+++ /dev/null
-/*
- * 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.
- */
-
-/*! \file */
-
-#if !defined(_BIT_OPERATIONS_H_)
-#define _BIT_OPERATIONS_H_
-
-#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;
-}
-
-/*! \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;
-}
-#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;
-}
-
-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;
-}
-#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
-}
-
-/*! \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);
-}
-
-/*! \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
-}
-
-/*! \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;
-}
-
-/*! \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;
-}
-
-/*! \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;
-}
-
-#endif
-/*- End of file ------------------------------------------------------------*/