On Sun, 2004-12-19 at 23:43, Jp Calderone wrote: > On Sun, 19 Dec 2004 23:12:27 -0500, Adam DePrince <[EMAIL PROTECTED]> wrote: > > [snip] > > > > Of course, to take advantage of this requires that writev be exposed. I > > have an implementation of writev. This implementation is reasonably > > smart, it "unrolls" only so as many iteration.next calls as necessary to > > fill the pointer list for the next invocation of writev. Of course, on > > many systems (Linux, BSD) writev's limit is 1024 items, so to > > accommodate users who don't want to peel off and hold in memory 1024 > > iteration.next()'s, you can set an optional parameter to a smaller > > value. > > > > I'm not sure where to take this as a "next step." It seems too small a > > change for a PEP. Any ideas? > > > > You can download the patch from > > http://deprince.net/software/writev/index.html > > > > writev() in the standard library would be nice. I have an > implementation too ;) I wonder how many other people do as > well. > > Regarding the implementation, just one part confuses me. > What's the idea behind this check at the beginning of the > iterator unrolling loop? > > + if ( !PyObject_CheckReadBuffer( buf ) ) > + continue; > > Is it me, or is that silently ignoring bad input? > > Other miscellaneous feedback: > > The use of alloca() isn't common in CPython. PyMem_Malloc > is probably what you want to be calling. At the very least, > alloca()'s return value should be checked to be sure it is > non-NULL. If you switch to PyMem_Malloc, you'll have to be > sure to free the memory, of course. > > The support of iterators is a cool idea, but I'm not sure > it is actually useful. Consider the case where not all bytes > are written. How is an application supposed to handle writing > the rest of the bytes, if they have been consumed from an > iterator? Hopefully I'm missing the obvious answer, because > supporting arbitrary iterators would be cool, but it seems like > only sequences can really be usefully supported. >
Fixed this. The return value is a tuple of bytes written and a tuple of stuff that didn't get shipped. And yes, the first element is replaced with a string that represents the fraction of that element that didn't get sent. Here is simple sample code that illustrates how this works. data = [ .... lots of little strings in this list ... ] data = iter( data ) import itertools import writev while 1: (count, leftovers ) = writev.writev( fd, data ) if leftovers == None: break data = itertools.chain( iter( leftovers ), data ) ... Of course, our loop would in a real example be controlled by a select. In this naive example we would want to sleep ... Adam DePrince -- http://mail.python.org/mailman/listinfo/python-list
