16进制String和int互转

+(unsigned long)getIntFromHexString:(NSString *) str{
//先以16为参数告诉strtoul字符串参数表示16进制数字，然后使用0x%X转为数字类型
//strtoul如果传入的字符开头是“0x”,那么第三个参数是0也可以
return strtoul([str UTF8String],0,16);
}

+(NSString *)toHex:(long long int)tmpid length:(int)length
{
NSString *nLetterValue;
NSString *str =@"";
long long int ttmpig;
for (int i = 0; i<9; i++) {
ttmpig=tmpid%16;
tmpid=tmpid/16;
switch (ttmpig)
{
case 10:
nLetterValue =@"A";break;
case 11:
nLetterValue =@"B";break;
case 12:
nLetterValue =@"C";break;
case 13:
nLetterValue =@"D";break;
case 14:
nLetterValue =@"E";break;
case 15:
nLetterValue =@"F";break;
default:nLetterValue=[[NSString alloc]initWithFormat:@"%lli",ttmpig];

}
str = [nLetterValue stringByAppendingString:str];
if (tmpid == 0) {
break;
}

}
while (str.length < length) {
str = [NSString stringWithFormat:@"0%@",str];
}
return [NSString stringWithFormat:@"0x%@",str];
}

// 十六进制转换为普通字符串的。
+ (NSString *)stringFromHexString:(NSString *)hexString { //

char *myBuffer = (char *)malloc((int)[hexString length] / 2 + 1);
bzero(myBuffer, [hexString length] / 2 + 1);
for (int i = 0; i < [hexString length] - 1; i += 2) {
unsigned int anInt;
NSString * hexCharStr = [hexString substringWithRange:NSMakeRange(i, 2)];
NSScanner * scanner = [[[NSScanner alloc] initWithString:hexCharStr] autorelease];
[scanner scanHexInt:&anInt];
myBuffer[i / 2] = (char)anInt;
}
NSString *unicodeString = [NSString stringWithCString:myBuffer encoding:4];
NSLog(@"------字符串=======%@",unicodeString);
return unicodeString;

}

//普通字符串转换为十六进制的。

+ (NSString *)hexStringFromString:(NSString *)string{
NSData *myD = [string dataUsingEncoding:NSUTF8StringEncoding];
Byte *bytes = (Byte *)[myD bytes];
//下面是Byte 转换为16进制。
NSString *hexStr=@"";
for(int i=0;i<[myD length];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];
}
return hexStr;
}

//int 转data
int i = 1;
NSData *data = [NSData dataWithBytes: &i length: sizeof(i)];
//data 转int
int i;
[data getBytes: &i length: sizeof(i)];