/*
 * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
 * Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#ifndef ASCIIFastPath_h
#define ASCIIFastPath_h

#include "wtf/Alignment.h"
#include "wtf/CPU.h"
#include "wtf/StdLibExtras.h"
#include "wtf/text/Unicode.h"
#include <stdint.h>

#if OS(MACOSX) && (CPU(X86) || CPU(X86_64))
#include <emmintrin.h>
#endif

namespace WTF {

// Assuming that a pointer is the size of a "machine word", then
// uintptr_t is an integer type that is also a machine word.
typedef uintptr_t MachineWord;
const uintptr_t machineWordAlignmentMask = sizeof(MachineWord) - 1;

inline bool isAlignedToMachineWord(const void* pointer) {
  return !(reinterpret_cast<uintptr_t>(pointer) & machineWordAlignmentMask);
}

template <typename T>
inline T* alignToMachineWord(T* pointer) {
  return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(pointer) &
                              ~machineWordAlignmentMask);
}

template <size_t size, typename CharacterType>
struct NonASCIIMask;
template <>
struct NonASCIIMask<4, UChar> {
  static inline uint32_t value() { return 0xFF80FF80U; }
};
template <>
struct NonASCIIMask<4, LChar> {
  static inline uint32_t value() { return 0x80808080U; }
};
template <>
struct NonASCIIMask<8, UChar> {
  static inline uint64_t value() { return 0xFF80FF80FF80FF80ULL; }
};
template <>
struct NonASCIIMask<8, LChar> {
  static inline uint64_t value() { return 0x8080808080808080ULL; }
};

template <typename CharacterType>
inline bool isAllASCII(MachineWord word) {
  return !(word & NonASCIIMask<sizeof(MachineWord), CharacterType>::value());
}

// Note: This function assume the input is likely all ASCII, and
// does not leave early if it is not the case.
template <typename CharacterType>
inline bool charactersAreAllASCII(const CharacterType* characters,
                                  size_t length) {
  MachineWord allCharBits = 0;
  const CharacterType* end = characters + length;

  // Prologue: align the input.
  while (!isAlignedToMachineWord(characters) && characters != end) {
    allCharBits |= *characters;
    ++characters;
  }

  // Compare the values of CPU word size.
  const CharacterType* wordEnd = alignToMachineWord(end);
  const size_t loopIncrement = sizeof(MachineWord) / sizeof(CharacterType);
  while (characters < wordEnd) {
    allCharBits |= *(reinterpret_cast_ptr<const MachineWord*>(characters));
    characters += loopIncrement;
  }

  // Process the remaining bytes.
  while (characters != end) {
    allCharBits |= *characters;
    ++characters;
  }

  MachineWord nonASCIIBitMask =
      NonASCIIMask<sizeof(MachineWord), CharacterType>::value();
  return !(allCharBits & nonASCIIBitMask);
}

inline void copyLCharsFromUCharSource(LChar* destination,
                                      const UChar* source,
                                      size_t length) {
#if OS(MACOSX) && (CPU(X86) || CPU(X86_64))
  const uintptr_t memoryAccessSize =
      16;  // Memory accesses on 16 byte (128 bit) alignment
  const uintptr_t memoryAccessMask = memoryAccessSize - 1;

  size_t i = 0;
  for (; i < length && !isAlignedTo<memoryAccessMask>(&source[i]); ++i) {
    ASSERT(!(source[i] & 0xff00));
    destination[i] = static_cast<LChar>(source[i]);
  }

  const uintptr_t sourceLoadSize =
      32;  // Process 32 bytes (16 UChars) each iteration
  const size_t ucharsPerLoop = sourceLoadSize / sizeof(UChar);
  if (length > ucharsPerLoop) {
    const size_t endLength = length - ucharsPerLoop + 1;
    for (; i < endLength; i += ucharsPerLoop) {
#if ENABLE(ASSERT)
      for (unsigned checkIndex = 0; checkIndex < ucharsPerLoop; ++checkIndex)
        ASSERT(!(source[i + checkIndex] & 0xff00));
#endif
      __m128i first8UChars =
          _mm_load_si128(reinterpret_cast<const __m128i*>(&source[i]));
      __m128i second8UChars =
          _mm_load_si128(reinterpret_cast<const __m128i*>(&source[i + 8]));
      __m128i packedChars = _mm_packus_epi16(first8UChars, second8UChars);
      _mm_storeu_si128(reinterpret_cast<__m128i*>(&destination[i]),
                       packedChars);
    }
  }

  for (; i < length; ++i) {
    ASSERT(!(source[i] & 0xff00));
    destination[i] = static_cast<LChar>(source[i]);
  }
#elif COMPILER(GCC) && CPU(ARM_NEON) && \
    !(CPU(BIG_ENDIAN) || CPU(MIDDLE_ENDIAN)) && defined(NDEBUG)
  const LChar* const end = destination + length;
  const uintptr_t memoryAccessSize = 8;

  if (length >= (2 * memoryAccessSize) - 1) {
    // Prefix: align dst on 64 bits.
    const uintptr_t memoryAccessMask = memoryAccessSize - 1;
    while (!isAlignedTo<memoryAccessMask>(destination))
      *destination++ = static_cast<LChar>(*source++);

    // Vector interleaved unpack, we only store the lower 8 bits.
    const uintptr_t lengthLeft = end - destination;
    const LChar* const simdEnd = end - (lengthLeft % memoryAccessSize);
    do {
      asm("vld2.8   { d0-d1 }, [%[SOURCE]] !\n\t"
          "vst1.8   { d0 }, [%[DESTINATION],:64] !\n\t"
          : [SOURCE] "+r"(source), [DESTINATION] "+r"(destination)
          :
          : "memory", "d0", "d1");
    } while (destination != simdEnd);
  }

  while (destination != end)
    *destination++ = static_cast<LChar>(*source++);
#else
  for (size_t i = 0; i < length; ++i) {
    ASSERT(!(source[i] & 0xff00));
    destination[i] = static_cast<LChar>(source[i]);
  }
#endif
}

}  // namespace WTF

#endif  // ASCIIFastPath_h
