HexWriter

const HexWriter = struct

File

Code

const HexWriter = struct {
    prev_addr: ?u32 = null,
    out: *File.Writer,

    /// Max data bytes per line of output
    const max_payload_len: u8 = 16;

    fn addressParts(address: u16) [2]u8 {
        const msb: u8 = @truncate(address >> 8);
        const lsb: u8 = @truncate(address);
        return [2]u8{ msb, lsb };
    }

    const Record = struct {
        const Type = enum(u8) {
            Data = 0,
            EOF = 1,
            ExtendedSegmentAddress = 2,
            ExtendedLinearAddress = 4,
        };

        address: u16,
        payload: union(Type) {
            Data: []const u8,
            EOF: void,
            ExtendedSegmentAddress: [2]u8,
            ExtendedLinearAddress: [2]u8,
        },

        fn EOF() Record {
            return Record{
                .address = 0,
                .payload = .EOF,
            };
        }

        fn Data(address: u32, data: []const u8) Record {
            return Record{
                .address = @intCast(address % 0x10000),
                .payload = .{ .Data = data },
            };
        }

        fn Address(address: u32) Record {
            assert(address > 0xFFFF);
            const segment: u16 = @intCast(address / 0x10000);
            if (address > 0xFFFFF) {
                return Record{
                    .address = 0,
                    .payload = .{ .ExtendedLinearAddress = addressParts(segment) },
                };
            } else {
                return Record{
                    .address = 0,
                    .payload = .{ .ExtendedSegmentAddress = addressParts(segment << 12) },
                };
            }
        }

        fn getPayloadBytes(self: *const Record) []const u8 {
            return switch (self.payload) {
                .Data => |d| d,
                .EOF => @as([]const u8, &.{}),
                .ExtendedSegmentAddress, .ExtendedLinearAddress => |*seg| seg,
            };
        }

        fn checksum(self: Record) u8 {
            const payload_bytes = self.getPayloadBytes();

            var sum: u8 = @intCast(payload_bytes.len);
            const parts = addressParts(self.address);
            sum +%= parts[0];
            sum +%= parts[1];
            sum +%= @backingInt(self.payload);
            for (payload_bytes) |byte| {
                sum +%= byte;
            }
            return (sum ^ 0xFF) +% 1;
        }

        fn write(self: Record, out: *File.Writer) !void {
            const linesep = "\r\n";
            // colon, (length, address, type, payload, checksum) as hex, CRLF
            const BUFSIZE = 1 + (1 + 2 + 1 + max_payload_len + 1) * 2 + linesep.len;
            var outbuf: [BUFSIZE]u8 = undefined;
            const payload_bytes = self.getPayloadBytes();
            assert(payload_bytes.len <= max_payload_len);

            const line = try std.fmt.bufPrint(&outbuf, ":{0X:0>2}{1X:0>4}{2X:0>2}{3X}{4X:0>2}" ++ linesep, .{
                @as(u8, @intCast(payload_bytes.len)),
                self.address,
                @backingInt(self.payload),
                payload_bytes,
                self.checksum(),
            });
            try out.interface.writeAll(line);
        }
    };

    pub fn writeSegment(self: *HexWriter, segment: *const BinaryElfSegment, in: *File.Reader) !void {
        var buf: [max_payload_len]u8 = undefined;
        var bytes_read: usize = 0;
        while (bytes_read < segment.fileSize) {
            const row_address: u32 = @intCast(segment.physicalAddress + bytes_read);

            const remaining = segment.fileSize - bytes_read;
            const dest = buf[0..@min(remaining, max_payload_len)];
            try in.seekTo(segment.elfOffset + bytes_read);
            try in.interface.readSliceAll(dest);
            try self.writeDataRow(row_address, dest);

            bytes_read += dest.len;
        }
    }

    fn writeDataRow(self: *HexWriter, address: u32, data: []const u8) !void {
        const record = Record.Data(address, data);
        if (address > 0xFFFF and (self.prev_addr == null or record.address != self.prev_addr.?)) {
            try Record.Address(address).write(self.out);
        }
        try record.write(self.out);
        self.prev_addr = @intCast(record.address + data.len);
    }

    fn writeEof(self: HexWriter) !void {
        try Record.EOF().write(self.out);
    }
}