Little buffer I/O libray

buffer.h

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

/* Buffer structure */
typedef struct
{
    void*    memory;
    uint64_t size;
    uint64_t nmemb;
}
buffer_t;

int buffer_allocate(buffer_t** buffer, uint64_t size, uint64_t nmemb)
{
    /* Double allocation protection */
    if((*buffer) != NULL) return EPERM;
    (*buffer) = (buffer_t*)malloc(sizeof(buffer_t));

    (*buffer)->size = size;
    (*buffer)->nmemb = nmemb;
    (*buffer)->memory = malloc(size * nmemb);
    
    /* OOM detection */
    if((*buffer)->memory == NULL) 
        return ENOMEM;

    return 0;
}

int buffer_deallocate(buffer_t** buffer)
{
    /* 'undefined' behaviour protection */
    if((*buffer) == NULL) return EPERM;
    if((*buffer)->memory == NULL) return EPERM;

    free((*buffer)->memory);
    free((*buffer));
    return 0;
}