update

mm.c

@@ -44,61 +44,390 @@ team_t team = {
 
 #define SIZE_T_SIZE (ALIGN(sizeof(size_t)))
 
+
+/* Basic constants and macros */
+#define WSIZE 4 	/* Word and header/footer size (bytes) */
+#define DSIZE 8 	/* Double word size (bytes) */
+#define CHUNKSIZE (1<<12) 	/* Extend heap by this amount (bytes) */
+
+#define MAX(x, y) ((x) > (y) ? (x) : (y))
+
+/* Pack a size and allocated bit into  word */
+#define PACK(size, alloc) ((size) | (alloc))
+
+/* Read and write a word at address p */
+#define GET(p) (*(unsigned int *)(p))
+#define PUT(p, val) (*(unsigned int *)(p) = (val))
+
+/* Read and write a pointer at address p */
+#define GET_PTR(p) ((unsigned int *)(long)(GET(p)))
+#define PUT_PTR(p, ptr) (*(unsigned int *)(p) = ((long)ptr))
+
+/* Read the size and allocated fields from address p */
+#define GET_SIZE(p) (GET(p) & ~0x7)
+#define GET_ALLOC(p) (GET(p) & 0x1)
+
+/* Given block ptr bp, compute address of its header and footer */
+#define HDRP(bp) ((char *)(bp) - WSIZE)
+#define FTRP(bp) ((char *)(bp) + GET_SIZE(HDRP(bp)) - DSIZE)
+
+/* Given block ptr bp, compute address of next and previous blocks */
+#define NEXT_BLKP(bp) ((char *)(bp) + GET_SIZE(((char *)(bp) - WSIZE)))
+#define PREV_BLKP(bp) ((char *)(bp) - GET_SIZE(((char *)(bp) - DSIZE)))
+
+
+/* 每个free list中块的大小范围 */
+#define SIZE1 (1<<4)
+#define SIZE2 (1<<5)
+#define SIZE3 (1<<6)
+#define SIZE4 (1<<7)
+#define SIZE5 (1<<8)
+#define SIZE6 (1<<9)
+#define SIZE7 (1<<10)  		/* 1 KB */
+#define SIZE8 (1<<11)
+#define SIZE9 (1<<12)
+#define SIZE10 (1<<13)
+#define SIZE11 (1<<14)
+#define SIZE12 (1<<15)
+#define SIZE13 (1<<16)
+#define SIZE14 (1<<17)
+#define SIZE15 (1<<18)
+#define SIZE16 (1<<19)
+#define SIZE17 (1<<20) 		/* 1 MB */
+
+#define LISTS_NUM 18 		/* free list 的数量 */
+
+/* Globe var */
+static char *heap_listp;
+
+/* 函数声明 */
+static void *extend_heap(size_t words);
+static void *coalesce(void *bp);
+static void *find_fit(size_t asize);
+static void place(void *bp, size_t asize);
+static void insert_list(void *bp);
+int getListOffset(size_t size);
+void delete_list(void *bp);
+
 /* 
  * mm_init - initialize the malloc package.
  */
 int mm_init(void)
 {
-    return 0;
+	char *bp;
+	int i;
+
+	if ((heap_listp = mem_sbrk((LISTS_NUM + 4) * WSIZE)) == (void *)-1) {
+		return -1;
+	}
+	PUT(heap_listp + LISTS_NUM * WSIZE, 0);
+	PUT(heap_listp + (1 + LISTS_NUM) * WSIZE, PACK(DSIZE, 1));
+	PUT(heap_listp + (2 + LISTS_NUM) * WSIZE, PACK(DSIZE, 1));
+	PUT(heap_listp + (3 + LISTS_NUM) * WSIZE, PACK(0, 1));
+
+	for (i = 0; i < LISTS_NUM; i++) {
+		PUT_PTR(heap_listp + WSIZE * i, NULL);
+	}
+
+	/* Extend the empty heap with a free block of CHUNKSIZE bytes */
+	if ((bp = extend_heap(CHUNKSIZE / WSIZE)) == NULL) {
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * 扩展heap的大小
+ */
+void *extend_heap(size_t words)
+{
+	char *bp;
+	size_t size;
+
+	/* Allocate an even number of words to maintain alignment */
+	size = (words % 2) ? ((words + 1) * WSIZE) : (words * WSIZE);
+	if ((long)(bp = mem_sbrk(size)) == -1) {
+		return NULL;
+	}
+
+	/* Initialize free block header/footer and the epilogue header */
+	PUT(HDRP(bp), PACK(size, 0)); 		/* Free block header */
+	PUT(FTRP(bp), PACK(size, 0)); 		/* Free block footer */
+	PUT(HDRP(NEXT_BLKP(bp)), PACK(0, 1)); 	/* New epilogue header */
+
+	/* Coalesce if the previous block was free */
+	return coalesce(bp);
+}
+
+
+/*
+ * 合并free block 
+ */
+void *coalesce(void *bp)
+{
+	size_t prev_alloc = GET_ALLOC(FTRP(PREV_BLKP(bp)));
+	size_t next_alloc = GET_ALLOC(HDRP(NEXT_BLKP(bp)));
+	size_t size = GET_SIZE(HDRP(bp));
+	
+	if (prev_alloc && next_alloc) { 	/* 前后都分配了  */
+		bp = bp;
+	} else if (prev_alloc && !next_alloc) { 	/* 前分配, 后未分配 */
+		delete_list(NEXT_BLKP(bp));
+		size += GET_SIZE(HDRP(NEXT_BLKP(bp)));
+		PUT(HDRP(bp), PACK(size, 0));
+		PUT(FTRP(bp), PACK(size, 0));
+	} else if (!prev_alloc && next_alloc) { 	/* 前未分配, 后分配 */
+		delete_list(PREV_BLKP(bp));
+		size += GET_SIZE(HDRP(PREV_BLKP(bp)));
+		PUT(FTRP(bp), PACK(size, 0));
+		PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0));
+		bp = PREV_BLKP(bp);
+	} else { 				/* 前后都未分配 */
+		delete_list(NEXT_BLKP(bp));
+		delete_list(PREV_BLKP(bp));
+		size = size + GET_SIZE(HDRP(PREV_BLKP(bp))) + 
+			GET_SIZE(HDRP(NEXT_BLKP(bp)));
+		PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0));
+		PUT(FTRP(NEXT_BLKP(bp)), PACK(size, 0));
+		bp = PREV_BLKP(bp);
+	}
+
+	insert_list(bp);
+	return bp;
 }
 
