stringprep.mbt

Preparation of Internationalized Strings ("stringprep") as defined in RFC 3454 in MoonBit

Installation

Add the library to your project as a dependency:

moon add chawyehsu/stringprep

API

⚠️ The API is subject to change.

stringprep.saslprep(s: String): String raise StringprepError

Prepares a string using the SASLprep profile of the stringprep algorithm, as defined in RFC 4013.

@stringprep.saslprep("user") // "user"
@stringprep.saslprep("I\u{00AD}X") // "IX" (soft hyphen removed)
@stringprep.saslprep("a\u{00A0}b") // "a b" (non-ASCII space mapped to ASCII space)
@stringprep.saslprep("\u{2168}") // "IX" (roman numeral normalized via NFKC)

stringprep.nameprep(s: String): String raise StringprepError

Prepares a string using the Nameprep profile of the stringprep algorithm, as defined in RFC 3491. Used for internationalized domain name (IDN) processing.

@stringprep.nameprep("CAFE") // "cafe" (case folding)
@stringprep.nameprep("\u{00DF}") // "ss" (German sharp s)
@stringprep.nameprep("安室奈美恵-with-SUPER-MONKEYS") // "安室奈美恵-with-super-monkeys"

stringprep.nodeprep(s: String): String raise StringprepError

Prepares a string using the Nodeprep profile of the stringprep algorithm, as defined in [RFC 3920, Appendix A]. Used for XMPP node identifier processing.

@stringprep.nodeprep("räksmörgås.josefßon.org") // "räksmörgås.josefsson.org"

stringprep.resourceprep(s: String): String raise StringprepError

Prepares a string using the Resourceprep profile of the stringprep algorithm, as defined in [RFC 3920, Appendix B]. Used for XMPP resource identifier processing.

@stringprep.resourceprep("foo@bar") // "foo@bar"

stringprep.x520prep(s: String, case_fold~ : Bool): String raise StringprepError

Prepares a string according to the procedures described in Section 7 of [ITU-T Recommendation X.520 (2019)]. Used for X.500 distinguished name processing.

@stringprep.x520prep("UPPERCASED", case_fold=true) // "uppercased"
@stringprep.x520prep("foo@bar", case_fold=true) // "foo@bar"

Error Handling

All profile functions raise StringprepError with the following variants:

• ProhibitedCharacter(Char) - The string contains a prohibited character
• ProhibitedBidirectionalText - The string violates bidirectional text rules
• StartsWithCombiningCharacter - The string starts with a combining character (x520prep only)
• EmptyString - The input string is empty (x520prep only)

try @stringprep.saslprep("a\u{007F}b") catch {
  StringprepError::ProhibitedCharacter(c) => println("Prohibited: \{c}")
  _ => ()
}

Contributing

The codebase might not yet be updated to support the latest version of MoonBit language. An explicit version of the MoonBit toolchain has been pinned in the moonbit-version file, which is used by the moonup tool.

moonup pin toolchain-version

To contribute, it is suggested to use moonup to manage the MoonBit toolchain.

Code Generation

The project uses code generation for Unicode tables:

# Generate NFKC normalization tables (Unicode 3.2)
python3 codegen/unicode_nfkc.py

# Generate RFC 3454 stringprep tables
python3 codegen/rfc3454_tables.py

Unicode data files are downloaded on first run and cached in codegen/data/.

References

• RFC 3454 - Preparation of Internationalized Strings ("stringprep")
• RFC 3491 - Nameprep: A Stringprep Profile for Internationalized Domain Names
• RFC 3920 - Extensible Messaging and Presence Protocol (XMPP): Core
• RFC 4013 - SASLprep: Stringprep Profile for User Names and Passwords
• ITU-T X.520 - Information technology – Open Systems Interconnection – The Directory: Selected attribute types
• Unicode 3.2.0 - Unicode Character Database

License

stringprep.mbt © Chawye Hsu. Licensed under either of the Apache License 2.0 or The Unlicense license at your option.

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