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// elfcpp_swap.h -- Handle swapping for elfcpp   -*- C++ -*-

// Copyright 2006, 2007, Free Software Foundation, Inc.

// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of elfcpp.

// This program 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, or

// (at your option) any later version.

// In addition to the permissions in the GNU Library General Public

// License, the Free Software Foundation gives you unlimited

// permission to link the compiled version of this file into

// combinations with other programs, and to distribute those

// combinations without any restriction coming from the use of this

// file.  (The Library Public License restrictions do apply in other

// respects; for example, they cover modification of the file, and

/// distribution when not linked into a combined executable.)

// This program 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 program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA

// 02110-1301, USA.

// This header file defines basic template classes to efficiently swap

// numbers between host form and target form.  When the host and

// target have the same endianness, these turn into no-ops.

#ifndef ELFCPP_SWAP_H

#define ELFCPP_SWAP_H

#include <stdint.h>

#include <endian.h>

#include <byteswap.h>

namespace elfcpp

{

// Endian simply indicates whether the host is big endian or not.

struct Endian

{

 public:

  // Used for template specializations.

  static const bool host_big_endian = __BYTE_ORDER == __BIG_ENDIAN;

};

// Valtype_base is a template based on size (8, 16, 32, 64) which

// defines the type Valtype as the unsigned integer, and

// Signed_valtype as the signed integer, of the specified size.

template<int size>

struct Valtype_base;

template<>

struct Valtype_base<8>

{

  typedef uint8_t Valtype;

  typedef int8_t Signed_valtype;

};

template<>

struct Valtype_base<16>

{

  typedef uint16_t Valtype;

  typedef int16_t Signed_valtype;

};

template<>

struct Valtype_base<32>

{

  typedef uint32_t Valtype;

  typedef int32_t Signed_valtype;

};

template<>

struct Valtype_base<64>

{

  typedef uint64_t Valtype;

  typedef int64_t Signed_valtype;

};

// Convert_endian is a template based on size and on whether the host

// and target have the same endianness.  It defines the type Valtype

// as Valtype_base does, and also defines a function convert_host

// which takes an argument of type Valtype and returns the same value,

// but swapped if the host and target have different endianness.

template<int size, bool same_endian>

struct Convert_endian;

template<int size>

struct Convert_endian<size, true>

{

  typedef typename Valtype_base<size>::Valtype Valtype;

  static inline Valtype

  convert_host(Valtype v)

  { return v; }

};

template<>

struct Convert_endian<8, false>

{

  typedef Valtype_base<8>::Valtype Valtype;

  static inline Valtype

  convert_host(Valtype v)

  { return v; }

};

template<>

struct Convert_endian<16, false>

{

  typedef Valtype_base<16>::Valtype Valtype;

  static inline Valtype

  convert_host(Valtype v)

  { return bswap_16(v); }

};

template<>

struct Convert_endian<32, false>

{

  typedef Valtype_base<32>::Valtype Valtype;

  static inline Valtype

  convert_host(Valtype v)

  { return bswap_32(v); }

};

template<>

struct Convert_endian<64, false>

{

  typedef Valtype_base<64>::Valtype Valtype;

  static inline Valtype

  convert_host(Valtype v)

  { return bswap_64(v); }

};

// Convert is a template based on size and on whether the target is

// big endian.  It defines Valtype and convert_host like

// Convert_endian.  That is, it is just like Convert_endian except in

// the meaning of the second template parameter.

template<int size, bool big_endian>

struct Convert

{

  typedef typename Valtype_base<size>::Valtype Valtype;

  static inline Valtype

  convert_host(Valtype v)

  {

    return Convert_endian<size, big_endian == Endian::host_big_endian>

      ::convert_host(v);

  }

};

// Swap is a template based on size and on whether the target is big

// endian.  It defines the type Valtype and the functions readval and

// writeval.  The functions read and write values of the appropriate

// size out of buffers, swapping them if necessary.  readval and

// writeval are overloaded to take pointers to the appropriate type or

// pointers to unsigned char.

template<int size, bool big_endian>

struct Swap

{

  typedef typename Valtype_base<size>::Valtype Valtype;

  static inline Valtype

  readval(const Valtype* wv)

  { return Convert<size, big_endian>::convert_host(*wv); }

  static inline void

  writeval(Valtype* wv, Valtype v)

