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Diffstat (limited to 'elfcpp/elfcpp_swap.h')
| -rw-r--r-- | elfcpp/elfcpp_swap.h | 350 |
1 files changed, 350 insertions, 0 deletions
diff --git a/elfcpp/elfcpp_swap.h b/elfcpp/elfcpp_swap.h new file mode 100644 index 0000000..979108e --- /dev/null +++ b/elfcpp/elfcpp_swap.h @@ -0,0 +1,350 @@ +// elfcpp_swap.h -- Handle swapping for elfcpp -*- C++ -*- + +// 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 of the specified +// size. + +template<int size> +struct Valtype_base; + +template<> +struct Valtype_base<8> +{ + typedef unsigned char Valtype; +}; + +template<> +struct Valtype_base<16> +{ + typedef uint16_t Valtype; +}; + +template<> +struct Valtype_base<32> +{ + typedef uint32_t Valtype; +}; + +template<> +struct Valtype_base<64> +{ + typedef uint64_t 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_unaligned and writeval_unaligned. 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_unaligned(const unsigned char* wv) + { return *wv; } + + static inline void + writeval_unaligned(unsigned char* wv, Valtype v) + { *wv = v; } +}; + +template<> +struct Swap_unaligned<16, false> +{ + typedef Valtype_base<16>::Valtype Valtype; + + static inline Valtype + readval_unaligned(const unsigned char* wv) + { + return (wv[1] << 8) | wv[0]; + } + + static inline void + writeval_unaligned(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_unaligned(const unsigned char* wv) + { + return (wv[0] << 8) | wv[1]; + } + + static inline void + writeval_unaligned(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_unaligned(const unsigned char* wv) + { + return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0]; + } + + static inline void + writeval_unaligned(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_unaligned(const unsigned char* wv) + { + return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3]; + } + + static inline void + writeval_unaligned(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_unaligned(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_unaligned(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_unaligned(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_unaligned(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; + } +}; + +} // End namespace elfcpp. + +#endif // !defined(ELFCPP_SWAP_H) |