Databases
StackOverflow2013
Postsdbo
POHow to convert an array of bits to a char
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow to convert an array of bits to a char
    primarykey
    data
    text
    <p>I am trying to edit each byte of a buffer by modifying the LSB(Least Significant Bit) according to some requirements. I am using the unsigned char type for the bytes, so please let me know <strong>IF</strong> that is correct/wrong.</p> <pre><code>unsigned char buffer[MAXBUFFER]; </code></pre> <p>Next, i'm using this function </p> <pre><code>char *uchartob(char s[9], unsigned char u) </code></pre> <p>which modifies and returns the first parameter as an array of bits. This function works just fine, as the bits in the array represent the second parameter.</p> <p>Here's where the hassle begins. I am going to point out what I'm trying to do <strong>step by step</strong> so you guys can let me know where i'm taking the wrong turn.</p> <p>I am <strong>saving the result</strong> of the above function (called for each element of the buffer) in a variable</p> <pre><code>char binary_byte[9]; // array of bits </code></pre> <p>I am <strong>testing the LSB</strong> simply comparing it to some flag like above. </p> <pre><code>if (binary_byte[7]==bit_flag) // i go on and modify it like this binary_byte[7]=0; // or 1, depending on the case </code></pre> <p>Next, I'm trying to <strong>convert the array of bits</strong> binary_byte (it is an array of bits, isn't it?) back into a byte/unsigned char <strong>and update the data in the buffer at the same time</strong>. I hope I am making myself clear enough, as I am really confused at the moment.</p> <pre><code>buffer[position_in_buffer]=binary_byte[0]&lt;&lt;7| // actualize the current BYTE in the buffer binary_byte[1]&lt;&lt;6| binary_byte[2]&lt;&lt;5| binary_byte[3]&lt;&lt;4| binary_byte[4]&lt;&lt;3| binary_byte[5]&lt;&lt;2| binary_byte[6]&lt;&lt;1| binary_byte[7]; </code></pre> <p>Keep in mind that the bit at the position binary_byte[7] may be modified, that's the point of all this.</p> <p>The solution is not really elegant, but <strong>it's working</strong>, even though i am really insecure of what i did (I tried to do it with bitwise operators but without success) </p> <p>The weird thing is when I am trying to print the updated character from the buffer. It has the same bits as the previous character, but it's a completely different one. <img src="https://i.stack.imgur.com/44bQ2.png" alt="enter image description here"></p> <p>My final question is : <strong>What effect does changing only the LSB in a byte have? What should I expect?</strong>. As you can see, I'm getting only "new" characters even when i shouldn't. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USappoll
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow to convert an array of bits to a char
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow to convert an array of bits to a char
      1. This table or related slice is empty.
      1. VTClose
    1. CObitwise: set bit => a |= 1 << 7; reset bit => a &= ~(1 << 7); bit check => 1 == a & (1 << 7); flip bit a ^= (1 << 7);
      singulars
      1. POHow to convert an array of bits to a char
      1. USneagoegab
    2. COYou are not testing your bits properly. I don't remember the bit operations off the top of my head, but it's along the lines of `if (binary_byte[7] | bit_flag ==bit_flag)`
      singulars
      1. POHow to convert an array of bits to a char
      1. USmetalhead
    3. COI would consider the use of `std::bitset` over an array.
      singulars
      1. POHow to convert an array of bits to a char
      1. USandre
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload