Re: Re: [PATCH/RFC] send-pack.c: Allow to disable side-band-64k

[Erik Faye-Lund <kusmabite@gmail.com>]

On Mon, May 19, 2014 at 10:00 PM, Erik Faye-Lund <kusmabite@gmail.com> wrote:
> On Mon, May 19, 2014 at 9:33 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
>> Hi,
>>
>> Thomas Braun wrote:
>>
>>> pushing over the dump git protocol with a windows git client.
>>
>> I've never heard of the dump git protocol.  Do you mean the git
>> protocol that's used with git:// URLs?
>>
>> [...]
>>> Alternative approaches considered but deemed too invasive:
>>> - Rewrite read/write wrappers in mingw.c in order to distinguish between
>>>   a file descriptor which has a socket behind and a file descriptor
>>>   which has a file behind.
>>
>> I assume here "too invasive" means "too much engineering effort"?
>>
>> It sounds like a clean fix, not too invasive at all.  But I can
>> understand wanting a stopgap in the meantime.
>>
>
> Yeah, now that the problem seems to be understood, I don't think that
> would be too bad. I recently killed off our previous write()-wrapper
> in c9df6f4, but I see no reason why we can't add a new one.
>
> Would we need to wrap both ends, shouldn't wrapping only reading be
> good enough to prevent deadlocking?
>
> compat/poll/poll.c already contains a function called IsSocketHandle
> that is able to tell if a HANDLE points to a socket or not.

This very quick attempt did not work out :(

diff --git a/compat/mingw.c b/compat/mingw.c
index 0335958..ec1d81f 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -370,6 +370,65 @@ int mingw_open (const char *filename, int oflags, ...)
     return fd;
 }

+#define is_console_handle(h) (((long) (h) & 3) == 3)
+
+static int is_socket_handle(HANDLE h)
+{
+    WSANETWORKEVENTS ev;
+
+    if (is_console_handle(h))
+        return 0;
+
+    /*
+     * Under Wine, it seems that getsockopt returns 0 for pipes too.
+     * WSAEnumNetworkEvents instead distinguishes the two correctly.
+     */
+    ev.lNetworkEvents = 0xDEADBEEF;
+    WSAEnumNetworkEvents((SOCKET) h, NULL, &ev);
+    return ev.lNetworkEvents != 0xDEADBEEF;
+}
+
+#undef read
+ssize_t mingw_read(int fd, void *buf, size_t count)
+{
+    int ret;
+    HANDLE fh = (HANDLE)_get_osfhandle(fd);
+
+    if (fh == INVALID_HANDLE_VALUE) {
+        errno = EBADF;
+        return -1;
+    }
+
+    if (!is_socket_handle(fh))
+        return read(fd, buf, count);
+
+    ret = recv((SOCKET)fh, buf, count, 0);
+    if (ret < 0)
+        errno = WSAGetLastError();
+    return ret;
+}
+
+#undef write
+ssize_t mingw_write(int fd, const void *buf, size_t count)
+{
+    int ret;
+    HANDLE fh = (HANDLE)_get_osfhandle(fd);
+
+    if (fh == INVALID_HANDLE_VALUE) {
+        errno = EBADF;
+        return -1;
+    }
+
+    if (!is_socket_handle(fh))
+        return write(fd, buf, count);
+
+    return send((SOCKET)fh, buf, count, 0);
+    if (ret < 0)
+        errno = WSAGetLastError();
+    return ret;
+}
+
+
 static BOOL WINAPI ctrl_ignore(DWORD type)
 {
     return TRUE;
diff --git a/compat/mingw.h b/compat/mingw.h
index 08b83fe..1690098 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -177,6 +177,12 @@ int mingw_rmdir(const char *path);
 int mingw_open (const char *filename, int oflags, ...);
 #define open mingw_open

+ssize_t mingw_read(int fd, void *buf, size_t count);
+#define read mingw_read
+
+ssize_t mingw_write(int fd, const void *buf, size_t count);
+#define write mingw_write
+
 int mingw_fgetc(FILE *stream);
 #define fgetc mingw_fgetc

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