在Swift中将十六进制字符串转换为NSData [英] Converting Hex String to NSData in Swift

问题描述

我得到了在Objective-C中将String转换为HEX-String的代码。

I got the code to convert String to HEX-String in objective-C.

- (NSString *) CreateDataWithHexString:(NSString*)inputString
{
NSUInteger inLength = [inputString length];


unichar *inCharacters = alloca(sizeof(unichar) * inLength);
[inputString getCharacters:inCharacters range:NSMakeRange(0, inLength)];

UInt8 *outBytes = malloc(sizeof(UInt8) * ((inLength / 2) + 1));

NSInteger i, o = 0;
UInt8 outByte = 0;

for (i = 0; i < inLength; i++) {
    UInt8 c = inCharacters[i];
    SInt8 value = -1;

    if      (c >= '0' && c <= '9') value =      (c - '0');
    else if (c >= 'A' && c <= 'F') value = 10 + (c - 'A');
    else if (c >= 'a' && c <= 'f') value = 10 + (c - 'a');

    if (value >= 0) {
        if (i % 2 == 1) {
            outBytes[o++] = (outByte << 4) | value;
            outByte = 0;
        } else {
            outByte = value;
        }

    } else {
        if (o != 0) break;
    }
}

NSData *a = [[NSData alloc] initWithBytesNoCopy:outBytes length:o freeWhenDone:YES];
NSString* newStr = [NSString stringWithUTF8String:[a bytes]];
return newStr;

}

我希望在Swift中也一样。任何人都可以在Swift中翻译这段代码，或者在Swift中有什么简单的方法吗？

I want the same in Swift. Can anybody translate this code in Swift, or is there any easy way to do this in Swift?

推荐答案

这是我的十六进制字符串到数据例程：

This is my hex string to Data routine:

extension String {

    /// Create `Data` from hexadecimal string representation
    ///
    /// This takes a hexadecimal representation and creates a `Data` object. Note, if the string has any spaces or non-hex characters (e.g. starts with '<' and with a '>'), those are ignored and only hex characters are processed.
    ///
    /// - returns: Data represented by this hexadecimal string.

    func hexadecimal() -> Data? {
        var data = Data(capacity: characters.count / 2)

        let regex = try! NSRegularExpression(pattern: "[0-9a-f]{1,2}", options: .caseInsensitive)
        regex.enumerateMatches(in: self, range: NSMakeRange(0, utf16.count)) { match, flags, stop in
            let byteString = (self as NSString).substring(with: match!.range)
            var num = UInt8(byteString, radix: 16)!
            data.append(&num, count: 1)
        }

        guard data.count > 0 else { return nil }

        return data
    }

}

为了完整起见，这是我的数据到十六进制字符串例程：

And for the sake of completeness, this is my Data to hex string routine:

extension Data {

    /// Create hexadecimal string representation of `Data` object.
    ///
    /// - returns: `String` representation of this `Data` object.

    func hexadecimal() -> String {
        return map { String(format: "%02x", $0) }
            .joined(separator: "")
    }
}

---

注意，如上所示，我通常只在十六进制表示和 NSData 实例（因为如果信息可能已经表示为字符串，那么您可能不会首先创建十六进制表示）。但是您的原始问题想要在十六进制表示和 String 对象之间进行转换，这可能是这样的：

---

Note, as shown in the above, I generally only convert between hexadecimal representations and NSData instances (because if the information could have been represented as a string you probably wouldn't have created a hexadecimal representation in the first place). But your original question wanted to convert between hexadecimal representations and String objects, and that might look like so:

extension String {

    /// Create `String` representation of `Data` created from hexadecimal string representation
    ///
    /// This takes a hexadecimal representation and creates a String object from that. Note, if the string has any spaces, those are removed. Also if the string started with a `<` or ended with a `>`, those are removed, too.
    ///
    /// For example,
    ///
    ///     String(hexadecimal: "<666f6f>")
    ///
    /// is
    ///
    ///     Optional("foo")
    ///
    /// - returns: `String` represented by this hexadecimal string.

    init?(hexadecimal string: String, encoding: String.Encoding = .utf8) {
        guard let data = string.hexadecimal() else {
            return nil
        }

        self.init(data: data, encoding: encoding)
    }

    /// Create hexadecimal string representation of `String` object.
    ///
    /// For example,
    ///
    ///     "foo".hexadecimalString()
    ///
    /// is
    ///
    ///     Optional("666f6f")
    ///
    /// - parameter encoding: The `String.Encoding` that indicates how the string should be converted to `Data` before performing the hexadecimal conversion.
    ///
    /// - returns: `String` representation of this String object.

    func hexadecimalString(encoding: String.Encoding = .utf8) -> String? {
        return data(using: encoding)?
            .hexadecimal()
    }

}

然后你就可以像上面那样使用上面的内容：

You could then use the above like so:

let hexString = "68656c6c 6f2c2077 6f726c64"
print(String(hexadecimal: hexString))

或者，

let originalString = "hello, world"
print(originalString.hexadecimalString())

对于早期Swift版本的上述排列，请参阅此问题的修订历史记录。

For permutations of the above for earlier Swift versions, see the revision history of this question.

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