workbench/libs/asyncio/src/ReadAsync.c

   1 #include "async.h"
   2
   3
   4 _LIBCALL LONG
   5 ReadAsync( _REG( a0 ) AsyncFile *file, _REG( a1 ) APTR buffer, _REG( d0 ) LONG numBytes )
   6 {
   7 #ifdef ASIO_NOEXTERNALS
   8         struct ExecBase *SysBase = file->af_SysBase;
   9 #endif
  10         LONG totalBytes = 0;
  11         LONG bytesArrived;
  12
  13         /* if we need more bytes than there are in the current buffer, enter the
  14          * read loop
  15          */
  16
  17         while( numBytes > file->af_BytesLeft )
  18         {
  19                 /* drain buffer */
  20                 CopyMem( file->af_Offset, buffer, file->af_BytesLeft );
  21
  22                 numBytes                -= file->af_BytesLeft;
  23                 buffer                  =  ( APTR ) ( ( ULONG ) buffer + file->af_BytesLeft );
  24                 totalBytes              += file->af_BytesLeft;
  25                 file->af_BytesLeft      =  0;
  26
  27                 bytesArrived = AS_WaitPacket( file );
  28
  29                 if( bytesArrived <= 0 )
  30                 {
  31                         if( bytesArrived == 0 )
  32                         {
  33                                 return( totalBytes );
  34                         }
  35
  36                         return( -1 );
  37                 }
  38
  39                 /* ask that the buffer be filled */
  40                 AS_SendPacket( file, file->af_Buffers[ 1 - file->af_CurrentBuf ] );
  41
  42                 /* in case we tried to seek past EOF */
  43                 if( file->af_SeekOffset > bytesArrived )
  44                 {
  45                         file->af_SeekOffset = bytesArrived;
  46                 }
  47
  48                 file->af_Offset         = file->af_Buffers[ file->af_CurrentBuf ] + file->af_SeekOffset;
  49                 file->af_CurrentBuf     = 1 - file->af_CurrentBuf;
  50                 file->af_BytesLeft      = bytesArrived - file->af_SeekOffset;
  51                 file->af_SeekOffset     = 0;
  52         }
  53
  54         CopyMem( file->af_Offset, buffer, numBytes );
  55         file->af_BytesLeft      -= numBytes;
  56         file->af_Offset         += numBytes;
  57
  58         return( totalBytes + numBytes );
  59 }