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Tcl schema ¶

Validation commands are pretty low-level and are inconvenient to write by hand, at least because of huge quantity of TAKEs. tcl/schema.tcl utility gives ability to convert much more nicer schemas written on Tcl language to the KEKS-encoded commands. We call that Tcl-written schemas KEKS/Schema.

Example with "our" structure can be written as:

ai {{field . {str} >0}}
fpr {{field . {bin} len=32}}
our {
    {field a {with ai}}
    {field v {bin str}}
    {field fpr {with fpr}}
    {field comment {str} optional}
}

and cm/pub as:

pub {
    {field load {with load}}
    {field sigs {list} {of sig} >0 optional}
    {field pubs {list} {of pub} >0 optional}
}

load {
    {field . {map}}
    {field t {str} =pub}
    {field v {with pub-load}}
}

av {
    {field . {map}}
    {field a {str} >0}
    {field v {bin}}
}

sig {
    {field tbs {with pub-sig-tbs}}
    {field sign {with av}}
}

schema-include fpr.tcl
schema-include pub-load.tcl
schema-include pub-sig-tbs.tcl

fpr {{field . {bin} len=32}}

pub-load {
    {field . {map}}
    {field id {with fpr}}
    {field crit {} !exists}
    {field ku {set} >0 optional}
    {field pub {list} {of av} >0}
    {field sub {map} {of str} >0}
}

exp-tai {{field . {tai} prec=s utc}}
expiration {{field . {list} {of exp-tai} len=2}}

pub-sig-tbs {
    {field . {map}}
    {field sid {with fpr}}
    {field cid {hexlet}}
    {field exp {with expiration}}
    {field nonce {bin} >0 optional}
    {field when {tai} utc prec=ms optional}
}

schema.tcl calls schemas{s0 cmds0 s1 cmds1 ...} commands to produce an encoded map with cmds* commands for s* schemas. There is field command that helps creation of commands related to the field.

Its first argument is either field’s name in the map, or list’s index or dot, meaning the self-structure itself.

Second argument is a list of allowable types, written in lowercase. If that list consists of with S, then SCHEMA command will be called instead of TYPE checking. If list consists of set, then it is checked to be a MAP with EACH value of NIL.

All other arguments are optional.

By default, if no optional argument is specified, then explicit EXISTS check is called for the field. If !exists argument is specified, then it is explicitly checked to be non-existent and you can specify empty list of types in second argument.

>n and <n arguments allow checking of the integer value or the lengths. >0 assures that either list/map or strings are not empty. len=n checks the exact length. =v checks that given element has specified string/binary value (use len= for integers).

prec=p issues TIMEPREC command, but instead of specifying the raw integer values, you choose one of: s, ms, us, ns, ps, fs, as. utc issues UTC command.

of s argument issues checking of EACH element of the list or map against the specified schema, or against specified type if s is a known type.

schema-include filename.tcl command used instead of field allows inclusion of the specified file with the path relative to given schema file.

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