libukcprog/src/alloc.c

/* alloc_pool.c - routines for allocating memory from tagged pools */

/*  Copyright 1991 Mark Russell, University of Kent at Canterbury.
 *
 *  You can do what you like with this source code as long as
 *  you don't try to make money out of it and you include an
 *  unaltered copy of this message (including the copyright).
 */

char ukcprog_alloc_sccsid[] = "$Id: alloc.c,v 1.10 1993/10/25 11:44:23 mtr Exp $ UKC";

#include <stdio.h>      /* for NULL - grrr */
#include <stdlib.h>
#include <string.h>
#ifndef __STDC__
#include <memory.h>
#endif

#include "ukcprog.h"

/*  This is a conservative guess at the per-request malloc overhead in
 *  bytes.  Nothing breaks if this is wrong.
 */
#define MALLOC_OVERHEAD 24

/*  When we run out a space in an alloc pool we add another block.
 *  We add small blocks (SBLOCKSIZE bytes each) for the first NSMALLBLOCKS
 *  requests, then switch switch to large (BLOCKSIZE) ones.
 *
 *  The intention is that we don't gobble large amounts of memory for
 *  a small alloc pool, but that we are reasonablty efficient for
 *  one that's continually growing.
 *
 *  Currently, we go slowly (256 bytes a go) for the first 8K, then
 *  fast (4K a go).
 */
#define NSMALLBLOCKS    32

/*  Size of the first block for an alloc pool (requested when the alloc
 *  pool is created) and for the subsequent NSMALLBLOCKS blocks.
 */
#define SBLOCKSIZE      (256 - sizeof(alloc_pool_t) - MALLOC_OVERHEAD)

/*  Size of the requested for an alloc pool after the first NSMALLBLOCKS
 *  block additions.
 *
 *  Try to make the malloc request size a bit less than a power of two
 *  to compensate for brain-damaged mallocs that add overhead then round
 *  up to a power of two.
 */
#define BLOCKSIZE       (4096 - sizeof(ablock_t) - MALLOC_OVERHEAD)

/*  Maximum alignment requirements for all types *including* float and double.
 */
#define ALIGN           sizeof(double)

typedef struct ablockst {
        union {
                double align;
                struct ablock {
                        char *abu_buf;
                        char *abu_pos;
                        char *abu_end;
                        size_t abu_size;
                        struct ablockst *abu_next;
                } a;
        } u;
} ablock_t;

#define ab_buf  u.a.abu_buf
#define ab_pos  u.a.abu_pos
#define ab_end  u.a.abu_end
#define ab_size u.a.abu_size
#define ab_next u.a.abu_next

struct alloc_pool_s {
        ablock_t *ap_ablock;
        ablock_t *ap_freelist;
        int ap_nblocks;
        bool ap_debug;
        ablock_t ap_first_ablock;
};

struct alloc_mark_s {
        alloc_pool_t *am_apool;
        ablock_t *am_ablock;
        char *am_pos;
        char *am_end;
};

static ablock_t *push_ablock PROTO((alloc_pool_t *ap, ablock_t *ab, unsigned size));
static ablock_t *find_ab PROTO((alloc_pool_t *ap, unsigned size));
static void reset_ablocks PROTO((alloc_pool_t *ap, ablock_t *limab));

/*  The default debug flag for a new alloc_pool.  When the debug flag
 *  is TRUE, we initialise memory to garbage, and set it to (different)
 *  garbage when free_alloc_pool is called.
 */
static bool Default_debug_flag = TRUE;

bool
alloc_set_default_debug_flag(val)
bool val;
{
        bool oldval;

        oldval = Default_debug_flag;
        Default_debug_flag = val;
        return oldval;
}

bool
alloc_set_debug_flag(ap, val)
alloc_pool_t *ap;
bool val;
{
        bool oldval;

        oldval = ap->ap_debug;
        ap->ap_debug = val;
        return oldval;
}

/*  Make a new alloc_pool().  We make an initial allocation of a small
 *  amount of memory, to make small alloc pool creation cheap (one malloc).
 */
alloc_pool_t *
alloc_create_pool()
{
        alloc_pool_t *ap;

        ap = (alloc_pool_t *)e_malloc(sizeof(alloc_pool_t) + SBLOCKSIZE);
        ap->ap_ablock = NULL;
        ap->ap_freelist = NULL;
        ap->ap_nblocks = 0;
        ap->ap_debug = Default_debug_flag;
        push_ablock(ap, &ap->ap_first_ablock, SBLOCKSIZE);

