1 /* $OpenBSD: buffer.c,v 1.35 2014/02/02 03:44:31 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 __RCSID("$FreeBSD$");
17
18 #include <sys/param.h>
19
20 #include <stdio.h>
21 #include <string.h>
22 #include <stdarg.h>
23 #include <stdlib.h>
24
25 #include "xmalloc.h"
26 #include "buffer.h"
27 #include "log.h"
28
29 #define BUFFER_MAX_CHUNK 0x100000
30 #define BUFFER_MAX_LEN 0x4000000 /* 64MB */
31 #define BUFFER_ALLOCSZ 0x008000
32
33 /* Initializes the buffer structure. */
34
35 void
buffer_init(Buffer * buffer)36 buffer_init(Buffer *buffer)
37 {
38 const u_int len = 4096;
39
40 buffer->alloc = 0;
41 buffer->buf = xmalloc(len);
42 buffer->alloc = len;
43 buffer->offset = 0;
44 buffer->end = 0;
45 }
46
47 /* Frees any memory used for the buffer. */
48
49 void
buffer_free(Buffer * buffer)50 buffer_free(Buffer *buffer)
51 {
52 if (buffer->alloc > 0) {
53 explicit_bzero(buffer->buf, buffer->alloc);
54 buffer->alloc = 0;
55 free(buffer->buf);
56 }
57 }
58
59 /*
60 * Clears any data from the buffer, making it empty. This does not actually
61 * zero the memory.
62 */
63
64 void
buffer_clear(Buffer * buffer)65 buffer_clear(Buffer *buffer)
66 {
67 buffer->offset = 0;
68 buffer->end = 0;
69 }
70
71 /* Appends data to the buffer, expanding it if necessary. */
72
73 void
buffer_append(Buffer * buffer,const void * data,u_int len)74 buffer_append(Buffer *buffer, const void *data, u_int len)
75 {
76 void *p;
77 p = buffer_append_space(buffer, len);
78 memcpy(p, data, len);
79 }
80
81 static int
buffer_compact(Buffer * buffer)82 buffer_compact(Buffer *buffer)
83 {
84 /*
85 * If the buffer is quite empty, but all data is at the end, move the
86 * data to the beginning.
87 */
88 if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
89 memmove(buffer->buf, buffer->buf + buffer->offset,
90 buffer->end - buffer->offset);
91 buffer->end -= buffer->offset;
92 buffer->offset = 0;
93 return (1);
94 }
95 return (0);
96 }
97
98 /*
99 * Appends space to the buffer, expanding the buffer if necessary. This does
100 * not actually copy the data into the buffer, but instead returns a pointer
101 * to the allocated region.
102 */
103
104 void *
buffer_append_space(Buffer * buffer,u_int len)105 buffer_append_space(Buffer *buffer, u_int len)
106 {
107 u_int newlen;
108 void *p;
109
110 if (len > BUFFER_MAX_CHUNK)
111 fatal("buffer_append_space: len %u not supported", len);
112
113 /* If the buffer is empty, start using it from the beginning. */
114 if (buffer->offset == buffer->end) {
115 buffer->offset = 0;
116 buffer->end = 0;
117 }
118 restart:
119 /* If there is enough space to store all data, store it now. */
120 if (buffer->end + len < buffer->alloc) {
121 p = buffer->buf + buffer->end;
122 buffer->end += len;
123 return p;
124 }
125
126 /* Compact data back to the start of the buffer if necessary */
127 if (buffer_compact(buffer))
128 goto restart;
129
130 /* Increase the size of the buffer and retry. */
131 newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
132 if (newlen > BUFFER_MAX_LEN)
133 fatal("buffer_append_space: alloc %u not supported",
134 newlen);
135 buffer->buf = xrealloc(buffer->buf, 1, newlen);
136 buffer->alloc = newlen;
137 goto restart;
138 /* NOTREACHED */
139 }
140
141 /*
142 * Check whether an allocation of 'len' will fit in the buffer
143 * This must follow the same math as buffer_append_space
