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/* 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);
}
}
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