1 files changed, 136 insertions, 0 deletions
diff --git a/src/row_description.zig b/src/row_description.zig
new file mode 100644
index 0000000..414c174
--- /dev/null
+++ b/src/row_description.zig
@@ -0,0 +1,136 @@
+const std = @import("std");
+const log = std.log.scoped(.pgz);
+const ByteArrayList = std.ArrayList(u8);
+const ProtocolError = @import("main.zig").ProtocolError;
+const ClientError = @import("main.zig").ClientError;
+const enum_from_int = @import("main.zig").enum_from_int;
+const FormatCode = @import("main.zig").FormatCode;
+
+pub const Tag: u8 = 'T';
+
+const RowDescription = @This();
+
+buf: ?[]const u8 = null, // owned
+fields: ?[]Field = null, // owned
+
+pub const Field = struct {
+    name: []const u8,
+    table_oid: u32,
+    attr_no: u16,
+    data_type_oid: u32,
+    data_type_size: i16,
+    data_type_modifier: u32,
+    format_code: FormatCode,
+};
+
+pub fn read(a: std.mem.Allocator, b: []const u8) !RowDescription {
+    var res: RowDescription = undefined;
+    res.buf = try a.dupe(u8, b);
+    errdefer res.deinit(a);
+    var fbs = std.io.fixedBufferStream(res.buf.?);
+    var reader = fbs.reader();
+    const n_fields = try reader.readIntBig(u16);
+    res.fields = try a.alloc(Field, n_fields);
+    for (0..n_fields) |i| {
+        const name_start = fbs.pos;
+        try reader.skipUntilDelimiterOrEof(0);
+        const name_end = fbs.pos-1;
+        const name = res.buf.?[name_start..name_end];
+        const field = Field{
+            .name = name,
+            .table_oid = try reader.readIntBig(u32),
+            .attr_no = try reader.readIntBig(u16),
+            .data_type_oid = try reader.readIntBig(u32),
+            .data_type_size = try reader.readIntBig(i16),
+            .data_type_modifier = try reader.readIntBig(u32),
+            .format_code = enum_from_int(FormatCode, try reader.readIntBig(u16)) orelse return ProtocolError.InvalidFormatCode,
+        };
+        res.fields.?[i] = field;
+    }
+    return res;
+}
+
+pub fn write(self: RowDescription, a: std.mem.Allocator, stream_writer: anytype) !void {
+    try stream_writer.writeByte(Tag);
+    var al = ByteArrayList.init(a);
+    defer al.deinit();
+    var cw = std.io.countingWriter(al.writer());
+    var writer = cw.writer();
+    try writer.writeIntBig(u32, 0); // length placeholder
+    try writer.writeIntBig(u16, @as(u16, @intCast(self.fields.?.len)));
+    for (self.fields.?) |field| {
+        try writer.writeAll(field.name);
+        try writer.writeByte(0);
+        try writer.writeIntBig(u32, field.table_oid);
+        try writer.writeIntBig(u16, field.attr_no);
+        try writer.writeIntBig(u32, field.data_type_oid);
+        try writer.writeIntBig(i16, field.data_type_size);
+        try writer.writeIntBig(u32, field.data_type_modifier);
+        try writer.writeIntBig(u16, @intFromEnum(field.format_code));
+    }
+    std.mem.writeIntBig(u32, al.items[0..4], @as(u32, @intCast(cw.bytes_written)));
+    try stream_writer.writeAll(al.items);
+}
+
+pub fn deinit(self: *RowDescription, a: std.mem.Allocator) void {
+    if (self.fields != null) a.free(self.fields.?);
+    if (self.buf != null) a.free(self.buf.?);
+}
+
+test "round trip" {
+    const allocator = std.testing.allocator;
+    var fields = try allocator.alloc(Field, 3);
+    fields[0] = .{
+        .name = "foo",
+        .table_oid = 1,
+        .attr_no = 2,
+        .data_type_oid = 3,
+        .data_type_size = 4,
+        .data_type_modifier = 5,
+        .format_code = .Binary,
+    };
+    fields[1] = .{
+        .name = "bar",
+        .table_oid = 1,
+        .attr_no = 2,
+        .data_type_oid = 3,
+        .data_type_size = 4,
+        .data_type_modifier = 5,
+        .format_code = .Binary,
+    };
+    fields[2] = .{
+        .name = "BAZZZZZ",
+        .table_oid = 99,
+        .attr_no = 98,
+        .data_type_oid = 97,
+        .data_type_size = 96,
+        .data_type_modifier = 95,
+        .format_code = .Text,
+    };
+    var f0 = fields[0];
+    var f1 = fields[1];
+    var f2 = fields[2];
+    var sm = RowDescription{
+        .fields = fields,
+    };
+    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 RowDescription.read(allocator, buf);
+    defer sm2.deinit(allocator);
+
+    try std.testing.expectEqualDeep(f0, sm2.fields.?[0]);
+    try std.testing.expectEqualDeep(f1, sm2.fields.?[1]);
+    try std.testing.expectEqualDeep(f2, sm2.fields.?[2]);
+}