包在一个字节串 [英] Pack in an octet string

问题描述

可能重复：结果
  填充字节串

我有不同的位长度的65参数，我需要填写字节串。 Parametrs将连续字节串来填补。例如，假设第一个参数是1位长，所以它将在字节串的第一个字节的第0位的位置来填补。现在，第二个参数是假设9位长。因此，这parametr的前7位将在同一个八比特填充和接下来的2位应该前往下一个八位位组的第0和第1位的位置。同样其他参数将得到填补的字节串。我试着写在那里我传递的指向当前八位位组的位位置，并从那里数据将被复制源指针的函数。但我发现在逻辑上实现的难度。我曾试过无数的逻辑（位操作，位移，旋转等），但无法获得正确的。我将不胜AP preciate，如果有人可以给我在C的逻辑/功能这样做。您还可以使用不同的函数原型。

I have 65 parameters of different bit length which I need to fill in an octet string. Parametrs would be filled continuously in octet string. For example, suppose the first parameter is 1 bit long so it would be filled at 0th bit position of 1st octet of the octet string. Now the second parameter is suppose 9 bit long. So the first 7 bits of this parametr would be filled in the same octet and the next 2 bits should go to 0th and 1st bit position of next octet. Similarly other parameters would get filled in the octet string. I tried to write a function where in I passed the pointer to the current octet, the bit position and the source pointer from where data would get copied. But I find difficulty in logic implemetation. I have tried numerous logics(bit operation, bit shifting, rotation etc.) but could not get the correct one. I would greatly appreciate if someone can give me a logic/function in "C" to do so. You can use different function prototype also.

推荐答案

这被称为比特流，而且是相当常见的如低级别的网络协议。

This is called a "bitstream", and is fairly common in e.g. low-level networking protocols.

如果有你的参数，例如一个合理的上限32位，你应该考虑在实施类似的条款：

If there's a reasonable upper bound on your parameters, e.g. 32 bits, you should think in terms of implementing something like:

void bitstream_append(uint32_t value, uint8_t bits);

这将追加位 价值的最右边位到流。这可能有助于想到你会如何实施，如果你已经有了 bitstream_append_bit（布尔位）;

which would append the bits rightmost bits of value to the stream. It might help to think how you would implement that if you already had bitstream_append_bit(bool bit);.

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