chiark - git - mdw - fwd/blob - conf.h

   1 /* -*-c-*-
   2  *
   3  * Configuration parsing
   4  *
   5  * (c) 1999 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the `fwd' port forwarder.
  11  *
  12  * `fwd' is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * `fwd' 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 General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with `fwd'; if not, write to the Free Software Foundation,
  24  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25  */
  26
  27 #ifndef CONF_H
  28 #define CONF_H
  29
  30 #ifdef __cplusplus
  31   extern "C" {
  32 #endif
  33
  34 /*----- Header files ------------------------------------------------------*/
  35
  36 #include <mLib/dstr.h>
  37
  38 #ifndef SCAN_H
  39 #  include "scan.h"
  40 #endif
  41
  42 /*----- Magic numbers -----------------------------------------------------*/
  43
  44 #define CTOK_EOF (-1)
  45 #define CTOK_WORD 256
  46
  47 /*----- Functions provided ------------------------------------------------*/
  48
  49 /* --- @conf_undelim@ --- *
  50  *
  51  * Arguments:   @scanner *sc@ = pointer to scanner definition
  52  *              @const char *d, *dd@ = pointer to characters to escape
  53  *
  54  * Returns:     ---
  55  *
  56  * Use:         Modifies the tokenizer.  Characters in the first list will
  57  *              always be considered to begin a word.  Characters in the
  58  *              second list will always be allowed to continue a word.
  59  */
  60
  61 extern void conf_undelim(scanner */*sc*/,
  62                          const char */*d*/, const char */*dd*/);
  63
  64 /* --- @token@ --- *
  65  *
  66  * Arguments:   @scanner *sc@ = pointer to scanner definition
  67  *
  68  * Returns:     Type of token scanned.
  69  *
  70  * Use:         Reads the next token from the character scanner.
  71  */
  72
  73 extern int token(scanner */*sc*/);
  74
  75 /* --- @error@ --- *
  76  *
  77  * Arguments:   @scanner *sc@ = pointer to scanner definition
  78  *              @const char *msg@ = message skeleton string
  79  *              @...@ = extra arguments for the skeleton
  80  *
  81  * Returns:     Doesn't
  82  *
  83  * Use:         Reports an error at the current scanner location.
  84  */
  85
  86 extern void error(scanner */*sc*/, const char */*msg*/, ...);
  87
  88 /* --- @pushback@ --- *
  89  *
  90  * Arguments:   @scanner *sc@ = pointer to scanner definition
  91  *
  92  * Returns:     ---
  93  *
  94  * Use:         Pushes the current token back.  This is normally a precursor
  95  *              to pushing a new scanner source.
  96  */
  97
  98 extern void pushback(scanner */*sc*/);
  99
 100 /* --- @conf_enum@ --- *
 101  *
 102  * Arguments:   @scanner *sc@ = pointer to a scanner object
 103  *              @const char *list@ = comma-separated things to allow
 104  *              @unsigned @f = flags for the search
 105  *              @const char *err@ = error message if not found
 106  *
 107  * Returns:     Index into list, zero-based, or @-1@.
 108  *
 109  * Use:         Checks whether the current token is a string which matches
 110  *              one of the comma-separated items given.  The return value is
 111  *              the index (zero-based) of the matched string in the list.
 112  *
 113  *              The flags control the behaviour if no exact match is found.
 114  *              If @ENUM_ABBREV@ is set, and the current token is a left
 115  *              substring of exactly one of the possibilities, then that one
 116  *              is chosen.  If @ENUM_NONE@ is set, the value @-1@ is
 117  *              returned; otherwise an error is reported and the program is
 118  *              terminated.
 119  */
 120
 121 #define ENUM_ABBREV 1u
 122 #define ENUM_NONE 2u
 123
 124 extern int conf_enum(scanner */*sc*/, const char */*list*/,
 125                      unsigned /*flags*/, const char */*err*/);
 126
 127 /* --- @conf_prefix@ --- *
 128  *
 129  * Arguments:   @scanner *sc@ = pointer to a scanner object
 130  *              @const char *p@ = pointer to prefix string to check
 131  *
 132  * Returns:     Nonzero if the prefix matches.
 133  *
 134  * Use:         If the current token is a word matching the given prefix
 135  *              string, then it and an optional `.' character are removed and
 136  *              a nonzero result is returned.  Otherwise the current token is
 137  *              left as it is, and zero is returned.
 138  *
 139  *              Typical options parsing code would remove an expected prefix,
 140  *              scan an option anyway (since qualifying prefixes are
 141  *              optional) and if a match is found, claim the option.  If no
 142  *              match is found, and a prefix was stripped, then an error
 143  *              should be reported.
 144  */
 145
 146 extern int conf_prefix(scanner */*sc*/, const char */*p*/);
 147
 148 /* --- @CONF_BEGIN@, @CONF_END@ --- *
 149  *
 150  * Arguments:   @sc@ = scanner to read from
 151  *              @prefix@ = prefix to scan for
 152  *              @desc@ = description of what we're parsing
 153  *
 154  * Use:         Bracket an options parsing routine.  The current token is
 155  *              checked to see whether it matches the prefix.  If so, it is
 156  *              removed and the following token examined.  If that's a `.'