        return ap;
}

static void
reset_ablocks(ap, limab)
alloc_pool_t *ap;
ablock_t *limab;
{
        ablock_t *ab, *next;
        bool debug;

        debug = ap->ap_debug;
        for (ab = ap->ap_ablock; ab != limab; ab = next) {
                next = ab->ab_next;
                if (debug)
                        memset(ab->ab_buf, 0x42, ab->ab_size);
                ab->ab_pos = ab->ab_buf;
                ab->ab_end = ab->ab_pos + ab->ab_size;
                ab->ab_next = ap->ap_freelist;
                ap->ap_freelist = ab;
        }
}

void
alloc_reset_pool(ap)
alloc_pool_t *ap;
{
        ablock_t *ab;

        ab = &ap->ap_first_ablock;

        reset_ablocks(ap, ab);

        if (ap->ap_debug)
                memset(ab->ab_buf, 0x42, ab->ab_size);
        ab->ab_pos = ab->ab_buf;
        ab->ab_end = ab->ab_pos + ab->ab_size;

        ap->ap_ablock = ab;
}

void
alloc_free_pool(ap)
alloc_pool_t *ap;
{
        ablock_t *ab, *next;
        bool debug;

        debug = ap->ap_debug;

        /*  The odd form of the loop here is because we want to overwrite
         *  all blocks with garbage (if debug is set), but we don't want
         *  to free the last block in the chain, which is allocated as part
         *  of the header block.
         */
        ab = ap->ap_ablock;
        for (;;) {
                next = ab->ab_next;
                if (debug)
                        memset(ab->ab_buf, 0x42, ab->ab_size);
                if (next == NULL)
                        break;
                free((char *)ab);
                ab = next;
        }

        free((char *)ap);
}

static ablock_t *
push_ablock(ap, ab, size)
alloc_pool_t *ap;
ablock_t *ab;
unsigned size;
{
        ab->ab_buf = ab->ab_pos = (char *)&ab[1];
        ab->ab_end = ab->ab_buf + size;
        ab->ab_size = size;
        ab->ab_next = ap->ap_ablock;
        ap->ap_ablock = ab;

        if (ap->ap_debug)
                memset(ab->ab_buf, 0x53, (size_t)size);
        
        return ab;
}

/*  Find an ablock with at least nbytes free.  If the block at the
 *  head of the free list is big enough, use that.  Otherwise malloc
 *  a new ablock and push it on the chain.
 */
static ablock_t *
find_ab(ap, size)
alloc_pool_t *ap;
unsigned size;
{
        ablock_t *ab;

        if (ap->ap_freelist != NULL && ap->ap_freelist->ab_size >= size) {
                ab = ap->ap_freelist;
                ap->ap_freelist = ap->ap_freelist->ab_next;
                ab->ab_next = ap->ap_ablock;
                ap->ap_ablock = ab;
        }
        else {
                voidptr buf;
                unsigned blocksize;

                blocksize = (ap->ap_nblocks < NSMALLBLOCKS) ? SBLOCKSIZE : BLOCKSIZE;
                if (size < blocksize)
                        size = blocksize;
                if ((buf = malloc((size_t)(sizeof(ablock_t) + size))) == NULL)
                        return NULL;
                ab = push_ablock(ap, (ablock_t *)buf, size);
                ++ap->ap_nblocks;
        }
        return ab;
}

/*  Allocate nbytes from alloc pool ap.  This interface never
 *  returns NULL - if memory runs out we panic.
 */
voidptr
alloc(ap, nbytes)
alloc_pool_t *ap;
size_t nbytes;
{
        ablock_t *ab;
        int over;
        char *ptr;

        over = nbytes % ALIGN;
        if (over != 0)
                nbytes += ALIGN - over;

        ab = ap->ap_ablock;

        if (nbytes > ab->ab_end - ab->ab_pos) {
                ab = find_ab(ap, (unsigned)nbytes);
                if (ab == NULL)
                        panic("out of memory in alloc");
        }

        ptr = ab->ab_pos;
        ab->ab_pos += nbytes;

        return ptr;
}

/*  Like alloc, but return NULL if we can't satisfy the request.
 */
voidptr
alloc_ck(ap, nbytes)
alloc_pool_t *ap;
size_t nbytes;
{
        ablock_t *ab;
        int over;
        char *ptr;

