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Diffstat (limited to 'librhash/byte_order.c')
| -rw-r--r-- | librhash/byte_order.c | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/librhash/byte_order.c b/librhash/byte_order.c new file mode 100644 index 0000000..8ce6fc8 --- /dev/null +++ b/librhash/byte_order.c @@ -0,0 +1,150 @@ +/* byte_order.c - byte order related platform dependent routines, + * + * Copyright: 2008-2012 Aleksey Kravchenko <rhash.admin@gmail.com> + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so. + * + * 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. Use this program at your own risk! + */ +#include "byte_order.h" + +#if !(__GNUC__ >= 4 || (__GNUC__ ==3 && __GNUC_MINOR__ >= 4)) /* if !GCC or GCC < 4.3 */ + +# if _MSC_VER >= 1300 && (_M_IX86 || _M_AMD64 || _M_IA64) /* if MSVC++ >= 2002 on x86/x64 */ +# include <intrin.h> +# pragma intrinsic(_BitScanForward) + +/** + * Returns index of the trailing bit of x. + * + * @param x the number to process + * @return zero-based index of the trailing bit + */ +unsigned rhash_ctz(unsigned x) +{ + unsigned long index; + unsigned char isNonzero = _BitScanForward(&index, x); /* MSVC intrinsic */ + return (isNonzero ? (unsigned)index : 0); +} +# else /* _MSC_VER >= 1300... */ + +/** + * Returns index of the trailing bit of a 32-bit number. + * This is a plain C equivalent for GCC __builtin_ctz() bit scan. + * + * @param x the number to process + * @return zero-based index of the trailing bit + */ +unsigned rhash_ctz(unsigned x) +{ + /* array for conversion to bit position */ + static unsigned char bit_pos[32] = { + 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, + 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 + }; + + /* The De Bruijn bit-scan was devised in 1997, according to Donald Knuth + * by Martin Lauter. The constant 0x077CB531UL is a De Bruijn sequence, + * which produces a unique pattern of bits into the high 5 bits for each + * possible bit position that it is multiplied against. + * See http://graphics.stanford.edu/~seander/bithacks.html + * and http://chessprogramming.wikispaces.com/BitScan */ + return (unsigned)bit_pos[((uint32_t)((x & -x) * 0x077CB531U)) >> 27]; +} +# endif /* _MSC_VER >= 1300... */ +#endif /* !(GCC >= 4.3) */ + +/** + * Copy a memory block with simultaneous exchanging byte order. + * The byte order is changed from little-endian 32-bit integers + * to big-endian (or vice-versa). + * + * @param to the pointer where to copy memory block + * @param index the index to start writing from + * @param from the source block to copy + * @param length length of the memory block + */ +void rhash_swap_copy_str_to_u32(void* to, int index, const void* from, size_t length) +{ + /* if all pointers and length are 32-bits aligned */ + if ( 0 == (( (int)((char*)to - (char*)0) | ((char*)from - (char*)0) | index | length ) & 3) ) { + /* copy memory as 32-bit words */ + const uint32_t* src = (const uint32_t*)from; + const uint32_t* end = (const uint32_t*)((const char*)src + length); + uint32_t* dst = (uint32_t*)((char*)to + index); + while (src < end) *(dst++) = bswap_32( *(src++) ); + } else { + const char* src = (const char*)from; + for (length += index; (size_t)index < length; index++) ((char*)to)[index ^ 3] = *(src++); + } +} + +/** + * Copy a memory block with changed byte order. + * The byte order is changed from little-endian 64-bit integers + * to big-endian (or vice-versa). + * + * @param to the pointer where to copy memory block + * @param index the index to start writing from + * @param from the source block to copy + * @param length length of the memory block + */ +void rhash_swap_copy_str_to_u64(void* to, int index, const void* from, size_t length) +{ + /* if all pointers and length are 64-bits aligned */ + if ( 0 == (( (int)((char*)to - (char*)0) | ((char*)from - (char*)0) | index | length ) & 7) ) { + /* copy aligned memory block as 64-bit integers */ + const uint64_t* src = (const uint64_t*)from; + const uint64_t* end = (const uint64_t*)((const char*)src + length); + uint64_t* dst = (uint64_t*)((char*)to + index); + while (src < end) *(dst++) = bswap_64( *(src++) ); + } else { + const char* src = (const char*)from; + for (length += index; (size_t)index < length; index++) ((char*)to)[index ^ 7] = *(src++); + } +} + +/** + * Copy data from a sequence of 64-bit words to a binary string of given length, + * while changing byte order. + * + * @param to the binary string to receive data + * @param from the source sequence of 64-bit words + * @param length the size in bytes of the data being copied + */ +void rhash_swap_copy_u64_to_str(void* to, const void* from, size_t length) +{ + /* if all pointers and length are 64-bits aligned */ + if ( 0 == (( (int)((char*)to - (char*)0) | ((char*)from - (char*)0) | length ) & 7) ) { + /* copy aligned memory block as 64-bit integers */ + const uint64_t* src = (const uint64_t*)from; + const uint64_t* end = (const uint64_t*)((const char*)src + length); + uint64_t* dst = (uint64_t*)to; + while (src < end) *(dst++) = bswap_64( *(src++) ); + } else { + size_t index; + char* dst = (char*)to; + for (index = 0; index < length; index++) *(dst++) = ((char*)from)[index ^ 7]; + } +} + +/** + * Exchange byte order in the given array of 32-bit integers. + * + * @param arr the array to process + * @param length array length + */ +void rhash_u32_mem_swap(unsigned *arr, int length) +{ + unsigned* end = arr + length; + for (; arr < end; arr++) { + *arr = bswap_32(*arr); + } +} |