From 50765b70dbb60cbe15ae70b13ff0b547c2135488 Mon Sep 17 00:00:00 2001
From: DocQuantum <shchurgood@gmail.com>
Date: Sun, 20 Oct 2019 23:04:54 -0500
Subject: [PATCH] Implemented coalescing when adding to list
---
mm.c | 134 ++++++++++++++++++++++++++++++++++++-----------------------
1 file changed, 82 insertions(+), 52 deletions(-)
diff --git a/mm.c b/mm.c
index 980a784..3e3a154 100644
--- a/mm.c
+++ b/mm.c
@@ -111,7 +111,6 @@ static void *extend_heap(size_t words);
static void place(void *bp, size_t asize);
static void *find_fit(size_t asize);
static void printblock(void *bp);
-static int mm_coalesce(void *bp);
static void mm_memcpy(void * dest, void * src);
static void add_to_list(void* bp);
static void remove_from_list(void* bp);
@@ -169,6 +168,7 @@ void *mm_malloc(size_t size)
/* Search the free list for a fit */
if ((bp = find_fit(asize)) != NULL) {
place(bp, asize);
+ //mm_checkheap(0);
return bp;
}
@@ -181,6 +181,8 @@ void *mm_malloc(size_t size)
place(bp, asize);
+ //mm_checkheap(0);
+
return bp;
}
/* $end mmmalloc */
@@ -200,15 +202,11 @@ void mm_free(void *bp)
return;
}
- // If allocated...
+ // If allocated, free
if(!GET_ALLOC(HDRP(bp))){
- // try to coalesce...
- if(mm_coalesce(bp)){
- // else free
- *HDRP(bp) |= 1;
- *FTRP(bp) |= 1;
- add_to_list(bp);
- }
+ *HDRP(bp) |= 1;
+ *FTRP(bp) |= 1;
+ add_to_list(bp);
} else {
fprintf(stderr, "mm_free(): memory not alloced or corrupted");
return;
@@ -218,42 +216,6 @@ void mm_free(void *bp)
/* $end mmfree */
-/**
- * mm_coalesce - Coalesce the freespace around a block
- *
- * Given a block pointer that has been freed, find empty
- * blocks near it to be combined into a large free chunk.
- *
- * Returns 0 on success, 1 on failure
- *
- */
-static int mm_coalesce(void *bp)
-{
- return 1;
-
- size_t nextBlock = GET_ALLOC(HDRP(NEXT_BLKP(bp)));
- size_t prevBlock = GET_ALLOC(HDRP(PREV_BLKP(bp)));
- size_t size = GET_SIZE(HDRP(bp));
-
- if(prevBlock && nextBlock){
- size += GET_SIZE(HDRP(PREV_BLKP(bp))) + GET_SIZE(HDRP(NEXT_BLKP(bp)));
- PUT(HDRP(PREV_BLKP(bp)), PACK(size, 1));
- PUT(FTRP(PREV_BLKP(bp)), PACK(size, 1));
- return 0;
- } else if(prevBlock && !nextBlock){
- size += GET_SIZE(HDRP(PREV_BLKP(bp)));
- PUT(HDRP(PREV_BLKP(bp)), PACK(size, 1));
- PUT(FTRP(PREV_BLKP(bp)), PACK(size, 1));
- return 0;
- } else if(!prevBlock && nextBlock){
- size += GET_SIZE(HDRP(NEXT_BLKP(bp)));
- PUT(HDRP(bp), PACK(size, 1));
- PUT(FTRP(bp), PACK(size, 1));
- return 0;
- }
- return 1;
-}
-
/*
* mm_realloc - naive implementation of mm_realloc
*
@@ -313,7 +275,6 @@ void *mm_realloc(void *ptr, size_t size)
PUT(FTRP(ptr), PACK(size, 0));
PUT(HDRP(NEXT_BLKP(ptr)), PACK(oldSize-size, 1));
PUT(FTRP(NEXT_BLKP(ptr)), PACK(oldSize-size, 1));
- mm_coalesce(NEXT_BLKP(ptr));
}
else {
PUT(HDRP(ptr), PACK(oldSize, 0));
@@ -331,7 +292,6 @@ void *mm_realloc(void *ptr, size_t size)
PUT(FTRP(ptr), PACK(size, 0));
PUT(HDRP(NEXT_BLKP(ptr)), PACK(nextSize-size, 1));
PUT(FTRP(NEXT_BLKP(ptr)), PACK(nextSize-size, 1));
- mm_coalesce(NEXT_BLKP(ptr));
}
else {
PUT(HDRP(ptr), PACK(nextSize, 0));
@@ -437,9 +397,9 @@ void mm_checkheap(int verbose)
}
/**
- * add_to_list - Adds free block to list
+ * add_to_list - Adds free block to list and coalesces
*
- * Will try to add block in address order
+ * Will try to add block in address order, or combine
*/
static void add_to_list(void* bp){
@@ -462,6 +422,21 @@ static void add_to_list(void* bp){
// case for 1 node in list.
