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 1.10 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:	Fri Mar 8 14:37:29 2002 UTC (22 years, 8 months ago) by tdb
Content type:	text/plain
Branch:	MAIN
CVS Tags:	IHOST_1_5_3, IHOST_1_5_2, IHOST_1_5_1, IHOST_1_5, IHOST_1_0_RC1
Log Message:	I'm not usually up for putting third party sources in here, but in this case I'll make an exception. This is ukcprog, a set of useful C functions which the ihost plugins Pete's writing uses. It's got a pretty free license too. I've munged the Makefile around, as all it needs to do now is make the library, not install anything. The idea is to statically compile the other programs against this library, making the final binary independent of this code etc.
#	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			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			}