[Python-ideas] Async API: some code to review

[Greg Ewing]

Mark Hackett wrote:

> Is that actually true? It may be guaranteed on Intel x86 compatibles and Linux 
> (because of the string operations available in the x86 instruction set), but I 
> don't thing anything other than an IPC message has a "you can write a string 
> atomically" guarantee. And I may be misremembering that.

It seems to be a POSIX requirement:

  PIPE_BUF
        POSIX.1-2001  says  that  write(2)s of less than PIPE_BUF bytes must be
        atomic: the output  data  is  written  to  the  pipe  as  a  contiguous
        sequence.

(From http://dell9.ma.utexas.edu/cgi-bin/man-cgi?pipe+7)

There's no corresponding guarantee for reading, though. The process
on the other end can't be sure of getting the data from one write()
call in a single read() call. In other words, the write does *not*
establish a record boundary.

-- 
Greg