Hi René,
On Sun, 7 Aug 2022, René Scharfe wrote:
> Am 05.08.2022 um 17:36 schrieb Jeff King:
> > On Wed, Aug 03, 2022 at 11:56:13PM +0200, René Scharfe wrote:
> > >> int enable_nonblock(int fd)
> >> {
> >> + DWORD mode;
> >> + HANDLE handle = winansi_get_osfhandle(fd);
> >> + if (!handle)
> >> + return -1;
> >> + if (!GetNamedPipeHandleState(handle, &mode, NULL, NULL, NULL, NULL, 0))
> >> + return -1;
> >> + if (mode & PIPE_NOWAIT)
> >> + return 0;
> >> + mode |= PIPE_NOWAIT;
> >> + if (!SetNamedPipeHandleState(handle, &mode, NULL, NULL))
> >> + return -1;
> >> return 0;
> >> }
> >
> > This looks plausibly correct to me. ;) We might want to change the name
> > of the compat layer to enable_pipe_nonblock(), since one assumes from
> > the function names this only works for pipes.
>
> Or how about this? Squashable. Needs testing.
>
> --- >8 ---
> Subject: [PATCH] nonblock: support Windows
>
> Implement enable_nonblock() using the Windows API. Supports only named
> and anonymous pipes for now, which suffices for the current caller.
>
> Signed-off-by: René Scharfe <l.s.r@xxxxxx>
> ---
> compat/nonblock.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/compat/nonblock.c b/compat/nonblock.c
> index 897c099010..78923cd2c3 100644
> --- a/compat/nonblock.c
> +++ b/compat/nonblock.c
> @@ -14,9 +14,40 @@ int enable_nonblock(int fd)
>
> #else
>
> +#ifdef GIT_WINDOWS_NATIVE
Maybe use an `#elif defined(GIT_WINDOWS_NATIVE)` here? That would make the
code structures clearer, methinks.
> +
> +#include "win32.h"
> +
> +int enable_nonblock(int fd)
> +{
> + HANDLE h = (HANDLE)_get_osfhandle(fd);
> + DWORD mode;
> + DWORD type = GetFileType(h);
> + if (type == FILE_TYPE_UNKNOWN && GetLastError() != NO_ERROR) {
> + errno = EBADF;
> + return -1;
> + }
> + if (type != FILE_TYPE_PIPE)
> + BUG("unsupported file type: %lu", type);
> + if (!GetNamedPipeHandleState(h, &mode, NULL, NULL, NULL, NULL, 0)) {
> + errno = err_win_to_posix(GetLastError());
> + return -1;
> + }
> + mode |= PIPE_NOWAIT;
> + if (!SetNamedPipeHandleState(h, &mode, NULL, NULL)) {
Nice.
FWIW the documentation of `PIPE_NOWAIT` says:
Note that nonblocking mode is supported for compatibility with
Microsoft LAN Manager version 2.0 and should not be used to
achieve asynchronous input and output (I/O) with named pipes.
(see
https://docs.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-setnamedpipehandlestate
for full details)
There is little more information to be found on the interwebs, the closest
to an in-depth explanation is here:
https://devblogs.microsoft.com/oldnewthing/20110114-00/?p=11753
Even if that comment suggests that this mode is deprecated, I think it is
safe to rely on it in Git's source code.
Thanks,
Dscho
> + errno = err_win_to_posix(GetLastError());
> + return -1;
> + }
> + return 0;
> +}
> +
> +#else
> +
> int enable_nonblock(int fd)
> {
> return 0;
> }
>
> #endif
> +
> +#endif
> --
> 2.37.1.windows.1
>
