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/*
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* Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
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* Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without modification,
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* are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list
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* of conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* 3. Neither the name of the copyright holder nor the names of its contributors may be used
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* to endorse or promote products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "los_bitmap.h"
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#include "los_printf.h"
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#include "los_toolchain.h"//GCC 编译器的内置函数
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/**
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位操作是指对二进制数的bit位进行操作。程序可以设置某一变量为状态字，状态字中的
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每一bit位（标志位）可以具有自定义的含义。
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系统提供标志位的置1和清0操作，可以改变标志位的内容，同时还提供获取状态字中标志位
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为1的最高位和最低位的功能。用户也可以对系统的寄存器进行位操作。
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*/
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#define OS_BITMAP_MASK 0x1FU
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#define OS_BITMAP_WORD_MASK ~0UL
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/* find first zero bit starting from LSB */
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STATIC INLINE UINT16 Ffz(UINTPTR x)
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{//__builtin_ffsl: 返回右起第一个1的位置，函数来自 glibc
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return __builtin_ffsl(~x) - 1;//从LSB开始查找第一个零位 LSB(最低有效位) 对应 最高有效位(MSB)
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}
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///对状态字的某一标志位进行置1操作
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VOID LOS_BitmapSet(UINT32 *bitmap, UINT16 pos)
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{
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if (bitmap == NULL) {
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return;
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}
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*bitmap |= 1U << (pos & OS_BITMAP_MASK);//在对应位上置1
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}
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///对状态字的某一标志位进行清0操作
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VOID LOS_BitmapClr(UINT32 *bitmap, UINT16 pos)
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{
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if (bitmap == NULL) {
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return;
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}
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*bitmap &= ~(1U << (pos & OS_BITMAP_MASK));//在对应位上置0
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}
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/**
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获取参数位图中最高位为1的索引位 例如: 00110110 返回 5
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CLZ 用于计算操作数最高端0的个数，这条指令主要用于以下两个场合
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1.计算操作数规范化（使其最高位为1）时需要左移的位数
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2.确定一个优先级掩码中最高优先级
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*/
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UINT16 LOS_HighBitGet(UINT32 bitmap)
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{
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if (bitmap == 0) {
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return LOS_INVALID_BIT_INDEX;
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}
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return (OS_BITMAP_MASK - CLZ(bitmap));//CLZ = count leading zeros 用于计算整数的前导零
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}
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/// 获取参数位图中最低位为1的索引位， 例如: 00110110 返回 1
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UINT16 LOS_LowBitGet(UINT32 bitmap)
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{
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if (bitmap == 0) {
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return LOS_INVALID_BIT_INDEX;
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}
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return CTZ(bitmap);// CTZ = count trailing zeros 用于计算给定整数的尾随零
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}
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/// 从start位置开始设置numsSet个bit位 置1
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VOID LOS_BitmapSetNBits(UINTPTR *bitmap, UINT32 start, UINT32 numsSet)
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{
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UINTPTR *p = bitmap + BITMAP_WORD(start);
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const UINT32 size = start + numsSet;
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UINT16 bitsToSet = BITMAP_BITS_PER_WORD - (start % BITMAP_BITS_PER_WORD);
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UINTPTR maskToSet = BITMAP_FIRST_WORD_MASK(start);
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while (numsSet > bitsToSet) {
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*p |= maskToSet;
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numsSet -= bitsToSet;
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bitsToSet = BITMAP_BITS_PER_WORD;
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maskToSet = OS_BITMAP_WORD_MASK;
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p++;
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}
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if (numsSet) {
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maskToSet &= BITMAP_LAST_WORD_MASK(size);
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*p |= maskToSet;
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}
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}
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///从start位置开始 清除numsSet个bit位置0 ,对状态字的连续标志位进行清0操作
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VOID LOS_BitmapClrNBits(UINTPTR *bitmap, UINT32 start, UINT32 numsClear)
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{
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UINTPTR *p = bitmap + BITMAP_WORD(start);
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const UINT32 size = start + numsClear;
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UINT16 bitsToClear = BITMAP_BITS_PER_WORD - (start % BITMAP_BITS_PER_WORD);
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UINTPTR maskToClear = BITMAP_FIRST_WORD_MASK(start);
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while (numsClear >= bitsToClear) {
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*p &= ~maskToClear;
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numsClear -= bitsToClear;
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bitsToClear = BITMAP_BITS_PER_WORD;
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maskToClear = OS_BITMAP_WORD_MASK;
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p++;
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}
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if (numsClear) {
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maskToClear &= BITMAP_LAST_WORD_MASK(size);
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*p &= ~maskToClear;
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}
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}
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///从numBits位置开始找到第一个0位
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INT32 LOS_BitmapFfz(UINTPTR *bitmap, UINT32 numBits)
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{
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INT32 bit, i;
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for (i = 0; i < BITMAP_NUM_WORDS(numBits); i++) {
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if (bitmap[i] == OS_BITMAP_WORD_MASK) {
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continue;
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}
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bit = i * BITMAP_BITS_PER_WORD + Ffz(bitmap[i]);
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if (bit < numBits) {
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return bit;
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}
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return -1;
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}
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return -1;
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}
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