1 /* $OpenBSD: buffer.c,v 1.31 2006/08/03 03:34:41 deraadt Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Functions for manipulating fifo buffers (that can grow if needed).
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 */
14
15 #include <sys/param.h>
16
17 #include <stdio.h>
18 #include <string.h>
19 #include <stdarg.h>
20
21 #include "xmalloc.h"
22 #include "buffer.h"
23 #include "log.h"
24
25 #define BUFFER_MAX_CHUNK 0x100000
26 #define BUFFER_MAX_LEN 0xa00000
27 #define BUFFER_ALLOCSZ 0x008000
28
29 /* Initializes the buffer structure. */
30
31 void
buffer_init(Buffer * buffer)32 buffer_init(Buffer *buffer)
33 {
34 const u_int len = 4096;
35
36 buffer->alloc = 0;
37 buffer->buf = xmalloc(len);
38 buffer->alloc = len;
39 buffer->offset = 0;
40 buffer->end = 0;
41 }
42
43 /* Frees any memory used for the buffer. */
44
45 void
buffer_free(Buffer * buffer)46 buffer_free(Buffer *buffer)
47 {
48 if (buffer->alloc > 0) {
49 memset(buffer->buf, 0, buffer->alloc);
50 buffer->alloc = 0;
51 xfree(buffer->buf);
52 }
53 }
54
55 /*
56 * Clears any data from the buffer, making it empty. This does not actually
57 * zero the memory.
58 */
59
60 void
buffer_clear(Buffer * buffer)61 buffer_clear(Buffer *buffer)
62 {
63 buffer->offset = 0;
64 buffer->end = 0;
65 }
66
67 /* Appends data to the buffer, expanding it if necessary. */
68
69 void
buffer_append(Buffer * buffer,const void * data,u_int len)70 buffer_append(Buffer *buffer, const void *data, u_int len)
71 {
72 void *p;
73 p = buffer_append_space(buffer, len);
74 memcpy(p, data, len);
75 }
76
77 static int
buffer_compact(Buffer * buffer)78 buffer_compact(Buffer *buffer)
79 {
80 /*
81 * If the buffer is quite empty, but all data is at the end, move the
82 * data to the beginning.
83 */
84 if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
85 memmove(buffer->buf, buffer->buf + buffer->offset,
86 buffer->end - buffer->offset);
87 buffer->end -= buffer->offset;
88 buffer->offset = 0;
89 return (1);
90 }
91 return (0);
92 }
93
94 /*
95 * Appends space to the buffer, expanding the buffer if necessary. This does
96 * not actually copy the data into the buffer, but instead returns a pointer
97 * to the allocated region.
98 */
99
100 void *
buffer_append_space(Buffer * buffer,u_int len)101 buffer_append_space(Buffer *buffer, u_int len)
102 {
103 u_int newlen;
104 void *p;
105
106 if (len > BUFFER_MAX_CHUNK)
107 fatal("buffer_append_space: len %u not supported", len);
108
109 /* If the buffer is empty, start using it from the beginning. */
110 if (buffer->offset == buffer->end) {
111 buffer->offset = 0;
112 buffer->end = 0;
113 }
114 restart:
115 /* If there is enough space to store all data, store it now. */
116 if (buffer->end + len < buffer->alloc) {
117 p = buffer->buf + buffer->end;
118 buffer->end += len;
119 return p;
120 }
121
122 /* Compact data back to the start of the buffer if necessary */
123 if (buffer_compact(buffer))
124 goto restart;
125
126 /* Increase the size of the buffer and retry. */
127 newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
128 if (newlen > BUFFER_MAX_LEN)
129 fatal("buffer_append_space: alloc %u not supported",
130 newlen);
131 buffer->buf = xrealloc(buffer->buf, 1, newlen);
132 buffer->alloc = newlen;
133 goto restart;
134 /* NOTREACHED */
135 }
136
137 /*
138 * Check whether an allocation of 'len' will fit in the buffer
139 * This must follow the same math as buffer_append_space
140 */
141 int
buffer_check_alloc(Buffer * buffer,u_int len)142 buffer_check_alloc(Buffer *buffer, u_int len)
143 {
144 if (buffer->offset == buffer->end) {
145 buffer->offset = 0;
146 buffer->end = 0;
147 }
148 restart:
149 if (buffer->end + len < buffer->alloc)
150 return (1);
151 if (buffer_compact(buffer))
152 goto restart;
153 if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
154 return (1);
155 return (0);
156 }
157
158 /* Returns the number of bytes of data in the buffer. */
159
160 u_int
buffer_len(Buffer * buffer)161 buffer_len(Buffer *buffer)
162 {
163 return buffer->end - buffer->offset;
164 }
165
166 /* Gets data from the beginning of the buffer. */
167
168 int
buffer_get_ret(Buffer * buffer,void * buf,u_int len)169 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
170 {
171 if (len > buffer->end - buffer->offset) {
172 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
173 len, buffer->end - buffer->offset);
174 return (-1);
175 }
176 memcpy(buf, buffer->buf + buffer->offset, len);
177 buffer->offset += len;
178 return (0);
179 }
180
181 void
buffer_get(Buffer * buffer,void * buf,u_int len)182 buffer_get(Buffer *buffer, void *buf, u_int len)
183 {
184 if (buffer_get_ret(buffer, buf, len) == -1)
185 fatal("buffer_get: buffer error");
186 }
187
188 /* Consumes the given number of bytes from the beginning of the buffer. */
189
190 int
buffer_consume_ret(Buffer * buffer,u_int bytes)191 buffer_consume_ret(Buffer *buffer, u_int bytes)
192 {
193 if (bytes > buffer->end - buffer->offset) {
194 error("buffer_consume_ret: trying to get more bytes than in buffer");
195 return (-1);
196 }
197 buffer->offset += bytes;
198 return (0);
199 }
200
201 void
buffer_consume(Buffer * buffer,u_int bytes)202 buffer_consume(Buffer *buffer, u_int bytes)
203 {
204 if (buffer_consume_ret(buffer, bytes) == -1)
205 fatal("buffer_consume: buffer error");
206 }
207
208 /* Consumes the given number of bytes from the end of the buffer. */
209
210 int
buffer_consume_end_ret(Buffer * buffer,u_int bytes)211 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
212 {
213 if (bytes > buffer->end - buffer->offset)
214 return (-1);
215 buffer->end -= bytes;
216 return (0);
217 }
218
219 void
buffer_consume_end(Buffer * buffer,u_int bytes)220 buffer_consume_end(Buffer *buffer, u_int bytes)
221 {
222 if (buffer_consume_end_ret(buffer, bytes) == -1)
223 fatal("buffer_consume_end: trying to get more bytes than in buffer");
224 }
225
226 /* Returns a pointer to the first used byte in the buffer. */
227
228 void *
buffer_ptr(Buffer * buffer)229 buffer_ptr(Buffer *buffer)
230 {
231 return buffer->buf + buffer->offset;
232 }
233
234 /* Dumps the contents of the buffer to stderr. */
235
236 void
buffer_dump(Buffer * buffer)237 buffer_dump(Buffer *buffer)
238 {
239 u_int i;
240 u_char *ucp = buffer->buf;
241
242 for (i = buffer->offset; i < buffer->end; i++) {
243 fprintf(stderr, "%02x", ucp[i]);
244 if ((i-buffer->offset)%16==15)
245 fprintf(stderr, "\r\n");
246 else if ((i-buffer->offset)%2==1)
247 fprintf(stderr, " ");
248 }
249 fprintf(stderr, "\r\n");
250 }
251