16进制字符串转化为字节(byte)数组，16进制字符串的异或运算：
-(NSString*)generateCRC:(NSString*)str{
//把16进制字符串转换成字节数组
long len = ([str length]/2);
int j=0;
Byte result[str.length/2];
for(inti=0;i<[str length];i++)
{
int int_ch; // 两位16进制数转化后的10进制数
unichar hex_char1 = [strcharacterAtIndex: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 = [strcharacterAtIndex: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_char2 >='A'&& hex_char2 <='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);
result[j] = int_ch; //将转化后的数放入Byte数组里
j++;
}
// 异或运算
Byte check[1];
NSString*hexStr=@"";
for(inti =0; i
if(i ==0) {
check[0] = result[0];
}else{
check[0] ^=result[i];
}
}
NSData*adata = [[NSData alloc]initWithBytes:checklength:1];
hexStr = [self HexStringWithData:adata];
hexStr = [hexStr uppercaseString];
return hexStr;
}
-(NSString*)HexStringWithData:(NSData*)data{
Byte*bytes = (Byte*)[databytes];
NSString*hexStr=@"";
for(inti=0;i<[datalength];i++) {
NSString*newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数
if([newHexStrlength]==1){
hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
}
else{
hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
}
}
hexStr = [hexStr uppercaseString];
return hexStr;
}
