1 files changed, 85 insertions, 0 deletions
diff --git a/src/startup_message.zig b/src/startup_message.zig
new file mode 100644
index 0000000..b5031c1
--- /dev/null
+++ b/src/startup_message.zig
@@ -0,0 +1,85 @@
+const std = @import("std");
+const ProtocolError = @import("main.zig").ProtocolError;
+const SSHashMap = std.StringHashMap([]const u8);
+const ByteArrayList = std.ArrayList(u8);
+
+const StartupMessage = @This();
+
+const ProtocolVersionNumber: u32 = 196608; // 3.0
+
+bytes: ?[]const u8 = null, // Owned
+parameters: SSHashMap,
+
+// message length should already have been read, b should contain the payload
+pub fn read(allocator: std.mem.Allocator, b: []const u8) !StartupMessage {
+    if (b.len < 4) return ProtocolError.InvalidMessageLength;
+
+    var bytes = try allocator.dupe(u8, b);
+    errdefer allocator.free(bytes);
+    const protocol_version = std.mem.readIntSliceBig(u32, bytes[0..4]);
+    if (protocol_version != ProtocolVersionNumber) return ProtocolError.InvalidProtocolVersion;
+
+    var parameters = SSHashMap.init(allocator);
+    var it = std.mem.splitScalar(u8, bytes[4..], 0);
+    while (it.next()) |next| {
+        const key = next;
+        const value = it.next() orelse return ProtocolError.InvalidKeyValuePair;
+        try parameters.put(key, value);
+    }
+
+    return .{
+        .bytes = bytes,
+        .parameters = parameters,
+    };
+}
+
+pub fn write(self: StartupMessage, allocator: std.mem.Allocator, stream_writer: anytype) !void {
+    var al = ByteArrayList.init(allocator);
+    defer al.deinit();
+    var cw = std.io.countingWriter(al.writer());
+    var writer = cw.writer();
+    try writer.writeIntBig(u32, 0); // length placeholder
+    try writer.writeIntBig(u32, ProtocolVersionNumber);
+    var it = self.parameters.iterator();
+    while (it.next()) |entry| {
+        try writer.writeAll(entry.key_ptr.*);
+        try writer.writeByte(0);
+        try writer.writeAll(entry.value_ptr.*);
+        try writer.writeByte(0);
+    }
+    try writer.writeByte(0);
+    std.mem.writeIntBig(u32, al.items[0..4], @as(u32, @intCast(cw.bytes_written)));
+    try stream_writer.writeAll(al.items);
+}
+
+pub fn deinit(self: *StartupMessage, allocator: std.mem.Allocator) void {
+    self.parameters.deinit();
+    if (self.bytes != null) {
+        allocator.free(self.bytes.?);
+    }
+}
+
+test "round trip" {
+    const allocator = std.testing.allocator;
+    var params = SSHashMap.init(allocator);
+    try params.put("hello", "postgres");
+    var sm = StartupMessage{
+        .parameters = params,
+    };
+    defer sm.deinit(allocator);
+
+    var bal = ByteArrayList.init(allocator);
+    defer bal.deinit();
+    try sm.write(allocator, bal.writer());
+
+    var fbs = std.io.fixedBufferStream(bal.items);
+    var reader = fbs.reader();
+    const len = try reader.readIntBig(u32);
+    const buf = try allocator.alloc(u8, len - 4);
+    defer allocator.free(buf);
+    try reader.readNoEof(buf);
+    var sm2 = try StartupMessage.read(allocator, buf);
+    defer sm2.deinit(allocator);
+
+    try std.testing.expectEqualStrings("postgres", sm2.parameters.get("hello").?);
+}