Memory Pool

In Melon, memory pools are divided into two categories:

• heap memory
• Shared memory

Among them, the shared memory memory pool only allows data to be shared between the main and child processes (also shared between sibling processes). That is, when used, the shared memory memory pool is created by the main process, and then the child process is created.

Header file

#include "mln_alloc.h"

Module

alloc

Functions

mln_alloc_init

mln_alloc_t *mln_alloc_init(mln_alloc_t *parent);

Description: Create a heap memory memory pool. The parameter parent is a memory pool instance. When the parameter is NULL, the memory pool created by this function will allocate memory from the heap. If it is not NULL, it will allocate memory from the pool where parent is located. That is, the pool structure can be cascaded.

Return value: If successful, return the memory pool structure pointer, otherwise return NULL

mln_alloc_shm_init

mln_alloc_t *mln_alloc_shm_init(mln_size_t size, void *locker, mln_alloc_shm_lock_cb_t lock, mln_alloc_shm_lock_cb_t unlock);

Description: Create a shared memory memory pool.

Parameters:

• size The pool size size (in bytes) needs to be given when creating this pool. Once created, it cannot be expanded later.
• locker is the lock resource pointer.
• lock is a callback function used to lock the lock resource. The function parameter is the lock resource pointer. If the lock fails, a non-0 value is returned.
• unlock is a callback function used to unlock the lock resource. The function parameter is the lock resource pointer. If unlocking fails, a non-0 value is returned.

typedef int (*mln_alloc_shm_lock_cb_t)(void *);

lock and unlock are only used when functions in the subpool are called. Therefore, if you directly operate on the shared memory pool, you need to unlock it externally. The allocation and release functions that act on the shared memory pool will not call this callback.

Return value: Returns the memory pool structure pointer if successful, otherwise returns NULL

mln_alloc_destroy

void mln_alloc_destroy(mln_alloc_t *pool);

Description: Destroy the memory pool. The destroy operation will release all the memory managed in the memory pool uniformly.

Return value: none

mln_alloc_m

void *mln_alloc_m(mln_alloc_t *pool, mln_size_t size);

Description: Allocate a memory of size size from the memory pool pool. If the memory pool is a shared memory memory pool, it will be allocated from shared memory, otherwise it will be allocated from heap memory.

Return value: If successful, return the memory start address, otherwise return NULL

mln_alloc_c

void *mln_alloc_c(mln_alloc_t *pool, mln_size_t size);

Description: Allocate a memory of size size from the memory pool pool, and the memory will be zeroed.

Return value: If successful, return the memory start address, otherwise return NULL

mln_alloc_re

void *mln_alloc_re(mln_alloc_t *pool, void *ptr, mln_size_t size);

Description: Allocate a size of size from the memory pool pool, and copy the data in the memory pointed to by ptr to the new memory.

ptr must be the starting address of memory allocated for the memory pool. If size is 0, the memory pointed to by ptr will be freed.

Return value: If successful, return the memory start address, otherwise return NULL

mln_alloc_free

void mln_alloc_free(void *ptr);

Description: Free the memory pointed to by ptr. Note: ptr must be the address returned by the allocation function, not a location in the allocated memory.

Return value: none

Example

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "mln_alloc.h"

int main(int argc, char *argv[])
{
    char *p;
    mln_alloc_t *pool;

    pool = mln_alloc_init(NULL);
    if (pool == NULL) {
        fprintf(stderr, "pool init failed\n");
        return -1;
    }

    p = (char *)mln_alloc_m(pool, 6);
    if (p == NULL) {
        fprintf(stderr, "alloc failed\n");
        return -1;
    }

    memcpy(p, "hello", 5);
    p[5] = 0;
    printf("%s\n", p);

    mln_alloc_free(p);
    mln_alloc_destroy(pool);

    return 0;
}