Support handing off socket write permission to external code.

Libraries like Xlib, some XCB language bindings, and potentially others
have a common problem: they want to share the X connection with XCB. This
requires coordination of request sequence numbers.  Previously, XCB had an
Xlib-specific lock, and allowed Xlib to block XCB from making requests.
Now we've replaced that lock with a handoff mechanism, xcb_take_socket,
allowing external code to ask XCB for permission to take over the write
side of the socket and send raw data with xcb_writev.  The caller of
xcb_take_socket must supply a callback which XCB can call when it wants
the write side of the socket back to make a request.  This callback
synchronizes with the external socket owner, flushes any output queues if
appropriate, and then returns the sequence number of the last request sent
over the socket.

Commit by Josh Triplett and Jamey Sharp.
Handoff mechanism inspired by Keith Packard.

1 files changed, 14 insertions, 1 deletions

diff --git a/src/xcbint.h b/src/xcbint.h
index 8c6bcaa..dac0a61 100644
--- a/src/xcbint.h
+++ b/src/xcbint.h
@@ -40,7 +40,8 @@
 
 enum workarounds {
     WORKAROUND_NONE,
-    WORKAROUND_GLX_GET_FB_CONFIGS_BUG
+    WORKAROUND_GLX_GET_FB_CONFIGS_BUG,
+    WORKAROUND_EXTERNAL_SOCKET_OWNER
 };
 
 enum lazy_reply_tag
@@ -55,6 +56,12 @@ enum lazy_reply_tag
 #define XCB_SEQUENCE_COMPARE(a,op,b)	((int64_t) ((a) - (b)) op 0)
 #define XCB_SEQUENCE_COMPARE_32(a,op,b)	(((int) (a) - (int) (b)) op 0)
 
+#ifndef offsetof
+#define offsetof(type,member) ((size_t) &((type *)0)->member)
+#endif
+
+#define container_of(pointer,type,member) ((type *)(((char *)(pointer)) - offsetof(type, member)))
+
 /* xcb_list.c */
 
 typedef void (*xcb_list_free_func_t)(void *);
@@ -73,6 +80,11 @@ typedef struct _xcb_out {
     pthread_cond_t cond;
     int writing;
 
+    pthread_cond_t socket_cond;
+    void (*return_socket)(void *closure);
+    void *socket_closure;
+    int socket_moving;
+
     char queue[XCB_QUEUE_BUFFER_SIZE];
     int queue_len;
 
@@ -122,6 +134,7 @@ int _xcb_in_init(_xcb_in *in);
 void _xcb_in_destroy(_xcb_in *in);
 
 int _xcb_in_expect_reply(xcb_connection_t *c, uint64_t request, enum workarounds workaround, int flags);
+void _xcb_in_replies_done(xcb_connection_t *c);
 
 int _xcb_in_read(xcb_connection_t *c);
 int _xcb_in_read_block(xcb_connection_t *c, void *buf, int nread);