//
//  ************************************************************************
//              Demonstration of how DosRead works with pipes.
//    (c) Copyright 1996 Jonathan de Boyne Pollard.  All rights reserved.
//  ************************************************************************
//

//
//  Permission is hereby granted to post, steal, and abuse this source for
//  your own purposes and to your heart's content as long as you understand
//  that I take no responsibility whatsoever for what it may do to your
//  machine, data, cat, or marital status.
//

#define INCL_BASE
#include 
#include 
#include 

//
//  This program demonstrates what appears to be a common misconception
//  with pipes.  The misconception is that DosRead will block indefinitely
//  until the read buffer is completely full.  This is not true.  DosRead
//  will empty the pipe's data buffer, and return immediately.  Only if
//  there are no data at all will DosRead block.  This is because a count
//  of zero bytes does *not* mean a partial buffer with zero bytes in it.
//  It has the special meaning that the write end of the pipe has been
//  closed.
//

static HFILE ReadHandle, WriteHandle ;

static
void
readthread ( void * )
{
    char buffer [1024] ;
    ULONG BytesRead ;
    do {
        DosRead(ReadHandle, buffer, sizeof buffer, &BytesRead) ;
        cout << "\t\t\t\tRead " << BytesRead <<
" bytes." << endl ;
    } while (BytesRead) ;
}

int
main ( int, char ** )
{
    DosCreatePipe(&ReadHandle, &WriteHandle, 256) ;
    cout << hex << "Created pipe, read = " << ReadHandle
         << ", write = " << WriteHandle << dec
<< endl ;
    TID Thread1 = _beginthread(readthread, 0x40000, 0) ;
    char buffer [1024] ;
    ULONG BytesWritten ;
    DosWrite(WriteHandle, buffer, sizeof buffer, &BytesWritten) ;
    cout << "Wrote " << BytesWritten << "
bytes." << endl ;
    DosWrite(WriteHandle, buffer, 1, &BytesWritten) ;
    cout << "Wrote " << BytesWritten << "
bytes." << endl ;
    DosWrite(WriteHandle, buffer, sizeof buffer, &BytesWritten) ;
    cout << "Wrote " << BytesWritten << "
bytes." << endl ;
    DosClose(WriteHandle) ;
    cout << "Closed write handle." << endl ;
    DosWaitThread(&Thread1, DCWW_WAIT) ;
    return 0 ;
}

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