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From: "Jason Winter" <jasonwinter AT hotmail DOT com>
To: cygwin AT cygwin DOT com
Subject: Fix for : read()
Date: Tue, 02 Mar 2004 01:38:16 +0000
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X-OriginalArrivalTime: 02 Mar 2004 01:38:16.0824 (UTC) FILETIME=[08ECAF80:01C3FFF7]

Hi Corinna,

(For continued reference:)
>The Tape Block Length information is in MSDN, within the document Q161338 
>in the
>knowledge base.

The CygWin read() function calls ReadFile() repeatedly while the programmers 
read buffer-length parameter value "#of bytes" hasn't been read from the 
handle.  Under Unix, low-level IO read() doesn't always return 100 bytes in 
this call:

rc = read (h, buf, 100);

In fact, if h refers to a tape, which also has a vaiable-block of data ready 
to be read at the current tape position..  You may only get, say, 80 bytes 
returned if it's a 80 byte block record.  In CygWin, since it continues to 
call ReadFile() in the cygwin1.dll read() function, the programmer, me 
actually, loses all record of the tapes original data-block-length - with 
CygWin read() you might think the block was 100 bytes long - having started 
to read the next block on the tape.  (20 bytes of it in this example.)

Jason.

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