254 lines
6.9 KiB
C
254 lines
6.9 KiB
C
|
/*
|
||
|
* SpanDSP - a series of DSP components for telephony
|
||
|
*
|
||
|
* bit_operations.h - Various bit level operations, such as bit reversal
|
||
|
*
|
||
|
* Written by Steve Underwood <steveu@coppice.org>
|
||
|
*
|
||
|
* Copyright (C) 2006 Steve Underwood
|
||
|
*
|
||
|
* All rights reserved.
|
||
|
*
|
||
|
* This program is free software; you can redistribute it and/or modify
|
||
|
* it under the terms of the GNU General Public License version 2, as
|
||
|
* published by the Free Software Foundation.
|
||
|
*
|
||
|
* 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 General Public License for more details.
|
||
|
*
|
||
|
* You should have received a copy of the GNU General Public License
|
||
|
* along with this program; if not, write to the Free Software
|
||
|
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
||
|
*
|
||
|
* $Id: bit_operations.h,v 1.11 2006/11/28 15:37:03 steveu Exp $
|
||
|
*/
|
||
|
|
||
|
/*! \file */
|
||
|
|
||
|
#if !defined(_BIT_OPERATIONS_H_)
|
||
|
#define _BIT_OPERATIONS_H_
|
||
|
|
||
|
#ifdef __cplusplus
|
||
|
extern "C" {
|
||
|
#endif
|
||
|
|
||
|
#if defined(__i386__) || defined(__x86_64__)
|
||
|
/*! \brief Find the bit position of the highest set bit in a word
|
||
|
\param bits The word to be searched
|
||
|
\return The bit number of the highest set bit, or -1 if the word is zero. */
|
||
|
static __inline__ int top_bit(unsigned int bits)
|
||
|
{
|
||
|
int res;
|
||
|
|
||
|
__asm__ (" xorl %[res],%[res];\n"
|
||
|
" decl %[res];\n"
|
||
|
" bsrl %[bits],%[res]\n"
|
||
|
: [res] "=&r" (res)
|
||
|
: [bits] "rm" (bits));
|
||
|
return res;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
/*! \brief Find the bit position of the lowest set bit in a word
|
||
|
\param bits The word to be searched
|
||
|
\return The bit number of the lowest set bit, or -1 if the word is zero. */
|
||
|
static __inline__ int bottom_bit(unsigned int bits)
|
||
|
{
|
||
|
int res;
|
||
|
|
||
|
__asm__ (" xorl %[res],%[res];\n"
|
||
|
" decl %[res];\n"
|
||
|
" bsfl %[bits],%[res]\n"
|
||
|
: [res] "=&r" (res)
|
||
|
: [bits] "rm" (bits));
|
||
|
return res;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
#else
|
||
|
static __inline__ int top_bit(unsigned int bits)
|
||
|
{
|
||
|
int i;
|
||
|
|
||
|
if (bits == 0)
|
||
|
return -1;
|
||
|
i = 0;
|
||
|
if (bits & 0xFFFF0000)
|
||
|
{
|
||
|
bits &= 0xFFFF0000;
|
||
|
i += 16;
|
||
|
}
|
||
|
if (bits & 0xFF00FF00)
|
||
|
{
|
||
|
bits &= 0xFF00FF00;
|
||
|
i += 8;
|
||
|
}
|
||
|
if (bits & 0xF0F0F0F0)
|
||
|
{
|
||
|
bits &= 0xF0F0F0F0;
|
||
|
i += 4;
|
||
|
}
|
||
|
if (bits & 0xCCCCCCCC)
|
||
|
{
|
||
|
bits &= 0xCCCCCCCC;
|
||
|
i += 2;
|
||
|
}
|
||
|
if (bits & 0xAAAAAAAA)
|
||
|
{
|
||
|
bits &= 0xAAAAAAAA;
|
||
|
i += 1;
|
||
|
}
|
||
|
return i;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
static __inline__ int bottom_bit(unsigned int bits)
|
||
|
{
|
||
|
int i;
|
||
|
|
||
|
if (bits == 0)
|
||
|
return -1;
|
||
|
i = 32;
|
||
|
if (bits & 0x0000FFFF)
|
||
|
{
|
||
|
bits &= 0x0000FFFF;
|
||
|
i -= 16;
|
||
|
}
|
||
|
if (bits & 0x00FF00FF)
|
||
|
{
|
||
|
bits &= 0x00FF00FF;
|
||
|
i -= 8;
|
||
|
}
|
||
|
if (bits & 0x0F0F0F0F)
|
||
|
{
|
||
|
bits &= 0x0F0F0F0F;
|
||
|
i -= 4;
|
||
|
}
|
||
|
if (bits & 0x33333333)
|
||
|
{
|
||
|
bits &= 0x33333333;
|
||
|
i -= 2;
|
||
|
}
|
||
|
if (bits & 0x55555555)
|
||
|
{
|
||
|
bits &= 0x55555555;
|
||
|
i -= 1;
|
||
|
}
|
||
|
return i;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
#endif
|
||
|
|
||
|
/*! \brief Bit reverse a byte.
