350 lines
7.5 KiB
C++
350 lines
7.5 KiB
C++
// elfcpp_swap.h -- Handle swapping for elfcpp -*- C++ -*-
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// This header file defines basic template classes to efficiently swap
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// numbers between host form and target form. When the host and
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// target have the same endianness, these turn into no-ops.
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#ifndef ELFCPP_SWAP_H
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#define ELFCPP_SWAP_H
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#include <stdint.h>
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#include <endian.h>
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#include <byteswap.h>
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namespace elfcpp
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{
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// Endian simply indicates whether the host is big endian or not.
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struct Endian
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{
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public:
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// Used for template specializations.
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static const bool host_big_endian = __BYTE_ORDER == __BIG_ENDIAN;
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};
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// Valtype_base is a template based on size (8, 16, 32, 64) which
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// defines the type Valtype as the unsigned integer of the specified
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// size.
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template<int size>
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struct Valtype_base;
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template<>
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struct Valtype_base<8>
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{
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typedef unsigned char Valtype;
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};
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template<>
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struct Valtype_base<16>
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{
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typedef uint16_t Valtype;
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};
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template<>
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struct Valtype_base<32>
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{
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typedef uint32_t Valtype;
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};
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template<>
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struct Valtype_base<64>
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{
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typedef uint64_t Valtype;
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};
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// Convert_endian is a template based on size and on whether the host
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// and target have the same endianness. It defines the type Valtype
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// as Valtype_base does, and also defines a function convert_host
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// which takes an argument of type Valtype and returns the same value,
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// but swapped if the host and target have different endianness.
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template<int size, bool same_endian>
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struct Convert_endian;
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template<int size>
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struct Convert_endian<size, true>
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{
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typedef typename Valtype_base<size>::Valtype Valtype;
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static inline Valtype
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convert_host(Valtype v)
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{ return v; }
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};
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template<>
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struct Convert_endian<8, false>
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{
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typedef Valtype_base<8>::Valtype Valtype;
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static inline Valtype
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convert_host(Valtype v)
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{ return v; }
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};
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template<>
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struct Convert_endian<16, false>
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{
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typedef Valtype_base<16>::Valtype Valtype;
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static inline Valtype
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convert_host(Valtype v)
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{ return bswap_16(v); }
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};
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template<>
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struct Convert_endian<32, false>
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{
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typedef Valtype_base<32>::Valtype Valtype;
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static inline Valtype
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convert_host(Valtype v)
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{ return bswap_32(v); }
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};
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template<>
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struct Convert_endian<64, false>
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{
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typedef Valtype_base<64>::Valtype Valtype;
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static inline Valtype
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convert_host(Valtype v)
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{ return bswap_64(v); }
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};
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// Convert is a template based on size and on whether the target is
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// big endian. It defines Valtype and convert_host like
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// Convert_endian. That is, it is just like Convert_endian except in
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// the meaning of the second template parameter.
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template<int size, bool big_endian>
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struct Convert
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{
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typedef typename Valtype_base<size>::Valtype Valtype;
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static inline Valtype
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convert_host(Valtype v)
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{
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return Convert_endian<size, big_endian == Endian::host_big_endian>
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::convert_host(v);
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}
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};
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// Swap is a template based on size and on whether the target is big
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// endian. It defines the type Valtype and the functions readval and
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// writeval. The functions read and write values of the appropriate
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// size out of buffers, swapping them if necessary. readval and
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// writeval are overloaded to take pointers to the appropriate type or
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// pointers to unsigned char.
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template<int size, bool big_endian>
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struct Swap
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{
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typedef typename Valtype_base<size>::Valtype Valtype;
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static inline Valtype
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readval(const Valtype* wv)
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{ return Convert<size, big_endian>::convert_host(*wv); }
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static inline void
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writeval(Valtype* wv, Valtype v)
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{ *wv = Convert<size, big_endian>::convert_host(v); }
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static inline Valtype
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readval(const unsigned char* wv)
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{ return readval(reinterpret_cast<const Valtype*>(wv)); }
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{ writeval(reinterpret_cast<Valtype*>(wv), v); }
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};
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// We need to specialize the 8-bit version of Swap to avoid
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// conflicting overloads, since both versions of readval and writeval
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// will have the same type parameters.
