Re: [Caml-list] Unix.single_write, doc and atomicity

["Török Edwin" <edwin+ml-ocaml@etorok.net>]

On 06/06/2012 04:06 PM, rixed@happyleptic.org wrote:
> I was reading the code for unix_single_write recently, and noticed two strange
> things that I prefer to discuss here before filling the bug tracker with
> dubious tickets.
> 
> First, the doc of Unix.single_write claims that this function "attemps to write
> only once", although the underlying unix_single_write C function clearly loops
> around a write if the buffer being written is larger than the internal buffer
> (16K).

Are we looking at the same file / function?
The one that loops is unix_write, I don't see any loops in unix_single_write:

CAMLprim value unix_single_write(value fd, value buf, value vofs, value vlen)
{
  long ofs, len;
  int numbytes, ret;
  char iobuf[UNIX_BUFFER_SIZE];

  Begin_root (buf);
    ofs = Long_val(vofs);
    len = Long_val(vlen);
    ret = 0;
    if (len > 0) {
      numbytes = len > UNIX_BUFFER_SIZE ? UNIX_BUFFER_SIZE : len;
      memmove (iobuf, &Byte(buf, ofs), numbytes);
      enter_blocking_section();
      ret = write(Int_val(fd), iobuf, numbytes);
      leave_blocking_section();
      if (ret == -1) uerror("single_write", Nothing);
    }
  End_roots();
  return Val_int(ret);


> 
> So this boils down to : unix_single_write really should perform a single write!

AFAICT it does only a single write.

Best regards,
--Edwin