74 lines
2.8 KiB
Swift
74 lines
2.8 KiB
Swift
// Copyright (c) 2022 and onwards The McBopomofo Authors.
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//
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// Permission is hereby granted, free of charge, to any person
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// obtaining a copy of this software and associated documentation
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// files (the "Software"), to deal in the Software without
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// restriction, including without limitation the rights to use,
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// copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following
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// conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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// OTHER DEALINGS IN THE SOFTWARE.
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import Foundation
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/// Utilities to convert the length of an NSString and a Swift string.
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class StringUtils: NSObject {
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/// Converts the index in an NSString to the index in a Swift string.
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///
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/// An Emoji might be compose by more than one UTF-16 code points, however
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/// the length of an NSString is only the sum of the UTF-16 code points. It
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/// causes that the NSString and Swift string representation of the same
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/// string have different lengths once the string contains such Emoji. The
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/// method helps to find the index in a Swift string by passing the index
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/// in an NSString.
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static func convertToCharIndex(from utf16Index: Int, in string: String) -> Int {
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var length = 0
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for (i, character) in string.enumerated() {
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if length >= utf16Index {
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return i
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}
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length += character.utf16.count
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}
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return string.count
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}
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@objc (nextUtf16PositionForIndex:in:)
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static func nextUtf16Position(for index: Int, in string: String) -> Int {
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var index = convertToCharIndex(from: index, in: string)
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if index < string.count {
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index += 1
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}
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let count = string[..<string.index(string.startIndex, offsetBy: index)].utf16.count
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return count
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}
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@objc (previousUtf16PositionForIndex:in:)
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static func previousUtf16Position(for index: Int, in string: String) -> Int {
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var index = convertToCharIndex(from: index, in: string)
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if index > 0 {
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index -= 1
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}
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let count = string[..<string.index(string.startIndex, offsetBy: index)].utf16.count
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return count
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}
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}
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extension NSString {
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@objc var count: Int {
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(self as String).count
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}
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}
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