xref: /freebsd/sbin/hastd/ebuf.c (revision 7778ab7e0cc22f0824eb1d1047a7ef8b4785267a)
1 /*-
2  * Copyright (c) 2009-2010 The FreeBSD Foundation
3  * All rights reserved.
4  *
5  * This software was developed by Pawel Jakub Dawidek under sponsorship from
6  * the FreeBSD Foundation.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
32 
33 #include <sys/param.h>
34 
35 #include <errno.h>
36 #include <stdbool.h>
37 #include <stdint.h>
38 #include <strings.h>
39 #include <unistd.h>
40 
41 #include <pjdlog.h>
42 
43 #include "ebuf.h"
44 
45 #ifndef	PJDLOG_ASSERT
46 #include <assert.h>
47 #define	PJDLOG_ASSERT(...)	assert(__VA_ARGS__)
48 #endif
49 
50 #define	EBUF_MAGIC	0xeb0f41c
51 struct ebuf {
52 	/* Magic to assert the caller uses valid structure. */
53 	int		 eb_magic;
54 	/* Address where we did the allocation. */
55 	unsigned char	*eb_start;
56 	/* Allocation end address. */
57 	unsigned char	*eb_end;
58 	/* Start of real data. */
59 	unsigned char	*eb_used;
60 	/* Size of real data. */
61 	size_t		 eb_size;
62 };
63 
64 static int ebuf_head_extend(struct ebuf *eb, size_t size);
65 static int ebuf_tail_extend(struct ebuf *eb, size_t size);
66 
67 struct ebuf *
68 ebuf_alloc(size_t size)
69 {
70 	struct ebuf *eb;
71 	int rerrno;
72 
73 	eb = malloc(sizeof(*eb));
74 	if (eb == NULL)
75 		return (NULL);
76 	size += PAGE_SIZE;
77 	eb->eb_start = malloc(size);
78 	if (eb->eb_start == NULL) {
79 		rerrno = errno;
80 		free(eb);
81 		errno = rerrno;
82 		return (NULL);
83 	}
84 	eb->eb_end = eb->eb_start + size;
85 	/*
86 	 * We set start address for real data not at the first entry, because
87 	 * we want to be able to add data at the front.
88 	 */
89 	eb->eb_used = eb->eb_start + PAGE_SIZE / 4;
90 	eb->eb_size = 0;
91 	eb->eb_magic = EBUF_MAGIC;
92 
93 	return (eb);
94 }
95 
96 void
97 ebuf_free(struct ebuf *eb)
98 {
99 
100 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
101 
102 	eb->eb_magic = 0;
103 
104 	free(eb->eb_start);
105 	free(eb);
106 }
107 
108 int
109 ebuf_add_head(struct ebuf *eb, const void *data, size_t size)
110 {
111 
112 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
113 
114 	if (size > (size_t)(eb->eb_used - eb->eb_start)) {
115 		/*
116 		 * We can't add more entries at the front, so we have to extend
117 		 * our buffer.
118 		 */
119 		if (ebuf_head_extend(eb, size) < 0)
120 			return (-1);
121 	}
122 	PJDLOG_ASSERT(size <= (size_t)(eb->eb_used - eb->eb_start));
123 
124 	eb->eb_size += size;
125 	eb->eb_used -= size;
126 	/*
127 	 * If data is NULL the caller just wants to reserve place.
128 	 */
129 	if (data != NULL)
130 		bcopy(data, eb->eb_used, size);
131 
132 	return (0);
133 }
134 
135 int
136 ebuf_add_tail(struct ebuf *eb, const void *data, size_t size)
137 {
138 
139 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
140 
141 	if (size > (size_t)(eb->eb_end - (eb->eb_used + eb->eb_size))) {
142 		/*
143 		 * We can't add more entries at the back, so we have to extend
144 		 * our buffer.
145 		 */
146 		if (ebuf_tail_extend(eb, size) < 0)
147 			return (-1);
148 	}
149 	PJDLOG_ASSERT(size <=
150 	    (size_t)(eb->eb_end - (eb->eb_used + eb->eb_size)));
151 
152 	/*
153 	 * If data is NULL the caller just wants to reserve space.
154 	 */
155 	if (data != NULL)
156 		bcopy(data, eb->eb_used + eb->eb_size, size);
157 	eb->eb_size += size;
158 
159 	return (0);
160 }
161 
162 void
163 ebuf_del_head(struct ebuf *eb, size_t size)
164 {
165 
166 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
167 	PJDLOG_ASSERT(size <= eb->eb_size);
168 
169 	eb->eb_used += size;
170 	eb->eb_size -= size;
171 }
172 
173 void
174 ebuf_del_tail(struct ebuf *eb, size_t size)
175 {
176 
177 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
178 	PJDLOG_ASSERT(size <= eb->eb_size);
179 
180 	eb->eb_size -= size;
181 }
182 
183 /*
184  * Return pointer to the data and data size.
185  */
186 void *
187 ebuf_data(struct ebuf *eb, size_t *sizep)
188 {
189 
190 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
191 
192 	if (sizep != NULL)
193 		*sizep = eb->eb_size;
194 	return (eb->eb_size > 0 ? eb->eb_used : NULL);
195 }
196 
197 /*
198  * Return data size.
199  */
200 size_t
201 ebuf_size(struct ebuf *eb)
202 {
203 
204 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
205 
206 	return (eb->eb_size);
207 }
208 
209 /*
210  * Function adds size + (PAGE_SIZE / 4) bytes at the front of the buffer..
211  */
212 static int
213 ebuf_head_extend(struct ebuf *eb, size_t size)
214 {
215 	unsigned char *newstart, *newused;
216 	size_t newsize;
217 
218 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
219 
220 	newsize = eb->eb_end - eb->eb_start + (PAGE_SIZE / 4) + size;
221 
222 	newstart = malloc(newsize);
223 	if (newstart == NULL)
224 		return (-1);
225 	newused =
226 	    newstart + (PAGE_SIZE / 4) + size + (eb->eb_used - eb->eb_start);
227 
228 	bcopy(eb->eb_used, newused, eb->eb_size);
229 
230 	eb->eb_start = newstart;
231 	eb->eb_used = newused;
232 	eb->eb_end = newstart + newsize;
233 
234 	return (0);
235 }
236 
237 /*
238  * Function adds size + ((3 * PAGE_SIZE) / 4) bytes at the back.
239  */
240 static int
241 ebuf_tail_extend(struct ebuf *eb, size_t size)
242 {
243 	unsigned char *newstart;
244 	size_t newsize;
245 
246 	PJDLOG_ASSERT(eb != NULL && eb->eb_magic == EBUF_MAGIC);
247 
248 	newsize = eb->eb_end - eb->eb_start + size + ((3 * PAGE_SIZE) / 4);
249 
250 	newstart = realloc(eb->eb_start, newsize);
251 	if (newstart == NULL)
252 		return (-1);
253 
254 	eb->eb_used = newstart + (eb->eb_used - eb->eb_start);
255 	eb->eb_start = newstart;
256 	eb->eb_end = newstart + newsize;
257 
258 	return (0);
259 }
260