malloc.c

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/*
 * Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
 * Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 *    conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
 *    of conditions and the following disclaimer in the documentation and/or other materials
 *    provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#include "stdlib.h"
#include "string.h"
#include "los_vm_map.h"
 
/*
 * Allocates the requested memory and returns a pointer to it. The requested
 * size is nitems each size bytes long (total memory requested is nitems*size).
 * The space is initialized to all zero bits.
 */
 
void *calloc(size_t nitems, size_t size)
{ /*lint !e578*/
    size_t real_size;
    void *ptr = NULL;
 
    if (nitems == 0 || size == 0) {
        return NULL;
    }
 
    real_size = (size_t)(nitems * size);
    ptr = LOS_KernelMalloc((UINT32) real_size);
    if (ptr != NULL) {
        (void) memset_s((void *) ptr, real_size, 0, real_size);
    }
    return ptr;
}
 
/*
 * Deallocates the memory previously allocated by a call to calloc, malloc, or
 * realloc. The argument ptr points to the space that was previously allocated.
 * If ptr points to a memory block that was not allocated with calloc, malloc,
 * or realloc, or is a space that has been deallocated, then the result is undefined.
 */
/// 释放ptr所指向的内存空间
void free(void *ptr)
{
    if (ptr == NULL) {
        return;
    }
 
    LOS_KernelFree(ptr);
}
 
/*
 * Allocates the requested memory and returns a pointer to it. The requested
 * size is size bytes. The value of the space is indeterminate.
 * 分配请求的内存并返回指向它的指针。 请求的大小是 size 字节。 内存值是不确定的。
 */
/// 动态分配内存块大小
void *malloc(size_t size)
{ /*lint !e31 !e10*/
    if (size == 0) {
        return NULL;
    }
 
    return LOS_KernelMalloc((UINT32) size);
}
/// 分配请求的内存并返回指向它的指针。 请求的大小是 size 字节。 内存值是0。
/// 原来 zalloc的含义是 zero malloc  
void *zalloc(size_t size)
{ /*lint !e10*/
    void *ptr = NULL;
 
    if (size == 0) {
        return NULL;
    }
 
    ptr = LOS_KernelMalloc((UINT32) size);
    if (ptr != NULL) {
        (void) memset_s(ptr, size, 0, size);
    }
    return ptr;
}
 
/*
 * allocates a block of size bytes whose address is a multiple of boundary.
 * The boundary must be a power of two!
 * 分配一个大小字节的块，其地址是边界的倍数。边界必须是 2 的幂！
 */
 
void *memalign(size_t boundary, size_t size)
{
    if (size == 0) {
        return NULL;
    }
 
    return LOS_KernelMallocAlign((UINT32) size, (UINT32) boundary);
}
 
/*
 * Attempts to resize the memory block pointed to by ptr that was previously
 * allocated with a call to malloc or calloc. The contents pointed to by ptr are
 * unchanged. If the value of size is greater than the previous size of the
 * block, then the additional bytes have an undeterminate value. If the value
 * of size is less than the previous size of the block, then the difference of
 * bytes at the end of the block are freed. If ptr is null, then it behaves like
 * malloc. If ptr points to a memory block that was not allocated with calloc
 * or malloc, or is a space that has been deallocated, then the result is
 * undefined. If the new space cannot be allocated, then the contents pointed
 * to by ptr are unchanged. If size is zero, then the memory block is completely
 * freed.
 * 尝试调整先前通过调用 malloc 或 calloc 分配的 ptr 指向的内存块的大小。 
 * ptr 指向的内容不变。 如果 size 的值大于块的先前大小，则附加字节具有不确定的值。 
 * 如果 size 的值小于块的先前大小，则释放块末尾的字节差。 如果 ptr 为 null，
 * 则它的行为类似于 malloc。 如果 ptr 指向未使用 calloc 或 malloc 分配的内存块，
 * 或者是已释放的空间，则结果未定义。 如果无法分配新空间，则 ptr 指向的内容不变。 
 * 如果大小为零，则内存块被完全释放。
 */
/// 重分配内存
void *realloc(void *ptr, size_t size)
{
    if (ptr == NULL) {
        ptr = malloc(size);
        return ptr;
    }
 
    if (size == 0) {
        free(ptr);
        return NULL;
    }
 
    return LOS_KernelRealloc(ptr, (UINT32) size);
}