| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: lbuf.h,v 1.2 1999/05/17 20:36:08 mdw Exp $ |
| 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 $ |
| 33 | * Revision 1.2 1999/05/17 20:36:08 mdw |
| 34 | * Make the magical constants for the buffer flags uppercase. |
| 35 | * |
| 36 | * Revision 1.1 1999/05/14 21:01:14 mdw |
| 37 | * Integrated `select' handling bits from the background resolver project. |
| 38 | * |
| 39 | */ |
| 40 | |
| 41 | #ifndef LBUF_H |
| 42 | #define LBUF_H |
| 43 | |
| 44 | #ifdef __cplusplus |
| 45 | extern "C" { |
| 46 | #endif |
| 47 | |
| 48 | /*----- Line buffering ----------------------------------------------------* |
| 49 | * |
| 50 | * The line buffer accepts as input arbitrary-sized lumps of data and |
| 51 | * converts them, by passing them to a client-supplied function, into a |
| 52 | * sequence of lines. It's particularly useful when performing multiplexed |
| 53 | * network I/O. It's not normally acceptable to block while waiting for the |
| 54 | * rest of a text line to arrive, for example. The line buffer stores the |
| 55 | * start of the line until the rest of it arrives later. |
| 56 | * |
| 57 | * A line is a piece of text terminated by either a linefeed or a carriage- |
| 58 | * return/linefeed pair. (The former is there to cope with Unix; the latter |
| 59 | * copes with Internet-format line ends.) |
| 60 | * |
| 61 | * There's a limit to the size of lines that the buffer can cope with. It's |
| 62 | * not hard to remove this limit, but it's probably a bad idea in a lot of |
| 63 | * cases, because it'd allow a remote user to gobble arbitrary amounts of |
| 64 | * your memory. If a line exceeds the limit, it is truncated: the initial |
| 65 | * portion of the line is processed normally, and the remaining portion is |
| 66 | * simply discarded. |
| 67 | * |
| 68 | * Lines extracted from the input data are passed, one at a time, to a |
| 69 | * `handler function', along with a caller-supplied pointer argument to |
| 70 | * provide the handler with some context. The line read is null-terminated |
| 71 | * and does not include the trailing newline characters. It is legal for a |
| 72 | * handler function to modify the string it is passed. However, writing |
| 73 | * beyond the terminating null byte is not allowed. An end-of-file condition |
| 74 | * is signalled to the handler by passing it a null pointer rather than the |
| 75 | * address of a string. |
| 76 | * |
| 77 | * A complexity arises because of the concept of a `disabled' buffer. |
| 78 | * Disablement is really a higher-level concept, but it turns out to be |
| 79 | * important to implement it here. It's useful for a line handler function |
| 80 | * to `disable' itself, so that it doesn't get called any more. For example, |
| 81 | * this might happen if it encouters an error, or when it finishes reading |
| 82 | * everything it wanted to read. The line buffer needs to be `in the loop' |
| 83 | * so that it stops attempting to flush any further lines stored in its |
| 84 | * buffer towards a handler function which isn't ready to accept them. |
| 85 | * Buffers are initially enabled, although higher- level buffering systems |
| 86 | * might well disable them immediately for their own purposes. |
| 87 | */ |
| 88 | |
| 89 | /*----- Header files ------------------------------------------------------*/ |
| 90 | |
| 91 | #include <stddef.h> |
| 92 | |
| 93 | /*----- Data structures ---------------------------------------------------*/ |
| 94 | |
| 95 | /* --- The buffer structure --- * |
| 96 | * |
| 97 | * The only thing that's safe to fiddle with in here is the @lbuf_enable@ |
| 98 | * flag. Only higher-level buffering systems should be playing with even |
| 99 | * that. |
| 100 | */ |
| 101 | |
| 102 | typedef struct lbuf { |
| 103 | void (*func)(char */*s*/, void */*p*/); /* Handler function */ |
| 104 | void *p; /* Argument for handler */ |
