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By Bob Jenkins, September 1996. recycle.h
You may use this code in any way you wish, and it is free. No warranty.
This manages memory for commonly-allocated structures.
It allocates RESTART to REMAX items at a time.
Timings have shown that, if malloc is used for every new structure,
malloc will consume about 90% of the time in a program. This
module cuts down the number of mallocs by an order of magnitude.
This also decreases memory fragmentation, and freeing all structures
only requires freeing the root.
#ifndef STANDARD
#include "standard.h"
#ifndef RECYCLE
#define RECYCLE
#define RESTART 0
#define REMAX 32000
struct recycle
struct recycle *next;
typedef struct recycle recycle;
struct reroot
struct recycle *list; /* list of malloced blocks */
struct recycle *trash; /* list of deleted items */
size_t size; /* size of an item */
size_t logsize; /* log_2 of number of items in a block */
size_t numleft; /* number of bytes left in this block */
typedef struct reroot reroot;
/* make a new recycling root */
reroot *remkroot(size_t size);
/* free a recycling root and all the items it has made */
void refree(struct reroot *r);
/* get a new (cleared) item from the root */
#define renew(r) ((r)->numleft ? \
(((char *)((r)->list+1))+((r)->numleft-=(r)->size)) : renewx(r))
char *renewx(struct reroot *r);
/* delete an item; let the root recycle it */
/* void redel(/o_ struct reroot *r, struct recycle *item _o/); */
#define redel(root,item) { \
((recycle *)item)->next=(root)->trash; \
(root)->trash=(recycle *)(item); \
/* malloc, but complain to stderr and exit program if no joy */
/* use plain free() to free memory allocated by remalloc() */
char *remalloc(size_t len, char *purpose);
#endif /* RECYCLE */