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Date: Thu, 11 Oct 2012 09:58:49 +0200
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Subject: Re: [PHP-DEV] =?UTF-8?Q?stream=5Fget=5Fline=20behaviour=20Bug=20?=
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From: glopes@nebm.ist.utl.pt (Gustavo Lopes)

Em 2012-10-10 15:52, Tjerk Meesters escreveu:
> Sent from my iPhone
>
> On 10 Oct, 2012, at 6:39 PM, Nicolai Scheer 
> <nicolai.scheer@gmail.com> wrote:
>
>> Hi again!
>>
>> Thanks for your help an comments on the issue.
>>
>> cataphract commented on the stream_get_line behaviour (returning 
>> false
>> when used on an empty file) on the bug report page.
>> I do agree that reading on an empty file can be considered an error
>> thus returning false, because there's nothing to read.
>>
>> Unfortunately, and that's why we stumbled upon this in the first
>> place, feof does not return true when opening an empty file.
>> I did not have a look at the internals, but my guess is that feof 
>> just
>> does not return true because no one did a read on the file handle 
>> yet.
>> To my mind if would be sensible to return true using feof on an 
>> empty
>> file, so that one does not actually try a read...
>
> That wouldn't be right. Technically the EOF should be discovered, not
> deduced from other information like stat(). Also, some streams don't
> support reporting an appropriate size.
>
>>
>> What do you think?

I second what Mr. Meesters has said. The end-of-file indicator should 
be discovered. That's how stdio works, which is what PHP's function is 
modeled after. There's nothing wrong about the indicator being set in a 
read call that returned no data, be it because the file is empty or 
because the read before just happened to read all the data left.

Before some recent bug fixes, the successive return values would depend 
somewhat on chance. bool(false) would only be returned after the 
end-of-file had been discovered. So if the last read had read all the 
data but had not found eof, then the next call would return an empty 
string. But if it had (the most common scenario), it would return false. 
This ambiguity, which is problematic mostly because stream_get_line() 
strips off the delimiter, has been eliminated. The only one left is that 
you cannot tell whether the input stream ends with the delimiter or not:

$ php -r '$fd = fopen("php://temp", "r+"); fwrite($fd, "aa"); 
rewind($fd); var_dump(stream_get_line($fd, 10, "MM"), 
stream_get_line($fd, 10, "MM"));'
string(2) "aa"
bool(false)
$ php -r '$fd = fopen("php://temp", "r+"); fwrite($fd, "aaMM"); 
rewind($fd); var_dump(stream_get_line($fd, 10, "MM"), 
stream_get_line($fd, 10, "MM"));'
string(2) "aa"
bool(false)


Finally, what I suggest is that use stream_get_line() in the same way 
that's recommended for fgets():

     while (($buffer = stream_get_line($handle, 8192, "MM")) !== false) 
{
         if (strlen($buffer) == 8192) {
             //You may consider this an error
         }
         echo $buffer;
     }

If you're using non-blocking sockets, stream_get_line() may return 
false temporarily. In those cases, you may want to do something like:

     //stream_get_line() will return false if the stream is temporarily 
out
     //of data, even if there's some data buffered, as long that 
buffered data
     //is less than the maxsize you specify and it doesn't contain the 
delimiter
     do {
         //call stream_select() here to wait to for data
         while (($buffer = stream_get_line($handle, 8192, "MM")) !== 
false) {
             if (strlen($buffer) == 8192) {
                 //You may consider this an error
             }
             echo $buffer;
         }
     } while (!feof($handle))


-- 
Gustavo Lopes