Question

我尝试使用用C编写的库。我已经在Xcode项目中导入了.a和.h个文件，并检查它是否正常工作。我已经让他们在Objective-C上工作了，现在他们正在为Swift工作。

我遇到的一个问题是功能＆＃39;参数。有一个函数需要一个参数widechar（在库中定义为typedef Unsigned short int），在Swift中是UnsafeMutablePointer<UInt16>。该函数将其转换并返回结果。

所以我应该将String转换为UnsafeMutablePointer<UInt16>。我试图找到转换它的正确方法，但我只是将其转换为UnsafeMutablePointer<UInt8>。我无法找到有关将String转换为UnsafeMutablePointer<UInt16>的答案/信息。

这是我编写的源代码。

extension String{
    var utf8CString: UnsafePointer<Int8> {
        return UnsafePointer((self as NSString).utf8String!)
    }
}

func translate(toBraille: String, withTable: String) -> [String]? {
    let filteredString = toBraille.onlyAlphabet

    let table = withTable.utf8CString

    var inputLength = CInt(filteredString.count)
    var outputLength = CInt(maxBufferSize)
    let inputValue = UnsafeMutablePointer<widechar>.allocate(capacity: Int(outputLength))
    let outputValue = UnsafeMutablePointer<widechar>.allocate(capacity: Int(outputLength))

    lou_translateString(table, inputValue, &inputLength, outputValue, &outputLength, nil, nil, 0)
    //This is a function that I should use. 

    let result:[String] = []

    return result
}

Answer 1

您必须使用Swift的UTF-16表示创建一个数组您可以传递给函数的字符串，并在返回时创建来自UTF-16数组结果的Swift字符串。

为简单起见，假设C函数作为

导入Swift

func translateString(_ source: UnsafeMutablePointer<UInt16>, _ sourceLen: UnsafeMutablePointer<CInt>,
               _ dest: UnsafeMutablePointer<UInt16>, _ destLen: UnsafeMutablePointer<CInt>)

然后以下内容应该有效（内联说明）：

// Create array with UTF-16 representation of source string:
let sourceString = "Hello world"
var sourceUTF16 = Array(sourceString.utf16)
var sourceLength = CInt(sourceUTF16.count)

// Allocate array for UTF-16 representation of destination string:
let maxBufferSize = 1000
var destUTF16 = Array<UInt16>(repeating: 0, count: maxBufferSize)
var destLength = CInt(destUTF16.count)

// Call translation function:
translateString(&sourceUTF16, &sourceLength, &destUTF16, &destLength)

// Create Swift string from UTF-16 representation in destination buffer:
let destString = String(utf16CodeUnits: destUTF16, count: Int(destLength))

我假设C函数更新destLength以反映返回时翻译的字符串的实际长度。

将字符串转换为UnsafeMutablePointer <uint16>

1 个答案: