buffer.c revision 65668 
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 1.8 2000/09/07 20:27:50 deraadt Exp $");
16
17#include "xmalloc.h"
18#include "buffer.h"
19#include "ssh.h"
20
21/* Initializes the buffer structure. */
22
23void
24buffer_init(Buffer *buffer)
25{
26	buffer->alloc = 4096;
27	buffer->buf = xmalloc(buffer->alloc);
28	buffer->offset = 0;
29	buffer->end = 0;
30}
31
32/* Frees any memory used for the buffer. */
33
34void
35buffer_free(Buffer *buffer)
36{
37	memset(buffer->buf, 0, buffer->alloc);
38	xfree(buffer->buf);
39}
40
41/*
42 * Clears any data from the buffer, making it empty.  This does not actually
43 * zero the memory.
44 */
45
46void
47buffer_clear(Buffer *buffer)
48{
49	buffer->offset = 0;
50	buffer->end = 0;
51}
52
53/* Appends data to the buffer, expanding it if necessary. */
54
55void
56buffer_append(Buffer *buffer, const char *data, unsigned int len)
57{
58	char *cp;
59	buffer_append_space(buffer, &cp, len);
60	memcpy(cp, data, len);
61}
62
63/*
64 * Appends space to the buffer, expanding the buffer if necessary. This does
65 * not actually copy the data into the buffer, but instead returns a pointer
66 * to the allocated region.
67 */
68
69void
70buffer_append_space(Buffer *buffer, char **datap, unsigned int len)
71{
72	/* If the buffer is empty, start using it from the beginning. */
73	if (buffer->offset == buffer->end) {
74		buffer->offset = 0;
75		buffer->end = 0;
76	}
77restart:
78	/* If there is enough space to store all data, store it now. */
79	if (buffer->end + len < buffer->alloc) {
80		*datap = buffer->buf + buffer->end;
81		buffer->end += len;
82		return;
83	}
84	/*
85	 * If the buffer is quite empty, but all data is at the end, move the
86	 * data to the beginning and retry.
87	 */
88	if (buffer->offset > buffer->alloc / 2) {
89		memmove(buffer->buf, buffer->buf + buffer->offset,
90			buffer->end - buffer->offset);
91		buffer->end -= buffer->offset;
92		buffer->offset = 0;
93		goto restart;
94	}
95	/* Increase the size of the buffer and retry. */
96	buffer->alloc += len + 32768;
97	buffer->buf = xrealloc(buffer->buf, buffer->alloc);
98	goto restart;
99}
100
101/* Returns the number of bytes of data in the buffer. */
102
103unsigned int
104buffer_len(Buffer *buffer)
105{
106	return buffer->end - buffer->offset;
107}
108
109/* Gets data from the beginning of the buffer. */
110
111void
112buffer_get(Buffer *buffer, char *buf, unsigned int len)
113{
114	if (len > buffer->end - buffer->offset)
115		fatal("buffer_get: trying to get more bytes than in buffer");
116	memcpy(buf, buffer->buf + buffer->offset, len);
117	buffer->offset += len;
118}
119
120/* Consumes the given number of bytes from the beginning of the buffer. */
121
122void
123buffer_consume(Buffer *buffer, unsigned int bytes)
124{
125	if (bytes > buffer->end - buffer->offset)
126		fatal("buffer_consume: trying to get more bytes than in buffer");
127	buffer->offset += bytes;
128}
129
130/* Consumes the given number of bytes from the end of the buffer. */
131
132void
133buffer_consume_end(Buffer *buffer, unsigned int bytes)
134{
135	if (bytes > buffer->end - buffer->offset)
136		fatal("buffer_consume_end: trying to get more bytes than in buffer");
137	buffer->end -= bytes;
138}
139
140/* Returns a pointer to the first used byte in the buffer. */
141
142char *
143buffer_ptr(Buffer *buffer)
144{
145	return buffer->buf + buffer->offset;
146}
147
148/* Dumps the contents of the buffer to stderr. */
149
150void
151buffer_dump(Buffer *buffer)
152{
153	int i;
154	unsigned char *ucp = (unsigned char *) buffer->buf;
155
156	for (i = buffer->offset; i < buffer->end; i++)
157		fprintf(stderr, " %02x", ucp[i]);
158	fprintf(stderr, "\n");
159}
160