Mishors / Dynamic-Memory-Allocator

Dynamic memory allocator project to implement malloc and free functions in C to perform like the built-int functions in malloc Package of C. Hint: The base code for this project is taken from Computer Systems_ A Programmer's Perspective by Randal E. Bryant, David R. O'Hallaron

Dynamic Memory Allocator

Dynamic memory allocator project to implement malloc and free functions in C to perform like the built-int functions in malloc Package of C. Hint: The base code for this project is taken from Computer Systems_ A Programmer's Perspective by Randal E. Bryant, David R. O'Hallaron

Assumptions

• Our allocator uses a model of the memory system provided by the memlib.c .The purpose of the model is to allow us to run our allocator without interfering with the existing system-level malloc package.
• The mem_init function models the virtual memory available to the heap as a large double-word aligned array of bytes.
• The bytes between mem_heap and mem_brk represent allocated virtual memory. The bytes following mem_brk represent unallocated virtual memory.
• The allocator requests additional heap memory by calling the mem_sbrk function, which has the same interface as the system's sbrk function, as well as the same semantics, except that it rejects requests to shrink the heap.
• The minimum block size is 16 bytes.
• The free list is organized as an implicit free list (The initial Commit Only will have another efficient lists like explicit lists or segregatted lists).
• In heap : The first word is an unused padding word aligned to a double-word boundary.
• In heap : The padding is followed by a special prologue block, which is an 8-byte allocated block consisting of only a header and a footer.
• In heap : Always ends with a special epilogue block, which is a zero-size allocated block that consists of only a header.
• HINT : The prologue and epilogue blocks are tricks that eliminate the edge conditions during merging free blocks.
• The allocator uses a single private (static) global variable heap_listp that always points to the prologue block.

mem_allocator.c

This is the file in which mm_malloc and mm_free are implemented

Functions Description

• int mm_init() : Creates the heap and initializes it with free block
• void *mm_malloc(size_t size) : Allocates block in memory of size (size_t size) . Returns (void *) pointer to the address of the block beginning
• void mm_free(void *bp) : Frees the requested block (bp) and then merges adjacent free blocks using the boundary-tags merging technique
• static void *extend_heap(size_t words) : The extend_heap function is invoked in two different circumstances: 1st: When the heap is initialized 2nd: when mm_malloc is unable to find a suitable fit To maintain alignment, extend_heap rounds up the requested size to the nearest multiple of 2 words (8 bytes) and then requests the additional heap space from the memory system.
• static void *merge(void *bp) : Returns Address of merged free blocks
• static void *find_fit(size_t asize) : First-fit search of the implicit free list to find free block
• void place (void *bp, size_t asize) : Places the requested block at the beginning of the free block, splitting only if the size of the remainder would equal or exceed the minimum block size.