workbench/libs/iffparse/readchunkbytes.c

   1 /*
   2     Copyright © 1995-2007, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "iffparse_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11 #include <proto/iffparse.h>
  12
  13     AROS_LH3(LONG, ReadChunkBytes,
  14
  15 /*  SYNOPSIS */
  16         AROS_LHA(struct IFFHandle *, iff, A0),
  17         AROS_LHA(APTR              , buf, A1),
  18         AROS_LHA(LONG              , numBytes, D0),
  19
  20 /*  LOCATION */
  21         struct Library *, IFFParseBase, 10, IFFParse)
  22
  23 /*  FUNCTION
  24         Read a number of bytes from the current chunk into a buffer.
  25         Attempts to read past the end of the chunk will be truncated.
  26
  27     INPUTS
  28         iff      - pointer to IFFHandle struct.
  29         buf      -  pointer to a buffer into which the data will be placed.
  30         numBtes  - number of bytes to read.
  31
  32     RESULT
  33         actual -   (positive) the actual number of bytes read.
  34                   (negative) IFFERR_#? error code if not succesfull.
  35
  36     NOTES
  37
  38     EXAMPLE
  39
  40     BUGS
  41
  42     SEE ALSO
  43         ReadChunkRecords(), ParseIFF(), WriteChunkBytes()
  44
  45     INTERNALS
  46
  47 *****************************************************************************/
  48 {
  49     AROS_LIBFUNC_INIT
  50
  51     struct ContextNode *cn;
  52
  53     LONG   lefttoread,
  54           bytesread;
  55
  56     DEBUG_READCHUNKBYTES(dprintf("ReadChunkBytes: iff %p buf %p bytes %ld\n",
  57                                  iff, buf, numBytes));
  58
  59     /* Get pointer to current contextnode */
  60     cn = TopChunk(iff);
  61
  62     lefttoread = cn->cn_Size - cn->cn_Scan;
  63
  64     /* If numBytes > lefttoread then we must truncate the readoperation */
  65     if (numBytes > lefttoread)
  66         numBytes = lefttoread;
  67
  68     DEBUG_READCHUNKBYTES(dprintf("ReadChunkBytes: cn %p cn_Size %ld cn_Scan %ld numBytes %ld\n",
  69                                  cn, cn->cn_Size, cn->cn_Scan, numBytes));
  70
  71     bytesread = ReadStream
  72     (
  73         iff,
  74         buf,
  75         numBytes,
  76         IPB(IFFParseBase)
  77     );
  78
  79     /* No error */
  80     if (bytesread > 0)
  81         cn->cn_Scan += bytesread;
  82
  83     DEBUG_READCHUNKBYTES(dprintf("ReadChunkBytes: return %ld\n", bytesread));
  84
  85     /* Return number of bytes actually read  (or error )*/
  86     return (bytesread);
  87
  88     AROS_LIBFUNC_EXIT
  89 } /* ReadChunkBytes */