        over = nbytes % ALIGN;
        if (over != 0)
                nbytes += ALIGN - over;

        ab = ap->ap_ablock;

        if (nbytes > ab->ab_end - ab->ab_pos) {
                ab = find_ab(ap, nbytes);
                if (ab == NULL)
                        return NULL;
        }

        ptr = ab->ab_pos;
        ab->ab_pos += nbytes;

        return ptr;
}

alloc_mark_t *
alloc_mark(ap)
alloc_pool_t *ap;
{
        alloc_mark_t *am;
        ablock_t *save_ab;
        char *save_pos, *save_end;

        save_ab = ap->ap_ablock;
        save_pos = save_ab->ab_pos;
        save_end = save_ab->ab_end;

        am = (alloc_mark_t *)alloc(ap, sizeof(alloc_mark_t));
        am->am_apool = ap;
        am->am_ablock = save_ab;
        am->am_pos = save_pos;
        am->am_end = save_end;

        return am;
}

void
alloc_release(ap, am)
alloc_pool_t *ap;
alloc_mark_t *am;
{
        ablock_t *ab;
        alloc_mark_t mark;

        if (am->am_apool != ap)
                panic("id botch in ar");

        /*  If debug is set, we are about to step on the store that
         *  the mark was allocated from, so save it.
         */
        mark = *am;
        ab = mark.am_ablock;

        reset_ablocks(ap, ab);

        if (ap->ap_debug) {
                memset(mark.am_pos, 0x42, (size_t)(ab->ab_pos - mark.am_pos));
                memset(ab->ab_end, 0x42, (size_t)(mark.am_end - ab->ab_end));
        }
        else {
                /*  Make sure the application can't use this mark again.
                 */
                am->am_apool = NULL;
        }

        ab->ab_pos = mark.am_pos;
        ab->ab_end = mark.am_end;
        ap->ap_ablock = ab;
}

/*  Like alloc(), except that the result is assumed not to need alignment.
 *  We work from the other end of the pool than alloc so hopefully all the
 *  string requests will be packed together with no alignment holes.
 *
 *  We never return NULL - if we can't fulfill the request we panic.
 */
char *
allocstr(ap, nbytes)
alloc_pool_t *ap;
size_t nbytes;
{
        ablock_t *ab;

        ab = ap->ap_ablock;

        if (nbytes > ab->ab_end - ab->ab_pos) {
                ab = find_ab(ap, (unsigned)nbytes);
                if (ab == NULL)
                        panic("out of memory in allocstr");
        }

        return ab->ab_end -= nbytes;
}

char *
allocstr_ck(ap, nbytes)
alloc_pool_t *ap;
size_t nbytes;
{
        ablock_t *ab;

        ab = ap->ap_ablock;

        /*  We cast nbytes to unsigned to catch negative values: they
         *  turn into huge positive values which get caught by e_malloc().
         */
        if ((unsigned)nbytes > ab->ab_end - ab->ab_pos) {
                ab = find_ab(ap, (unsigned)nbytes);
                if (ab == NULL)
                        return NULL;
        }

        return ab->ab_end -= nbytes;
}

char *
alloc_strdup(ap, s)
alloc_pool_t *ap;
const char *s;
{
        size_t nbytes;

