1 /* $OpenBSD: buffer.c,v 1.32 2010/02/09 03:56:28 djm 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 "includes.h"
16
17 #include <sys/param.h>
18
19 #include <stdio.h>
20 #include <string.h>
21 #include <stdarg.h>
22
23 #include "xmalloc.h"
24 #include "buffer.h"
25 #include "log.h"
26
27 #define BUFFER_MAX_CHUNK 0x100000
28 #define BUFFER_MAX_LEN 0xa00000
29 #define BUFFER_ALLOCSZ 0x008000
30
31 /* Initializes the buffer structure. */
32
33 void
buffer_init(Buffer * buffer)34 buffer_init(Buffer *buffer)
35 {
36 const u_int len = 4096;
37
38 buffer->alloc = 0;
39 buffer->buf = xmalloc(len);
40 buffer->alloc = len;
41 buffer->offset = 0;
42 buffer->end = 0;
43 }
44
45 /* Frees any memory used for the buffer. */
46
47 void
buffer_free(Buffer * buffer)48 buffer_free(Buffer *buffer)
49 {
50 if (buffer->alloc > 0) {
51 memset(buffer->buf, 0, buffer->alloc);
52 buffer->alloc = 0;
53 xfree(buffer->buf);
54 }
55 }
56
57 /*
58 * Clears any data from the buffer, making it empty. This does not actually
59 * zero the memory.
60 */
61
62 void
buffer_clear(Buffer * buffer)63 buffer_clear(Buffer *buffer)
64 {
65 buffer->offset = 0;
66 buffer->end = 0;
67 }
68
69 /* Appends data to the buffer, expanding it if necessary. */
70
71 void
buffer_append(Buffer * buffer,const void * data,u_int len)72 buffer_append(Buffer *buffer, const void *data, u_int len)
73 {
74 void *p;
75 p = buffer_append_space(buffer, len);
76 memcpy(p, data, len);
77 }
78
79 static int
buffer_compact(Buffer * buffer)80 buffer_compact(Buffer *buffer)
81 {
82 /*
83 * If the buffer is quite empty, but all data is at the end, move the
84 * data to the beginning.
85 */
86 if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
87 memmove(buffer->buf, buffer->buf + buffer->offset,
88 buffer->end - buffer->offset);
89 buffer->end -= buffer->offset;
90 buffer->offset = 0;
91 return (1);
92 }
93 return (0);
94 }
95
96 /*
97 * Appends space to the buffer, expanding the buffer if necessary. This does
98 * not actually copy the data into the buffer, but instead returns a pointer
99 * to the allocated region.
100 */
101
102 void *
buffer_append_space(Buffer * buffer,u_int len)103 buffer_append_space(Buffer *buffer, u_int len)
104 {
105 u_int newlen;
106 void *p;
107
108 if (len > BUFFER_MAX_CHUNK)
109 fatal("buffer_append_space: len %u not supported", len);
110
111 /* If the buffer is empty, start using it from the beginning. */
112 if (buffer->offset == buffer->end) {
113 buffer->offset = 0;
114 buffer->end = 0;
115 }
116 restart:
117 /* If there is enough space to store all data, store it now. */
118 if (buffer->end + len < buffer->alloc) {
119 p = buffer->buf + buffer->end;
120 buffer->end += len;
121 return p;
122 }
123
124 /* Compact data back to the start of the buffer if necessary */
125 if (buffer_compact(buffer))
126 goto restart;
127
128 /* Increase the size of the buffer and retry. */
129 newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
130 if (newlen > BUFFER_MAX_LEN)
131 fatal("buffer_append_space: alloc %u not supported",
132 newlen);
133 buffer->buf = xrealloc(buffer->buf, 1, newlen);
134 buffer->alloc = newlen;
135 goto restart;
136 /* NOTREACHED */
137 }
138
139 /*
140 * Check whether an allocation of 'len' will fit in the buffer
141 * This must follow the same math as buffer_append_space
142 */
143 int
buffer_check_alloc(Buffer * buffer,u_int len)144 buffer_check_alloc(Buffer *buffer, u_int len)
145 {
146 if (buffer->offset == buffer->end) {
147 buffer->offset = 0;
148 buffer->end = 0;
149 }
150 restart:
151 if (buffer->end + len < buffer->alloc)
152 return (1);
153 if (buffer_compact(buffer))
154 goto restart;
155 if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
156 return (1);
157 return (0);
158 }
159
160 /* Returns the number of bytes of data in the buffer. */
161
162 u_int
buffer_len(const Buffer * buffer)163 buffer_len(const Buffer *buffer)
164 {
165 return buffer->end - buffer->offset;
166 }
167
168 /* Gets data from the beginning of the buffer. */
169
170 int
buffer_get_ret(Buffer * buffer,void * buf,u_int len)171 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
172 {
173 if (len > buffer->end - buffer->offset) {
174 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
175 len, buffer->end - buffer->offset);
176 return (-1);
177 }
178 memcpy(buf, buffer->buf + buffer->offset, len);
179 buffer->offset += len;
180 return (0);
181 }
182
183 void
buffer_get(Buffer * buffer,void * buf,u_int len)184 buffer_get(Buffer *buffer, void *buf, u_int len)
185 {
186 if (buffer_get_ret(buffer, buf, len) == -1)
187 fatal("buffer_get: buffer error");
188 }
189
190 /* Consumes the given number of bytes from the beginning of the buffer. */
191
192 int
buffer_consume_ret(Buffer * buffer,u_int bytes)193 buffer_consume_ret(Buffer *buffer, u_int bytes)
194 {
195 if (bytes > buffer->end - buffer->offset) {
196 error("buffer_consume_ret: trying to get more bytes than in buffer");
197 return (-1);
198 }
199 buffer->offset += bytes;
200 return (0);
201 }
202
203 void
buffer_consume(Buffer * buffer,u_int bytes)204 buffer_consume(Buffer *buffer, u_int bytes)
205 {
206 if (buffer_consume_ret(buffer, bytes) == -1)
207 fatal("buffer_consume: buffer error");
208 }
209
210 /* Consumes the given number of bytes from the end of the buffer. */
211
212 int
buffer_consume_end_ret(Buffer * buffer,u_int bytes)213 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
214 {
215 if (bytes > buffer->end - buffer->offset)
216 return (-1);
217 buffer->end -= bytes;
218 return (0);
219 }
220
221 void
buffer_consume_end(Buffer * buffer,u_int bytes)222 buffer_consume_end(Buffer *buffer, u_int bytes)
223 {
224 if (buffer_consume_end_ret(buffer, bytes) == -1)
225 fatal("buffer_consume_end: trying to get more bytes than in buffer");
226 }
227
228 /* Returns a pointer to the first used byte in the buffer. */
229
230 void *
buffer_ptr(const Buffer * buffer)231 buffer_ptr(const Buffer *buffer)
232 {
233 return buffer->buf + buffer->offset;
234 }
235
236 /* Dumps the contents of the buffer to stderr. */
237
238 void
buffer_dump(const Buffer * buffer)239 buffer_dump(const Buffer *buffer)
240 {
241 u_int i;
242 u_char *ucp = buffer->buf;
243
244 for (i = buffer->offset; i < buffer->end; i++) {
245 fprintf(stderr, "%02x", ucp[i]);
246 if ((i-buffer->offset)%16==15)
247 fprintf(stderr, "\r\n");
248 else if ((i-buffer->offset)%2==1)
249 fprintf(stderr, " ");
250 }
251 fprintf(stderr, "\r\n");
252 }
253