Fixed packet deserialization and tests and made improvements to code readability

src/packet.zig

@@ -1,15 +1,6 @@
-///////////////// Imports
-//
-
-const std = @import("std");
-
 ///////////////// Constants
 //
 
-const expect = std.testing.expect;
-const memeql = std.mem.eql;
-const asBytes = std.mem.asBytes;
-
 const MAX_DATA_SIZE = 465;
 const ADDRESS_SIZE = 16;
 
@@ -24,11 +15,15 @@ const HeaderType = enum(u1) {
     type1 = 0,  // One address field
     type2 = 1,  // Two address fields
 };
-const ContextFlag = enum(u1) { // Meaning depends on packet context
+const ContextFlag = enum(u1) {
+    // Meaning depends on packet context
     unset = 0,
     set   = 1,
 };
-const PropagationType = enum(u1) { broadcast = 0, transport = 1 };
+const PropagationType = enum(u1) {
+    broadcast = 0,
+    transport = 1
+};
 
 const DestinationType = enum(u2) {
     single = 0b0,
@@ -86,21 +81,44 @@ const Packet = struct {
     address1: [ADDRESS_SIZE]u8,
     address2: [ADDRESS_SIZE]u8,
     context:  PacketContext,
-    data: []const u8,
+    data:     []u8,
 };
 
 ///////////////// Functions
 //
 
+//////// Helper functions
+//
+
+// Copies serialized data (as a byte array) into any structure type
+fn copyToPacket(dst: anytype, src: []const u8, offset: usize, count: usize) !usize {
+    if (count == 0) return 0;
+    if (src.len < offset + count) return error.BufferTooShort;
+    
+
+    const dst_ptr: []u8 = @ptrCast(dst);
+    if (dst_ptr.len != count) return error.MismatchedLengths;
+    
+
+    @memcpy(dst_ptr, src[offset .. offset + count]);
+
+    return offset + count;
+}
+
+// Returns the size of the packet in bytes
+fn getPacketSize(data_size: usize, has_two_addresses: bool) usize {
+    var res = @sizeOf(PacketHeader) + ADDRESS_SIZE + @sizeOf(PacketContext) + data_size;
+    if (has_two_addresses) res += ADDRESS_SIZE;
+    return res;
+}
+
+//////// Public functions
+//
+
 pub fn serializePacket(packet: Packet, output_buffer: []u8) !usize {
     const has_two_addresses = packet.header.header == HeaderType.type2;
 
-    // Compute size of final packet (in bytes)
+    const target_size = getPacketSize(packet.data.len, has_two_addresses);
-    var target_size: u16 = @sizeOf(Packet);
-    if (!has_two_addresses) {
-        target_size -= packet.address2.len;
-    }
-    // TODO check data len
 
     if (output_buffer.len < target_size) {
         return error.BufferTooShort;
@@ -132,17 +150,6 @@ pub fn serializePacket(packet: Packet, output_buffer: []u8) !usize {
     return offset;
 }
 
-fn copyToPacket(dst: anytype, src: []const u8, offset: usize, count: usize) !usize {
-    if (src.len < offset + count) {
-        return error.BufferTooShort;
-    }
-
-    const dst_ptr: []u8 = @ptrCast(dst);
-    @memcpy(dst_ptr, src[offset .. offset + count]);
-
-    return offset + count;
-}
-
 // Reads the message buffer and builds the corresponding packet struct inside dest_packet
 pub fn deserializePacket(message_buffer: []u8, dest_packet: *Packet) !void {
     var offset: usize = 0;
@@ -154,14 +161,18 @@ pub fn deserializePacket(message_buffer: []u8, dest_packet: *Packet) !void {
         offset = try copyToPacket(&dest_packet.address2, message_buffer, offset, ADDRESS_SIZE);
     }
     offset = try copyToPacket(&dest_packet.context, message_buffer, offset, @sizeOf(PacketContext));
-    // TODO compute data length
+    offset = try copyToPacket(dest_packet.data, message_buffer, offset, message_buffer.len - offset);
-    const data_len = 0;
-    offset = try copyToPacket(&dest_packet.data, message_buffer, offset, data_len);
 }
 