        nbytes = strlen(s) + 1;
        return memcpy(allocstr(ap, nbytes), s, nbytes);
}
Revision:	1.1
Committed:	Sat Mar 29 16:30:33 2003 UTC (22 years, 7 months ago) by tdb
Content type:	text/plain
Branch:	MAIN
CVS Tags:	LIBUKCPROG_1_0_2, LIBUKCPROG_1_0_1, LIBUKCPROG_1_0, HEAD
Log Message:	libukcprog is now a seperate package. I doubt this will be much use to anyone other than us, but I see no reason why we can't package it up and distribute it. Obviously we can't attach the GPL to this, as we don't own it.
#	Content
1	/* alloc_pool.c - routines for allocating memory from tagged pools */
2
3	/* Copyright 1991 Mark Russell, University of Kent at Canterbury.
4	*
5	* You can do what you like with this source code as long as
6	* you don't try to make money out of it and you include an
7	* unaltered copy of this message (including the copyright).
8	*/
9
10	char ukcprog_alloc_sccsid[] = "$Id: alloc.c,v 1.10 1993/10/25 11:44:23 mtr Exp $ UKC";
11
12	#include <stdio.h> /* for NULL - grrr */
13	#include <stdlib.h>
14	#include <string.h>
15	#ifndef __STDC__
16	#include <memory.h>
17	#endif
18
19	#include "ukcprog.h"
20
21	/* This is a conservative guess at the per-request malloc overhead in
22	* bytes. Nothing breaks if this is wrong.
23	*/
24	#define MALLOC_OVERHEAD 24
25
26	/* When we run out a space in an alloc pool we add another block.
27	* We add small blocks (SBLOCKSIZE bytes each) for the first NSMALLBLOCKS
28	* requests, then switch switch to large (BLOCKSIZE) ones.
29	*
30	* The intention is that we don't gobble large amounts of memory for
31	* a small alloc pool, but that we are reasonablty efficient for
32	* one that's continually growing.
33	*
34	* Currently, we go slowly (256 bytes a go) for the first 8K, then
35	* fast (4K a go).
36	*/
37	#define NSMALLBLOCKS 32
38
39	/* Size of the first block for an alloc pool (requested when the alloc
40	* pool is created) and for the subsequent NSMALLBLOCKS blocks.
41	*/
42	#define SBLOCKSIZE (256 - sizeof(alloc_pool_t) - MALLOC_OVERHEAD)
43
44	/* Size of the requested for an alloc pool after the first NSMALLBLOCKS
45	* block additions.
46	*
47	* Try to make the malloc request size a bit less than a power of two
48	* to compensate for brain-damaged mallocs that add overhead then round
49	* up to a power of two.
50	*/
51	#define BLOCKSIZE (4096 - sizeof(ablock_t) - MALLOC_OVERHEAD)
52
53	/* Maximum alignment requirements for all types including float and double.
54	*/
55	#define ALIGN sizeof(double)
56
57	typedef struct ablockst {
58	union {
59	double align;
60	struct ablock {
61	char *abu_buf;
62	char *abu_pos;
63	char *abu_end;
64	size_t abu_size;
65	struct ablockst *abu_next;
66	} a;
67	} u;
68	} ablock_t;
69
70	#define ab_buf u.a.abu_buf
71	#define ab_pos u.a.abu_pos
72	#define ab_end u.a.abu_end
73	#define ab_size u.a.abu_size
74	#define ab_next u.a.abu_next
75
76	struct alloc_pool_s {
77	ablock_t *ap_ablock;
78	ablock_t *ap_freelist;
79	int ap_nblocks;
80	bool ap_debug;
81	ablock_t ap_first_ablock;
82	};
83
84	struct alloc_mark_s {
85	alloc_pool_t *am_apool;
86	ablock_t *am_ablock;
87	char *am_pos;
88	char *am_end;
89	};
90
91	static ablock_t push_ablock PROTO((alloc_pool_t ap, ablock_t *ab, unsigned size));
92	static ablock_t find_ab PROTO((alloc_pool_t ap, unsigned size));
93	static void reset_ablocks PROTO((alloc_pool_t ap, ablock_t limab));
94
95	/* The default debug flag for a new alloc_pool. When the debug flag
96	* is TRUE, we initialise memory to garbage, and set it to (different)
97	* garbage when free_alloc_pool is called.
98	*/
