Packet

pub const Packet = union(enum)

File

Code

pub const Packet = union(enum) {
    flush,
    delimiter,
    response_end,
    data: []const u8,

    pub const max_data_length = 65516;

    /// Reads a packet in pkt-line format.
    fn read(reader: *Io.Reader) !Packet {
        const packet: Packet = try .peek(reader);
        switch (packet) {
            .data => |data| reader.toss(data.len),
            else => {},
        }
        return packet;
    }

    /// Consumes the header of a pkt-line packet and reads any associated data
    /// into the reader's buffer, but does not consume the data.
    fn peek(reader: *Io.Reader) !Packet {
        const length = std.fmt.parseUnsigned(u16, try reader.take(4), 16) catch return error.InvalidPacket;
        switch (length) {
            0 => return .flush,
            1 => return .delimiter,
            2 => return .response_end,
            3 => return error.InvalidPacket,
            else => if (length - 4 > max_data_length) return error.InvalidPacket,
        }
        return .{ .data = try reader.peek(length - 4) };
    }

    /// Writes a packet in pkt-line format.
    fn write(packet: Packet, writer: *Io.Writer) !void {
        switch (packet) {
            .flush => try writer.writeAll("0000"),
            .delimiter => try writer.writeAll("0001"),
            .response_end => try writer.writeAll("0002"),
            .data => |data| {
                assert(data.len <= max_data_length);
                try writer.print("{x:0>4}", .{data.len + 4});
                try writer.writeAll(data);
            },
        }
    }

    /// Returns the normalized form of textual packet data, stripping any
    /// trailing '\n'.
    ///
    /// As documented in
    /// [protocol-common](https://git-scm.com/docs/protocol-common#_pkt_line_format),
    /// non-binary (textual) pkt-line data should contain a trailing '\n', but
    /// is not required to do so (implementations must support both forms).
    fn normalizeText(data: []const u8) []const u8 {
        return if (mem.endsWith(u8, data, "\n"))
            data[0 .. data.len - 1]
        else
            data;
    }
}