1/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 *                    All rights reserved
5 * Functions for manipulating fifo buffers (that can grow if needed).
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose.  Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 */
13/*
14 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
15 * Use is subject to license terms.
16 */
17
18/* $OpenBSD: buffer.c,v 1.31 2006/08/03 03:34:41 deraadt Exp $ */
19
20#include "includes.h"
21
22#include "xmalloc.h"
23#include "buffer.h"
24#include "log.h"
25
26#define	BUFFER_MAX_CHUNK	0x100000
27#define	BUFFER_MAX_LEN		0xa00000
28#define	BUFFER_ALLOCSZ		0x008000
29
30/* Initializes the buffer structure. */
31
32void
33buffer_init(Buffer *buffer)
34{
35	const u_int len = 4096;
36
37	buffer->alloc = 0;
38	buffer->buf = xmalloc(len);
39	buffer->alloc = len;
40	buffer->offset = 0;
41	buffer->end = 0;
42}
43
44/* Frees any memory used for the buffer. */
45
46void
47buffer_free(Buffer *buffer)
48{
49	if (buffer->alloc > 0) {
50		memset(buffer->buf, 0, buffer->alloc);
51		buffer->alloc = 0;
52		xfree(buffer->buf);
53	}
54}
55
56/*
57 * Clears any data from the buffer, making it empty.  This does not actually
58 * zero the memory.
59 */
60
61void
62buffer_clear(Buffer *buffer)
63{
64	buffer->offset = 0;
65	buffer->end = 0;
66}
67
68/* Appends data to the buffer, expanding it if necessary. */
69
70void
71buffer_append(Buffer *buffer, const void *data, u_int len)
72{
73	void *p;
74	p = buffer_append_space(buffer, len);
75	memcpy(p, data, len);
76}
77
78static int
79buffer_compact(Buffer *buffer)
80{
81	/*
82	 * If the buffer is quite empty, but all data is at the end, move the
83	 * data to the beginning.
84	 */
85	if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
86		memmove(buffer->buf, buffer->buf + buffer->offset,
87			buffer->end - buffer->offset);
88		buffer->end -= buffer->offset;
89		buffer->offset = 0;
90		return (1);
91	}
92	return (0);
93}
94
95/*
96 * Appends space to the buffer, expanding the buffer if necessary. This does
97 * not actually copy the data into the buffer, but instead returns a pointer
98 * to the allocated region.
99 */
100
101void *
102buffer_append_space(Buffer *buffer, u_int len)
103{
104	u_int newlen;
105	void *p;
106
107	if (len > BUFFER_MAX_CHUNK)
108		fatal("buffer_append_space: len %u not supported", len);
109
110	/* If the buffer is empty, start using it from the beginning. */
111	if (buffer->offset == buffer->end) {
112		buffer->offset = 0;
113		buffer->end = 0;
114	}
115restart:
116	/* If there is enough space to store all data, store it now. */
117	if (buffer->end + len < buffer->alloc) {
118		p = buffer->buf + buffer->end;
119		buffer->end += len;
120		return p;
121	}
122
123	/* Compact data back to the start of the buffer if necessary */
124	if (buffer_compact(buffer))
125		goto restart;
126
127	/* Increase the size of the buffer and retry. */
128	newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
129	if (newlen > BUFFER_MAX_LEN)
130		fatal("buffer_append_space: alloc %u not supported",
131		    newlen);
132	buffer->buf = xrealloc(buffer->buf, newlen);
133	buffer->alloc = newlen;
134	goto restart;
135	/* NOTREACHED */
136}
137
138/*
139 * Check whether an allocation of 'len' will fit in the buffer
140 * This must follow the same math as buffer_append_space
141 */
142int
143buffer_check_alloc(Buffer *buffer, u_int len)
144{
145	if (buffer->offset == buffer->end) {
146		buffer->offset = 0;
147		buffer->end = 0;
148	}
149 restart:
150	if (buffer->end + len < buffer->alloc)
151		return (1);
152	if (buffer_compact(buffer))
153		goto restart;
154	if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
155		return (1);
156	return (0);
157}
158
159/* Returns the number of bytes of data in the buffer. */
160
161u_int
162buffer_len(Buffer *buffer)
163{
164	return buffer->end - buffer->offset;
165}
166
167/* Gets data from the beginning of the buffer. */
168
169int
170buffer_get_ret(Buffer *buffer, void *buf, u_int len)
171{
172	if (len > buffer->end - buffer->offset) {
173		error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
174		    len, buffer->end - buffer->offset);
175		return (-1);
176	}
177	memcpy(buf, buffer->buf + buffer->offset, len);
178	buffer->offset += len;
179	return (0);
180}
181
182void
183buffer_get(Buffer *buffer, void *buf, u_int len)
184{
185	if (buffer_get_ret(buffer, buf, len) == -1)
186		fatal("buffer_get: buffer error");
187}
188
189/* Consumes the given number of bytes from the beginning of the buffer. */
190
191int
192buffer_consume_ret(Buffer *buffer, u_int bytes)
193{
194	if (bytes > buffer->end - buffer->offset) {
195		error("buffer_consume_ret: trying to get more bytes than in buffer");
196		return (-1);
197	}
198	buffer->offset += bytes;
199	return (0);
200}
201
202void
203buffer_consume(Buffer *buffer, u_int bytes)
204{
205	if (buffer_consume_ret(buffer, bytes) == -1)
206		fatal("buffer_consume: buffer error");
207}
208
209/* Consumes the given number of bytes from the end of the buffer. */
210
211int
212buffer_consume_end_ret(Buffer *buffer, u_int bytes)
213{
214	if (bytes > buffer->end - buffer->offset)
215		return (-1);
216	buffer->end -= bytes;
217	return (0);
218}
219
220void
221buffer_consume_end(Buffer *buffer, u_int bytes)
222{
223	if (buffer_consume_end_ret(buffer, bytes) == -1)
224		fatal("buffer_consume_end: trying to get more bytes than in buffer");
225}
226
227/* Returns a pointer to the first used byte in the buffer. */
228
229void *
230buffer_ptr(Buffer *buffer)
231{
232	return buffer->buf + buffer->offset;
233}
234
235/* Dumps the contents of the buffer to stderr. */
236void
237buffer_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, "\n");
246		else if ((i-buffer->offset)%2==1)
247			fprintf(stderr, " ");
248	}
249
250	if (buffer->offset == buffer->end) {
251		/* explicitly state when the buffer is empty */
252		fprintf(stderr, "<EMPTY BUFFER>\n");
253	} else {
254		/* print the terminal '\n' if it wasn't already printed */
255		if ((i - buffer->offset) % 16 != 0)
256			fprintf(stderr, "\n");
257	}
258	/*
259	 * We want an extra empty line after the packet dump for better
260	 * readability.
261	 */
262	fprintf(stderr, "\n");
263}
264