Crate roe 

This crate provides Unicode case mapping routines and iterators for conventionally UTF-8 binary strings.

Unicode case mapping or case conversion can be used to transform the characters in a string. To quote the Unicode FAQ:

Case mapping or case conversion is a process whereby strings are converted to a particular form—uppercase, lowercase, or titlecase—possibly for display to the user.

Roe supports full Unicode, Turkic, and ASCII lowercase, uppercase, and capitalization and swapcase mappings. Full Unicode case folding is available through LowercaseMode::Fold. Invalid UTF-8 is preserved.

Mappings use bundled Unicode 18.0.0 tables, independent of the Rust compiler. Like MRI Ruby, mappings are context-independent and Lithuanian mode is an alias for full Unicode mapping. The API is still evolving ahead of 1.0.

Usage

You can convert case like:

assert_eq!(
    roe::lowercase(b"Artichoke Ruby", LowercaseMode::Ascii).collect::<Vec<_>>(),
    b"artichoke ruby"
);
assert_eq!(
    roe::uppercase("Αύριο".as_bytes(), UppercaseMode::Full).collect::<Vec<_>>(),
    "ΑΎΡΙΟ".as_bytes()
);
assert_eq!(
    capitalize("ffi".as_bytes(), CapitalizeMode::Full).collect::<Vec<_>>(),
    "Ffi".as_bytes()
);

Roe provides fast path routines that assume the byte slice is ASCII-only.

To detect a change without allocating, compare the mapped byte iterator with the original bytes:

let input = b"artichoke";
assert!(lowercase(input, LowercaseMode::Full).eq(input.iter().copied()));

Crate Features

Roe is no_std compatible with an optional dependency on the alloc crate.

The alloc feature is enabled by default and provides APIs that allocate String or Vec. Disable default features to use Roe without allocation.

Modules

ruby

Case mapping with Ruby string semantics.

unicode_termsdoc

Roe is derived from Unicode Data Files and is subject to Unicode License v3.

Structs

InvalidCaseMappingMode

Error that indicates a failure to parse a LowercaseMode, UppercaseMode, SwapcaseMode, or ruby::CapitalizeMode.

Lowercase

An iterator that yields the lowercase equivalent of a conventionally UTF-8 byte string.

Swapcase

An iterator yielding bytes with the case of each character swapped.

Uppercase

An iterator that yields the uppercase equivalent of a conventionally UTF-8 byte string.

Enums

LowercaseMode

Options to configure the behavior of lowercase.

SwapcaseMode

Options to configure the behavior of swapcase.

UppercaseMode

Options to configure the behavior of uppercase.

Constants

UNICODE_VERSION

The bundled Unicode case mapping version as (major, minor, patch).

Functions

lowercase

Returns an iterator that yields a copy of the bytes in the given slice with all uppercase letters replaced with their lowercase counterparts.

make_ascii_lowercase

Converts the given slice to its ASCII lower case equivalent in-place.

make_ascii_swapcase

Swap the case of ASCII letters in-place, preserving all other bytes.

make_ascii_uppercase

Converts the given slice to its ASCII upper case equivalent in-place.

swapcase

Returns an iterator that yields a copy of the bytes in the given slice with the case of each character swapped.

to_ascii_lowercasealloc

Returns a vector containing a copy of the given slice where each byte is mapped to its ASCII lower case equivalent.

to_ascii_swapcasealloc

Return a copy with ASCII letters case-swapped and all other bytes preserved.

to_ascii_uppercasealloc

Returns a vector containing a copy of the given slice where each byte is mapped to its ASCII upper case equivalent.

to_titlecase

Take a char and return its Unicode titlecase as 3 chars.

try_to_lowercasealloc

Fallibly lowercase a byte string, borrowing it when no bytes change.

try_to_swapcasealloc

Fallibly swap the case of a byte string, borrowing it when no bytes change.

try_to_uppercasealloc

Fallibly uppercase a byte string, borrowing it when no bytes change.

uppercase

Returns an iterator that yields a copy of the bytes in the given slice with all lowercase letters replaced with their uppercase counterparts.