将NSInteger附加到NSMutableData [英] Append NSInteger to NSMutableData

问题描述

如何将NSInteger附加到NSMutableData. ......的所有东西

How do you append a NSInteger to NSMutableData. Something allong the lines of...

NSMutableData *myData = [[NSMutableData alloc] init];
NSInteger myInteger = 42;

[myData appendBytes:myInteger length:sizeof(myInteger)];

以便将0x0000002A附加到myData.

So that 0x0000002A will get appended to myData.

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推荐答案

传递整数的地址，而不是整数本身的地址. appendBytes:length:需要一个指向数据缓冲区的指针和该数据缓冲区的大小.在这种情况下，数据缓冲区"是整数.

Pass the address of the integer, not the integer itself. appendBytes:length: expects a pointer to a data buffer and the size of the data buffer. In this case, the "data buffer" is the integer.

[myData appendBytes:&myInteger length:sizeof(myInteger)];

但是请记住，这将使用计算机的字节序对其进行编码.如果计划将数据写入文件或通过网络发送数据，则应改用已知的字节序.例如，要从主机(您的计算机)转换为网络字节序，请使用 htonl() :

Keep in mind, though, that this will use your computer's endianness to encode it. If you plan on writing the data to a file or sending it across the network, you should use a known endianness instead. For example, to convert from host (your machine) to network endianness, use htonl():

uint32_t theInt = htonl((uint32_t)myInteger);
[myData appendBytes:&theInt length:sizeof(theInt)];

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