kernel/lib/stdio/read.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   4  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   5  *  Copyright (C) 2009  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   6  *  Copyright (C) 2009  Martin 'povik' Poviser (martin.povik@gmail.com)
   7  *  Copyright (C) 2010  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   8  *
   9  *  This program is free software: you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation, either version 3 of the License, or
  12  *  (at your option) any later version.
  13  *
  14  *  This program is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21  */
  22
  23
  24 #include <system.h>
  25 #include <string.h>
  26 #include <file.h>
  27 #include <dev.h>
  28 #include <fd.h>
  29 #include <pipe.h>
  30 #include <cache.h>
  31 #include <errno.h>
  32 #include <proc.h>
  33
  34 int read (unsigned fd, void *buf, unsigned len)
  35 {
  36         fd_t *d = fd_get (fd);
  37
  38         if (!d)
  39                 return 0;
  40
  41         if (d->flags & O_WRONLY)
  42                 return 0;
  43
  44         if (!d->s)
  45                 return 0;
  46
  47         if (d->flags & FD_PIPE) {
  48                 pipe_t *p = pipe_get (fd);
  49
  50                 if (p)
  51                         return pipe_read (p, buf, len);
  52                 else
  53                         return 0;
  54         }
  55
  56         if (len > d->e)
  57                 len = d->e;
  58
  59         /* copy data from cache to buffer */
  60         memcpy ((char *) buf, d->s+d->p, len);
  61
  62         d->e -= len;
  63         d->p += len;
  64
  65         /* HACK: this should call UPDATE handler */
  66         if (d->dev)
  67                 d->dev->handler (DEV_ACT_UPDATE);
  68
  69         return len;
  70 }