Using variables from parent scope in a 'choice'

Hey Keichi

I was wondering if it’s somehow possible to use a variable from a parent scope from inside a choice type item. If it’s not implemented I would greatly appreciate a pointer on how to do so. My use-case is parsing of a DNSRecord:

var TXTRecord = new Parser()
    .string('txt' { length: 'rdlength' }) // rdlength is undefined

var answer = new Parser()
    .nest('name', { type: fqdn_pretty })
    .uint16be('type')
    .uint16be('class')
    .uint32be('ttl')
    .uint16be('rdlength')
    .choice('record', {
        tag: 'type',
        choices: {
            0x01: ARecord,
            0x02: PTRRecord, 0x05: PTRRecord, 0x0c: PTRRecord,
            0x10: TXTRecord,
            0x21: SRVRecord,
            0x1C: AAAARecord
        },
        defaultChoice: new Parser().buffer('rdata', { length: 'rdlength' }) //rdlength is undefined
    })

I enjoy working with your module, thanks for the help in advance!

[keichi]

I understand your situation. Unfortunately, there’s currently no way to do that. One idea would be to introduce a special variable name like $parent, with which you can reference the parent scope: defaultChoice: new Parser().buffer('rdata', { length: '$parent.rdlength' }) What do you think about this?

[avi91]

+1