99	static bool Default_debug_flag = TRUE;
100
101	bool
102	alloc_set_default_debug_flag(val)
103	bool val;
104	{
105	bool oldval;
106
107	oldval = Default_debug_flag;
108	Default_debug_flag = val;
109	return oldval;
110	}
111
112	bool
113	alloc_set_debug_flag(ap, val)
114	alloc_pool_t *ap;
115	bool val;
116	{
117	bool oldval;
118
119	oldval = ap->ap_debug;
120	ap->ap_debug = val;
121	return oldval;
122	}
123
124	/* Make a new alloc_pool(). We make an initial allocation of a small
125	* amount of memory, to make small alloc pool creation cheap (one malloc).
126	*/
127	alloc_pool_t *
128	alloc_create_pool()
129	{
130	alloc_pool_t *ap;
131
132	ap = (alloc_pool_t *)e_malloc(sizeof(alloc_pool_t) + SBLOCKSIZE);
133	ap->ap_ablock = NULL;
134	ap->ap_freelist = NULL;
135	ap->ap_nblocks = 0;
136	ap->ap_debug = Default_debug_flag;
137	push_ablock(ap, &ap->ap_first_ablock, SBLOCKSIZE);
138
139	return ap;
140	}
141
142	static void
143	reset_ablocks(ap, limab)
144	alloc_pool_t *ap;
145	ablock_t *limab;
146	{
147	ablock_t ab, next;
148	bool debug;
149
150	debug = ap->ap_debug;
151	for (ab = ap->ap_ablock; ab != limab; ab = next) {
152	next = ab->ab_next;
153	if (debug)
154	memset(ab->ab_buf, 0x42, ab->ab_size);
155	ab->ab_pos = ab->ab_buf;
156	ab->ab_end = ab->ab_pos + ab->ab_size;
157	ab->ab_next = ap->ap_freelist;
158	ap->ap_freelist = ab;
159	}
160	}
161
162	void
163	alloc_reset_pool(ap)
164	alloc_pool_t *ap;
165	{
166	ablock_t *ab;
167
168	ab = &ap->ap_first_ablock;
169
170	reset_ablocks(ap, ab);
171
172	if (ap->ap_debug)
173	memset(ab->ab_buf, 0x42, ab->ab_size);
174	ab->ab_pos = ab->ab_buf;
175	ab->ab_end = ab->ab_pos + ab->ab_size;
176
177	ap->ap_ablock = ab;
178	}
179
180	void
181	alloc_free_pool(ap)
182	alloc_pool_t *ap;
183	{
184	ablock_t ab, next;
185	bool debug;
186
187	debug = ap->ap_debug;
188
189	/* The odd form of the loop here is because we want to overwrite
190	* all blocks with garbage (if debug is set), but we don't want
191	* to free the last block in the chain, which is allocated as part
192	* of the header block.
193	*/
194	ab = ap->ap_ablock;
195	for (;;) {
196	next = ab->ab_next;
197	if (debug)
198	memset(ab->ab_buf, 0x42, ab->ab_size);
199	if (next == NULL)
200	break;
201	free((char *)ab);
202	ab = next;
203	}
204
205	free((char *)ap);
206	}
207
208	static ablock_t *
209	push_ablock(ap, ab, size)
210	alloc_pool_t *ap;
211	ablock_t *ab;
212	unsigned size;
213	{
214	ab->ab_buf = ab->ab_pos = (char *)&ab[1];
215	ab->ab_end = ab->ab_buf + size;
216	ab->ab_size = size;
217	ab->ab_next = ap->ap_ablock;
218	ap->ap_ablock = ab;
219
220	if (ap->ap_debug)
221	memset(ab->ab_buf, 0x53, (size_t)size);
222
223	return ab;
224	}
225
226	/* Find an ablock with at least nbytes free. If the block at the
227	* head of the free list is big enough, use that. Otherwise malloc
228	* a new ablock and push it on the chain.
229	*/
230	static ablock_t *
231	find_ab(ap, size)
232	alloc_pool_t *ap;
233	unsigned size;
234	{
235	ablock_t *ab;
236
237	if (ap->ap_freelist != NULL && ap->ap_freelist->ab_size >= size) {
238	ab = ap->ap_freelist;
239	ap->ap_freelist = ap->ap_freelist->ab_next;
240	ab->ab_next = ap->ap_ablock;
241	ap->ap_ablock = ab;
242	}
243	else {
244	voidptr buf;
245	unsigned blocksize;
246
247	blocksize = (ap->ap_nblocks < NSMALLBLOCKS) ? SBLOCKSIZE : BLOCKSIZE;
248	if (size < blocksize)
249	size = blocksize;
250	if ((buf = malloc((size_t)(sizeof(ablock_t) + size))) == NULL)
251	return NULL;
252	ab = push_ablock(ap, (ablock_t *)buf, size);
253	++ap->ap_nblocks;
254	}
255	return ab;
256	}
257