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template<bool big_endian>
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struct Swap<8, big_endian>
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{
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typedef typename Valtype_base<8>::Valtype Valtype;
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static inline Valtype
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readval(const Valtype* wv)
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{ return *wv; }
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static inline void
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writeval(Valtype* wv, Valtype v)
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{ *wv = v; }
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};
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// Swap_unaligned is a template based on size and on whether the
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// target is big endian. It defines the type Valtype and the
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// functions readval and writeval. The functions read and write
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// values of the appropriate size out of buffers which may be
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// misaligned.
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template<int size, bool big_endian>
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struct Swap_unaligned;
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template<bool big_endian>
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struct Swap_unaligned<8, big_endian>
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{
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typedef typename Valtype_base<8>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{ return *wv; }
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{ *wv = v; }
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};
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template<>
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struct Swap_unaligned<16, false>
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{
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typedef Valtype_base<16>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{
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return (wv[1] << 8) | wv[0];
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}
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{
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wv[1] = v >> 8;
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wv[0] = v;
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}
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};
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template<>
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struct Swap_unaligned<16, true>
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{
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typedef Valtype_base<16>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{
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return (wv[0] << 8) | wv[1];
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}
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{
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wv[0] = v >> 8;
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wv[1] = v;
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}
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};
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template<>
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struct Swap_unaligned<32, false>
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{
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typedef Valtype_base<32>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{
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return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0];
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}
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{
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wv[3] = v >> 24;
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wv[2] = v >> 16;
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wv[1] = v >> 8;
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wv[0] = v;
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}
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};
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template<>
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struct Swap_unaligned<32, true>
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{
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typedef Valtype_base<32>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{
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return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3];
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}
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{
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wv[0] = v >> 24;
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wv[1] = v >> 16;
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wv[2] = v >> 8;
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wv[3] = v;
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}
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};
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template<>
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struct Swap_unaligned<64, false>
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{
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typedef Valtype_base<64>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{
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return ((static_cast<Valtype>(wv[7]) << 56)
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| (static_cast<Valtype>(wv[6]) << 48)
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| (static_cast<Valtype>(wv[5]) << 40)
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| (static_cast<Valtype>(wv[4]) << 32)
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| (static_cast<Valtype>(wv[3]) << 24)
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| (static_cast<Valtype>(wv[2]) << 16)
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| (static_cast<Valtype>(wv[1]) << 8)
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| static_cast<Valtype>(wv[0]));
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}
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{
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wv[7] = v >> 56;
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wv[6] = v >> 48;
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wv[5] = v >> 40;
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wv[4] = v >> 32;
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wv[3] = v >> 24;
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wv[2] = v >> 16;
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wv[1] = v >> 8;
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wv[0] = v;
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}
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};
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template<>
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struct Swap_unaligned<64, true>
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{
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typedef Valtype_base<64>::Valtype Valtype;
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static inline Valtype
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readval(const unsigned char* wv)
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{
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return ((static_cast<Valtype>(wv[0]) << 56)
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| (static_cast<Valtype>(wv[1]) << 48)
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| (static_cast<Valtype>(wv[2]) << 40)
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| (static_cast<Valtype>(wv[3]) << 32)
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| (static_cast<Valtype>(wv[4]) << 24)
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| (static_cast<Valtype>(wv[5]) << 16)
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| (static_cast<Valtype>(wv[6]) << 8)
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| static_cast<Valtype>(wv[7]));
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}
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static inline void
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writeval(unsigned char* wv, Valtype v)
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{
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wv[7] = v >> 56;
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wv[6] = v >> 48;
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wv[5] = v >> 40;
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wv[4] = v >> 32;
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wv[3] = v >> 24;
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wv[2] = v >> 16;
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wv[1] = v >> 8;
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wv[0] = v;
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}
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};
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} // End namespace elfcpp.
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#endif // !defined(ELFCPP_SWAP_H)
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