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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: lbuf.h,v 1.6 2001/02/03 16:23:33 mdw Exp $ |
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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 $ |
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33 | * Revision 1.6 2001/02/03 16:23:33 mdw |
34 | * Bug fix: handle a disable during a close-induced flush without dumping |
35 | * core. |
36 | * |
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37 | * Revision 1.5 2001/01/20 12:06:01 mdw |
38 | * Define flags with macros, to ensure unsignedness. |
39 | * |
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40 | * Revision 1.4 2000/06/17 10:38:14 mdw |
41 | * Add support for variable buffer sizes. |
42 | * |
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43 | * Revision 1.3 1999/12/10 23:42:04 mdw |
44 | * Change header file guard names. |
45 | * |
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46 | * Revision 1.2 1999/05/17 20:36:08 mdw |
47 | * Make the magical constants for the buffer flags uppercase. |
48 | * |
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49 | * Revision 1.1 1999/05/14 21:01:14 mdw |
50 | * Integrated `select' handling bits from the background resolver project. |
51 | * |
52 | */ |
53 | |
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54 | #ifndef MLIB_LBUF_H |
55 | #define MLIB_LBUF_H |
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56 | |
57 | #ifdef __cplusplus |
58 | extern "C" { |
59 | #endif |
60 | |
61 | /*----- Line buffering ----------------------------------------------------* |
62 | * |
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. |
69 | * |
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.) |
73 | * |
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 |
79 | * simply discarded. |
80 | * |
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. |
89 | * |
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. |
100 | */ |
101 | |
102 | /*----- Header files ------------------------------------------------------*/ |
103 | |
104 | #include <stddef.h> |
105 | |
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106 | #ifndef MLIB_ARENA_H |
107 | # include "arena.h" |
108 | #endif |
109 | |
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110 | /*----- Data structures ---------------------------------------------------*/ |
111 | |
112 | /* --- The buffer structure --- * |
113 | * |
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 |
116 | * that. |
117 | */ |
118 | |
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 */ |
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123 | size_t sz; /* Buffer size */ |
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124 | unsigned f; /* Various useful state flags */ |
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125 | arena *a; /* Memory allocation arena */ |
126 | char *buf; /* The actual buffer */ |
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127 | } lbuf; |
128 | |
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129 | #define LBUF_CR 1u /* Read a carriage return */ |
130 | #define LBUF_ENABLE 2u /* Buffer is currently enabled */ |
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131 | #define LBUF_CLOSE 4u /* Buffer is now closed */ |
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132 | |
133 | /*----- Functions provided ------------------------------------------------*/ |
134 | |
135 | /* --- @lbuf_flush@ --- * |
136 | * |
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 |
140 | * |
141 | * Returns: --- |
142 | * |
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 |
147 | * of @len@. |
148 | * |
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 |
155 | * re-enabled. |
156 | */ |
157 | |
158 | extern void lbuf_flush(lbuf */*b*/, char */*p*/, size_t /*len*/); |
159 | |
160 | /* --- @lbuf_close@ --- * |
161 | * |
162 | * Arguments: @lbuf *b@ = pointer to buffer block |
163 | * |
164 | * Returns: --- |
165 | * |
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. |
170 | */ |
171 | |
172 | extern void lbuf_close(lbuf */*b*/); |
173 | |
174 | /* --- @lbuf_free@ --- * |
175 | * |
176 | * Arguments: @lbuf *b@ = pointer to buffer block |
177 | * @char **p@ = output pointer to free space |
178 | * |
179 | * Returns: Free buffer size. |
180 | * |
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 |
183 | * @lbuf_flush@. |
184 | */ |
185 | |
186 | extern size_t lbuf_free(lbuf */*b*/, char **/*p*/); |
187 | |
188 | /* --- @lbuf_snarf@ --- * |
189 | * |
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 |
193 | * |
194 | * Returns: --- |
195 | * |
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. |
200 | */ |
201 | |
202 | extern void lbuf_snarf(lbuf */*b*/, const void */*p*/, size_t /*sz*/); |
203 | |
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204 | /* --- @lbuf_setsize@ --- * |
205 | * |
206 | * Arguments: @lbuf *b@ = pointer to buffer block |
207 | * @size_t sz@ = requested maximum line size |
208 | * |
209 | * Returns: --- |
210 | * |
211 | * Use: Allocates a buffer of the requested size reading lines. |
212 | */ |
213 | |
214 | extern void lbuf_setsize(lbuf */*b*/, size_t /*sz*/); |
215 | |
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216 | /* --- @lbuf_init@ --- * |
217 | * |
218 | * Arguments: @lbuf *b@ = pointer to buffer block |
219 | * @void (*func)(char *s, void *p)@ = handler function |
220 | * @void *p@ = argument pointer for @func@ |
221 | * |
222 | * Returns: --- |
223 | * |
224 | * Use: Initializes a line buffer block. Any recognized lines are |
225 | * passed to @func@ for processing. |
226 | */ |
227 | |
228 | extern void lbuf_init(lbuf */*b*/, |
229 | void (*/*func*/)(char */*s*/, void */*p*/), |
230 | void */*p*/); |
231 | |
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232 | /* --- @lbuf_destroy@ --- * |
233 | * |
234 | * Arguments: @lbuf *b@ = pointer to buffer block |
235 | * |
236 | * Returns: --- |
237 | * |
238 | * Use: Deallocates a line buffer and frees any resources it owned. |
239 | */ |
240 | |
241 | extern void lbuf_destroy(lbuf */*b*/); |
242 | |
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243 | /*----- That's all, folks -------------------------------------------------*/ |
244 | |
245 | #ifdef __cplusplus |
246 | } |
247 | #endif |
248 | |
249 | #endif |