|
||
|
\param data The byte to be reversed.
|
||
|
\return The bit reversed version of data. */
|
||
|
static __inline__ uint8_t bit_reverse8(uint8_t x)
|
||
|
{
|
||
|
#if defined(__i386__) || defined(__x86_64__)
|
||
|
/* If multiply is fast */
|
||
|
return ((x*0x0802U & 0x22110U) | (x*0x8020U & 0x88440U))*0x10101U >> 16;
|
||
|
#else
|
||
|
/* If multiply is slow, but we have a barrel shifter */
|
||
|
x = (x >> 4) | (x << 4);
|
||
|
x = ((x & 0xCC) >> 2) | ((x & 0x33) << 2);
|
||
|
return ((x & 0xAA) >> 1) | ((x & 0x55) << 1);
|
||
|
#endif
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
/*! \brief Bit reverse a 16 bit word.
|
||
|
\param data The word to be reversed.
|
||
|
\return The bit reversed version of data. */
|
||
|
uint16_t bit_reverse16(uint16_t data);
|
||
|
|
||
|
/*! \brief Bit reverse a 32 bit word.
|
||
|
\param data The word to be reversed.
|
||
|
\return The bit reversed version of data. */
|
||
|
uint32_t bit_reverse32(uint32_t data);
|
||
|
|
||
|
/*! \brief Bit reverse each of the four bytes in a 32 bit word.
|
||
|
\param data The word to be reversed.
|
||
|
\return The bit reversed version of data. */
|
||
|
uint32_t bit_reverse_4bytes(uint32_t data);
|
||
|
|
||
|
/*! \brief Find the number of set bits in a 32 bit word.
|
||
|
\param x The word to be searched.
|
||
|
\return The number of set bits. */
|
||
|
int one_bits32(uint32_t x);
|
||
|
|
||
|
/*! \brief Create a mask as wide as the number in a 32 bit word.
|
||
|
\param x The word to be searched.
|
||
|
\return The mask. */
|
||
|
uint32_t make_mask32(uint32_t x);
|
||
|
|
||
|
/*! \brief Create a mask as wide as the number in a 16 bit word.
|
||
|
\param x The word to be searched.
|
||
|
\return The mask. */
|
||
|
uint16_t make_mask16(uint16_t x);
|
||
|
|
||
|
/*! \brief Find the least significant one in a word, and return a word
|
||
|
with just that bit set.
|
||
|
\param x The word to be searched.
|
||
|
\return The word with the single set bit. */
|
||
|
static __inline__ uint32_t least_significant_one32(uint32_t x)
|
||
|
{
|
||
|
return (x & (-(int32_t) x));
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
/*! \brief Find the most significant one in a word, and return a word
|
||
|
with just that bit set.
|
||
|
\param x The word to be searched.
|
||
|
\return The word with the single set bit. */
|
||
|
static __inline__ uint32_t most_significant_one32(uint32_t x)
|
||
|
{
|
||
|
#if defined(__i386__) || defined(__x86_64__)
|
||
|
return 1 << top_bit(x);
|
||
|
#else
|
||
|
x = make_mask32(x);
|
||
|
return (x ^ (x >> 1));
|
||
|
#endif
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
/*! \brief Find the parity of a byte.
|
||
|
\param x The byte to be checked.
|
||
|
\return 1 for odd, or 0 for even. */
|
||
|
static __inline__ int parity8(uint8_t x)
|
||
|
{
|
||
|
x = (x ^ (x >> 4)) & 0x0F;
|
||
|
return (0x6996 >> x) & 1;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
/*! \brief Find the parity of a 16 bit word.
|
||
|
\param x The word to be checked.
|
||
|
\return 1 for odd, or 0 for even. */
|
||
|
static __inline__ int parity16(uint16_t x)
|
||
|
{
|
||
|
x ^= (x >> 8);
|
||
|
x = (x ^ (x >> 4)) & 0x0F;
|
||
|
return (0x6996 >> x) & 1;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
/*! \brief Find the parity of a 32 bit word.
|
||
|
\param x The word to be checked.
|
||
|
\return 1 for odd, or 0 for even. */
|
||
|
static __inline__ int parity32(uint32_t x)
|
||
|
{
|
||
|
x ^= (x >> 16);
|
||
|
x ^= (x >> 8);
|
||
|
x = (x ^ (x >> 4)) & 0x0F;
|
||
|
return (0x6996 >> x) & 1;
|
||
|
}
|
||
|
/*- End of function --------------------------------------------------------*/
|
||
|
|
||
|
#ifdef __cplusplus
|
||
|
}
|
||
|
#endif
|
||
|
|
||
|
#endif
|
||
|
/*- End of file ------------------------------------------------------------*/
|