自学教程：C++ GET_SIZE函数代码示例

/********************************************************** * place * Mark the block as allocated. * Also create a new free block of the size difference if possible. **********************************************************/void place(void* bp, size_t asize){    remove_free_block(bp);    /* Get the current block size */    size_t bsize = GET_SIZE(HDRP(bp));    // Create a block of the size difference and insert it into the free list.    if (bsize - asize > 8*DSIZE) {        PUT(HDRP(bp), PACK(asize, 1));        PUT(FTRP(bp), PACK(asize, 1));        PUT(HDRP(NEXT_BLKP(bp)), PACK(bsize-asize, 0));        PUT(FTRP(NEXT_BLKP(bp)), PACK(bsize-asize, 0));        add_free_block(NEXT_BLKP(bp));    } else {        PUT(HDRP(bp), PACK(bsize, 1));        PUT(FTRP(bp), PACK(bsize, 1));    }}

static void *match( size_t asize ){    if(asize == 8 && list_for_8 != NULL_POINTER) return list_for_8;    if(asize <= 16 && list_for_16 != NULL_POINTER) return list_for_16;	/* the most fit block */	void *fit = NULL_POINTER;	/* temporary location of the search */	void *temp = root;	/* use tree to implement a comparative best fit search */	while(temp != NULL_POINTER){		if( asize <= GET_SIZE(temp) ){			fit = temp;			temp = (void *)GET_LEFT(temp);		} else			temp = (void *)GET_RIGHT(temp);	}	return fit;}

/********************************************************** * mm_free * Free the block and coalesce with neighbouring blocks **********************************************************/void mm_free(void *bp){    logg(3, "/n============ mm_free() starts ==============");    if (LOGGING_LEVEL>0)        mm_check();	logg(1, "mm_free() with bp: %p; header: %zx(h); footer: %zx(h)", bp, GET(HDRP(bp)), GET(FTRP(bp)));    if(bp == NULL){      return;    }    // Mark the current block as free and do coalescing.    size_t size = GET_SIZE(HDRP(bp));    PUT(HDRP(bp), PACK(size,0));    PUT(FTRP(bp), PACK(size,0));    coalesce(bp);    logg(3, "============ mm_free() ends ==============/n");}

static void place(void *bp,size_t asize){	size_t csize = GET_SIZE(bp);	delete_node( bp );	if((csize-asize) >= ALIGN_REQ){	    size_t sign = 1 | GET_PRE_ALLOC_INFO(bp) | GET_PRE_8_INFO(bp);		PUT_HDRP( bp,PACK(asize,sign) );		void * temp = GET_NEXT(bp);		PUT_HDRP( temp, PACK(csize-asize,2) );		PUT_FTRP( temp, PACK(csize-asize,2) );				insert_node( coalesce(temp) );	} else{	    size_t sign = 1 | GET_PRE_ALLOC_INFO(bp) | GET_PRE_8_INFO(bp);		PUT_HDRP(bp,PACK(csize, sign) );	}}

/********************************************************** * free_list_marked_as_free * check if there are two consecutive free blocks in the * heap * we start at second block and check if previous one is * free, if current block is free *********************************************************/int find_two_free_blocks(void){    void *bp;    if (heap_listp == NULL) return 1; //no blocks    if (NEXT_BLKP(heap_listp) == NULL) return 1; //only one block    for (bp = NEXT_BLKP(heap_listp); GET_SIZE(HDRP(bp)) > 0; bp = NEXT_BLKP(bp))    {        if (!GET_ALLOC(HDRP(bp))) {            if (!GET_ALLOC(PREV_BLKP(bp))) {                return 0;            }        }    }    return 1;}

/*  Place block of asize bytes at start of free block bp and split if remainder would be at least minimum block size  the requested size of free block */static void place(void *bp, size_t asize){    size_t csize = GET_SIZE(bp);    if ((csize - asize) >= BLKSIZE) {        SET_HDRP(bp, PACK(asize, 1));        SET_FTRP(bp, PACK(asize, 1));        mm_delete(bp);        bp = NEXT_BLKP(bp);        SET_HDRP(bp, PACK(csize-asize, 0));        SET_FTRP(bp, PACK(csize-asize, 0));        coalesce(bp);    }    else {        SET_HDRP(bp, PACK(csize, 1));        SET_FTRP(bp, PACK(csize, 1));        mm_delete(bp);    }}

/* $begin mmfree */void mm_free(void *bp){/* $end mmfree */    if(bp == 0) 	return;/* $begin mmfree */    size_t size = GET_SIZE(HDRP(bp));/* $end mmfree */    if (heap_listp == 0){	mm_init();    }/* $begin mmfree */    PUT(HDRP(bp), PACK(size, 0));    PUT(FTRP(bp), PACK(size, 0));    coalesce(bp);}

/* $begin mmfree */void mm_free(void *bp){    /*     * mm_free(NULL) is now a no-op.  Previously _malloc(5); _free(0);     * resulted in a page fault.     *     *  -- Mike Kasick <[email
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