mid_alloc

This project implements a simple custom memory allocator and a garbage collector in C, providing three primary functions for memory management: allocating memory on the heap, freeing allocated memory and garbage collection.

User APIs

void init_allocator(size_t memcap_in_bytes)

Initializes the memory allocator with memcap_in_bytes amount of pre-allocated memory. If input is zero it will allocate a pre-defined amount of memory.Must be called before any allocation or deallocation operations. It only need to call once.

void* mid_alloc(size_t size_in_bytes)

Allocates size_in_bytes amount of bytes on the heap and returns a pointer to the allocated memory. All allocations happens from the amount of bytes pre-allocated by void init_allocator(size_t).

bool mid_free(void* ptr)

Frees the memory at the specified location. Returns true if successful, false otherwise.

void mid_collect()

Garbage collector. When called, it will free all the unreachable memory which are allocated before calling it.

Usage

1. Initialization

   Pre-allocating pre-defined amount of bytes of memory

   #include "allocator.h"
   int main(){
       init_allocator(0);
   }

   Pre-allocating 4096 bytes of memory.

   #include "allocator.h"
   int main(){
       init_allocator(4096);
   }

2. Allocation

   #include "allocator.h"
   typedef struct Node{
       int val;
       struct Node * next;
   }Node_t;
   int main(){
       init_allocator(0);
       Node_t*head =(Node_t*) mid_alloc(sizeof(Node_t));
       if(head!=NULL)
       printf("Successfully created linked list head.");
       else
       printf("Failed to create linked list head.");
   }

3. Deallocation

   #include "allocator.h"
   int main(){
       init_allocator(0);
       char * str=(char *)mid_alloc(10 * sizeof(char));
       bool result = mid_free(ptr);
       if(result)
           printf("String de-allocated successfully.");
       else
           printf("Failed to de-allocate the string.")
   }

4. Garbage Collection

   #include "allocator.h"
   int main(){
       init_allocator(0);
       int * arr=(int*)mid_alloc(5*sizeof(int));
       char * str=(char *)mid_alloc(10 * sizeof(char));
       arr=NULL
       mid_collect();
       // All the memory allocated by 'arr' has been deallocated but
       // not the string 'str' as it still reachable.
   }

Running Tests

To run the test cases, add your test case in the folder tests in similar way I have written (array_test.c, tree_test.c etc.) then import your testing function to test.c via test.h then run following :

make test
./test

Usage

Compile the project into a shared library using :

make lib

It will create libmid_alloc.so. then dynamically link the shared library and run your program.

// main.c
#include "allocator.h"
typedef struct Node{
    int val;
    struct Node * next;
}Node_t;
int main(){
    init_allocator(0);
    Node_t*head =(Node_t*) mid_alloc(sizeof(Node_t));
    if(head!=NULL)
    printf("Successfully created linked list head.");
    else
    printf("Failed to create linked list head.");
}

gcc main.c -L <Path to library> -lmid_alloc -o main
LD_LIBRARY_PATH=. ./main

Or you can install the library using :

sudo make install

It will copy the created shared library to /usr/local/lib and run ldconfig then run :

gcc main.c -lmid_alloc -o main
./main