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1 | /* -*-c-*- |
2 | * |
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3 | * Block-to-line buffering |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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9 | * |
10 | * This file is part of the mLib utilities library. |
11 | * |
12 | * mLib is free software; you can redistribute it and/or modify |
13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the |
15 | * License, or (at your option) any later version. |
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16 | * |
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17 | * mLib is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU Library General Public License for more details. |
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21 | * |
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22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with mLib; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
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28 | #ifndef MLIB_LBUF_H |
29 | #define MLIB_LBUF_H |
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30 | |
31 | #ifdef __cplusplus |
32 | extern "C" { |
33 | #endif |
34 | |
35 | /*----- Line buffering ----------------------------------------------------* |
36 | * |
37 | * The line buffer accepts as input arbitrary-sized lumps of data and |
38 | * converts them, by passing them to a client-supplied function, into a |
39 | * sequence of lines. It's particularly useful when performing multiplexed |
40 | * network I/O. It's not normally acceptable to block while waiting for the |
41 | * rest of a text line to arrive, for example. The line buffer stores the |
42 | * start of the line until the rest of it arrives later. |
43 | * |
44 | * A line is a piece of text terminated by either a linefeed or a carriage- |
45 | * return/linefeed pair. (The former is there to cope with Unix; the latter |
46 | * copes with Internet-format line ends.) |
47 | * |
48 | * There's a limit to the size of lines that the buffer can cope with. It's |
49 | * not hard to remove this limit, but it's probably a bad idea in a lot of |
50 | * cases, because it'd allow a remote user to gobble arbitrary amounts of |
51 | * your memory. If a line exceeds the limit, it is truncated: the initial |
52 | * portion of the line is processed normally, and the remaining portion is |
53 | * simply discarded. |
54 | * |
55 | * Lines extracted from the input data are passed, one at a time, to a |
56 | * `handler function', along with a caller-supplied pointer argument to |
57 | * provide the handler with some context. The line read is null-terminated |
58 | * and does not include the trailing newline characters. It is legal for a |
59 | * handler function to modify the string it is passed. However, writing |
60 | * beyond the terminating null byte is not allowed. An end-of-file condition |
61 | * is signalled to the handler by passing it a null pointer rather than the |
62 | * address of a string. |
63 | * |
64 | * A complexity arises because of the concept of a `disabled' buffer. |
65 | * Disablement is really a higher-level concept, but it turns out to be |
66 | * important to implement it here. It's useful for a line handler function |
67 | * to `disable' itself, so that it doesn't get called any more. For example, |
68 | * this might happen if it encouters an error, or when it finishes reading |
69 | * everything it wanted to read. The line buffer needs to be `in the loop' |
70 | * so that it stops attempting to flush any further lines stored in its |
71 | * buffer towards a handler function which isn't ready to accept them. |
72 | * Buffers are initially enabled, although higher- level buffering systems |
73 | * might well disable them immediately for their own purposes. |
74 | */ |
75 | |
76 | /*----- Header files ------------------------------------------------------*/ |
77 | |
78 | #include <stddef.h> |
79 | |
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80 | #ifndef MLIB_ARENA_H |
81 | # include "arena.h" |
82 | #endif |
83 | |
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84 | /*----- Data structures ---------------------------------------------------*/ |
85 | |
86 | /* --- The buffer structure --- * |
87 | * |
88 | * The only thing that's safe to fiddle with in here is the @lbuf_enable@ |
89 | * flag. Only higher-level buffering systems should be playing with even |
90 | * that. |
91 | */ |
92 | |
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93 | struct lbuf; |
94 | |
95 | typedef void lbuf_func(char */*s*/, size_t /*len*/, void */*p*/); |
96 | |
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97 | typedef struct lbuf { |
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98 | lbuf_func *func; /* Handler function */ |
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99 | void *p; /* Argument for handler */ |
100 | size_t len; /* Length of data in buffer */ |
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101 | size_t sz; /* Buffer size */ |
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102 | unsigned delim; /* Delimiter to look for */ |
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103 | unsigned f; /* Various useful state flags */ |