144 */
145 int
buffer_check_alloc(Buffer * buffer,u_int len)146 buffer_check_alloc(Buffer *buffer, u_int len)
147 {
148 if (buffer->offset == buffer->end) {
149 buffer->offset = 0;
150 buffer->end = 0;
151 }
152 restart:
153 if (buffer->end + len < buffer->alloc)
154 return (1);
155 if (buffer_compact(buffer))
156 goto restart;
157 if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
158 return (1);
159 return (0);
160 }
161
162 /* Returns the number of bytes of data in the buffer. */
163
164 u_int
buffer_len(const Buffer * buffer)165 buffer_len(const Buffer *buffer)
166 {
167 return buffer->end - buffer->offset;
168 }
169
170 /* Returns the maximum number of bytes of data that may be in the buffer. */
171 u_int
buffer_get_max_len(void)172 buffer_get_max_len(void)
173 {
174 return (BUFFER_MAX_LEN);
175 }
176
177 /* Gets data from the beginning of the buffer. */
178
179 int
buffer_get_ret(Buffer * buffer,void * buf,u_int len)180 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
181 {
182 if (len > buffer->end - buffer->offset) {
183 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
184 len, buffer->end - buffer->offset);
185 return (-1);
186 }
187 memcpy(buf, buffer->buf + buffer->offset, len);
188 buffer->offset += len;
189 return (0);
190 }
191
192 void
buffer_get(Buffer * buffer,void * buf,u_int len)193 buffer_get(Buffer *buffer, void *buf, u_int len)
194 {
195 if (buffer_get_ret(buffer, buf, len) == -1)
196 fatal("buffer_get: buffer error");
197 }
198
199 /* Consumes the given number of bytes from the beginning of the buffer. */
200
201 int
buffer_consume_ret(Buffer * buffer,u_int bytes)202 buffer_consume_ret(Buffer *buffer, u_int bytes)
203 {
204 if (bytes > buffer->end - buffer->offset) {
205 error("buffer_consume_ret: trying to get more bytes than in buffer");
206 return (-1);
207 }
208 buffer->offset += bytes;
209 return (0);
210 }
211
212 void
buffer_consume(Buffer * buffer,u_int bytes)213 buffer_consume(Buffer *buffer, u_int bytes)
214 {
215 if (buffer_consume_ret(buffer, bytes) == -1)
216 fatal("buffer_consume: buffer error");
217 }
218
219 /* Consumes the given number of bytes from the end of the buffer. */
220
221 int
buffer_consume_end_ret(Buffer * buffer,u_int bytes)222 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
223 {
224 if (bytes > buffer->end - buffer->offset)
225 return (-1);
226 buffer->end -= bytes;
227 return (0);
228 }
229
230 void
buffer_consume_end(Buffer * buffer,u_int bytes)231 buffer_consume_end(Buffer *buffer, u_int bytes)
232 {
233 if (buffer_consume_end_ret(buffer, bytes) == -1)
234 fatal("buffer_consume_end: trying to get more bytes than in buffer");
235 }
236
237 /* Returns a pointer to the first used byte in the buffer. */
238
239 void *
buffer_ptr(const Buffer * buffer)240 buffer_ptr(const Buffer *buffer)
241 {
242 return buffer->buf + buffer->offset;
243 }
244
245 /* Dumps the contents of the buffer to stderr. */
246
247 void
buffer_dump(const Buffer * buffer)248 buffer_dump(const Buffer *buffer)
249 {
250 u_int i;
251 u_char *ucp = buffer->buf;
252
253 for (i = buffer->offset; i < buffer->end; i++) {
254 fprintf(stderr, "%02x", ucp[i]);
255 if ((i-buffer->offset)%16==15)
256 fprintf(stderr, "\r\n");
257 else if ((i-buffer->offset)%2==1)
258 fprintf(stderr, " ");
259 }
260 fprintf(stderr, "\r\n");
261 }
262