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
33void
34buffer_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
47void
48buffer_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
62void
63buffer_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
71void
72buffer_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
79static int
80buffer_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
102void *
103buffer_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	}
116restart:
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 */
143int
144buffer_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
162u_int
163buffer_len(const Buffer *buffer)
164{
165	return buffer->end - buffer->offset;
166}
167
168/* Gets data from the beginning of the buffer. */
169
170int
171buffer_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
183void
184buffer_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
192int
193buffer_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
203void
204buffer_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
212int
213buffer_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
221void
222buffer_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
230void *
231buffer_ptr(const Buffer *buffer)
232{
233	return buffer->buf + buffer->offset;
234}
235
236/* Dumps the contents of the buffer to stderr. */
237
238void
239buffer_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