workbench/libs/asyncio/src/PeekAsync.c

   1 #include "async.h"
   2
   3
   4 _LIBCALL LONG
   5 PeekAsync( _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
  11         /* Try to fill a new buffer, if needed */
  12         if( !file->af_BytesLeft )
  13         {
  14                 LONG    bytes;
  15
  16                 if( ( bytes = ReadAsync( file, &bytes, 1 ) ) <= 0 )
  17                 {
  18                         return( bytes );
  19                 }
  20
  21                 /* Unread byte */
  22                 --file->af_Offset;
  23                 ++file->af_BytesLeft;
  24         }
  25
  26         /* Copy what we can */
  27         numBytes = MIN( numBytes, file->af_BytesLeft );
  28         CopyMem( file->af_Offset, buffer, numBytes );
  29         return( numBytes );
  30 }