3 * $Id: lbuf.h,v 1.4 2000/06/17 10:38:14 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 1.4 2000/06/17 10:38:14 mdw
34 * Add support for variable buffer sizes.
36 * Revision 1.3 1999/12/10 23:42:04 mdw
37 * Change header file guard names.
39 * Revision 1.2 1999/05/17 20:36:08 mdw
40 * Make the magical constants for the buffer flags uppercase.
42 * Revision 1.1 1999/05/14 21:01:14 mdw
43 * Integrated `select' handling bits from the background resolver project.
54 /*----- Line buffering ----------------------------------------------------*
56 * The line buffer accepts as input arbitrary-sized lumps of data and
57 * converts them, by passing them to a client-supplied function, into a
58 * sequence of lines. It's particularly useful when performing multiplexed
59 * network I/O. It's not normally acceptable to block while waiting for the
60 * rest of a text line to arrive, for example. The line buffer stores the
61 * start of the line until the rest of it arrives later.
63 * A line is a piece of text terminated by either a linefeed or a carriage-
64 * return/linefeed pair. (The former is there to cope with Unix; the latter
65 * copes with Internet-format line ends.)
67 * There's a limit to the size of lines that the buffer can cope with. It's
68 * not hard to remove this limit, but it's probably a bad idea in a lot of
69 * cases, because it'd allow a remote user to gobble arbitrary amounts of
70 * your memory. If a line exceeds the limit, it is truncated: the initial
71 * portion of the line is processed normally, and the remaining portion is
74 * Lines extracted from the input data are passed, one at a time, to a
75 * `handler function', along with a caller-supplied pointer argument to
76 * provide the handler with some context. The line read is null-terminated
77 * and does not include the trailing newline characters. It is legal for a
78 * handler function to modify the string it is passed. However, writing
79 * beyond the terminating null byte is not allowed. An end-of-file condition
80 * is signalled to the handler by passing it a null pointer rather than the
81 * address of a string.
83 * A complexity arises because of the concept of a `disabled' buffer.
84 * Disablement is really a higher-level concept, but it turns out to be
85 * important to implement it here. It's useful for a line handler function
86 * to `disable' itself, so that it doesn't get called any more. For example,
87 * this might happen if it encouters an error, or when it finishes reading
88 * everything it wanted to read. The line buffer needs to be `in the loop'
89 * so that it stops attempting to flush any further lines stored in its
90 * buffer towards a handler function which isn't ready to accept them.
91 * Buffers are initially enabled, although higher- level buffering systems
92 * might well disable them immediately for their own purposes.
95 /*----- Header files ------------------------------------------------------*/
103 /*----- Data structures ---------------------------------------------------*/
105 /* --- The buffer structure --- *
107 * The only thing that's safe to fiddle with in here is the @lbuf_enable@
108 * flag. Only higher-level buffering systems should be playing with even
112 typedef struct lbuf
{
113 void (*func
)(char */
*s*/
, void */
*p*/
); /* Handler function */
114 void *p
; /* Argument for handler */
115 size_t len
; /* Length of data in buffer */
116 size_t sz
; /* Buffer size */
117 unsigned f
; /* Various useful state flags */
118 arena
*a
; /* Memory allocation arena */
119 char *buf
; /* The actual buffer */
123 LBUF_CR
= 1, /* Read a carriage return */
124 LBUF_ENABLE
= 2 /* Buffer is currently enabled */
127 /*----- Functions provided ------------------------------------------------*/
129 /* --- @lbuf_flush@ --- *
131 * Arguments: @lbuf *b@ = pointer to buffer block
132 * @char *p@ = pointer to where to start searching
133 * @size_t len@ = length of new material added
137 * Use: Flushes any complete lines in a line buffer. New material
138 * is assumed to have been added starting at @p@. If @p@ is
139 * null, then the scan starts at the beginning of the buffer,
140 * and the size of data already in the buffer is used in place
143 * It is assumed that the buffer is initially enabled. You
144 * shouldn't be contributing data to a disabled buffer anyway.
145 * However, the buffer handler may at some point disable itself,
146 * and @lbuf_flush@ can cope with this eventuality. Any pending
147 * data is left at the start of the buffer and can be flushed
148 * out by calling @lbuf_flush(b, 0, 0)@ if the buffer is ever
152 extern void lbuf_flush(lbuf */
*b*/
, char */
*p*/
, size_t /*len*/);
154 /* --- @lbuf_close@ --- *
156 * Arguments: @lbuf *b@ = pointer to buffer block
160 * Use: Empties the buffer of any data currently lurking in it, and
161 * informs the client that this has happened. It's assumed that
162 * the buffer is enabled: you shouldn't be reading close events
163 * on disabled buffers.
166 extern void lbuf_close(lbuf */
*b*/
);
168 /* --- @lbuf_free@ --- *
170 * Arguments: @lbuf *b@ = pointer to buffer block
171 * @char **p@ = output pointer to free space
173 * Returns: Free buffer size.
175 * Use: Returns the free portion of a line buffer. Data can then be
176 * written to this portion, and split out into lines by calling
180 extern size_t lbuf_free(lbuf */
*b*/
, char **/
*p*/
);
182 /* --- @lbuf_snarf@ --- *
184 * Arguments: @lbuf *b@ = pointer to buffer block
185 * @const void *p@ = pointer to input data buffer
186 * @size_t sz@ = size of data in input buffer
190 * Use: Snarfs the data from the input buffer and spits it out as
191 * lines. This interface ignores the complexities of dealing
192 * with disablement: you should be using @lbuf_free@ to
193 * contribute data if you want to cope with that.
196 extern void lbuf_snarf(lbuf */
*b*/
, const void */
*p*/
, size_t /*sz*/);
198 /* --- @lbuf_setsize@ --- *
200 * Arguments: @lbuf *b@ = pointer to buffer block
201 * @size_t sz@ = requested maximum line size
205 * Use: Allocates a buffer of the requested size reading lines.
208 extern void lbuf_setsize(lbuf */
*b*/
, size_t /*sz*/);
210 /* --- @lbuf_init@ --- *
212 * Arguments: @lbuf *b@ = pointer to buffer block
213 * @void (*func)(char *s, void *p)@ = handler function
214 * @void *p@ = argument pointer for @func@
218 * Use: Initializes a line buffer block. Any recognized lines are
219 * passed to @func@ for processing.
222 extern void lbuf_init(lbuf */
*b*/
,
223 void (*/
*func*/
)(char */
*s*/
, void */
*p*/
),
226 /* --- @lbuf_destroy@ --- *
228 * Arguments: @lbuf *b@ = pointer to buffer block
232 * Use: Deallocates a line buffer and frees any resources it owned.
235 extern void lbuf_destroy(lbuf */
*b*/
);
237 /*----- That's all, folks -------------------------------------------------*/