从NSString转换到NSData(On conversion from NSString to NSData)

 假设我有一些字符串： 
 
NSString *someString = @"123";
 
 然后，我将这个字符串转换为NSData的实例，如下所示： 
 
NSData *someData = [NSData dataWithBytes:[someString UTF8String] length:[someString length]];
 
 据我所知，NSData实质上只是一个无编码位数据流。 我的问题是：是否NSData通过检查长度参数的值来确定每个UTF8String中有多少位？ 换句话说，[someString UTF8String]返回包含字符“123”的C字符串，[someString length]返回整数3. NSData是否理解每个字符必须包含8位？ 我完全错过了这一点吗？ 
 
 谢谢。 

Let's say I have some string as such:
 
NSString *someString = @"123";
 
Then, I convert this string to an instance of NSData as such:
 
NSData *someData = [NSData dataWithBytes:[someString UTF8String] length:[someString length]];
 
As far as I understand, NSData is essentially just an encoding-less stream of bits. My question is: does NSData determine how many bits are in each UTF8String by checking the value for the length parameter? In other words, [someString UTF8String] returns a C string containing the characters "123", and [someString length] returns the integer 3. Does NSData understand that each character then must consist of 8 bits? Am I totally missing the point?
 
Thank you.

原文：https://stackoverflow.com/questions/19853482