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Change header file guard names.
[mLib] / lbuf.h
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97f65b00 1/* -*-c-*-
2 *
c6e0eaf0 3 * $Id: lbuf.h,v 1.3 1999/12/10 23:42:04 mdw Exp $
97f65b00 4 *
5 * Block-to-line buffering
6 *
7 * (c) 1999 Straylight/Edgeware
8 */
9
10/*----- Licensing notice --------------------------------------------------*
11 *
12 * This file is part of the mLib utilities library.
13 *
14 * mLib is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU Library General Public License as
16 * published by the Free Software Foundation; either version 2 of the
17 * License, or (at your option) any later version.
18 *
19 * mLib is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU Library General Public License for more details.
23 *
24 * You should have received a copy of the GNU Library General Public
25 * License along with mLib; if not, write to the Free
26 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
27 * MA 02111-1307, USA.
28 */
29
30/*----- Revision history --------------------------------------------------*
31 *
32 * $Log: lbuf.h,v $
c6e0eaf0 33 * Revision 1.3 1999/12/10 23:42:04 mdw
34 * Change header file guard names.
35 *
1ef7279c 36 * Revision 1.2 1999/05/17 20:36:08 mdw
37 * Make the magical constants for the buffer flags uppercase.
38 *
97f65b00 39 * Revision 1.1 1999/05/14 21:01:14 mdw
40 * Integrated `select' handling bits from the background resolver project.
41 *
42 */
43
c6e0eaf0 44#ifndef MLIB_LBUF_H
45#define MLIB_LBUF_H
97f65b00 46
47#ifdef __cplusplus
48 extern "C" {
49#endif
50
51/*----- Line buffering ----------------------------------------------------*
52 *
53 * The line buffer accepts as input arbitrary-sized lumps of data and
54 * converts them, by passing them to a client-supplied function, into a
55 * sequence of lines. It's particularly useful when performing multiplexed
56 * network I/O. It's not normally acceptable to block while waiting for the
57 * rest of a text line to arrive, for example. The line buffer stores the
58 * start of the line until the rest of it arrives later.
59 *
60 * A line is a piece of text terminated by either a linefeed or a carriage-
61 * return/linefeed pair. (The former is there to cope with Unix; the latter
62 * copes with Internet-format line ends.)
63 *
64 * There's a limit to the size of lines that the buffer can cope with. It's
65 * not hard to remove this limit, but it's probably a bad idea in a lot of
66 * cases, because it'd allow a remote user to gobble arbitrary amounts of
67 * your memory. If a line exceeds the limit, it is truncated: the initial
68 * portion of the line is processed normally, and the remaining portion is
69 * simply discarded.
70 *
71 * Lines extracted from the input data are passed, one at a time, to a
72 * `handler function', along with a caller-supplied pointer argument to
73 * provide the handler with some context. The line read is null-terminated
74 * and does not include the trailing newline characters. It is legal for a
75 * handler function to modify the string it is passed. However, writing
76 * beyond the terminating null byte is not allowed. An end-of-file condition
77 * is signalled to the handler by passing it a null pointer rather than the
78 * address of a string.
79 *
80 * A complexity arises because of the concept of a `disabled' buffer.
81 * Disablement is really a higher-level concept, but it turns out to be
82 * important to implement it here. It's useful for a line handler function
83 * to `disable' itself, so that it doesn't get called any more. For example,
84 * this might happen if it encouters an error, or when it finishes reading
85 * everything it wanted to read. The line buffer needs to be `in the loop'
86 * so that it stops attempting to flush any further lines stored in its
87 * buffer towards a handler function which isn't ready to accept them.
88 * Buffers are initially enabled, although higher- level buffering systems
89 * might well disable them immediately for their own purposes.
90 */
91
92/*----- Header files ------------------------------------------------------*/
93
94#include <stddef.h>
95
96/*----- Data structures ---------------------------------------------------*/
97
98/* --- The buffer structure --- *
99 *
100 * The only thing that's safe to fiddle with in here is the @lbuf_enable@
101 * flag. Only higher-level buffering systems should be playing with even
102 * that.
