| /* |
| * 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 ------------------------------------------------------------*/ |