedbackId None() { return TypeFeedbackId(kNoneId); }

  bool IsNone() const { return id_ == kNoneId; }

 private:

  static const int kNoneId = -1;

  int id_;

};

class BailoutId {

 public:

  explicit BailoutId(int id) : id_(id) { }

  int ToInt() const { return id_; }

  static BailoutId None() { return BailoutId(kNoneId); }

  static BailoutId FunctionEntry() { return BailoutId(kFunctionEntryId); }

  static BailoutId Declarations() { return BailoutId(kDeclarationsId); }

  static BailoutId FirstUsable() { return BailoutId(kFirstUsableId); }

  static BailoutId StubEntry() { return BailoutId(kStubEntryId); }

  bool IsNone() const { return id_ == kNoneId; }

  bool operator==(const BailoutId& other) const { return id_ == other.id_; }

 private:

  static const int kNoneId = -1;

  // Using 0 could disguise errors.

  static const int kFunctionEntryId = 2;

  // This AST id identifies the point after the declarations have been visited.

  // We need it to capture the environment effects of declarations that emit

  // code (function declarations).

  static const int kDeclarationsId = 3;

  // Every FunctionState starts with this id.

  static const int kFirstUsableId = 4;

  // Every compiled stub starts with this id.

  static const int kStubEntryId = 5;

  int id_;

};

} }  // namespace v8::internal

#endif  // V8_UTILS_H_