Add spatial-filter extension in contrib/filter-extensions

See Makefile for build instructions.

contrib/filter-extensions/spatial/Makefile

@@ -0,0 +1,39 @@
+# Run this from the main git directory. That way we inherit useful variables.
+#
+# make FILTER_EXTENSIONS=contrib/filter-extensions/spatial/spatial.a \
+#      LDFLAGS=-lstdc++ \
+#      EXTENSION_LIBS=-lsqlite3
+#
+
+ifneq ($(findstring s,$(MAKEFLAGS)),s)
+ifndef V
+	QUIET_CC       = @echo '   ' CC $@;
+	QUIET_CXX      = @echo '   ' CXX $@;
+	QUIET_AR       = @echo '   ' AR $@;
+endif
+endif
+
+FILTER_STATIC_LIB = spatial.a
+
+FILTER_CFLAGS = -std=c99 -I../../..
+FILTER_CXXFLAGS = -std=c++11
+
+all: $(FILTER_STATIC_LIB)
+ifeq ($(MAKELEVEL),0)
+	$(error "Run via parent git make")
+endif
+	@:
+
+$(FILTER_STATIC_LIB): spatial_filter.o adapter_functions.o
+	$(QUIET_AR)$(AR) $(ARFLAGS) $@ $^
+
+spatial_filter.o: spatial_filter.cpp
+	$(QUIET_CXX)$(CXX) -c $(ALL_CFLAGS) $(FILTER_CFLAGS) $(ALL_CXXFLAGS) $(FILTER_CXXFLAGS) $<
+
+adapter_functions.o: adapter_functions.c
+	$(QUIET_CC)$(CC) -c $(ALL_CFLAGS) $(FILTER_CFLAGS) $<
+
+clean:
+	$(RM) *.a *.o
+
+.PHONY: all clean

contrib/filter-extensions/spatial/adapter_functions.c

@@ -0,0 +1,41 @@
+#include <git-compat-util.h>
+#include <hash.h>
+#include <object.h>
+#include <repository.h>
+#include <trace.h>
+
+#include "adapter_functions.h"
+
+// Allows access to C structs or functions that are defined
+// in C++ incompatible headers.
+
+void sf_trace_printf(const char* format, ...) {
+    static struct trace_key key = TRACE_KEY_INIT(FILTER);
+    struct strbuf buf = STRBUF_INIT;
+    va_list args;
+    va_start(args, format);
+    strbuf_vaddf(&buf, format, args);
+    va_end(args);
+    trace_strbuf(&key, &buf);
+    strbuf_release(&buf);
+}
+
+const struct object_id* sf_obj2oid(const struct object *obj) {
+    return &obj->oid;
+}
+
+const unsigned char* sf_oid2hash(const struct object_id *oid) {
+    return oid->hash;
+}
+
+unsigned sf_obj2type(const struct object *obj) {
+    return obj->type;
+}
+
+const char* sf_repo2gitdir(const struct repository *repo) {
+    return repo->gitdir;
+}
+
+int sf_repo2hashsz(const struct repository *repo) {
+    return repo->hash_algo->rawsz;
+}

contrib/filter-extensions/spatial/adapter_functions.h

@@ -0,0 +1,29 @@
+#ifndef SPATIAL_FILTER_ADAPTER_FUNCTIONS_H
+#define SPATIAL_FILTER_ADAPTER_FUNCTIONS_H
+
+// C++ compatible header that allows access to C structs
+// or functions that are defined in C++ incompatible headers.
+
+// From trace.h
+uint64_t getnanotime(void);
+
+// Delegates to trace_strbuf from trace.h
+void sf_trace_printf(const char* format, ...);
+
+struct object;
+struct object_id;
+
+// Accessors for struct object from object.h
+const struct object_id* sf_obj2oid(const struct object *obj);
+unsigned sf_obj2type(const struct object *obj);
+
+// Accessors for struct object_id from hash.h
+const unsigned char* sf_oid2hash(const struct object_id *oid);
+
+struct repository;
+
+// Accessors for struct repository from repository.h
+const char* sf_repo2gitdir(const struct repository *repo);
+int sf_repo2hashsz(const struct repository *repo);
+
+#endif /* SPATIAL_FILTER_ADAPTER_FUNCTIONS_H */