From f75eb0307c989890c72ca4cbbe69ce06022a8cef Mon Sep 17 00:00:00 2001
From: Sandro Santilli <strk@keybit.net>
Date: Tue, 21 Oct 2014 10:08:54 +0000
Subject: [PATCH] Add interruptability API to liblwgeom

git-svn-id: http://svn.osgeo.org/postgis/trunk@13099 b70326c6-7e19-0410-871a-916f4a2858ee
---
 NEWS                           |  1 +
 liblwgeom/liblwgeom.h.in       | 27 +++++++++++++++++++++++++++
 liblwgeom/liblwgeom_internal.h | 13 +++++++++++++
 liblwgeom/lwgeom_api.c         | 12 ++++++++++++
 postgis/postgis_module.c       | 10 +++++-----
 5 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/NEWS b/NEWS
index 4b35d1127..060831111 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,7 @@ PostGIS 2.2.0
 
  * New Features *
 
+  - Interruptibility API for liblwgeom (Sandro Santilli / CartoDB)
   - #2939, ST_ClipByBox2D (Sandro Santilli / CartoDB)
   - #2247, ST_Retile and ST_CreateOverview: in-db raster overviews creation
            (Sandro Santilli / Vizzuality)
diff --git a/liblwgeom/liblwgeom.h.in b/liblwgeom/liblwgeom.h.in
index 68233070b..f3da1c473 100644
--- a/liblwgeom/liblwgeom.h.in
+++ b/liblwgeom/liblwgeom.h.in
@@ -189,6 +189,33 @@ extern void lwgeom_set_handlers(lwallocator allocator,
         lwreallocator reallocator, lwfreeor freeor, lwreporter errorreporter,
         lwreporter noticereporter);
 
+/**
+ * Request interruption of any running code
+ *
+ * Safe for use from signal handlers
+ *
+ * Interrupted code will (as soon as it finds out
+ * to be interrupted) cleanup and return as soon as possible.
+ *
+ * The return value from interrupted code is undefined,
+ * it is the caller responsibility to not take it in consideration.
+ * 
+ */
+extern void lwgeom_request_interrupt(void);
+
+/**
+ * Install a callback to be called periodically during
+ * algorithm execution. Mostly only needed on WIN32 to
+ * dispatch queued signals.
+ *
+ * The callback is invoked before checking for interrupt
+ * being requested, so you can request interruption from
+ * the callback, if you want (see lwgeom_request_interrupt).
+ *
+ */
+typedef void (lwinterrupt_callback)();
+extern lwinterrupt_callback *lwgeom_register_interrupt_callback(lwinterrupt_callback *);
+
 /**
  * Write a notice out to the notice handler.
  *
diff --git a/liblwgeom/liblwgeom_internal.h b/liblwgeom/liblwgeom_internal.h
index 61a747cd5..77eb6dcb4 100644
--- a/liblwgeom/liblwgeom_internal.h
+++ b/liblwgeom/liblwgeom_internal.h
@@ -405,4 +405,17 @@ extern void trim_trailing_zeros(char *num);
 
 extern uint8_t MULTITYPE[NUMTYPES];
 
+extern lwinterrupt_callback *_lwgeom_interrupt_callback;
+extern int _lwgeom_interrupt_requested;
+#define LW_ON_INTERRUPT(x) { \
+  if ( _lwgeom_interrupt_callback ) { \
+    (*_lwgeom_interrupt_callback)(); \
+  } \
+  if ( _lwgeom_interrupt_requested ) { \
+    _lwgeom_interrupt_requested = 0; \
+    lwnotice("liblwgeom code interrupted"); \
+    x; \
+  } \
+}
+
 #endif /* _LIBLWGEOM_INTERNAL_H */
diff --git a/liblwgeom/lwgeom_api.c b/liblwgeom/lwgeom_api.c
index 3323e0949..7ae2a9c75 100644
--- a/liblwgeom/lwgeom_api.c
+++ b/liblwgeom/lwgeom_api.c
@@ -762,4 +762,16 @@ interpolate_point4d(POINT4D *A, POINT4D *B, POINT4D *I, double F)
 }
 
 
+int _lwgeom_interrupt_requested = 0;
+void
+lwgeom_request_interrupt() {
+  _lwgeom_interrupt_requested = 1;
+}
 
+lwinterrupt_callback *_lwgeom_interrupt_callback = 0;
+lwinterrupt_callback *
+lwgeom_register_interrupt_callback(lwinterrupt_callback *cb) {
+  lwinterrupt_callback *old = _lwgeom_interrupt_callback;
+  _lwgeom_interrupt_callback = cb;
+  return old;
+}
diff --git a/postgis/postgis_module.c b/postgis/postgis_module.c
index cefb7d408..c787e39d1 100644
--- a/postgis/postgis_module.c
+++ b/postgis/postgis_module.c
@@ -32,13 +32,11 @@ static pqsigfunc coreIntHandler = 0;
 static void handleInterrupt(int sig);
 
 #ifdef WIN32
-#if POSTGIS_GEOS_VERSION >= 34 
-static void geosInterruptCallback() {
+static void interruptCallback() {
   if (UNBLOCKED_SIGNAL_QUEUE()) 
     pgwin32_dispatch_queued_signals(); 
 }
 #endif
-#endif
 
 /*
  * Module load callback
@@ -52,8 +50,9 @@ _PG_init(void)
 
 #ifdef WIN32
 #if POSTGIS_GEOS_VERSION >= 34 
-  GEOS_interruptRegisterCallback(geosInterruptCallback);
+  GEOS_interruptRegisterCallback(interruptCallback);
 #endif
+  lwgeom_register_interrupt_callback(interruptCallback);
 #endif
 
 #if 0
@@ -120,7 +119,8 @@ handleInterrupt(int sig)
   GEOS_interruptRequest();
 #endif
 
-  /* TODO: request interruption of liblwgeom as well ? */
+  /* request interruption of liblwgeom as well */
+  lwgeom_request_interrupt();
 
   if ( coreIntHandler ) {
     (*coreIntHandler)(sig);
-- 
2.50.1