buffer.c revision 124208 
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#include "includes.h"
15RCSID("$OpenBSD: buffer.c,v 1.19 2003/09/18 07:54:48 markus Exp $");
16
17#include "xmalloc.h"
18#include "buffer.h"
19#include "log.h"
20
21/* Initializes the buffer structure. */
22
23void
24buffer_init(Buffer *buffer)
25{
26	const u_int len = 4096;
27
28	buffer->alloc = 0;
29	buffer->buf = xmalloc(len);
30	buffer->alloc = len;
31	buffer->offset = 0;
32	buffer->end = 0;
33}
34
35/* Frees any memory used for the buffer. */
36
37void
38buffer_free(Buffer *buffer)
39{
40	if (buffer->alloc > 0) {
41		memset(buffer->buf, 0, buffer->alloc);
42		buffer->alloc = 0;
43		xfree(buffer->buf);
44	}
45}
46
47/*
48 * Clears any data from the buffer, making it empty.  This does not actually
49 * zero the memory.
50 */
51
52void
53buffer_clear(Buffer *buffer)
54{
55	buffer->offset = 0;
56	buffer->end = 0;
57}
58
59/* Appends data to the buffer, expanding it if necessary. */
60
61void
62buffer_append(Buffer *buffer, const void *data, u_int len)
63{
64	void *p;
65	p = buffer_append_space(buffer, len);
66	memcpy(p, data, len);
67}
68
69/*
70 * Appends space to the buffer, expanding the buffer if necessary. This does
71 * not actually copy the data into the buffer, but instead returns a pointer
72 * to the allocated region.
73 */
74
75void *
76buffer_append_space(Buffer *buffer, u_int len)
77{
78	u_int newlen;
79	void *p;
80
81	if (len > 0x100000)
82		fatal("buffer_append_space: len %u not supported", len);
83
84	/* If the buffer is empty, start using it from the beginning. */
85	if (buffer->offset == buffer->end) {
86		buffer->offset = 0;
87		buffer->end = 0;
88	}
89restart:
90	/* If there is enough space to store all data, store it now. */
91	if (buffer->end + len < buffer->alloc) {
92		p = buffer->buf + buffer->end;
93		buffer->end += len;
94		return p;
95	}
96	/*
97	 * If the buffer is quite empty, but all data is at the end, move the
98	 * data to the beginning and retry.
99	 */
100	if (buffer->offset > buffer->alloc / 2) {
101		memmove(buffer->buf, buffer->buf + buffer->offset,
102			buffer->end - buffer->offset);
103		buffer->end -= buffer->offset;
104		buffer->offset = 0;
105		goto restart;
106	}
107	/* Increase the size of the buffer and retry. */
108
109	newlen = buffer->alloc + len + 32768;
110	if (newlen > 0xa00000)
111		fatal("buffer_append_space: alloc %u not supported",
112		    newlen);
113	buffer->buf = xrealloc(buffer->buf, newlen);
114	buffer->alloc = newlen;
115	goto restart;
116	/* NOTREACHED */
117}
118
119/* Returns the number of bytes of data in the buffer. */
120
121u_int
122buffer_len(Buffer *buffer)
123{
124	return buffer->end - buffer->offset;
125}
126
127/* Gets data from the beginning of the buffer. */
128
129void
130buffer_get(Buffer *buffer, void *buf, u_int len)
131{
132	if (len > buffer->end - buffer->offset)
133		fatal("buffer_get: trying to get more bytes %d than in buffer %d",
134		    len, buffer->end - buffer->offset);
135	memcpy(buf, buffer->buf + buffer->offset, len);
136	buffer->offset += len;
137}
138
139/* Consumes the given number of bytes from the beginning of the buffer. */
140
141void
142buffer_consume(Buffer *buffer, u_int bytes)
143{
144	if (bytes > buffer->end - buffer->offset)
145		fatal("buffer_consume: trying to get more bytes than in buffer");
146	buffer->offset += bytes;
147}
148
149/* Consumes the given number of bytes from the end of the buffer. */
150
151void
152buffer_consume_end(Buffer *buffer, u_int bytes)
153{
154	if (bytes > buffer->end - buffer->offset)
155		fatal("buffer_consume_end: trying to get more bytes than in buffer");
156	buffer->end -= bytes;
157}
158
159/* Returns a pointer to the first used byte in the buffer. */
160
161void *
162buffer_ptr(Buffer *buffer)
163{
164	return buffer->buf + buffer->offset;
165}
166
167/* Dumps the contents of the buffer to stderr. */
168
169void
170buffer_dump(Buffer *buffer)
171{
172	int i;
173	u_char *ucp = buffer->buf;
174
175	for (i = buffer->offset; i < buffer->end; i++) {
176		fprintf(stderr, "%02x", ucp[i]);
177		if ((i-buffer->offset)%16==15)
178			fprintf(stderr, "\r\n");
179		else if ((i-buffer->offset)%2==1)
180			fprintf(stderr, " ");
181	}
182	fprintf(stderr, "\r\n");
183}
184