• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 321
  • Last Modified:

Set bits

I would like to set each bit in a byte, then write the byte out to a binary file.
I then need to take a value from 0 - 12, convert it to 4 bits, then write the 4 bits out to a file.

Could someone provide me with some sample code?

This is running on a linux platform.  Thanks!
0
jewee
Asked:
jewee
  • 2
  • 2
  • 2
2 Solutions
 
PaulCaswellCommented:
Hi jewee,

The clearest way to set all bits in a byte is to set it to -1 (with casts if necessary).

I am sure you can do a loop from 0 to 12.

Writing 4 bits to a file is impossible, file writing is restricted to a minimum of 8-bit bytes. Are you expected to write these bytes out as '1'/'0' characters?

Paul
0
 
jeweeAuthor Commented:
For the 4 bit value - there is also an additional 4 bit value following this.

I don't need a loop from 0 - 12.  I need to have a function which will take in a value ranging from 0 - 12, and convert it to 4 bits.
0
 
PaulCaswellCommented:
jewee,

A number taking 4 bits can range between 0 and 15. You already have only 4 bits! Why is this difficult?

Have a go at some code and post it describing your difficulties.

Paul
0
Improve Your Query Performance Tuning

In this FREE six-day email course, you'll learn from Janis Griffin, Database Performance Evangelist. She'll teach 12 steps that you can use to optimize your queries as much as possible and see measurable results in your work. Get started today!

 
dark_archonCommented:
Paul's right; the number from 0-12 will already be using no more than four bits. If you want to convert it to ASCII, just do a loop from 0 to 3 and perform an "AND" against the number with one bit set depending on the value of the counter in the loop.
0
 
dark_archonCommented:
And to output the two four-bit values to the file, do something like the following:

fputc( ( a << 4 ) | ( b & 0x0F ), fpout );

The left shift by four bits moves the value, a, into the higher "nibble", eliminating the four bits that were previously there. The b & 0x0F clears the higher four bits, leaving the lower four bits in place. And "OR" operation merges them together into the one byte.
0
 
jeweeAuthor Commented:
Paul,

Sorry, I originally misunderstood your question.  thank you.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

  • 2
  • 2
  • 2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now