258	/* Allocate nbytes from alloc pool ap. This interface never
259	* returns NULL - if memory runs out we panic.
260	*/
261	voidptr
262	alloc(ap, nbytes)
263	alloc_pool_t *ap;
264	size_t nbytes;
265	{
266	ablock_t *ab;
267	int over;
268	char *ptr;
269
270	over = nbytes % ALIGN;
271	if (over != 0)
272	nbytes += ALIGN - over;
273
274	ab = ap->ap_ablock;
275
276	if (nbytes > ab->ab_end - ab->ab_pos) {
277	ab = find_ab(ap, (unsigned)nbytes);
278	if (ab == NULL)
279	panic("out of memory in alloc");
280	}
281
282	ptr = ab->ab_pos;
283	ab->ab_pos += nbytes;
284
285	return ptr;
286	}
287
288	/* Like alloc, but return NULL if we can't satisfy the request.
289	*/
290	voidptr
291	alloc_ck(ap, nbytes)
292	alloc_pool_t *ap;
293	size_t nbytes;
294	{
295	ablock_t *ab;
296	int over;
297	char *ptr;
298
299	over = nbytes % ALIGN;
300	if (over != 0)
301	nbytes += ALIGN - over;
302
303	ab = ap->ap_ablock;
304
305	if (nbytes > ab->ab_end - ab->ab_pos) {
306	ab = find_ab(ap, nbytes);
307	if (ab == NULL)
308	return NULL;
309	}
310
311	ptr = ab->ab_pos;
312	ab->ab_pos += nbytes;
313
314	return ptr;
315	}
316
317	alloc_mark_t *
318	alloc_mark(ap)
319	alloc_pool_t *ap;
320	{
321	alloc_mark_t *am;
322	ablock_t *save_ab;
323	char save_pos, save_end;
324
325	save_ab = ap->ap_ablock;
326	save_pos = save_ab->ab_pos;
327	save_end = save_ab->ab_end;
328
329	am = (alloc_mark_t *)alloc(ap, sizeof(alloc_mark_t));
330	am->am_apool = ap;
331	am->am_ablock = save_ab;
332	am->am_pos = save_pos;
333	am->am_end = save_end;
334
335	return am;
336	}
337
338	void
339	alloc_release(ap, am)
340	alloc_pool_t *ap;
341	alloc_mark_t *am;
342	{
343	ablock_t *ab;
344	alloc_mark_t mark;
345
346	if (am->am_apool != ap)
347	panic("id botch in ar");
348
349	/* If debug is set, we are about to step on the store that
350	* the mark was allocated from, so save it.
351	*/
352	mark = *am;
353	ab = mark.am_ablock;
354
355	reset_ablocks(ap, ab);
356
357	if (ap->ap_debug) {
358	memset(mark.am_pos, 0x42, (size_t)(ab->ab_pos - mark.am_pos));
359	memset(ab->ab_end, 0x42, (size_t)(mark.am_end - ab->ab_end));
360	}
361	else {
362	/* Make sure the application can't use this mark again.
363	*/
364	am->am_apool = NULL;
365	}
366
367	ab->ab_pos = mark.am_pos;
368	ab->ab_end = mark.am_end;
369	ap->ap_ablock = ab;
370	}
371
372	/* Like alloc(), except that the result is assumed not to need alignment.
373	* We work from the other end of the pool than alloc so hopefully all the
374	* string requests will be packed together with no alignment holes.
375	*
376	* We never return NULL - if we can't fulfill the request we panic.
377	*/
378	char *
379	allocstr(ap, nbytes)
380	alloc_pool_t *ap;
381	size_t nbytes;
382	{
383	ablock_t *ab;
384
385	ab = ap->ap_ablock;
386
387	if (nbytes > ab->ab_end - ab->ab_pos) {
388	ab = find_ab(ap, (unsigned)nbytes);
389	if (ab == NULL)
390	panic("out of memory in allocstr");
391	}
392
393	return ab->ab_end -= nbytes;
394	}
395
396	char *
397	allocstr_ck(ap, nbytes)
398	alloc_pool_t *ap;
399	size_t nbytes;
400	{
401	ablock_t *ab;
402
403	ab = ap->ap_ablock;
404
405	/* We cast nbytes to unsigned to catch negative values: they
406	* turn into huge positive values which get caught by e_malloc().
407	*/
408	if ((unsigned)nbytes > ab->ab_end - ab->ab_pos) {
409	ab = find_ab(ap, (unsigned)nbytes);
410	if (ab == NULL)
411	return NULL;
412	}
413
414	return ab->ab_end -= nbytes;
415	}
416
417	char *
418	alloc_strdup(ap, s)
419	alloc_pool_t *ap;
420	const char *s;
421	{
422	size_t nbytes;
423
424	nbytes = strlen(s) + 1;
425	return memcpy(allocstr(ap, nbytes), s, nbytes);
426	}