easy_alloc.c

#include <stdio.h>
#include <assert.h>

#define TEST
#define EASY_ALLOC_MAX_SIZE 0x100000

void* alloc(unsigned long size);
void free(void* ptr);
unsigned long get_index(void);

typedef unsigned char byte;

byte memory[EASY_ALLOC_MAX_SIZE];
unsigned long alloc_index = 0;

/**
 * void* easy_alloc
 * @unsigned long size : byte to allocate.
 */
void* easy_alloc(unsigned long size)
{
    unsigned long i;
    void* ret;


    i = get_index();
    ret = memory + i;

    if ( size < EASY_ALLOC_MAX_SIZE ) {
        alloc_index += size;
    } else {
        printf("oops!\n");
    }

    return ret;
}

/**
 * void easy_free
 * @void* ptr : address to free.
 */
void easy_free(void* ptr)
{
    return;
}

unsigned long get_index(void)
{
    return alloc_index;
}

#ifdef TEST
int test_alloc_5byte(void)
{
    unsigned long before;
    void *ptr;
    unsigned long size = 6;

    before = get_index();
    ptr = easy_alloc(size);

    assert( ( before + size ) == get_index() );
    assert( ( ptr + size ) == ( memory + get_index() ) );

    return 0;
}


int test_alloc_15byte(void)
{
    unsigned long before;
    void *ptr;
    unsigned long size = 15;

    before = get_index();
    ptr = easy_alloc(size);

    assert( ( before + size ) == get_index() );
    assert( ( ptr + size ) == ( memory + get_index() ) );

    return 0;
}

int test_alloc_90000byte(void)
{
    unsigned long before;
    void *ptr;
    unsigned long size = 90000;

    before = get_index();
    ptr = easy_alloc(size);

    assert( ( before + size ) == get_index() );
    assert( ( ptr + size ) == ( memory + get_index() ) );

    return 0;
}

int print_before_test(void)
{
    printf("MAX size %u\n",EASY_ALLOC_MAX_SIZE);
    printf("memory %p\n",memory);
}

int print_after_test(void)
{
    printf("index %lu\n",get_index());
    printf("memory %p\n", (void*)( memory + get_index() ) );
}

int main(int argc,char* argv)
{   
    // test it!.
    print_before_test();
    test_alloc_5byte();
    test_alloc_15byte();
    test_alloc_90000byte();
    print_after_test();
    return 0;
}
#endif

Makefile

all:
	gcc easy_alloc.c -o easy_alloc
	./easy_alloc
clean:
	rm -rf easy_alloc