rom/dos/read.c

   1 /*
   2     Copyright © 1995-2007, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Read a couple of bytes from a file.
   6     Lang: english
   7 */
   8 #include <aros/debug.h>
   9 #include <proto/exec.h>
  10 #include <dos/dosextens.h>
  11 #include <dos/filesystem.h>
  12 #include "dos_intern.h"
  13
  14 /*****************************************************************************
  15
  16     NAME */
  17 #include <proto/dos.h>
  18
  19         AROS_LH3(LONG, Read,
  20
  21 /*  SYNOPSIS */
  22         AROS_LHA(BPTR, file,   D1),
  23         AROS_LHA(APTR, buffer, D2),
  24         AROS_LHA(LONG, length, D3),
  25
  26 /*  LOCATION */
  27         struct DosLibrary *, DOSBase, 7, Dos)
  28
  29 /*  FUNCTION
  30         Read some data from a given file. The request is directly
  31         given to the filesystem - no buffering is involved. For
  32         small amounts of data it's probably better to use the
  33         buffered I/O routines.
  34
  35     INPUTS
  36         file   - filehandle
  37         buffer - pointer to buffer for the data
  38         length - number of bytes to read. The filesystem is
  39                  advised to try to fulfill the request as good
  40                  as possible.
  41
  42     RESULT
  43         The number of bytes actually read, 0 if the end of the
  44         file was reached, -1 if an error happened. IoErr() will
  45         give additional information in that case.
  46
  47     NOTES
  48
  49     EXAMPLE
  50
  51     BUGS
  52
  53     SEE ALSO
  54
  55     INTERNALS
  56
  57 *****************************************************************************/
  58 {
  59     AROS_LIBFUNC_INIT
  60
  61     /* Get pointer to filehandle */
  62     struct FileHandle *fh = (struct FileHandle *)BADDR(file);
  63
  64     /* Get pointer to I/O request. Use stackspace for now. */
  65     struct IOFileSys iofs;
  66
  67     ASSERT_VALID_PTR(fh);
  68     ASSERT_VALID_PTR(fh->fh_Device);
  69     ASSERT_VALID_PTR(fh->fh_Unit);
  70     ASSERT_VALID_PTR(buffer);
  71
  72     /* Prepare I/O request. */
  73     InitIOFS(&iofs, FSA_READ, DOSBase);
  74
  75     iofs.IOFS.io_Device = fh->fh_Device;
  76     iofs.IOFS.io_Unit   = fh->fh_Unit;
  77
  78     iofs.io_Union.io_READ.io_Buffer = buffer;
  79     iofs.io_Union.io_READ.io_Length = length;
  80
  81     /* Send the request. */
  82     DosDoIO(&iofs.IOFS);
  83
  84     /* Set error code and return */
  85
  86     if(iofs.io_DosError != 0)
  87     {
  88         SetIoErr(iofs.io_DosError);
  89         return -1;
  90     }
  91     else
  92         return iofs.io_Union.io_READ.io_Length;
  93
  94     AROS_LIBFUNC_EXIT
  95 } /* Read */