NSString / NSData / char* 类型之间的转

一、NSData 与 NSString

NSData -> NSString（根据需要设置编码方式）

let data = Data()
let str = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
print("test \(str)")

NSString -> NSData（根据需要设置编码方式）

let str = ""
let data = str.data(using: String.Encoding.utf8)

二、NSData 与char

NSData -> char*（根据需要设置编码方式）

let str = "123"
let data = str.data(using: String.Encoding.utf8)
print("test \((data as! NSData).bytes)")

char -> byte（根据需要设置编码方式）

- (void)test {
    NSString *str = [[NSString alloc] initWithString:@"123"];
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    char * ss = (char *)data.bytes;
    NSLog(@"%d",strlen(ss));
    
    for (int i =0; i<strlen(ss); i++) {
        NSLog(@"%02X",ss[i]);
    }
}

char * -> NSData（根据需要设置编码方式）

let s:NSString = "123"
let str = NSString(utf8String: s.utf8String!)
let data = str?.data(using: String.Encoding.utf8.rawValue)
print(data)

三、byte与NSData

NSData -> Byte数组（根据需要设置编码方式）

- (void)test {
    NSString *testString = @"1234567890";
    NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];
    Byte *testByte = (Byte*)[testData bytes];
    for(int i=0;i<[testData length];i++) {
        NSLog(@"%d",testByte[i]);
    }
}

Byte数组 -> NSData

- (void)test {
    Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};
    NSData *data = [[NSData alloc] initWithBytes:byte length:24];
    NSLog(@"%@",data);
}

Byte数组－>16进制数

- (void)test {
    Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};
    NSData *aData = [[NSData alloc] initWithBytes:byte length:24];
    
    Byte *bytes = (Byte *)[aData bytes];
    NSString *hexStr=@"";
    for(int i=0;i<24;i++)
    {
        NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数
        if([newHexStr length]==1)
        hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
        else
        hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
    }
    NSLog(@"bytes 的16进制数为:%@",hexStr);
}

16进制数－>Byte数组

- (void)test {
    ///// 将16进制数据转化成Byte 数组
    NSString *hexString = @"3e435fab9c34891f"; //16进制字符串
    int j=0;
    Byte bytes[128];  ///3ds key的Byte 数组， 128位
    for(int i=0;i<[hexString length];i++)
    {
        int int_ch;  /// 两位16进制数转化后的10进制数
        
        unichar hex_char1 = [hexString characterAtIndex:i]; ////两位16进制数中的第一位(高位*16)
        int int_ch1;
        if(hex_char1 >= '0' && hex_char1 <='9')
        int_ch1 = (hex_char1-48)*16;   //// 0 的Ascll - 48
        else if(hex_char1 >= 'A' && hex_char1 <='F')
        int_ch1 = (hex_char1-55)*16; //// A 的Ascll - 65
        else
        int_ch1 = (hex_char1-87)*16; //// a 的Ascll - 97
        i++;
        
        unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位)
        int int_ch2;
        if(hex_char2 >= '0' && hex_char2 <='9')
        int_ch2 = (hex_char2-48); //// 0 的Ascll - 48
        else if(hex_char1 >= 'A' && hex_char1 <='F')
        int_ch2 = hex_char2-55; //// A 的Ascll - 65
        else
        int_ch2 = hex_char2-87; //// a 的Ascll - 97
        
        int_ch = int_ch1+int_ch2;
        NSLog(@"int_ch=%d",int_ch);
        bytes[j] = int_ch;  ///将转化后的数放入Byte数组里
        j++;
    }
    NSData *newData = [[NSData alloc] initWithBytes:bytes length:128];
    NSLog(@"newData=%@",newData);
}

四、NSString 与 char

NSString -> char *（根据需要设置编码方式）

let s:NSString = ""
s.utf8String

char * -> NSString

char * 转化为 NSString

五、URL 与 NSString（根据需要设置编码方式）

guard let path = Bundle.main.path(forResource: "1.html", ofType: nil) else {
    return
}

guard let url = URL(string: path) else {
    return
}
do {
    let data = try Data(contentsOf: url)
    let enc = CFStringConvertEncodingToNSStringEncoding(CFStringEncoding(CFStringEncodings.GB_18030_2000.rawValue))
    let str = NSString(data: data, encoding: enc)
    print(str)
} catch {
    print(error.localizedDescription)
}