如何将NSData转换为NSString十六进制字符串？ [英] How to convert an NSData into an NSString Hex string?

问题描述

当我在 NSData 对象上调用 -description 时，我看到一个漂亮的十六进制字符串 NSData 对象的字节如：

When I call -description on an NSData object, I see a pretty Hex string of the NSData object's bytes like:

<f6e7cd28 0fc5b5d4 88f8394b af216506 bc1bba86 4d5b483d>

我想将这个数据表示内存中 NSString 所以我可以使用它..我不喜欢调用 - [NSData description] 然后只是修剪lt / gt引号（因为我认为这不是 NSData 的公共接口的保证方面，并且将来会发生变化）。

I'd like to get this representation of the data (minus the lt/gt quotes) into an in-memory NSString so I can work with it.. I'd prefer not to call -[NSData description] and then just trim the lt/gt quotes (because I assume that is not a guaranteed aspect of NSData's public interface and is subject change in the future).

最简单的方法是将 NSData 对象表示成 NSString 对象（除了调用 -description ）？

What's the simplest way to get this representation of an NSData object into an NSString object (other than calling -description)?

推荐答案

NSData *data = ...;
NSUInteger capacity = data.length * 2;
NSMutableString *sbuf = [NSMutableString stringWithCapacity:capacity];
const unsigned char *buf = data.bytes;
NSInteger i;
for (i=0; i<data.length; ++i) {
  [sbuf appendFormat:@"%02X", (NSUInteger)buf[i]];
}

如果您需要更高效的产品，请尝试：

If you need something more performant try this:

static inline char itoh(int i) {
    if (i > 9) return 'A' + (i - 10);
    return '0' + i;
}

NSString * NSDataToHex(NSData *data) {
    NSUInteger i, len;
    unsigned char *buf, *bytes;

    len = data.length;
    bytes = (unsigned char*)data.bytes;
    buf = malloc(len*2);

    for (i=0; i<len; i++) {
        buf[i*2] = itoh((bytes[i] >> 4) & 0xF);
        buf[i*2+1] = itoh(bytes[i] & 0xF);
    }

    return [[NSString alloc] initWithBytesNoCopy:buf
                                          length:len*2
                                        encoding:NSASCIIStringEncoding
                                    freeWhenDone:YES];
}

Swift版本

extension NSData {

    var hexString: String? {
        let buf = UnsafePointer<UInt8>(bytes)
        let charA = UInt8(UnicodeScalar("a").value)
        let char0 = UInt8(UnicodeScalar("0").value)

        func itoh(value: UInt8) -> UInt8 {
            return (value > 9) ? (charA + value - 10) : (char0 + value)
        }

        let ptr = UnsafeMutablePointer<UInt8>.alloc(length * 2)

        for i in 0 ..< length {
            ptr[i*2] = itoh((buf[i] >> 4) & 0xF)
            ptr[i*2+1] = itoh(buf[i] & 0xF)
        }

        return String(bytesNoCopy: ptr, length: length*2, encoding: NSUTF8StringEncoding, freeWhenDone: true)
    }
}

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