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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- saved from url=(0038)http://gene.wins.uva.nl/~dpersons/mm.c --><HTML><HEAD><META http-equiv=Content-Type content="text/html; charset=gb2312"><META content="MSHTML 6.00.2800.1264" name=GENERATOR></HEAD><BODY><PRE>/* * Simple allocator based on implicit free lists with boundary * tag coalescing. Each block has header and footer of the form: * * 31 3 2 1 0 * ----------------------------------- * | s s s s ... s s s 0 0 a/f * ----------------------------------- * * where s are the meaningful size bits and a/f is set * iff the block is allocated. The list has the following form: * * begin end * heap heap * ----------------------------------------------------------------- * | pad | hdr(8:a) | ftr(8:a) | zero or more usr blks | hdr(8:a) | * ----------------------------------------------------------------- * | prologue | | epilogue | * | block | | block | * * The allocated prologue and epilogue blocks are overhead that * eliminate edge conditions during coalescing. */#include <stdio.h>#include "mm.h"#include "memlib.h"team_t team = { /* Team name */ "DavidPersons0100722StanKlabbers0100714", /* First member's full name */ "David Persons", /* First member's email address */ "David.Persons@student.uva.nl", /* Second member's full name (leave blank if none) */ "Stan Klabbers", /* Second member's email address (leave blank if none) */ "stan.klabbers@student.uva.nl"};/* $begin mallocmacros *//* Basic constants and macros */#define WSIZE 4 /* word size (bytes) */ #define DSIZE 8 /* doubleword size (bytes) */#define CHUNKSIZE (1<<12) /* initial heap size (bytes) */#define OVERHEAD 8 /* overhead of header and footer (bytes) */#define MAX(x, y) ((x) > (y)? (x) : (y)) /* Pack a size and allocated bit into a word */#define PACK(size, alloc) ((size) | (alloc))/* Read and write a word at address p */#define GET(p) (*(size_t *)(p))#define PUT(p, val) (*(size_t *)(p) = (val)) /* 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)))/* $end mallocmacros *//* The only global variable is a pointer to the first block */static char *heap_listp; /* function prototypes for internal helper routines */static void *extend_heap(size_t words);static void place(void *bp, size_t asize);static void *find_fit(size_t asize);static void *coalesce(void *bp);static void printblock(void *bp); static void checkblock(void *bp);/* * mm_init - Initialize the memory manager *//* $begin mminit */int mm_init(void) { /* create the initial empty heap */ if ((heap_listp = mem_sbrk(4*WSIZE)) == NULL) return -1; PUT(heap_listp, 0); /* alignment padding */ PUT(heap_listp+WSIZE, PACK(OVERHEAD, 1)); /* prologue header */ PUT(heap_listp+DSIZE, PACK(OVERHEAD, 1)); /* prologue footer */ PUT(heap_listp+WSIZE+DSIZE, PACK(0, 1)); /* epilogue header */ heap_listp += DSIZE; /* Extend the empty heap with a free block of CHUNKSIZE bytes */ if (extend_heap(CHUNKSIZE/WSIZE) == NULL) return -1; return 0;}/* $end mminit *//* * mm_malloc - Allocate a block with at least size bytes of payload *//* $begin mmmalloc */void *mm_malloc(size_t size) { size_t asize; /* adjusted block size */ size_t extendsize; /* amount to extend heap if no fit */ char *bp; /* Ignore spurious requests */ if (size <= 0) return NULL; /* Adjust block size to include overhead and alignment reqs. */ if (size <= DSIZE) asize = DSIZE + OVERHEAD; else asize = DSIZE * ((size + (OVERHEAD) + (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;} /* $end mmmalloc *//* * mm_free - Free a block *//* $begin mmfree */void mm_free(void *bp){ size_t size = GET_SIZE(HDRP(bp)); PUT(HDRP(bp), PACK(size, 0)); PUT(FTRP(bp), PACK(size, 0)); coalesce(bp);}/* $end mmfree *//* Not implemented. For consistency with 15-213 malloc driver */void *mm_realloc(void *ptr, size_t size){ void * newPointer; int i; if(ptr == NULL) return mm_malloc(size); else if(size == 0) mm_free(ptr); else { newPointer = mm_malloc(size); if (newPointer == NULL) return NULL; for(i=0;i<DSIZE*size;i+=4) PUT(newPointer+i,(GET(ptr+i))); mm_free(ptr); return newPointer; } return NULL;}/* * mm_checkheap - Check the heap for consistency */void mm_checkheap(int verbose) { char *bp = heap_listp; if (verbose) printf("Heap (%p):\n", heap_listp); if ((GET_SIZE(HDRP(heap_listp)) != DSIZE) || !GET_ALLOC(HDRP(heap_listp))) printf("Bad prologue header\n"); checkblock(heap_listp); for (bp = heap_listp; GET_SIZE(HDRP(bp)) > 0; bp = NEXT_BLKP(bp)) { if (verbose) printblock(bp); checkblock(bp); } if (verbose) printblock(bp); if ((GET_SIZE(HDRP(bp)) != 0) || !(GET_ALLOC(HDRP(bp)))) printf("Bad epilogue header\n");}/* The remaining routines are internal helper routines *//* * extend_heap - Extend heap with free block and return its block pointer *//* $begin mmextendheap */static 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 ((int)(bp = mem_sbrk(size)) < 0) 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);}/* $end mmextendheap *//* * place - Place block of asize bytes at start of free block bp * and split if remainder would be at least minimum block size *//* $begin mmplace *//* $begin mmplace-proto */static void place(void *bp, size_t asize)/* $end mmplace-proto */{ size_t csize = GET_SIZE(HDRP(bp)); if ((csize - asize) >= (DSIZE + OVERHEAD)) { 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)); } else { PUT(HDRP(bp), PACK(csize, 1)); PUT(FTRP(bp), PACK(csize, 1)); }}/* $end mmplace *//* * find_fit - Find a fit for a block with asize bytes *//* $begin mmfirstfit *//* $begin mmfirstfit-proto */static void *find_fit(size_t asize)/* $end mmfirstfit-proto */{ void *bp; /* first fit search */ for (bp = heap_listp; GET_SIZE(HDRP(bp)) > 0; bp = NEXT_BLKP(bp)) { if (!GET_ALLOC(HDRP(bp)) && (asize <= GET_SIZE(HDRP(bp)))) { return bp; } } return NULL; /* no fit */}/* $end mmfirstfit *//* * coalesce - boundary tag coalescing. Return ptr to coalesced block *//* $begin mmfree */static 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) { /* Case 1 */ return bp; } else if (prev_alloc && !next_alloc) { /* Case 2 */ size += GET_SIZE(HDRP(NEXT_BLKP(bp))); PUT(HDRP(bp), PACK(size, 0)); PUT(FTRP(bp), PACK(size,0)); return(bp); } else if (!prev_alloc && next_alloc) { /* Case 3 */ size += GET_SIZE(HDRP(PREV_BLKP(bp))); PUT(FTRP(bp), PACK(size, 0)); PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0)); return(PREV_BLKP(bp)); } else { /* Case 4 */ size += GET_SIZE(HDRP(PREV_BLKP(bp))) + GET_SIZE(FTRP(NEXT_BLKP(bp))); PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0)); PUT(FTRP(NEXT_BLKP(bp)), PACK(size, 0)); return(PREV_BLKP(bp)); }}/* $end mmfree */static void printblock(void *bp) { size_t hsize, halloc, fsize, falloc; hsize = GET_SIZE(HDRP(bp)); halloc = GET_ALLOC(HDRP(bp)); fsize = GET_SIZE(FTRP(bp)); falloc = GET_ALLOC(FTRP(bp)); if (hsize == 0) { printf("%p: EOL\n", bp); return; } printf("%p: header: [%d:%c] footer: [%d:%c]\n", bp, hsize, (halloc ? 'a' : 'f'), fsize, (falloc ? 'a' : 'f')); }static void checkblock(void *bp) { if ((size_t)bp % 8) printf("Error: %p is not doubleword aligned\n", bp); if (GET(HDRP(bp)) != GET(FTRP(bp))) printf("Error: header does not match footer\n");}</PRE></BODY></HTML>⌨️ 快捷键说明
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