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172 lines
3.8 KiB
C
172 lines
3.8 KiB
C
/*
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* Copyright (C) 2017 Kaspar Schleiser <kaspar@schleiser.de>
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* 2014 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup core_util
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* @{
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*
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* @file
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* @brief Helper functions for bit arithmetic
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*
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* @author Kaspar Schleiser <kaspar@schleiser.de>
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* @author Martine Lenders <mlenders@inf.fu-berlin.de>
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*/
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#ifndef BITARITHM_H
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#define BITARITHM_H
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#include <stdint.h>
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#include "cpu_conf.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @def SETBIT
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* @brief Sets a bitmask for a bitfield
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*
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* @param[in] val The bitfield
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* @param[in] bit Specifies the bits to be set
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*
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* @return The modified bitfield
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*/
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#define SETBIT(val, bit) val |= (bit)
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/**
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* @def CLRBIT
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* @brief Clears bitmask for a bitfield
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*
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* @param[in] val The bitfield
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* @param[in] bit Specifies the bits to be cleared
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*
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* @return The modified bitfield
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*/
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#define CLRBIT(val, bit) val &= (~(bit))
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/**
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* @name Single Bit Defines
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* @{
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*/
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#ifndef BIT0
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#define BIT0 0x00000001
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#define BIT1 0x00000002
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#define BIT2 0x00000004
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#define BIT3 0x00000008
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#define BIT4 0x00000010
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#define BIT5 0x00000020
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#define BIT6 0x00000040
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#define BIT7 0x00000080
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#define BIT8 0x00000100
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#define BIT9 0x00000200
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#define BIT10 0x00000400
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#define BIT11 0x00000800
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#define BIT12 0x00001000
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#define BIT13 0x00002000
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#define BIT14 0x00004000
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#define BIT15 0x00008000
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#endif
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#ifndef BIT16
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#define BIT16 0x00010000
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#define BIT17 0x00020000
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#define BIT18 0x00040000
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#define BIT19 0x00080000
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#define BIT20 0x00100000
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#define BIT21 0x00200000
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#define BIT22 0x00400000
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#define BIT23 0x00800000
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#define BIT24 0x01000000
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#define BIT25 0x02000000
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#define BIT26 0x04000000
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#define BIT27 0x08000000
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#define BIT28 0x10000000
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#define BIT29 0x20000000
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#define BIT30 0x40000000
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#define BIT31 0x80000000
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#endif
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/** @} */
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#define ARCH_32_BIT (__INT_MAX__ == 2147483647) /**< 1 for 32 bit architectures, 0 otherwise */
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/**
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* @brief Returns the number of the highest '1' bit in a value
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* @param[in] v Input value
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* @return Bit Number
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*
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* Source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogObvious
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*/
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unsigned bitarithm_msb(unsigned v);
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/**
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* @brief Returns the number of the lowest '1' bit in a value
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* @param[in] v Input value - must be unequal to '0', otherwise the
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* function will produce an infinite loop
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* @return Bit Number
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*
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*/
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static inline unsigned bitarithm_lsb(unsigned v);
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/**
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* @brief Returns the number of bits set in a value
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* @param[in] v Input value with platform-dependent word size
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* @return Number of set bits
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*
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*/
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unsigned bitarithm_bits_set(unsigned v);
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/**
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* @brief Returns the (uint32_t version) number of bits set in a value
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* @param[in] v Input value with 32 bit size
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* @return Number of set bits
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*
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*/
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#if ARCH_32_BIT
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static inline uint8_t bitarithm_bits_set_u32(uint32_t v)
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{
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return bitarithm_bits_set(v);
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}
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#else
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uint8_t bitarithm_bits_set_u32(uint32_t v);
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#endif
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/* implementations */
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static inline unsigned bitarithm_lsb(unsigned v)
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#if defined(BITARITHM_LSB_BUILTIN)
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{
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return __builtin_ffs(v) - 1;
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}
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#elif defined(BITARITHM_LSB_LOOKUP)
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{
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/* Source: http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightMultLookup */
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extern const uint8_t MultiplyDeBruijnBitPosition[32];
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return MultiplyDeBruijnBitPosition[((uint32_t)((v & -v) * 0x077CB531U)) >> 27];
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}
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#else
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{
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/* Source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogObvious */
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unsigned r = 0;
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while ((v & 0x01) == 0) {
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v >>= 1;
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r++;
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};
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return r;
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}
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif /* BITARITHM_H */
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/** @} */
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