if(free_listp == GET_NEXT_FREE(free_listp)){
+ //make sure they're not next to eachother
+ if((char *) NEXT_BLKP(bp) == free_listp){
+ size_t size = GET_SIZE(HDRP(free_listp)) + GET_SIZE(HDRP(bp));
+ PUT(HDRP(bp), PACK(size, 1));
+ PUT(FTRP(bp), PACK(size, 1));
+ free_listp = bp;
+ SET_NEXT_FREE(free_listp, free_listp);
+ SET_PREV_FREE(free_listp, free_listp);
+ return;
+ } else if((char *) PREV_BLKP(bp) == free_listp){
+ size_t size = GET_SIZE(HDRP(PREV_BLKP(bp))) + GET_SIZE(HDRP(bp));
+ PUT(HDRP(free_listp), PACK(size, 1));
+ PUT(FTRP(free_listp), PACK(size, 1));
+ return;
+ }
// Set head next to new
SET_NEXT_FREE(free_listp, bp);
// Set pre prev as new
@@ -482,7 +457,33 @@ static void add_to_list(void* bp){
{
if((char *) bp > node){
if((char *) bp < GET_NEXT_FREE(node) || node > GET_NEXT_FREE(node)){
- //printf("Adding %p between %p -> %p\n\n", bp, node, GET_NEXT_FREE(node));
+ if((char *) PREV_BLKP(bp) == node && (char *) NEXT_BLKP(bp) == GET_NEXT_FREE(node)){
+ size_t size = GET_SIZE(HDRP(node)) + GET_SIZE(HDRP(bp)) + GET_SIZE(HDRP(GET_NEXT_FREE(node)));
+ PUT(HDRP(node), PACK(size, 1));
+ PUT(FTRP(node), PACK(size, 1));
+ remove_from_list(GET_NEXT_FREE(node));
+ free_listp = node;
+ return;
+ } else if((char *) PREV_BLKP(bp) == node && (char *) NEXT_BLKP(bp) != GET_NEXT_FREE(node) && GET_ALLOC(HDRP(NEXT_BLKP(bp)))){
+ size_t size = GET_SIZE(HDRP(node)) + GET_SIZE(HDRP(bp));
+ PUT(HDRP(node), PACK(size, 1));
+ PUT(FTRP(node), PACK(size, 1));
+ free_listp = node;
+ return;
+ } else if((char *) PREV_BLKP(bp) != node && (char *) NEXT_BLKP(bp) == GET_NEXT_FREE(node)){
+ size_t size = GET_SIZE(HDRP(bp)) + GET_SIZE(HDRP(GET_NEXT_FREE(node)));
+ PUT(HDRP(bp), PACK(size, 1));
+ PUT(FTRP(bp), PACK(size, 1));
+ char * old = GET_NEXT_FREE(node);
+ // set next to the next of next-next
+ SET_NEXT_FREE(bp, GET_NEXT_FREE(old));
+ // set the prev of next-next node to bp
+ SET_PREV_FREE(GET_NEXT_FREE(old), bp);
+ SET_PREV_FREE(bp, node);
+ SET_NEXT_FREE(node, bp);
+ free_listp = node;
+ return;
+ }
/* bp inserted after node */
// Set new next as current next
SET_NEXT_FREE(bp, GET_NEXT_FREE(node));
@@ -500,7 +501,36 @@ static void add_to_list(void* bp){
}
else if((char *) bp < node){
if((char *) bp > GET_PREV_FREE(node) || node < GET_PREV_FREE(node)){
- //printf("Adding %p between %p -> %p\n\n", bp, GET_PREV_FREE(node), node);
+ if((char *) NEXT_BLKP(bp) == node && (char *) PREV_BLKP(bp) == GET_PREV_FREE(node)){
+ node = GET_PREV_FREE(node);
+ size_t size = GET_SIZE(HDRP(node)) + GET_SIZE(HDRP(bp)) + GET_SIZE(HDRP(GET_NEXT_FREE(node)));
+ PUT(HDRP(node), PACK(size, 1));
+ PUT(FTRP(node), PACK(size, 1));
+ remove_from_list(GET_NEXT_FREE(node));
+ free_listp = node;
+ return;
+ } else if((char *) PREV_BLKP(bp) == GET_PREV_FREE(node) && (char *) NEXT_BLKP(bp) != node){
+ node = GET_PREV_FREE(node);
+ size_t size = GET_SIZE(HDRP(node)) + GET_SIZE(HDRP(bp));
+ PUT(HDRP(node), PACK(size, 1));
+ PUT(FTRP(node), PACK(size, 1));
+ free_listp = node;
+ return;
+ } else if((char *) NEXT_BLKP(bp) == node && (char *) PREV_BLKP(bp) != GET_PREV_FREE(node)){
+ node = GET_PREV_FREE(node);
+ size_t size = GET_SIZE(HDRP(bp)) + GET_SIZE(HDRP(GET_NEXT_FREE(node)));
+ PUT(HDRP(bp), PACK(size, 1));
+ PUT(FTRP(bp), PACK(size, 1));
+ char * old = GET_NEXT_FREE(node);
+ // set next to the next of next-next
+ SET_NEXT_FREE(bp, GET_NEXT_FREE(old));
+ // set the prev of next-next node to bp
+ SET_PREV_FREE(GET_NEXT_FREE(old), bp);
+ SET_PREV_FREE(bp, node);
+ SET_NEXT_FREE(node, bp);
+ free_listp = node;
+ return;
+ }
/* bp inserted before node */
// Set new next to node
SET_NEXT_FREE(bp, node);
@@ -570,8 +600,8 @@ static void *extend_heap(size_t words)
/* Initialize free block and the epilogue header */
PUT(HDRP(bp), PACK(size, 1)); /* free block header */
PUT(FTRP(bp), PACK(size, 1)); /* free block footer */
+ PUT(HDRP(NEXT_BLKP(bp)), PACK(8, 0)); /* new epilogue header */
add_to_list(bp);
- PUT(HDRP(NEXT_BLKP(bp)), PACK(0, 0)); /* new epilogue header */
return bp;
}
/* $end mmextendheap */
--
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