 /* 
- * mm_malloc - Allocate a block by incrementing the brk pointer.
- *     Always allocate a block whose size is a multiple of the alignment.
+ * mm_malloc - Allocate a block by searching the free list.
+ *	 Always allocate a block whose size is a multiple of the alignment.
  */
 void *mm_malloc(size_t size)
+{	
+	size_t asize; 		/* Adjusted block size */
+	size_t extendsize; 	/* Amount to extend heap if no fit */
+	char *bp;
+
+	/* Igore spurious requests */
+	if (0 == size) {
+		return NULL;
+	}
+
+	/* Adjusted block size to include overhead and alignment reqs */
+	if (size <= DSIZE) {
+		asize = 2 * DSIZE;
+	} else {
+		asize = DSIZE * ((size + (DSIZE) + (DSIZE - 1)) / DSIZE);
+	}
+
+	/* Search the free list for a fit */
+	if ((bp = find_fit(asize)) != NULL) {
+		place(bp, asize);
+		return bp;
+	}
+
+	/* No fit found. Get more memory and place the block */
+	extendsize = MAX(asize, CHUNKSIZE);
+	if ((bp = extend_heap(extendsize / WSIZE)) == NULL) {
+		return NULL;
+	}
+	place(bp, asize);
+	return bp;
+}
+
+
+/*
+ * getListOffset - 得到大小为size的块应该在哪个list中
+ */
+int getListOffset(size_t size)
+{
+	if (size <= SIZE1) {
+		return 0;
+	} else if (size <= SIZE2) {
+		return 1;
+	} else if (size <= SIZE3) {
+		return 2;
+	} else if (size <= SIZE4) {
+		return 3;
+	} else if (size <= SIZE5) {
+		return 4;
+	} else if (size <= SIZE6) {
+		return 5;
+	} else if (size <= SIZE7) {
+		return 6;
+	} else if (size <= SIZE8) {
+		return 7;
+	} else if (size <= SIZE9) {
+		return 8;
+	} else if (size <= SIZE10) {
+		return 9;
+	} else if (size <= SIZE11) {
+		return 10;
+	} else if (size <= SIZE12) {
+		return 11;
+	} else if (size <= SIZE13) {
+		return 12;
+	} else if (size <= SIZE14) {
+		return 13;
+	} else if (size <= SIZE15) {
+		return 14;
+	} else if (size <= SIZE16) {
+		return 15;
+	} else if (size <= SIZE17) {
+		return 16;
+	} else {
+		return 17;
+	}
+}
+
+/*
+ * insert_list - 将free block插入到相应大小的free list中, 插入位置为表头
+ */
+void insert_list(void *bp)
+{
+	int index;
+	size_t size;
+	size = GET_SIZE(HDRP(bp));
+	index = getListOffset(size);
+
+	if (GET_PTR(heap_listp + WSIZE * index) == NULL) {
+		PUT_PTR(heap_listp + WSIZE * index, bp);
+		PUT_PTR(bp, NULL);
+		PUT_PTR((unsigned int *)bp + 1, NULL);
+	} else {
+		PUT_PTR(bp, GET_PTR(heap_listp + WSIZE * index));
+		PUT_PTR(GET_PTR(heap_listp + WSIZE * index) + 1, bp);  	/* 修改前一个位置 */
+		PUT_PTR((unsigned int *)bp + 1, NULL);
+		PUT_PTR(heap_listp + WSIZE * index, bp);
+	}
+}
+
+/* 
+ * delete_list - 删除链表结点
+ */
+void delete_list(void *bp)
+{
+	int index;
+	size_t size;
+	size = GET_SIZE(HDRP(bp));
+	index = getListOffset(size);
+	if (GET_PTR(bp) == NULL && GET_PTR((unsigned int *)bp + 1) == NULL) { 
+		/* 链表中唯一结点 */
+		PUT_PTR(heap_listp + WSIZE * index, NULL);
+	} else if (GET_PTR(bp) == NULL && GET_PTR((unsigned int *)bp + 1) != NULL) {
+		/* 链表中最后一个结点, 不是唯一一个 */
+		PUT_PTR(GET_PTR((unsigned int *)bp + 1), NULL);
+	} else if (GET_PTR(bp) != NULL && GET_PTR((unsigned int *)bp + 1) == NULL){
+		/* 链表中第一个结点, 不是唯一一个 */
+		PUT_PTR(heap_listp + WSIZE * index, GET_PTR(bp));
+		PUT_PTR(GET_PTR(bp) + 1, NULL);
+	} else if (GET_PTR(bp) != NULL && GET_PTR((unsigned int *)bp + 1) != NULL) {
+		/* 链表中的中间结点 */
+		PUT_PTR(GET_PTR((unsigned int *)bp + 1), GET_PTR(bp));
+		PUT_PTR(GET_PTR(bp) + 1, GET_PTR((unsigned int*)bp + 1));
+	}
+}
+
+/*
+ * find_fit - Search the free list for a fit 
+ */
+void *find_fit(size_t asize)
 {
-    int newsize = ALIGN(size + SIZE_T_SIZE);
-    void *p = mem_sbrk(newsize);
-    if (p == (void *)-1)
+	int index;
+	index = getListOffset(asize);
+	unsigned int *ptr;
+
+	/* 小的class内找不到就到大的class内找 */
+	while (index < 18) {
+		ptr = GET_PTR(heap_listp + 4 * index);
+		while (ptr != NULL) {
+			if (GET_SIZE(HDRP(ptr)) >= asize) {
+				return (void *)ptr;
+			}
+			ptr = GET_PTR(ptr);
+		}
+		index++;
+	}
+
 	return NULL;
-    else {
-        *(size_t *)p = size;
-        return (void *)((char *)p + SIZE_T_SIZE);
-    }
 }
 