| 105 | size_t len; /* Length of data in buffer */ |
| 106 | unsigned f; /* Various useful state flags */ |
| 107 | char buf[256]; /* The actual buffer */ |
| 108 | } lbuf; |
| 109 | |
| 110 | enum { |
| 111 | LBUF_CR = 1, /* Read a carriage return */ |
| 112 | LBUF_ENABLE = 2 /* Buffer is currently enabled */ |
| 113 | }; |
| 114 | |
| 115 | /*----- Functions provided ------------------------------------------------*/ |
| 116 | |
| 117 | /* --- @lbuf_flush@ --- * |
| 118 | * |
| 119 | * Arguments: @lbuf *b@ = pointer to buffer block |
| 120 | * @char *p@ = pointer to where to start searching |
| 121 | * @size_t len@ = length of new material added |
| 122 | * |
| 123 | * Returns: --- |
| 124 | * |
| 125 | * Use: Flushes any complete lines in a line buffer. New material |
| 126 | * is assumed to have been added starting at @p@. If @p@ is |
| 127 | * null, then the scan starts at the beginning of the buffer, |
| 128 | * and the size of data already in the buffer is used in place |
| 129 | * of @len@. |
| 130 | * |
| 131 | * It is assumed that the buffer is initially enabled. You |
| 132 | * shouldn't be contributing data to a disabled buffer anyway. |
| 133 | * However, the buffer handler may at some point disable itself, |
| 134 | * and @lbuf_flush@ can cope with this eventuality. Any pending |
| 135 | * data is left at the start of the buffer and can be flushed |
| 136 | * out by calling @lbuf_flush(b, 0, 0)@ if the buffer is ever |
| 137 | * re-enabled. |
| 138 | */ |
| 139 | |
| 140 | extern void lbuf_flush(lbuf */*b*/, char */*p*/, size_t /*len*/); |
| 141 | |
| 142 | /* --- @lbuf_close@ --- * |
| 143 | * |
| 144 | * Arguments: @lbuf *b@ = pointer to buffer block |
| 145 | * |
| 146 | * Returns: --- |
| 147 | * |
| 148 | * Use: Empties the buffer of any data currently lurking in it, and |
| 149 | * informs the client that this has happened. It's assumed that |
| 150 | * the buffer is enabled: you shouldn't be reading close events |
| 151 | * on disabled buffers. |
| 152 | */ |
| 153 | |
| 154 | extern void lbuf_close(lbuf */*b*/); |
| 155 | |
| 156 | /* --- @lbuf_free@ --- * |
| 157 | * |
| 158 | * Arguments: @lbuf *b@ = pointer to buffer block |
| 159 | * @char **p@ = output pointer to free space |
| 160 | * |
| 161 | * Returns: Free buffer size. |
| 162 | * |
| 163 | * Use: Returns the free portion of a line buffer. Data can then be |
| 164 | * written to this portion, and split out into lines by calling |
| 165 | * @lbuf_flush@. |
| 166 | */ |
| 167 | |
| 168 | extern size_t lbuf_free(lbuf */*b*/, char **/*p*/); |
| 169 | |
| 170 | /* --- @lbuf_snarf@ --- * |
| 171 | * |
| 172 | * Arguments: @lbuf *b@ = pointer to buffer block |
| 173 | * @const void *p@ = pointer to input data buffer |
| 174 | * @size_t sz@ = size of data in input buffer |
| 175 | * |
| 176 | * Returns: --- |
| 177 | * |
| 178 | * Use: Snarfs the data from the input buffer and spits it out as |
| 179 | * lines. This interface ignores the complexities of dealing |
| 180 | * with disablement: you should be using @lbuf_free@ to |
| 181 | * contribute data if you want to cope with that. |
| 182 | */ |
| 183 | |
| 184 | extern void lbuf_snarf(lbuf */*b*/, const void */*p*/, size_t /*sz*/); |
| 185 | |
| 186 | /* --- @lbuf_init@ --- * |
| 187 | * |
| 188 | * Arguments: @lbuf *b@ = pointer to buffer block |
| 189 | * @void (*func)(char *s, void *p)@ = handler function |
| 190 | * @void *p@ = argument pointer for @func@ |
| 191 | * |
| 192 | * Returns: --- |
| 193 | * |
| 194 | * Use: Initializes a line buffer block. Any recognized lines are |
| 195 | * passed to @func@ for processing. |
| 196 | */ |
| 197 | |
| 198 | extern void lbuf_init(lbuf */*b*/, |
| 199 | void (*/*func*/)(char */*s*/, void */*p*/), |
| 200 | void */*p*/); |
| 201 | |
| 202 | /*----- That's all, folks -------------------------------------------------*/ |
| 203 | |
| 204 | #ifdef __cplusplus |
| 205 | } |
| 206 | #endif |
| 207 | |
| 208 | #endif |