Keep in mind that any String(format: ...)
solution will be terribly slow (for large data)
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]];
}
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 version
private extension Data {
var hexadecimalString: String {
let charA: UInt8 = 0x61
let char0: UInt8 = 0x30
func byteToChar(_ b: UInt8) -> Character {
Character(UnicodeScalar(b > 9 ? charA + b - 10 : char0 + b))
}
let hexChars = flatMap {[
byteToChar(($0 >> 4) & 0xF),
byteToChar($0 & 0xF)
]}
return String(hexChars)
}
}
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