a bunch of minor changes combined:

- From instead of Into
- unsafe_data_ref for other payloads
- CByteSlice for returning memory spans
- send Packet instead of Into<Packet>
- expose packet layer to C/C#

examples/lang_c/Makefile

@@ -3,11 +3,11 @@ OUT_DIR := ${ROOT_DIR}/out
 
 SP2_DIR := ${ROOT_DIR}/../../servicepoint2
 SP2_INCLUDE := ${ROOT_DIR}/../../servicepoint2-binding-c
-SP2_TARGET_RELEASE := ${ROOT_DIR}/../../target/release
+SP2_TARGET_RELEASE := ${SP2_DIR}/target/release
 
 .PHONY: build run clean
 
-build: ${OUT_DIR}/lang_c
+all: ${OUT_DIR}/lang_c
 
 run: ${OUT_DIR}/lang_c
 	out/lang_c

examples/lang_c/main.c

@@ -8,11 +8,11 @@ int main(void) {
 
     sp2_PixelGrid *pixels = sp2_pixel_grid_new(sp2_PIXEL_WIDTH, sp2_PIXEL_HEIGHT);
     sp2_pixel_grid_fill(pixels, true);
+
     sp2_Command *command = sp2_command_bitmap_linear_win(0, 0, pixels);
-    if (command == NULL)
-        return 4;
-    if (!sp2_connection_send(connection, command))
-        return 5;
+    sp2_Packet *packet = sp2_packet_from_command(command);
+    if (!sp2_connection_send(connection, packet))
+        return 1;
 
     sp2_connection_dealloc(connection);
     return 0;