  { *wv = Convert<size, big_endian>::convert_host(v); }

  static inline Valtype

  readval(const unsigned char* wv)

  { return readval(reinterpret_cast<const Valtype*>(wv)); }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  { writeval(reinterpret_cast<Valtype*>(wv), v); }

};

// We need to specialize the 8-bit version of Swap to avoid

// conflicting overloads, since both versions of readval and writeval

// will have the same type parameters.

template<bool big_endian>

struct Swap<8, big_endian>

{

  typedef typename Valtype_base<8>::Valtype Valtype;

  static inline Valtype

  readval(const Valtype* wv)

  { return *wv; }

  static inline void

  writeval(Valtype* wv, Valtype v)

  { *wv = v; }

};

// Swap_unaligned is a template based on size and on whether the

// target is big endian.  It defines the type Valtype and the

// functions readval and writeval.  The functions read and write

// values of the appropriate size out of buffers which may be

// misaligned.

template<int size, bool big_endian>

struct Swap_unaligned;

template<bool big_endian>

struct Swap_unaligned<8, big_endian>

{

  typedef typename Valtype_base<8>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  { return *wv; }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  { *wv = v; }

};

template<>

struct Swap_unaligned<16, false>

{

  typedef Valtype_base<16>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  {

    return (wv[1] << 8) | wv[0];

  }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  {

    wv[1] = v >> 8;

    wv[0] = v;

  }

};

template<>

struct Swap_unaligned<16, true>

{

  typedef Valtype_base<16>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  {

    return (wv[0] << 8) | wv[1];

  }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  {

    wv[0] = v >> 8;

    wv[1] = v;

  }

};

template<>

struct Swap_unaligned<32, false>

{

  typedef Valtype_base<32>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  {

    return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0];

  }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  {

    wv[3] = v >> 24;

    wv[2] = v >> 16;

    wv[1] = v >> 8;

    wv[0] = v;

  }

};

template<>

struct Swap_unaligned<32, true>

{

  typedef Valtype_base<32>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  {

    return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3];

  }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  {

    wv[0] = v >> 24;

    wv[1] = v >> 16;

    wv[2] = v >> 8;

    wv[3] = v;

  }

};

template<>

struct Swap_unaligned<64, false>

{

  typedef Valtype_base<64>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  {

    return ((static_cast<Valtype>(wv[7]) << 56)

            | (static_cast<Valtype>(wv[6]) << 48)

            | (static_cast<Valtype>(wv[5]) << 40)

            | (static_cast<Valtype>(wv[4]) << 32)

            | (static_cast<Valtype>(wv[3]) << 24)

            | (static_cast<Valtype>(wv[2]) << 16)

            | (static_cast<Valtype>(wv[1]) << 8)

            | static_cast<Valtype>(wv[0]));

  }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  {

    wv[7] = v >> 56;

    wv[6] = v >> 48;

    wv[5] = v >> 40;

    wv[4] = v >> 32;

    wv[3] = v >> 24;

    wv[2] = v >> 16;

    wv[1] = v >> 8;

    wv[0] = v;

  }

};

template<>

struct Swap_unaligned<64, true>

{

  typedef Valtype_base<64>::Valtype Valtype;

  static inline Valtype

  readval(const unsigned char* wv)

  {

    return ((static_cast<Valtype>(wv[0]) << 56)

            | (static_cast<Valtype>(wv[1]) << 48)

            | (static_cast<Valtype>(wv[2]) << 40)

            | (static_cast<Valtype>(wv[3]) << 32)

            | (static_cast<Valtype>(wv[4]) << 24)

            | (static_cast<Valtype>(wv[5]) << 16)

            | (static_cast<Valtype>(wv[6]) << 8)

            | static_cast<Valtype>(wv[7]));

  }

  static inline void

  writeval(unsigned char* wv, Valtype v)

  {

    wv[0] = v >> 56;

    wv[1] = v >> 48;

    wv[2] = v >> 40;

    wv[3] = v >> 32;

    wv[4] = v >> 24;

    wv[5] = v >> 16;

    wv[6] = v >> 8;

    wv[7] = v;

  }

};

} // End namespace elfcpp.

#endif // !defined(ELFCPP_SWAP_H)