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design: Document option type

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Sasha Koshka 2025-10-15 18:15:07 -04:00
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commit 50ca98f3c6
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8
design/pdl-language.md
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@ -33,6 +33,11 @@ PDL allows defining a protocol using HOPP and TAPE.
| {...} | KTV | * | Table with defined schema
| Any | * | * | Value of an undefined type
Tables with a defined schema can specify some fields as optional using a
question mark before the type. This will wrap the field the go-util
ucontainer.Option type. When encoding, void fields will not be included in the
output, and when decoding, unspecified fields are left void.
[^1]: Excluding SI and SBA. I5 and U5 cannot be used in an array, but String and
Buffer are simply forced to use their "long" variant.
@ -48,6 +53,7 @@ structures. They are separated by whitespace.
| Method | `M[0-9A-Fa-f]{4}` | A 16-bit hexadecimal method code.
| Key | `[0-9A-Fa-f]{4}` | A 16-bit hexadecimal table key.
| Ident | `[A-Z][A-Za-z0-9]` | An identifier.
| Option | `?` | A question mark.
| Comma | `,` | A comma separator.
| LBrace | `{` | A left curly brace.
| RBrace | `}` | A right curly brace.
@ -107,7 +113,7 @@ Below is an EBNF description of the language.
<method> -> /M[0-9A-Fa-f]{4}/
<key> -> /[0-9A-Fa-f]{4}/
<ident> -> /[A-Z][A-Za-z0-9]/
<field> -> <key> <ident> <type>
<field> -> <key> <ident> ["?"] <type>
<type> -> <ident>
| "[" "]" <type>
| "{" (<comment>* <field> ",")* [<comment>* <field>] "}"