将字符串转换成重位presentation一个字节 [英] Converting a String representation of bits to a byte

问题描述

我刚开始学习有关文件COM pression和我碰到一个有点路障。我有一个应用程序，将连接codeA字符串，如计划作为一个COM pressed二进制重新presentation 010100111111011000（注意，这是还是存储为一个字符串）。

I'm just beginning to learn about file compression and I've run into a bit of a roadblock. I have an application that will encode a string such as "program" as a compressed binary representation "010100111111011000"(note this is still stored as a String).

Encoding
g       111
r       10
a       110
p       010
o       011
m       00

现在我需要用写这文件系统中的的FileOutputStream ，我遇到的问题是，我怎么能转换成字符串010100111111011000发送字节[] / 字节 s到写入文件系统的FileOutputStream ？

Now I need to write this to the file system using a FileOutputStream, the problem I'm having is, how can I convert the string "010100111111011000" to a byte[]/bytes to be written to the file system with FileOutputStream?

我从来没有同位工作/字节之前，所以我这里开一个死胡同就是那种。

I've never worked with bits/bytes before so I'm kind of at a dead end here.

推荐答案

这是介绍位移位运算符：

An introduction to bit-shift operators:

首先，我们有左移位运算符， X＆LT;＆LT; ñ。这将在所有位移位X 按向左移动n个位，零填充新位：

First, we have the left-shift operator, x << n. This will shift all the bits in x left by n bits, filling the new bits with zero:

      1111 1111 
<< 3: 1111 1000

接下来，我们有签署右移位运算符， X＆GT;＆GT; ñ。这种转变在所有位X 右移n，复制符号位到新的位：

Next, we have the signed right-shift operator, x >> n. This shifts all the bits in x right by n, copying the sign bit into the new bits:

      1111 1111 
>> 3: 1111 1111

      1000 0000
>> 3: 1111 0000

      0111 1111 
>> 3: 0000 1111

最后，我们有填零右移位运算符， X＆GT;＆GT;＆GT; ñ。这种转变在所有位X 向右 N 位，充新位零：

Finally, we have the zero-fill right-shift operator, x >>> n. This shifts all bits in x right by n bits, filling the new bits with zero:

       1111 1111 
>>> 3: 0001 1111

您也可以找到有用的按位或操作， X |是。这在每一个位置上的位比较了 X 和是，设置新号码的位上，如果它是在任 X 或是，否则断：

You may also find useful the bitwise-or operator, x | y. This compares the bits in each position in x and y, setting the new number's bit on if it was on in either x or y, off otherwise:

  1010 0101
| 1010 1010
  ---------
  1010 1111

您应该只需要为手头的问题previous运营商，但对完整起见，这里是最后两个：

You should only need the previous operators for the problem at hand, but for the sake of completeness, here are the last two:

按位与运算符， X'放大器;是设置输出的比特一当且仅当该位是在这两个 X 和是：

The bitwise-and operator, x & y sets the bits in the output to one if and only if the bit is on in both x and y:

  1010 0101
& 1010 1010
  ---------
  1010 0000

按位异或运算符， X ^是设置输出位之一，如果该位是在一个数字或其他，但不能两者都：

The bitwise-xor operator, x ^ y sets the output bits to one if the bit is on in one number or the other but not both:

  1010 0101
^ 1010 1010
  ---------
  0000 1111

现在，手头这些应用的情况：

Now, applying these to the situation at hand:

您将需要使用比特移位运算符来添加和处理位。根据它们的字符串重新presentations在右侧开始设定位与移位他们。继续，直到你打一个字节的结束，然后移动到下一个字节。假设我们要创建一个字节再presentation1100 1010：

You will need to use the bit-shift operators to add and manipulate bits. Start setting bits at the right side according to their string representations and shift them over. Continue until you hit the end of a byte, and then move to the next byte. Say we want to create a byte representation of "1100 1010":

Our byte    Target
---------   --------
0000 0000
            1100 1010
0000 0001   ^
            1100 1010
0000 0011    ^
            1100 1010
0000 0110     ^
            1100 1010
0000 1100      ^
            1100 1010
0001 1001        ^
            1100 1010
0011 0010         ^
            1100 1010
0110 0101          ^
            1100 1010
1100 1010           ^

我会的，当然，它留给你这适用于你的工作。

I will, of course, leave it to you to apply this to your work.

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