Situation, when tcp protocol doesn't have "len" field

[predator89090]

Some protocols running over a TCP connection don't have a length field.
When we attempting to parse this protocol using spicy, we encounter a problem: spicy needs to know the length of each segment to correctly process packets.
The example is given here

Is there any way we can get the payload length other than the protocol length field, for example via tcp analyzer, or TCP protocol parsers should be implemented on spicy only if the protocol itself provides the length ?

[evantypanski]

It's hard for me to help without a concrete example in the protocol you're trying to parse, I'm not sure I fully understand

There are lots of ways for Spicy to have Spicy parse "until" certain scenarios, like with &until:

module Test;

public type Foo = unit {
    x: bytes &until=b"\x00" &max-size=1024;
    on %done { print self; }
};

# printf '\001\002\003\004\005\000' | spicy-driver foo.spicy
[$x=b"\x01\x02\x03\x04\x05"]

or with lookahead:

module Test;

public type Foo = unit {
    data: uint8[];
        : /EOD/;
    x   : int8;

    on %done { print self; }
};

# printf '\01\02\03EOD\04' | spicy-driver foo.spicy
[$data=[1, 2, 3], $x=4]

or a fair few other constructs in the parsing section

Are those sufficient for this case? It's hard for me to tell without a concrete example. In general, Spicy doesn't need a len field, it's just nice when protocols provide them