将十六进制 NSString 转换为 NSData

Question

我正在尝试将十六进制 NSString 转换为 NSData （我正在使用下面附加的代码）。以下是输出：

<00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000>

这看起来与我完全无关。关于哪里出了问题有什么想法/建议吗？

NSString *strData = @"72ff63cea198b3edba8f7e0c23acc345050187a0cde5a9872cbab091ab73e553";

NSLog(@"string Data length is %d",[strData length]);

NSMutableData *commandToSend= [[NSMutableData alloc] init];
unsigned char whole_byte;
char byte_chars[2];
int i;
for (i=0; i < [strData length]/2; i++) {

    byte_chars[0] = [strData characterAtIndex:i*2];
    byte_chars[1] = [strData characterAtIndex:i*2+1];
    whole_byte = strtol(byte_chars, NULL, [strData length]);
    [commandToSend appendBytes:&whole_byte length:1]; 
}
NSLog(@"%@", commandToSend);    

Answer 1

NSString *command = @"72ff63cea198b3edba8f7e0c23acc345050187a0cde5a9872cbab091ab73e553";

command = [command stringByReplacingOccurrencesOfString:@" " withString:@""];
NSMutableData *commandToSend= [[NSMutableData alloc] init];
unsigned char whole_byte;
char byte_chars[3] = {'\0','\0','\0'};
int i;
for (i=0; i < [command length]/2; i++) {
    byte_chars[0] = [command characterAtIndex:i*2];
    byte_chars[1] = [command characterAtIndex:i*2+1];
    whole_byte = strtol(byte_chars, NULL, 16);
    [commandToSend appendBytes:&whole_byte length:1]; 
}
NSLog(@"%@", commandToSend);

Answer 2

这是另一种方法，它还处理前导 <、尾随 > 和嵌入空格，例如

<9dc69faf a7434ba9 aef57f5c 365d571f 4c3753c4 ae13db42 57d184ca e00246c5>

Code：

+ (NSData *)dataFromHexString:(NSString *)string
{
    string = [string lowercaseString];
    NSMutableData *data= [NSMutableData new];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i = 0;
    int length = string.length;
    while (i < length-1) {
        char c = [string characterAtIndex:i++];
        if (c < '0' || (c > '9' && c < 'a') || c > 'f')
            continue;
        byte_chars[0] = c;
        byte_chars[1] = [string characterAtIndex:i++];
        whole_byte = strtol(byte_chars, NULL, 16);
        [data appendBytes:&whole_byte length:1];
    }
    return data;
}

这是基于 @Nikunj R. Jadav 的答案

Answer 3

这可能更有用，Apple 共享了一个 NSData 类别。

NSData+HexString.m

代码是：

@implementation NSData (HexString)

// Not efficent
+(id)dataWithHexString:(NSString *)hex
{
    char buf[3];
    buf[2] = '\0';
    NSAssert(0 == [hex length] % 2, @"Hex strings should have an even number of digits (%@)", hex);
    unsigned char *bytes = malloc([hex length]/2);
    unsigned char *bp = bytes;
    for (CFIndex i = 0; i < [hex length]; i += 2) {
        buf[0] = [hex characterAtIndex:i];
        buf[1] = [hex characterAtIndex:i+1];
        char *b2 = NULL;
        *bp++ = strtol(buf, &b2, 16);
        NSAssert(b2 == buf + 2, @"String should be all hex digits: %@ (bad digit around %d)", hex, i);
    }

    return [NSData dataWithBytesNoCopy:bytes length:[hex length]/2 freeWhenDone:YES];
}

@end

Answer 4

我看到发布的几个解决方案只能转换偶数长度的字符串。

所以这是我的解决方案，如果字符串是奇数长度，如“DBA”变成这样的数据，它也能够返回正确的数据“\x0D\xBA”

+ (NSData *)dataFromHexString:(NSString *) string {
    if([string length] % 2 == 1){
        string = [@"0"stringByAppendingString:string];
    }

    const char *chars = [string UTF8String];
    int i = 0, len = (int)[string length];

    NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
    char byteChars[3] = {'\0','\0','\0'};
    unsigned long wholeByte;

    while (i < len) {
        byteChars[0] = chars[i++];
        byteChars[1] = chars[i++];
        wholeByte = strtoul(byteChars, NULL, 16);
        [data appendBytes:&wholeByte length:1];
    }
    return data;

}