 /*
- * mm_free - Freeing a block does nothing.
+ * place - place the requested block at the beginning of the free block
+ */
+void place(void *bp, size_t asize)
+{
+	size_t csize = GET_SIZE(HDRP(bp));
+	delete_list(bp);
+	if ((csize - asize) >= (2 * DSIZE)) {
+		PUT(HDRP(bp), PACK(asize, 1));	
+		PUT(FTRP(bp), PACK(asize, 1));
+		bp = NEXT_BLKP(bp);
+		PUT(HDRP(bp), PACK(csize - asize, 0));
+		PUT(FTRP(bp), PACK(csize - asize, 0));
+		insert_list(bp);
+	} else {
+		PUT(HDRP(bp), PACK(csize, 1));
+		PUT(FTRP(bp), PACK(csize, 1));
+	}
+}
+
+/*
+ * mm_free - Freeing a block.
  */
 void mm_free(void *ptr)
 {
+	size_t size = GET_SIZE(HDRP(ptr));
+
+	PUT(HDRP(ptr), PACK(size, 0));
+	PUT(FTRP(ptr), PACK(size, 0));
+	coalesce(ptr);
 }
 
+
 /*
- * mm_realloc - Implemented simply in terms of mm_malloc and mm_free
+ * mm_realloc - 直接用malloc和free组合实现
  */
 void *mm_realloc(void *ptr, size_t size)
 {
-    void *oldptr = ptr;
-    void *newptr;
-    size_t copySize;
-    
-    newptr = mm_malloc(size);
-    if (newptr == NULL)
-      return NULL;
-    copySize = *(size_t *)((char *)oldptr - SIZE_T_SIZE);
-    if (size < copySize)
-      copySize = size;
-    memcpy(newptr, oldptr, copySize);
-    mm_free(oldptr);
-    return newptr;
-}
+	size_t asize;
+	void *oldptr = ptr;
+	void *newptr;
 
+	/* free */
+	if (0 == size) {
+		free(oldptr);
+		return NULL;
+	}
 
 
+	if (size <= DSIZE) {
+		asize = 2 * DSIZE;
+	} else {
+		asize = DSIZE * ((size + (DSIZE) + (DSIZE - 1)) / DSIZE);
+	}
 
+	if (asize == GET_SIZE(HDRP(oldptr))) {
+		return oldptr;
+	}
+	
+	/* 缩小空间 */
+	if (asize < GET_SIZE(HDRP(oldptr))) {
+		newptr = mm_malloc(size);
+		memmove(newptr, oldptr, size);
+		mm_free(oldptr);
 
+		return newptr;
+	}
+
+
+	newptr = mm_malloc(size);
+	if (NULL == newptr)
+		return NULL;
+	memmove(newptr, oldptr, size);
+	mm_free(oldptr);
+
+	return newptr;
+}