iOS HexString转换为NSData

即 与NSData的description方法的相反

- (NSData *)dataWithHexString:(NSString *)hexString {

NSString *newStr = [hexString stringByReplacingOccurrencesOfString:@" " withString:@""];   //去掉空格

NSString *replaceString = [newStr substringWithRange:NSMakeRange(1, newStr.length-2)];   //去掉<>符号

const char *hexChar = [replaceString UTF8String];  //转换为 char 字符串

Byte *bt = malloc(sizeof(Byte)*(replaceString.length/2));   // 开辟空间 用来存放  转换后的byte

char tmpChar[3] = {'\0','\0','\0'};

int btIndex = 0;

for (int i=0; i<replaceString.length; i += 2) {

tmpChar[0] = hexChar[i];

tmpChar[1] = hexChar[i+1]; 

bt[btIndex] = strtoul(tmpChar, NULL, 16);   // 将 hexstring 转换为 byte 的c方法   16 为16进制  

btIndex ++;

}

NSData *data = [NSData dataWithBytes:bt length:btIndex]; //创建 nsdata 对象

free(bt);  //释放空间

return data;

}

这里核心转换代码用到了 c String库里的 unsigned long strtoul(const char *, char **, int); 

完成转换