3 * $Id: lbuf.h,v 1.6 2001/02/03 16:23:33 mdw Exp $
5 * Block-to-line buffering
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of the mLib utilities library.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.6 2001/02/03 16:23:33 mdw
34 * Bug fix: handle a disable during a close-induced flush without dumping
37 * Revision 1.5 2001/01/20 12:06:01 mdw
38 * Define flags with macros, to ensure unsignedness.
40 * Revision 1.4 2000/06/17 10:38:14 mdw
41 * Add support for variable buffer sizes.
43 * Revision 1.3 1999/12/10 23:42:04 mdw
44 * Change header file guard names.
46 * Revision 1.2 1999/05/17 20:36:08 mdw
47 * Make the magical constants for the buffer flags uppercase.
49 * Revision 1.1 1999/05/14 21:01:14 mdw
50 * Integrated `select' handling bits from the background resolver project.
61 /*----- Line buffering ----------------------------------------------------*
63 * The line buffer accepts as input arbitrary-sized lumps of data and
64 * converts them, by passing them to a client-supplied function, into a
65 * sequence of lines. It's particularly useful when performing multiplexed
66 * network I/O. It's not normally acceptable to block while waiting for the
67 * rest of a text line to arrive, for example. The line buffer stores the
68 * start of the line until the rest of it arrives later.
70 * A line is a piece of text terminated by either a linefeed or a carriage-
71 * return/linefeed pair. (The former is there to cope with Unix; the latter
72 * copes with Internet-format line ends.)
74 * There's a limit to the size of lines that the buffer can cope with. It's
75 * not hard to remove this limit, but it's probably a bad idea in a lot of
76 * cases, because it'd allow a remote user to gobble arbitrary amounts of
77 * your memory. If a line exceeds the limit, it is truncated: the initial
78 * portion of the line is processed normally, and the remaining portion is
81 * Lines extracted from the input data are passed, one at a time, to a
82 * `handler function', along with a caller-supplied pointer argument to
83 * provide the handler with some context. The line read is null-terminated
84 * and does not include the trailing newline characters. It is legal for a
85 * handler function to modify the string it is passed. However, writing
86 * beyond the terminating null byte is not allowed. An end-of-file condition
87 * is signalled to the handler by passing it a null pointer rather than the
88 * address of a string.
90 * A complexity arises because of the concept of a `disabled' buffer.
91 * Disablement is really a higher-level concept, but it turns out to be
92 * important to implement it here. It's useful for a line handler function
93 * to `disable' itself, so that it doesn't get called any more. For example,
94 * this might happen if it encouters an error, or when it finishes reading
95 * everything it wanted to read. The line buffer needs to be `in the loop'
96 * so that it stops attempting to flush any further lines stored in its
97 * buffer towards a handler function which isn't ready to accept them.
98 * Buffers are initially enabled, although higher- level buffering systems
99 * might well disable them immediately for their own purposes.
102 /*----- Header files ------------------------------------------------------*/
110 /*----- Data structures ---------------------------------------------------*/
112 /* --- The buffer structure --- *
114 * The only thing that's safe to fiddle with in here is the @lbuf_enable@
115 * flag. Only higher-level buffering systems should be playing with even
119 typedef struct lbuf {
120 void (*func)(char */*s*/, void */*p*/); /* Handler function */
121 void *p; /* Argument for handler */
122 size_t len; /* Length of data in buffer */
123 size_t sz; /* Buffer size */
124 unsigned f; /* Various useful state flags */
125 arena *a; /* Memory allocation arena */
126 char *buf; /* The actual buffer */
129 #define LBUF_CR 1u /* Read a carriage return */
130 #define LBUF_ENABLE 2u /* Buffer is currently enabled */
131 #define LBUF_CLOSE 4u /* Buffer is now closed */
133 /*----- Functions provided ------------------------------------------------*/
135 /* --- @lbuf_flush@ --- *
137 * Arguments: @lbuf *b@ = pointer to buffer block
138 * @char *p@ = pointer to where to start searching
139 * @size_t len@ = length of new material added
143 * Use: Flushes any complete lines in a line buffer. New material
144 * is assumed to have been added starting at @p@. If @p@ is
145 * null, then the scan starts at the beginning of the buffer,
146 * and the size of data already in the buffer is used in place
149 * It is assumed that the buffer is initially enabled. You
150 * shouldn't be contributing data to a disabled buffer anyway.
151 * However, the buffer handler may at some point disable itself,
152 * and @lbuf_flush@ can cope with this eventuality. Any pending
153 * data is left at the start of the buffer and can be flushed
154 * out by calling @lbuf_flush(b, 0, 0)@ if the buffer is ever
158 extern void lbuf_flush(lbuf */*b*/, char */*p*/, size_t /*len*/);
160 /* --- @lbuf_close@ --- *
162 * Arguments: @lbuf *b@ = pointer to buffer block
166 * Use: Empties the buffer of any data currently lurking in it, and
167 * informs the client that this has happened. It's assumed that
168 * the buffer is enabled: you shouldn't be reading close events
169 * on disabled buffers.
172 extern void lbuf_close(lbuf */*b*/);
174 /* --- @lbuf_free@ --- *
176 * Arguments: @lbuf *b@ = pointer to buffer block
177 * @char **p@ = output pointer to free space
179 * Returns: Free buffer size.
181 * Use: Returns the free portion of a line buffer. Data can then be
182 * written to this portion, and split out into lines by calling
186 extern size_t lbuf_free(lbuf */*b*/, char **/*p*/);
188 /* --- @lbuf_snarf@ --- *
190 * Arguments: @lbuf *b@ = pointer to buffer block
191 * @const void *p@ = pointer to input data buffer
192 * @size_t sz@ = size of data in input buffer
196 * Use: Snarfs the data from the input buffer and spits it out as
197 * lines. This interface ignores the complexities of dealing
198 * with disablement: you should be using @lbuf_free@ to
199 * contribute data if you want to cope with that.
202 extern void lbuf_snarf(lbuf */*b*/, const void */*p*/, size_t /*sz*/);
204 /* --- @lbuf_setsize@ --- *
206 * Arguments: @lbuf *b@ = pointer to buffer block
207 * @size_t sz@ = requested maximum line size
211 * Use: Allocates a buffer of the requested size reading lines.
214 extern void lbuf_setsize(lbuf */*b*/, size_t /*sz*/);
216 /* --- @lbuf_init@ --- *
218 * Arguments: @lbuf *b@ = pointer to buffer block
219 * @void (*func)(char *s, void *p)@ = handler function
220 * @void *p@ = argument pointer for @func@
224 * Use: Initializes a line buffer block. Any recognized lines are
225 * passed to @func@ for processing.
228 extern void lbuf_init(lbuf */*b*/,
229 void (*/*func*/)(char */*s*/, void */*p*/),
232 /* --- @lbuf_destroy@ --- *
234 * Arguments: @lbuf *b@ = pointer to buffer block
238 * Use: Deallocates a line buffer and frees any resources it owned.
241 extern void lbuf_destroy(lbuf */*b*/);
243 /*----- That's all, folks -------------------------------------------------*/