summaryrefslogtreecommitdiff
path: root/utils/pool.c
blob: 5f08e7591d77345dd20deb6831ec70daeec0a686 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
/*
 * This file is part of NetSurf, http://netsurf.sourceforge.net/
 * Licensed under the GNU General Public License,
 *                http://www.opensource.org/licenses/gpl-license
 * Copyright 2003 James Bursa <bursa@users.sourceforge.net>
 */

/** \file
 * Memory pool manager (implementation).
 *
 * A memory pool is implemented as a linked list of blocks. The current
 * position and end of the last block are stored for fast access, so that
 * pool_alloc() can allocate space very fast if available.
 */

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "netsurf/utils/pool.h"

struct pool_block {
	char desc[20];
	struct pool_block *prev;
};

struct pool {
	struct pool_block *last_block;
	char *current_pos;
	char *end;
	size_t block_size;
	unsigned int block_count;
};


/**
 * Create a memory pool.
 *
 * \param block_size suggested size of each block
 * \return opaque pool handle, 0 on failure
 */

pool pool_create(size_t block_size)
{
	pool p;
	struct pool_block *b;

	p = malloc(sizeof *p);
	if (!p)
		return 0;
	b = malloc(sizeof *b + block_size + 8);
	if (!b) {
		free(p);
		return 0;
	}

	p->last_block = b;
	p->current_pos = (char *) b + sizeof *b;
	p->end = (char *) b + sizeof *b + block_size;
	p->block_size = block_size;
	p->block_count = 0;

	sprintf(b->desc, "POOL %p %u", p, p->block_count++);
	b->prev = 0;
	strcpy(p->end, "POOLEND");

	return p;
}


/**
 * Frees a memory pool.
 *
 * \param p a memory pool handle as returned by pool_create()
 */

void pool_destroy(pool p)
{
	struct pool_block *b, *prev;
	for (b = (struct pool_block *) p->last_block; b; b = prev) {
		prev = b->prev;
		free(b);
	}
	free(p);
}


/**
 * Allocates space from a memory pool.
 *
 * \param p a memory pool handle as returned by pool_create()
 * \param size number of bytes to allocate
 * \return pointer to the space in the pool, 0 on failure
 */

void *pool_alloc(pool p, size_t size)
{
	void *r;

	if (p->end < p->current_pos + size) {
		/* insufficient space: allocate new block */
		struct pool_block *b;
		size_t block_size = p->block_size;
		if (block_size < size)
			block_size += size;
		b = malloc(sizeof *b + block_size + 8);
		if (!b)
			return 0;

		sprintf(b->desc, "POOL %p %u", p, p->block_count++);
		b->prev = p->last_block;
		strcpy(p->end, "POOLEND");
		
		p->last_block = b;
		p->current_pos = (char *) b + sizeof *b;
		p->end = (char *) b + sizeof *b + block_size;
	}

	r = p->current_pos;
	p->current_pos += size;
	return r;
}


/**
 * Copies a string into a memory pool.
 *
 * \param p a memory pool handle as returned by pool_create()
 * \param s zero-terminated character string
 * \return pointer to the string in the pool, 0 on failure
 */

char *pool_string(pool p, const char *s)
{
	size_t len = strlen(s);
	char *buf = pool_alloc(p, len);
	if (!buf)
		return 0;

	memcpy(buf, s, len + 1);
	return buf;
}


#ifdef TEST

int main(void)
{
	unsigned int i;
	pool p1, p2;

	puts("testing pool_create()");
	p1 = pool_create(10000);
	assert(p1);
	p2 = pool_create(1000);
	assert(p2);

	puts("testing pool_alloc()");
	for (i = 0; i != 100000; i++) {
		size_t s = random() % 200;
		char *b1, *b2;
		unsigned int j;

		b1 = pool_alloc(p1, s);
		//b1 = malloc(s);
		assert(b1);
		b2 = pool_alloc(p2, s);
		//b2 = malloc(s);
		assert(b2);
		for (j = 0; j != s; j++)
			b1[j] = b2[j] = i % 256;
	}

	puts("testing pool_string()");
	for (i = 0; i != 10000; i++) {
		size_t s = random() % 200;
		char str[201];
		unsigned int j;
		char *b;

		for (j = 0; j != s; j++)
			str[j] = 'A' + j % 26;
		str[s] = 0;
		
		b = pool_string(p1, str);
		//b = strdup(str);
		assert(b);
		assert(strcmp(str, b) == 0);
	}

	puts("testing pool_destroy() (press enter)");
	getc(stdin);

	pool_destroy(p1);
	pool_destroy(p2);

	puts("done");
	return 0;
}

#endif