Make C struct match the binary API more closely

Also make the internal conversion function return errors properly

include/zaprus.h

@@ -11,5 +11,41 @@ int zaprus_send_relay(const char* payload, size_t len, char dest[4]);
 
 int zaprus_send_initial_connection(const char* payload, size_t len, uint16_t initial_port);
 
-void* zaprus_connect(const char* payload, size_t len);
+struct SaprusMessage* zaprus_connect(const char* payload, size_t len);
 
+// message
+#define SAPRUS_RELAY_MESSAGE_TYPE 0x003C
+#define SAPRUS_FILE_TRANSFER_MESSAGE_TYPE 0x8888
+#define SAPRUS_CONNECTION_MESSAGE_TYPE 0x00E9
+
+struct SaprusMessage {
+  uint16_t packet_type;
+  uint16_t payload_len;
+  union {
+    struct {
+      struct {
+	char dest[4];
+      };
+    } relay;
+    struct {
+      struct {
+	uint16_t src_port;
+	uint16_t dest_port;
+	uint32_t seq_num;
+	uint32_t msg_id;
+	char _reserved;
+	char options;
+      };
+      
+    } connection;
+  } headers;
+  char *payload;
+};
+
+// ptr should be freed by the caller.
+int zaprus_message_to_bytes(struct SaprusMessage msg, char** ptr, size_t* len);
+
+// Return value should be destroyed with zaprus_message_deinit.
+struct SaprusMessage* zaprus_message_from_bytes(const char* bytes, size_t len);
+
+void zaprus_message_deinit(struct SaprusMessage* msg);

src/Client.zig

@@ -76,7 +76,7 @@ pub fn sendInitialConnection(payload: []const u8, initial_port: u16, allocator:
     return msg;
 }
 
-pub fn connect(payload: []const u8, allocator: Allocator) !SaprusMessage {
+pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusMessage {
     var initial_port: u16 = 0;
     if (rand) |r| {
         initial_port = r.intRangeAtMost(u16, 1024, 65000);
@@ -109,7 +109,7 @@ pub fn connect(payload: []const u8, allocator: Allocator) !SaprusMessage {
     // Complete handshake after awaiting response
     try broadcastSaprusMessage(msg, randomPort(), allocator);
 
-    return initial_conn_res.?;
+    return initial_conn_res;
 }
 
 const SaprusMessage = @import("message.zig").Message;

src/c_api.zig

@@ -1,3 +1,54 @@
+const c = @cImport({
+    @cInclude("zaprus.h");
+});
+
+fn zigToCMessage(msg: ?*zaprus.Message) !?*c.SaprusMessage {
+    if (msg) |m| {
+        var res = c.SaprusMessage{
+            .packet_type = @intFromEnum(m.*),
+        };
+        switch (m.*) {
+            .relay => |r| {
+                res.headers.relay = .{
+                    .unnamed_0 = .{
+                        .dest = r.header.dest,
+                    },
+                };
+                res.payload_len = @intCast(r.payload.len);
+                res.payload = (try allocator.alloc(u8, r.payload.len)).ptr;
+            },
+            .connection => |con| {
+                res.headers.connection = .{
+                    .unnamed_0 = .{
+                        .src_port = con.header.src_port,
+                        .dest_port = con.header.dest_port,
+                        .seq_num = con.header.seq_num,
+                        .msg_id = con.header.msg_id,
+                        ._reserved = con.header.reserved,
+                        .options = @bitCast(con.header.options),
+                    },
+                };
+
+                res.payload_len = @intCast(con.payload.len);
+                res.payload = (try allocator.alloc(u8, con.payload.len)).ptr;
+            },
+            .file_transfer => return zaprus.Error.NotImplementedSaprusType,
+            else => return zaprus.Error.UnknownSaprusType,
+        }
+        return &res;
+    } else return null;
+}
+
+fn cToZigMessage(msg: ?*c.SaprusMessage) ?*zaprus.Message {
+    _ = msg;
+    return @constCast(&zaprus.Message{
+        .relay = .{
+            .header = .{ .dest = @splat(0) },
+            .payload = &.{0},
+        },
+    });
+}
+
 // client
 export fn zaprus_init() c_int {
     SaprusClient.init() catch return 1;
@@ -14,16 +65,48 @@ export fn zaprus_send_relay(payload: [*]const u8, len: usize, dest: [*]u8) c_int
     return 0;
 }
 
-export fn zaprus_connect(payload: [*]const u8, len: usize, output: *SaprusConnection) c_int {
-    output.* = (SaprusClient.connect(payload[0..len], allocator) catch return 1).?;
+export fn zaprus_send_initial_connection(payload: [*]const u8, len: usize, initial_port: u16) c_int {
+    _ = SaprusClient.sendInitialConnection(payload[0..len], initial_port, allocator) catch return 1;
     return 0;
 }
 
+export fn zaprus_connect(payload: [*]const u8, len: usize) ?*c.SaprusMessage {
+    if (SaprusClient.connect(payload[0..len], allocator)) |msg| {
+        return zigToCMessage(@constCast(&(msg.?))) catch null;
+    } else |_| {
+        return null;
+    }
+}
+
+// message
+
+/// ptr should be freed by the caller.
+export fn zaprus_message_to_bytes(msg: c.SaprusMessage, ptr: *[*]u8, len: *usize) c_int {
+    if (cToZigMessage(@constCast(&msg))) |m| {
+        const bytes = m.toBytes(allocator) catch return 1;
+        ptr.* = bytes.ptr;
+        len.* = bytes.len;
+        return 0;
+    } else return 1;
+}
+
+/// Return value should be destroyed with zaprus_message_deinit.
+export fn zaprus_message_from_bytes(bytes: [*]const u8, len: usize) ?*c.SaprusMessage {
+    if (zaprus.Message.fromBytes(bytes[0..len], allocator)) |msg| {
+        return zigToCMessage(@constCast(&msg)) catch null;
+    } else |_| return null;
+}
+
+export fn zaprus_message_deinit(msg: *c.SaprusMessage) void {
+    // noop
+    _ = msg;
+    // msg.*.deinit(allocator);
+}
+
 const std = @import("std");
 
 const zaprus = @import("./root.zig");
 const SaprusClient = zaprus.Client;
-const SaprusConnection = zaprus.Connection;
 
 const allocator = std.heap.c_allocator;
 

src/main.zig

@@ -75,7 +75,7 @@ pub fn main() !void {
     return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});
 }
 
-fn parseDest(in: ?[]const u8) [4]u8 {
+fn parseDest(in: ?[]const u8) ![4]u8 {
     if (in) |dest| {
         if (dest.len <= 4) {
             var res: [4]u8 = @splat(0);
@@ -83,10 +83,10 @@ fn parseDest(in: ?[]const u8) [4]u8 {
             return res;
         }
 
-        const addr = std.net.Ip4Address.parse(dest, 0) catch return "FAIL".*;
+        const addr = try std.net.Ip4Address.parse(dest, 0);
         return @bitCast(addr.sa.addr);
     }
-    return "zap".*;
+    return .{ 70, 70, 70, 70 };
 }
 
 const builtin = @import("builtin");