swift-protobuf/Sources/SwiftProtobufPluginLibrary/UnicodeScalar+Extensions.swift

// Sources/SwiftProtobufPluginLibrary/UnicodeScalar+Extensions.swift - Utilities for working with UnicodeScalars
//
// Copyright (c) 2014 - 2017 Apple Inc. and the project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See LICENSE.txt for license information:
// https://github.com/apple/swift-protobuf/blob/main/LICENSE.txt
//
// -----------------------------------------------------------------------------
///
/// Internal utility functions and properties for working with UnicodeScalars.
///
/// NOTE: This is a purely internal extension that provides the limited
/// functionality needed to manipulate ASCII characters that are represented as
/// UnicodeScalars. It does not support the full range of Unicode code points.
///
// -----------------------------------------------------------------------------

extension UnicodeScalar {

    /// True if the receiver is a numeric digit.
    var isASCDigit: Bool {
        if case "0"..."9" = self { return true }
        return false
    }

    /// True if the receiver is a lowercase character.
    var isASCLowercase: Bool {
        if case "a"..."z" = self { return true }
        return false
    }

    /// True if the receiver is an uppercase character.
    var isASCUppercase: Bool {
        if case "A"..."Z" = self { return true }
        return false
    }

    /// Returns the lowercased version of the receiver, or the receiver itself if
    /// it is not a cased character.
    ///
    /// - Precondition: The receiver is 7-bit ASCII.
    /// - Returns: The lowercased version of the receiver, or `self`.
    func ascLowercased() -> UnicodeScalar {
        if isASCUppercase { return UnicodeScalar(value + 0x20)! }
        return self
    }

    /// Returns the uppercased version of the receiver, or the receiver itself if
    /// it is not a cased character.
    ///
    /// - Precondition: The receiver is 7-bit ASCII.
    /// - Returns: The uppercased version of the receiver, or `self`.
    func ascUppercased() -> UnicodeScalar {
        if isASCLowercase { return UnicodeScalar(value - 0x20)! }
        return self
    }
}