1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2009-2010 The FreeBSD Foundation
5 * All rights reserved.
6 *
7 * This software was developed by Pawel Jakub Dawidek under sponsorship from
8 * the FreeBSD Foundation.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <sys/param.h>
33
34#include <errno.h>
35#include <stdbool.h>
36#include <stdint.h>
37#include <strings.h>
38#include <unistd.h>
39
40#include <pjdlog.h>
41
42#include "ebuf.h"
43
44#ifndef	PJDLOG_ASSERT
45#include <assert.h>
46#define	PJDLOG_ASSERT(...)	assert(__VA_ARGS__)
47#endif
48
49#define	EBUF_MAGIC	0xeb0f41c
50struct ebuf {
51	/* Magic to assert the caller uses valid structure. */
52	int		 eb_magic;
53	/* Address where we did the allocation. */
54	unsigned char	*eb_start;
55	/* Allocation end address. */
56	unsigned char	*eb_end;
57	/* Start of real data. */
58	unsigned char	*eb_used;
59	/* Size of real data. */
60	size_t		 eb_size;
61};
62
63static int ebuf_head_extend(struct ebuf *eb, size_t size);
64static int ebuf_tail_extend(struct ebuf *eb, size_t size);
65
66struct ebuf *
67ebuf_alloc(size_t size)
68{
69	struct ebuf *eb;
70	size_t page_size;
71	int rerrno;
72
73	eb = malloc(sizeof(*eb));
74	if (eb == NULL)
75		return (NULL);
76	page_size = getpagesize();
77	size += page_size;
78	eb->eb_start = malloc(size);
79	if (eb->eb_start == NULL) {
80		rerrno = errno;
81		free(eb);
82		errno = rerrno;
83		return (NULL);
84	}
85	eb->eb_end = eb->eb_start + size;
86	/*
87	 * We set start address for real data not at the first entry, because
88	 * we want to be able to add data at the front.
89	 */
90	eb->eb_used = eb->eb_start + page_size / 4;
91	eb->eb_size = 0;
92	eb->eb_magic = EBUF_MAGIC;
93
94	return (eb);
95}
96
97void
98ebuf_free(struct ebuf *eb)
99{
100
101	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
102
103	eb->eb_magic = 0;
104
105	free(eb->eb_start);
106	free(eb);
107}
108
109int
110ebuf_add_head(struct ebuf *eb, const void *data, size_t size)
111{
112
113	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
114
115	if (size > (size_t)(eb->eb_used - eb->eb_start)) {
116		/*
117		 * We can't add more entries at the front, so we have to extend
118		 * our buffer.
119		 */
120		if (ebuf_head_extend(eb, size) == -1)
121			return (-1);
122	}
123	PJDLOG_ASSERT(size <= (size_t)(eb->eb_used - eb->eb_start));
124
125	eb->eb_size += size;
126	eb->eb_used -= size;
127	/*
128	 * If data is NULL the caller just wants to reserve place.
129	 */
130	if (data != NULL)
131		bcopy(data, eb->eb_used, size);
132
133	return (0);
134}
135
136int
137ebuf_add_tail(struct ebuf *eb, const void *data, size_t size)
138{
139
140	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
141
142	if (size > (size_t)(eb->eb_end - (eb->eb_used + eb->eb_size))) {
143		/*
144		 * We can't add more entries at the back, so we have to extend
145		 * our buffer.
146		 */
147		if (ebuf_tail_extend(eb, size) == -1)
148			return (-1);
149	}
150	PJDLOG_ASSERT(size <=
151	    (size_t)(eb->eb_end - (eb->eb_used + eb->eb_size)));
152
153	/*
154	 * If data is NULL the caller just wants to reserve space.
155	 */
156	if (data != NULL)
157		bcopy(data, eb->eb_used + eb->eb_size, size);
158	eb->eb_size += size;
159
160	return (0);
161}
162
163void
164ebuf_del_head(struct ebuf *eb, size_t size)
165{
166
167	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
168	PJDLOG_ASSERT(size <= eb->eb_size);
169
170	eb->eb_used += size;
171	eb->eb_size -= size;
172}
173
174void
175ebuf_del_tail(struct ebuf *eb, size_t size)
176{
177
178	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
179	PJDLOG_ASSERT(size <= eb->eb_size);
180
181	eb->eb_size -= size;
182}
183
184/*
185 * Return pointer to the data and data size.
186 */
187void *
188ebuf_data(struct ebuf *eb, size_t *sizep)
189{
190
191	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
192
193	if (sizep != NULL)
194		*sizep = eb->eb_size;
195	return (eb->eb_size > 0 ? eb->eb_used : NULL);
196}
197
198/*
199 * Return data size.
200 */
201size_t
202ebuf_size(struct ebuf *eb)
203{
204
205	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
206
207	return (eb->eb_size);
208}
209
210/*
211 * Function adds size + (PAGE_SIZE / 4) bytes at the front of the buffer..
212 */
213static int
214ebuf_head_extend(struct ebuf *eb, size_t size)
215{
216	unsigned char *newstart, *newused;
217	size_t newsize, page_size;
218
219	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
220
221	page_size = getpagesize();
222	newsize = eb->eb_end - eb->eb_start + (page_size / 4) + size;
223
224	newstart = malloc(newsize);
225	if (newstart == NULL)
226		return (-1);
227	newused =
228	    newstart + (page_size / 4) + size + (eb->eb_used - eb->eb_start);
229
230	bcopy(eb->eb_used, newused, eb->eb_size);
231
232	eb->eb_start = newstart;
233	eb->eb_used = newused;
234	eb->eb_end = newstart + newsize;
235
236	return (0);
237}
238
239/*
240 * Function adds size + ((3 * PAGE_SIZE) / 4) bytes at the back.
241 */
242static int
243ebuf_tail_extend(struct ebuf *eb, size_t size)
244{
245	unsigned char *newstart;
246	size_t newsize, page_size;
247
248	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
249
250	page_size = getpagesize();
251	newsize = eb->eb_end - eb->eb_start + size + ((3 * page_size) / 4);
252
253	newstart = realloc(eb->eb_start, newsize);
254	if (newstart == NULL)
255		return (-1);
256
257	eb->eb_used = newstart + (eb->eb_used - eb->eb_start);
258	eb->eb_start = newstart;
259	eb->eb_end = newstart + newsize;
260
261	return (0);
262}
263