 157  *              then it's removed.  If it's a `{' then the enclosed
 158  *              option-parsing code is executed in a loop until a matching
 159  *              '}' is found.  If the options parser doesn't accept an
 160  *              option, the behaviour is dependent on whether a prefix was
 161  *              seen: if so, an error is reported; otherwse a zero return is
 162  *              made.
 163  */
 164
 165 #define CS_PLAIN 0
 166 #define CS_PREFIX 1
 167 #define CS_BRACE 2
 168 #define CS_UNKNOWN 3
 169
 170 #define CONF_BEGIN(sc, prefix, desc) do {                               \
 171   scanner *_conf_sc = (sc);                                             \
 172   const char *_conf_desc = (desc);                                      \
 173   int _conf_state = CS_PLAIN;                                           \
 174                                                                         \
 175   /* --- Read the initial prefix --- */                                 \
 176                                                                         \
 177   if (_conf_sc->t == CTOK_WORD &&                                       \
 178       strcmp(_conf_sc->d.buf, (prefix)) == 0) {                         \
 179     token(_conf_sc);                                                    \
 180     _conf_state = CS_PREFIX;                                            \
 181     if (_conf_sc->t == '.')                                             \
 182       token(_conf_sc);                                                  \
 183     else if (_conf_sc->t == '{') {                                      \
 184       token(_conf_sc);                                                  \
 185       _conf_state = CS_BRACE;                                           \
 186     }                                                                   \
 187   }                                                                     \
 188                                                                         \
 189   /* --- Ensure the next token is a word --- */                         \
 190                                                                         \
 191   if (_conf_sc->t != CTOK_WORD)                                         \
 192     error(_conf_sc, "parse error, expected option keyword");            \
 193   do {
 194
 195 #define CONF_END                                                        \
 196                                                                         \
 197     /* --- Reject an option --- *                                       \
 198      *                                                                  \
 199      * We could get here as a result of an explicit @CONF_REJECT@ or    \
 200      * because the option wasn't accepted.                              \
 201      */                                                                 \
 202                                                                         \
 203     goto _conf_reject;                                                  \
 204   _conf_reject:                                                         \
 205     if (_conf_state == CS_PLAIN)                                        \
 206       _conf_state = CS_UNKNOWN;                                         \
 207     else {                                                              \
 208       error(_conf_sc, "unknown %s option `%s'",                         \
 209             _conf_desc, _conf_sc->d.buf);                               \
 210     }                                                                   \
 211                                                                         \
 212     /* --- Accept an option --- *                                       \
 213      *                                                                  \
 214      * It's safe to drop through from above.  Either an error will have \
 215      * been reported, or the state is not @CS_BRACE@.                   \
 216      */                                                                 \
 217                                                                         \
 218   _conf_accept:                                                         \
 219     if (_conf_state == CS_BRACE && _conf_sc->t == ';')                  \
 220       token(_conf_sc);                                                  \
 221   } while (_conf_state == CS_BRACE && _conf_sc->t == CTOK_WORD);        \
 222                                                                         \
 223   /* --- Check for a closing brace --- */                               \
 224                                                                         \
 225   if (_conf_state == CS_BRACE) {                                        \
 226     if (_conf_sc->t == '}')                                             \
 227       token(_conf_sc);                                                  \
 228     else                                                                \
 229       error(_conf_sc, "parse error, expected `}'");                     \
 230   }                                                                     \
 231                                                                         \
 232   /* --- Return an appropriate value --- */                             \
 233                                                                         \
 234   return (_conf_state != CS_UNKNOWN);                                   \
 235 } while (0)
 236
 237 /* --- @CONF_ACCEPT@, @CONF_REJECT@ --- *
 238  *
 239  * Arguments:   ---
 240  *
 241  * Use:         Within an options parser (between @CONF_BEGIN@ and
 242  *              @CONF_END@), accept or reject an option.
 243  */
 244
 245 #define CONF_ACCEPT goto _conf_accept
 246 #define CONF_REJECT goto _conf_reject
 247
 248 /* --- @CONF_QUAL@ --- *
 249  *
 250  * Arguments:   ---
 251  *
 252  * Use:         Evaluates to a nonzero value if the current option is
 253  *              qualified.  This can be used to decide whether abbreviations
 254  *              for options should be accepted.
 255  */
 256
 257 #define CONF_QUAL (_conf_state != CS_PLAIN)
 258
 259 /* --- @conf_name@ --- *
 260  *
 261  * Arguments:   @scanner *sc@ = pointer to scanner
 262  *              @char delim@ = delimiter character to look for
 263  *              @dstr *d@ = pointer to dynamic string for output
 264  *
 265  * Returns:     ---
 266  *
 267  * Use:         Reads in a compound name consisting of words separated by
 268  *              delimiters.  Leading and trailing delimiters are permitted,
 269  *              although they'll probably cause confusion if used.  The name
 270  *              may be enclosed in square brackets if that helps at all.
 271  *
 272  *              Examples of compound names are filenames (delimited by `/')
 273  *              and IP addresses (delimited by `.').
 274  */
 275
 276 extern void conf_name(scanner */*sc*/, char /*delim*/, dstr */*d*/);
 277
 278 /*----- That's all, folks -------------------------------------------------*/
 279
 280 #ifdef __cplusplus
 281   }
 282 #endif
 283
 284 #endif