include "cowgol.coh";

sub VLQEncode(number: uint32, buf: [uint8]) is
    var step := number;
    while step > 0 loop
        step := step >> 7;
        buf := @next buf;
    end loop;

    var mark: uint8 := 0;
    while number > 0 loop
        buf := @prev buf;
        [buf] := mark | (number as uint8 & 0x7F);
        mark := 0x80;
        number := number >> 7;
    end loop;
end sub;

sub VLQDecode(buf: [uint8]): (result: uint32) is
    result := 0;
    loop
        var byte := [buf];
        buf := @next buf;
        result := (result << 7) | (byte & 0x7F) as uint32;

        if byte & 0x80 == 0 then
            return;
        end if;
    end loop;
end sub;

sub VLQPrint(buf: [uint8]) is
    loop
        print_hex_i8([buf]);
        if [buf] & 0x80 == 0 then
            break;
        end if;
        buf := @next buf;
    end loop;
end sub;

sub VLQTest(value: uint32) is
    var buf: uint8[8];

    print("Input:   ");
    print_hex_i32(value);
    print_nl();

    print("Encoded: ");
    VLQEncode(value, &buf[0]);
    VLQPrint(&buf[0]);
    print_nl();

    print("Decoded: ");
    value := VLQDecode(&buf[0]);
    print_hex_i32(value);
    print_nl();
end sub;

VLQTest(0x200000);
print_nl();
VLQTest(0x1FFFFF);
print_nl();