[Python-Dev] fileobj.read(float): warning or error?

[Jesus Cea]

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Isaac Morland wrote:
> On Tue, 2 Sep 2008, Jesus Cea wrote:
> 
>>> Indeed. read(0) is quite often generated as an edge case when one is
>>> computing buffer sizes, and returning an empty string is most
>>> definitely the right thing to do here (otherwise some application code
>>> becomes more complex by having to avoid calling read(0) at all).
>>
>> How do you differenciate between that empty string (when doing
>> "read(0)"), from EOF (that is signaled by an empty string)?.
> 
> Why would you expect a difference between reading 0 bytes at EOF and
> reading 0 bytes anywhere else?  If you read(4) when at offset 996 in a
> 1000-byte file I doubt you expect any special notification that you are
> now at EOF.

My message was an answer to Guido one, saying that some programs
calculate the read len substracting buffer lengths, so, then can try to
read 0 bytes. Guido argues that returning a empty string is the way to go.

My point is: we are simplifying the program considering "0" a valid len
counter, but we complicates it because now the code can't consider "" =
EOF if it actually asked for 0 bytes.

> The Unix read() system call doesn't treat EOF as special other than it
> won't return bytes from "beyond" EOF and therefore even when reading a
> regular file could return fewer (including 0) bytes than asked for in
> the call.

I always consider ""==EOF. I thought that was correct for non-blocking
sockets. Am I wrong?.

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