3 files changed, 170 insertions, 0 deletions
diff --git a/src/authentication_ok.zig b/src/authentication_ok.zig
new file mode 100644
index 0000000..3c31375
--- /dev/null
+++ b/src/authentication_ok.zig
@@ -0,0 +1,46 @@
+const std = @import("std");
+const ProtocolError = @import("main.zig").ProtocolError;
+const AuthType = @import("main.zig").AuthType;
+const enum_from_int = @import("main.zig").enum_from_int;
+const ClientError = @import("main.zig").ClientError;
+const AuthenticationOk = @This();
+const ByteArrayList = std.ArrayList(u8);
+
+pub const Tag: u8 = 'R';
+
+pub fn read(_: std.mem.Allocator, b: []const u8) !AuthenticationOk {
+    if (b.len != 4) return ProtocolError.InvalidMessageLength;
+
+    const auth_type = enum_from_int(AuthType, std.mem.readIntBig(u32, b[0..4])) orelse return ClientError.UnsupportedAuthType;
+    if (auth_type != AuthType.AuthTypeOk) return ProtocolError.InvalidAuthType;
+    return .{};
+}
+
+pub fn write(_: AuthenticationOk, _: std.mem.Allocator, stream_writer: anytype) !void {
+    try stream_writer.writeByte(Tag);
+    try stream_writer.writeIntBig(u32, 8);
+    try stream_writer.writeIntBig(u32, @intFromEnum(AuthType.AuthTypeOk));
+}
+
+pub fn deinit(_: *AuthenticationOk, _: std.mem.Allocator) void {}
+
+test "round trip" {
+    const allocator = std.testing.allocator;
+    var sm = AuthenticationOk{};
+    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 tag = try reader.readByte();
+    try std.testing.expectEqual(Tag, tag);
+    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 AuthenticationOk.read(allocator, buf);
+    defer sm2.deinit(allocator);
+}
diff --git a/src/main.zig b/src/main.zig
new file mode 100644
index 0000000..4bed468
--- /dev/null
+++ b/src/main.zig
@@ -0,0 +1,39 @@
+const std = @import("std");
+const testing = std.testing;
+const StartupMessage = @import("startup_message.zig");
+const AuthenticationOk = @import("authentication_ok.zig");
+
+pub const ProtocolError = error{
+    InvalidProtocolVersion,
+    InvalidKeyValuePair,
+    InvalidMessageLength,
+    InvalidAuthType,
+};
+
+pub const ClientError = error{
+    UnsupportedAuthType,
+};
+
+pub const AuthType = enum(u32) {
+    AuthTypeOk = 0,
+};
+
+// Fallible version of enumFromInt
+pub fn enum_from_int(comptime e: type, i: anytype) ?e {
+    const enum_ti = @typeInfo(e);
+    if (enum_ti != .Enum) @compileError("e should be an enum but instead it's a " ++ @typeName(e));
+    const ei = enum_ti.Enum;
+    if (@TypeOf(i) != ei.tag_type) @compileError("i should be of type " ++ @typeName(e) ++ " but instead it's " ++ @typeName(@TypeOf(i)));
+    inline for (ei.fields) |field| {
+        if (field.value == i) {
+            return @enumFromInt(i);
+        }
+    } else {
+        return null;
+    }
+}
+
+test {
+    _ = StartupMessage;
+    _ = AuthenticationOk;
+}
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").?);
+}