Re: [PATCH 09/19] index-helper: add Windows support

[Johannes Schindelin]

Hi Duy,

On Wed, 16 Mar 2016, Duy Nguyen wrote:

> I think it's safe to drop this patch now. It's mostly to prove that it
> could work on Windows. But I don't think it's tested a lot (even I
> only occasionally test it under wine).

I agree that it is more important to get the basics right (such as:
concurrent access, elegant interface to watchman, pluggable backends
different than watchman, support for *other* Git clients modifying the
index under index-helper's feet, etc).

We will try to keep the Windows end going at the same time.

Please note that there is one very important difference between Windows vs
Linux when it comes to shared memory: on Windows, the memory is released
as soon as the last user goes away.

Ciao,
Dscho
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Re: [PATCH 09/19] index-helper: add Windows support

[Duy Nguyen]

I think it's safe to drop this patch now. It's mostly to prove that it
could work on Windows. But I don't think it's tested a lot (even I
only occasionally test it under wine).

On Thu, Mar 10, 2016 at 1:36 AM, David Turner  wrote:
> From: Nguyễn Thái Ngọc Duy 
>
> Windows supports shared memory, but the semantics is a bit different
> than POSIX shm. The most noticeable thing is there's no way to get the
> shared memory's size by the reader, and wrapping fstat to do that
> would be hell. So the shm size is added near the end, hidden away from
> shm users (storing it in headers would cause more problems with munmap,
> storing it as a separate shm is even worse).
>
> PostMessage is used instead of UNIX signals for
> notification. Lightweight (at least code-wise) on the client side.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy 
> ---
>  config.mak.uname |  2 ++
>  index-helper.c   | 48 
>  read-cache.c | 13 
>  shm.c| 96 
> 
>  4 files changed, 159 insertions(+)
>
> diff --git a/config.mak.uname b/config.mak.uname
> index b5108e1..49320c7 100644
> --- a/config.mak.uname
> +++ b/config.mak.uname
> @@ -394,6 +394,7 @@ ifndef DEBUG
>  else
> BASIC_CFLAGS += -Zi -MDd
>  endif
> +   PROGRAM_OBJS += index-helper.o
> X = .exe
>  endif
>  ifeq ($(uname_S),Interix)
> @@ -574,6 +575,7 @@ else
> NO_CURL = YesPlease
> endif
>  endif
> +   PROGRAM_OBJS += index-helper.o
>  endif
>  ifeq ($(uname_S),QNX)
> COMPAT_CFLAGS += -DSA_RESTART=0
> diff --git a/index-helper.c b/index-helper.c
> index 4dd9656..cf26da7 100644
> --- a/index-helper.c
> +++ b/index-helper.c
> @@ -155,6 +155,51 @@ static void loop(const char *pid_file, int 
> idle_in_seconds)
> ; /* do nothing, all is handled by signal handlers already */
>  }
>
> +#elif defined(GIT_WINDOWS_NATIVE)
> +
> +static void loop(const char *pid_file, int idle_in_seconds)
> +{
> +   HWND hwnd;
> +   UINT_PTR timer = 0;
> +   MSG msg;
> +   HINSTANCE hinst = GetModuleHandle(NULL);
> +   WNDCLASS wc;
> +
> +   /*
> +* Emulate UNIX signals by sending WM_USER+x to a
> +* window. Register window class and create a new window to
> +* catch these messages.
> +*/
> +   memset(, 0, sizeof(wc));
> +   wc.lpfnWndProc   = DefWindowProc;
> +   wc.hInstance = hinst;
> +   wc.lpszClassName = "git-index-helper";
> +   if (!RegisterClass())
> +   die_errno(_("could not register new window class"));
> +
> +   hwnd = CreateWindow("git-index-helper", pid_file,
> +   0, 0, 0, 1, 1, NULL, NULL, hinst, NULL);
> +   if (!hwnd)
> +   die_errno(_("could not register new window"));
> +
> +   refresh(0);
> +   while (1) {
> +   timer = SetTimer(hwnd, timer, idle_in_seconds * 1000, NULL);
> +   if (!timer)
> +   die(_("no timer!"));
> +   if (!GetMessage(, hwnd, 0, 0) || msg.message == WM_TIMER)
> +   break;
> +   switch (msg.message) {
> +   case WM_USER:
> +   refresh(0);
> +   break;
> +   default:
> +   /* just reset the timer */
> +   break;
> +   }
> +   }
> +}
> +
>  #else
>
>  static void loop(const char *pid_file, int idle_in_seconds)
> @@ -198,6 +243,9 @@ int main(int argc, char **argv)
> fd = hold_lock_file_for_update(,
>git_path("index-helper.pid"),
>LOCK_DIE_ON_ERROR);
> +#ifdef GIT_WINDOWS_NATIVE
> +   strbuf_addstr(, "HWND");
> +#endif
> strbuf_addf(, "%" PRIuMAX, (uintmax_t) getpid());
> write_in_full(fd, sb.buf, sb.len);
> commit_lock_file();
> diff --git a/read-cache.c b/read-cache.c
> index 1a0ab0c..16fbdf6 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -1546,6 +1546,18 @@ static void post_read_index_from(struct index_state 
> *istate)
> tweak_untracked_cache(istate);
>  }
>
> +#if defined(GIT_WINDOWS_NATIVE)
> +static void do_poke(struct strbuf *sb, int refresh_cache)
> +{
> +   HWND hwnd;
> +   if (!starts_with(sb->buf, "HWND"))
> +   return;
> +   hwnd = FindWindow("git-index-helper", sb->buf);
> +   if (!hwnd)
> +   return;
> +   PostMessage(hwnd, refresh_cache ? WM_USER : WM_USER + 1, 0, 0);
> +}
> +#else
>  static void do_poke(struct strbuf *sb, int refresh_cache)
>  {
> char*start = sb->buf;
> @@ -1555,6 +1567,7 @@ static void do_poke(struct strbuf *sb, int 
> refresh_cache)
> return;
> kill(pid, refresh_cache ? SIGHUP : SIGUSR1);
>  }
> +#endif
>
>  static void poke_daemon(struct index_state 

Re: [PATCH 09/19] index-helper: add Windows support

[Duy Nguyen]

On Thu, Mar 17, 2016 at 7:18 PM, Johannes Schindelin
 wrote:
> Please note that there is one very important difference between Windows vs
> Linux when it comes to shared memory: on Windows, the memory is released
> as soon as the last user goes away.

I assume that can be taken care of without changing anything else
fundamentally, or you need to tell us now. I guess that by making
index-helper hold the shared memory all the time, we can avoid that.
You may also want to check if my solution for the lack of ftruncate on
Windows shm is correct.
-- 
Duy
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