ihost/libukcprog/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 1.1 2002/03/08 14:37:29 tdb 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:	1.2
Committed:	Sat Mar 29 18:05:09 2003 UTC (21 years, 8 months ago) by tdb
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.1:	+1 -1 lines
State:	*FILE REMOVED*
Log Message:	ihost now makes use of an external copy of libukcprog. This is available as a seperate download. All files updated accordingly to make this version 1.5.4.
#	User	Rev	Content
1	tdb	1.1	/* 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	tdb	1.2	char ukcprog_alloc_sccsid[] = "$Id: alloc.c,v 1.1 2002/03/08 14:37:29 tdb Exp $ UKC";
11	tdb	1.1
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			}