Add vector tile boilerplate

Makefile

@@ -6,13 +6,16 @@ install: jsonpull.h libjsonpull.a
 	cp jsonpull.h $(PREFIX)/include/jsonpull.h
 	cp libjsonpull.a $(PREFIX)/lib/libjsonpull.a
 
+vector_tile.pb.cc vector_tile.pb.h: vector_tile.proto
+	protoc --cpp_out=. vector_tile.proto
+
 PG=
 
 jsoncat: jsoncat.o jsonpull.o
 	cc $(PG) -g -Wall -o $@ $^
 
-geojson: geojson.o jsonpull.o
-	cc $(PG) -O3 -g -Wall -o $@ $^ -lm
+geojson: geojson.o jsonpull.o vector_tile.pb.o
+	cc $(PG) -O3 -g -Wall -o $@ $^ -lm -lz -lprotobuf-lite
 
 jsoncat.o jsonpull.o: jsonpull.h
 
@@ -22,3 +25,6 @@ libjsonpull.a: jsonpull.o
 
 %.o: %.c
 	cc $(PG) -O3 -g -Wall -c $<
+
+%.o: %.cc
+	g++ -g -Wall -O3 -c $<

vector_tile.proto

@@ -0,0 +1,92 @@
+// Protocol Version 1
+
+package mapnik.vector;
+
+option optimize_for = LITE_RUNTIME;
+
+message tile {
+        enum GeomType {
+             Unknown = 0;
+             Point = 1;
+             LineString = 2;
+             Polygon = 3;
+        }
+
+        // Variant type encoding
+        message value {
+                // Exactly one of these values may be present in a valid message
+                optional string string_value = 1;
+                optional float float_value = 2;
+                optional double double_value = 3;
+                optional int64 int_value = 4;
+                optional uint64 uint_value = 5;
+                optional sint64 sint_value = 6;
+                optional bool bool_value = 7;
+
+                extensions 8 to max;
+        }
+
+        message feature {
+                optional uint64 id = 1;
+
+                // Tags of this feature. Even numbered values refer to the nth
+                // value in the keys list on the tile message, odd numbered
+                // values refer to the nth value in the values list on the tile
+                // message.
+                repeated uint32 tags = 2 [ packed = true ];
+
+                // The type of geometry stored in this feature.
+                optional GeomType type = 3 [ default = Unknown ];
+
+                // Contains a stream of commands and parameters (vertices). The
+                // repeat count is shifted to the left by 3 bits. This means
+                // that the command has 3 bits (0-7). The repeat count
+                // indicates how often this command is to be repeated. Defined
+                // commands are:
+                // - MoveTo:    1   (2 parameters follow)
+                // - LineTo:    2   (2 parameters follow)
+                // - ClosePath: 7   (no parameters follow)
+                //
+                // Ex.: MoveTo(3, 6), LineTo(8, 12), LineTo(20, 34), ClosePath
+                // Encoded as: [ 9 3 6 18 5 6 12 22 7 ]
+                //                                  == command type 7 (ClosePath)
+                //                             ===== relative LineTo(+12, +22) == LineTo(20, 34)
+                //                         === relative LineTo(+5, +6) == LineTo(8, 12)
+                //                      == [00010 010] = command type 2 (LineTo), length 2
+                //                  === relative MoveTo(+3, +6)
+                //              == [00001 001] = command type 1 (MoveTo), length 1
+                // Commands are encoded as uint32 varints, vertex parameters are
+                // encoded as sint32 varints (zigzag). Vertex parameters are
+                // also encoded as deltas to the previous position. The original
+                // position is (0,0)
+                repeated uint32 geometry = 4 [ packed = true ];
+        }
+
+        message layer {
+                // Any compliant implementation must first read the version
+                // number encoded in this message and choose the correct
+                // implementation for this version number before proceeding to
+                // decode other parts of this message.
+                required uint32 version = 15 [ default = 1 ];
+
+                required string name = 1;
+
+                // The actual features in this tile.
+                repeated feature features = 2;
+
+                // Dictionary encoding for keys
+                repeated string keys = 3;
+
+                // Dictionary encoding for values
+                repeated value values = 4;
+
+                // The bounding box in this tile spans from 0..4095 units
+                optional uint32 extent = 5 [ default = 4096 ];
+
+                extensions 16 to max;
+        }
+
+        repeated layer layers = 3;
+
+        extensions 16 to 8191;
+}