小小进制转化

1.16进制字符串转10进制数字

例如：@"FF"，是否有方法可以转为数字255

方法一：

NSString *hexString = @"3e435fab9c34891f"; //16进制字符串
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);
}

方法二：NSScanner

NSScanner *redScanner = [NSScanner scannerWithString:@"0B"];
unsigned int redIntValue;
[redScanner scanHexInt:&redIntValue];
NSLog(@"redIntValue = %u",redIntValue);
打印：redIntValue = 11

2.NSString类型十六进制转换为十进制

例如587596b8转化为1484101304
int red = strtoul([@“587596b8” UTF8String],0,16);
strtoul