How to read a null terminated String from Data?-CodePudding

An iOS/Swift library delivers a Data object containing a null terminated string. When converting it to a String by calling String(data: dataInstance, encoding: .utf8), the returned String ends with "\0". Question now is, how do you convert the Data instance to a String without having "\0" appended? I.e. how can you omit the null terminating character at the end?

Trying to just .trimmingCharacters(in: .whitespacesAndNewlines) doesn't have any effect, so your advise is very much appreciated. Thank you.

CodePudding user response：

A possible solution: Determine the index of the terminating zero, and convert only the preceding part of the data:

let data = Data([65, 66, 0, 67, 0])
let end = data.firstIndex(where: { $0 == 0 }) ?? data.endIndex
if let string = String(data: data[..<end], encoding:.utf8) {
    print(string.debugDescription) // "AB"
}

If the data does not contain a null byte then everything will be converted.

CodePudding user response：

You can do some pointer operations and use the init(cString:) initialiser, which takes a null terminated string.

let resultString = data.withUnsafeBytes { buffer in
    guard let pointer = buffer.baseAddress?.assumingMemoryBound(to: CChar.self) else { 
        return "" 
    }
    return String(cString: pointer)
}