103 */
104
105typedef struct lbuf {
106 void (*func)(char */*s*/, void */*p*/); /* Handler function */
107 void *p; /* Argument for handler */
108 size_t len; /* Length of data in buffer */
109 unsigned f; /* Various useful state flags */
110 char buf[256]; /* The actual buffer */
111} lbuf;
112
113enum {
1ef7279c 114 LBUF_CR = 1, /* Read a carriage return */
115 LBUF_ENABLE = 2 /* Buffer is currently enabled */
97f65b00 116};
117
118/*----- Functions provided ------------------------------------------------*/
119
120/* --- @lbuf_flush@ --- *
121 *
122 * Arguments: @lbuf *b@ = pointer to buffer block
123 * @char *p@ = pointer to where to start searching
124 * @size_t len@ = length of new material added
125 *
126 * Returns: ---
127 *
128 * Use: Flushes any complete lines in a line buffer. New material
129 * is assumed to have been added starting at @p@. If @p@ is
130 * null, then the scan starts at the beginning of the buffer,
131 * and the size of data already in the buffer is used in place
132 * of @len@.
133 *
134 * It is assumed that the buffer is initially enabled. You
135 * shouldn't be contributing data to a disabled buffer anyway.
136 * However, the buffer handler may at some point disable itself,
137 * and @lbuf_flush@ can cope with this eventuality. Any pending
138 * data is left at the start of the buffer and can be flushed
139 * out by calling @lbuf_flush(b, 0, 0)@ if the buffer is ever
140 * re-enabled.
141 */
142
143extern void lbuf_flush(lbuf */*b*/, char */*p*/, size_t /*len*/);
144
145/* --- @lbuf_close@ --- *
146 *
147 * Arguments: @lbuf *b@ = pointer to buffer block
148 *
149 * Returns: ---
150 *
151 * Use: Empties the buffer of any data currently lurking in it, and
152 * informs the client that this has happened. It's assumed that
153 * the buffer is enabled: you shouldn't be reading close events
154 * on disabled buffers.
155 */
156
157extern void lbuf_close(lbuf */*b*/);
158
159/* --- @lbuf_free@ --- *
160 *
161 * Arguments: @lbuf *b@ = pointer to buffer block
162 * @char **p@ = output pointer to free space
163 *
164 * Returns: Free buffer size.
165 *
166 * Use: Returns the free portion of a line buffer. Data can then be
167 * written to this portion, and split out into lines by calling
168 * @lbuf_flush@.
169 */
170
171extern size_t lbuf_free(lbuf */*b*/, char **/*p*/);
172
173/* --- @lbuf_snarf@ --- *
174 *
175 * Arguments: @lbuf *b@ = pointer to buffer block
176 * @const void *p@ = pointer to input data buffer
177 * @size_t sz@ = size of data in input buffer
178 *
179 * Returns: ---
180 *
181 * Use: Snarfs the data from the input buffer and spits it out as
182 * lines. This interface ignores the complexities of dealing
183 * with disablement: you should be using @lbuf_free@ to
184 * contribute data if you want to cope with that.
185 */
186
187extern void lbuf_snarf(lbuf */*b*/, const void */*p*/, size_t /*sz*/);
188
189/* --- @lbuf_init@ --- *
190 *
191 * Arguments: @lbuf *b@ = pointer to buffer block
192 * @void (*func)(char *s, void *p)@ = handler function
193 * @void *p@ = argument pointer for @func@
194 *
195 * Returns: ---
196 *
197 * Use: Initializes a line buffer block. Any recognized lines are
198 * passed to @func@ for processing.
199 */
200
201extern void lbuf_init(lbuf */*b*/,
202 void (*/*func*/)(char */*s*/, void */*p*/),
203 void */*p*/);
204
205/*----- That's all, folks -------------------------------------------------*/
206
207#ifdef __cplusplus
208 }
209#endif
210
211#endif