 ///////////////// Tests
 //
 
+const std = @import("std");
+
+const expect = std.testing.expect;
+const memeql = std.mem.eql;
+const asBytes = std.mem.asBytes;
+
 //////// Helper functions
 //
 
@@ -170,11 +181,8 @@ fn testPacketSerialization(packet: Packet) !void {
     const buf_size = comptime @sizeOf(Packet) + MAX_DATA_SIZE;
     var buf: [buf_size]u8 = undefined;
     const res: usize = try serializePacket(packet, &buf);
-    var expected_res: usize = @sizeOf(PacketHeader) + packet.address1.len + @sizeOf(PacketContext) + packet.data.len;
     const has_second_address = packet.header.header == HeaderType.type2;
-    if (has_second_address) {
+    const expected_res: usize = getPacketSize(packet.data.len, has_second_address);
-        expected_res += packet.address2.len;
-    }
 
     try expect(res == expected_res);
 
@@ -186,6 +194,11 @@ fn testPacketSerialization(packet: Packet) !void {
     try expect(memeql(u8, buf[offset .. offset + packet.address1.len], asBytes(&packet.address1)));
     offset += packet.address1.len;
 
+    if (has_second_address) {
+        try expect(memeql(u8, buf[offset .. offset + packet.address2.len], asBytes(&packet.address2)));
+        offset += packet.address2.len;
+    }
+
     try expect(memeql(u8, buf[offset .. offset + @sizeOf(PacketContext)], asBytes(&packet.context)));
     offset += @sizeOf(PacketContext);
 
@@ -231,9 +244,9 @@ test "Basic serialization: header type 1, max data size" {
     };
 
     const data_size = MAX_DATA_SIZE;
-    const data: [data_size]u8 = undefined;
+    var data: [data_size]u8 = undefined;
 
-    const packet: Packet = .{ //
+    const packet: Packet = .{
         .header = header,
         .address1 = undefined,
         .address2 = undefined,
@@ -256,9 +269,9 @@ test "Basic serialization: header type 2, max data size" {
     };
 
     const data_size = MAX_DATA_SIZE;
-    const data: [data_size]u8 = undefined;
+    var data: [data_size]u8 = undefined;
 
-    const packet: Packet = .{ //
+    const packet: Packet = .{
         .header = header,
         .address1 = undefined,
         .address2 = undefined,
@@ -281,9 +294,9 @@ test "Basic serialization: header type 1, medium data size" {
     };
 
     const data_size = MAX_DATA_SIZE / 2 + 3;
-    const data: [data_size]u8 = undefined;
+    var data: [data_size]u8 = undefined;
 
-    const packet: Packet = .{ //
+    const packet: Packet = .{
         .header = header,
         .address1 = undefined,
         .address2 = undefined,
@@ -306,9 +319,9 @@ test "Basic serialization: header type 2, medium data size" {
     };
 
     const data_size = MAX_DATA_SIZE / 2 + 3;
-    const data: [data_size]u8 = undefined;
+    var data: [data_size]u8 = undefined;
 
-    const packet: Packet = .{ //
+    const packet: Packet = .{
         .header = header,
         .address1 = undefined,
         .address2 = undefined,
@@ -331,9 +344,9 @@ test "Serialize / Deserialize Packet: Header type2, Medium data size" {
     };
 
     const data_size = MAX_DATA_SIZE / 2 + 3;
-    const data: [data_size]u8 = undefined;
+    var data: [data_size]u8 = undefined;
 
-    const packet: Packet = .{ //
+    const packet: Packet = .{
         .header = header,
         .address1 = undefined,
         .address2 = undefined,
@@ -341,9 +354,11 @@ test "Serialize / Deserialize Packet: Header type2, Medium data size" {
         .data = &data,
     };
 
-    const buf_size = comptime @sizeOf(Packet) + MAX_DATA_SIZE;
+    const buf_size = comptime @sizeOf(PacketHeader) + 2*ADDRESS_SIZE + @sizeOf(PacketContext) + data_size;
     var buf: [buf_size]u8 = undefined;
     var res_packet: Packet = undefined;
+    var res_data: [data_size]u8 = undefined;
+    res_packet.data = &res_data;
     _ = try serializePacket(packet, &buf);
     try deserializePacket(&buf, &res_packet);