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104 | arena *a; /* Memory allocation arena */ |
105 | char *buf; /* The actual buffer */ |
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106 | } lbuf; |
107 | |
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108 | #define LBUF_CR 1u /* Read a carriage return */ |
109 | #define LBUF_ENABLE 2u /* Buffer is currently enabled */ |
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110 | #define LBUF_CLOSE 4u /* Buffer is now closed */ |
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111 | |
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112 | enum { |
113 | LBUF_CRLF = 256, |
114 | LBUF_STRICTCRLF = 257 |
115 | }; |
116 | |
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117 | /*----- Functions provided ------------------------------------------------*/ |
118 | |
119 | /* --- @lbuf_flush@ --- * |
120 | * |
121 | * Arguments: @lbuf *b@ = pointer to buffer block |
122 | * @char *p@ = pointer to where to start searching |
123 | * @size_t len@ = length of new material added |
124 | * |
125 | * Returns: --- |
126 | * |
127 | * Use: Flushes any complete lines in a line buffer. New material |
128 | * is assumed to have been added starting at @p@. If @p@ is |
129 | * null, then the scan starts at the beginning of the buffer, |
130 | * and the size of data already in the buffer is used in place |
131 | * of @len@. |
132 | * |
133 | * It is assumed that the buffer is initially enabled. You |
134 | * shouldn't be contributing data to a disabled buffer anyway. |
135 | * However, the buffer handler may at some point disable itself, |
136 | * and @lbuf_flush@ can cope with this eventuality. Any pending |
137 | * data is left at the start of the buffer and can be flushed |
138 | * out by calling @lbuf_flush(b, 0, 0)@ if the buffer is ever |
139 | * re-enabled. |
140 | */ |
141 | |
142 | extern void lbuf_flush(lbuf */*b*/, char */*p*/, size_t /*len*/); |
143 | |
144 | /* --- @lbuf_close@ --- * |
145 | * |
146 | * Arguments: @lbuf *b@ = pointer to buffer block |
147 | * |
148 | * Returns: --- |
149 | * |
150 | * Use: Empties the buffer of any data currently lurking in it, and |
151 | * informs the client that this has happened. It's assumed that |
152 | * the buffer is enabled: you shouldn't be reading close events |
153 | * on disabled buffers. |
154 | */ |
155 | |
156 | extern void lbuf_close(lbuf */*b*/); |
157 | |
158 | /* --- @lbuf_free@ --- * |
159 | * |
160 | * Arguments: @lbuf *b@ = pointer to buffer block |
161 | * @char **p@ = output pointer to free space |
162 | * |
163 | * Returns: Free buffer size. |
164 | * |
165 | * Use: Returns the free portion of a line buffer. Data can then be |
166 | * written to this portion, and split out into lines by calling |
167 | * @lbuf_flush@. |
168 | */ |
169 | |
170 | extern size_t lbuf_free(lbuf */*b*/, char **/*p*/); |
171 | |
172 | /* --- @lbuf_snarf@ --- * |
173 | * |
174 | * Arguments: @lbuf *b@ = pointer to buffer block |
175 | * @const void *p@ = pointer to input data buffer |
176 | * @size_t sz@ = size of data in input buffer |
177 | * |
178 | * Returns: --- |
179 | * |
180 | * Use: Snarfs the data from the input buffer and spits it out as |
181 | * lines. This interface ignores the complexities of dealing |
182 | * with disablement: you should be using @lbuf_free@ to |
183 | * contribute data if you want to cope with that. |
184 | */ |
185 | |
186 | extern void lbuf_snarf(lbuf */*b*/, const void */*p*/, size_t /*sz*/); |
187 | |
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188 | /* --- @lbuf_setsize@ --- * |
189 | * |
190 | * Arguments: @lbuf *b@ = pointer to buffer block |
191 | * @size_t sz@ = requested maximum line size |
192 | * |
193 | * Returns: --- |
194 | * |
195 | * Use: Allocates a buffer of the requested size reading lines. |
196 | */ |
197 | |
198 | extern void lbuf_setsize(lbuf */*b*/, size_t /*sz*/); |
199 | |
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200 | /* --- @lbuf_init@ --- * |
201 | * |
202 | * Arguments: @lbuf *b@ = pointer to buffer block |
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203 | * @lbuf_func *func@ = handler function |
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204 | * @void *p@ = argument pointer for @func@ |
205 | * |
206 | * Returns: --- |
207 | * |
208 | * Use: Initializes a line buffer block. Any recognized lines are |
209 | * passed to @func@ for processing. |
210 | */ |
211 | |
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212 | extern void lbuf_init(lbuf */*b*/, lbuf_func */*func*/, void */*p*/); |
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213 | |
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214 | /* --- @lbuf_destroy@ --- * |
215 | * |
216 | * Arguments: @lbuf *b@ = pointer to buffer block |
217 | * |
218 | * Returns: --- |
219 | * |
220 | * Use: Deallocates a line buffer and frees any resources it owned. |
221 | */ |
222 | |
223 | extern void lbuf_destroy(lbuf */*b*/); |
224 | |
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225 | /*----- That's all, folks -------------------------------------------------*/ |
226 | |
227 | #ifdef __cplusplus |
228 | } |
229 | #endif |
230 | |
231 | #endif |