write your own malloc

Question

I am writing my own malloc() and i have already figured the following

struct myblock
{
 struct myblock *next;
 struct myblock *prev;
 int isFree;
 unsigned availablesize;
 char *buffer;
}

and space #define MEM_BUFFER (1024) which will be "my ram". and if i am not wrong then i would have

char *array[MEM_BUFFER];

to have array of 1024 bytes (kindly correct me if i am wrong).

As we know that MEM_BUFFER will also contain the matadata of occupied space. I am bit confused that how should i start.

This is my main question. should i assign the struct to the array on each allocation request (if yes then from struct char array ?) .

should i handle double linked list on heap and skip sizeof(myblock) bytes from the array.

I am thinking on this solution for last 2 days and I am still confused.

Answer 1

No,

char *array[MEM_BUFFER];

is not an array of 1024 bytes (unless MEM_BUFFER is set to 1024 / sizeof (char *)) typically. It's an array of MEM_BUFFER character pointers.

You need just:

char array[MEM_BUFFER];

although a better name might be heap_space.

To make it consist of blocks, you'd need an additional pointer that is the first block:

struct myblock *heap = (struct myblock *) heap_space;

Then you can initialize that:

heap->next = NULL;
heap->prev = NULL;
heap->isFree = 1;
heap->availablesize = sizeof heap_space - sizeof *heap;

Not sure what struct myblock.buffer should do, I put the blocks inside the heap so the user memory for a block is at (void *) (block + 1);

• abidkhan303: @unwind.. thanks you very much to giving me direction and i have started working. my second question is: struct myblock *heap = (struct myblock *) heap_space; this is how we can start by creating root node by type casting heap_space, but what about the second node, I mean when the rquests will start coming then? how i will create the second node to start working. Same as we are creating first or .... how ?