mdw@git.distorted.org.uk Git - mLib/blob - fwatch.c

   1 /* -*-c-*-
   2  *
   3  * $Id: fwatch.c,v 1.2 2004/04/08 01:36:11 mdw Exp $
   4  *
   5  * Watch a file for changes
   6  *
   7  * (c) 2001 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 /*----- Header files ------------------------------------------------------*/
  31
  32 #include <errno.h>
  33 #include <string.h>
  34
  35 #include <sys/types.h>
  36 #include <sys/stat.h>
  37
  38 #include "fwatch.h"
  39
  40 /*----- Main code ---------------------------------------------------------*/
  41
  42 /* --- @doupdate@ --- *
  43  *
  44  * Arguments:   @fwatch *f@ = pointer to an @fwatch@ structure
  45  *              @struct stat *st@ = pointer to file state
  46  *              @int err@ = whether there was an error
  47  *
  48  * Returns:     Nonzero if the file has changed.
  49  *
  50  * Use:         Updates the information in an @fwatch@ block.
  51  */
  52
  53 static void copy(fwatch *f, struct stat *st)
  54 {
  55   f->dev = st->st_dev; f->ino = st->st_ino;
  56   f->mtime = st->st_mtime; f->size = st->st_size;
  57   f->mode = st->st_mode;
  58   f->uid = st->st_uid; f->gid = st->st_gid;
  59 }
  60
  61 static int doupdate(fwatch *f, struct stat *st, int err)
  62 {
  63   /* --- Fiddle with the error state --- *
  64    *
  65    * Only the presence or absence of error is interesting to someone wanting
  66    * to read the file.
  67    */
  68
  69   if (err)
  70     err = errno;
  71   if (err || f->err) {
  72     if (!err != !f->err) {
  73       f->err = err;
  74       if (!err)
  75         copy(f, st);
  76       return (1);
  77     }
  78     return (0);
  79   }
  80
  81   /* --- Check everything else --- */
  82
  83   if (st->st_dev != f->dev || st->st_ino != f->ino ||
  84       st->st_mtime != f->mtime || st->st_size != f->size ||
  85       st->st_mode != f->mode ||
  86       st->st_uid != f->uid || st->st_gid != f->gid) {
  87     copy(f, st);
  88     return (1);
  89   }
  90   return (0);
  91 }
  92
  93 /* --- @fwatch_init@, @fwatch_update@, etc --- *
  94  *
  95  * Arguments:   @fwatch *f@ = pointer to an @fwatch@ structure
  96  *              @const char *name@ = name of the file to watch
  97  *              @int fd@ = a file descriptor to watch
  98  *
  99  * Returns:     The @update@ functions return nonzero if the file has
 100  *              changed.
 101  *
 102  * Use:         Stores information about a file which can be used to watch
 103  *              for changes.  The structures may be freed without telling
 104  *              anyone.
 105  */
 106
 107 void fwatch_init(fwatch *f, const char *name)
 108 {
 109   struct stat st;
 110   memset(f, 0, sizeof(*f));
 111   doupdate(f, &st, stat(name, &st));
 112 }
 113
 114 void fwatch_initfd(fwatch *f, int fd)
 115 {
 116   struct stat st;
 117   memset(f, 0, sizeof(*f));
 118   doupdate(f, &st, fstat(fd, &st));
 119 }
 120
 121 int fwatch_update(fwatch *f, const char *name)
 122 {
 123   struct stat st;
 124   return (doupdate(f, &st, stat(name, &st)));
 125 }
 126
 127 int fwatch_updatefd(fwatch *f, int fd)
 128 {
 129   struct stat st;
 130   return (doupdate(f, &st, fstat(fd, &st)));
 131 }
 132
 133 /*----- That's all, folks -------------------------------------------------*/