Challenge 08: Masked Bits

Tanner and Josh¹ are in the Logic Design lab helping Siddharth debug some finicky FPGAs. To track down one of the errors in their circuit, they have to analyze a series of bitstreams (ie. 32-bit integers) and count how many times a particular mask appears in each bitstream.

For instance, given a mask of 1001 (ie. 9 in hexadecimal) and a bitstream of 10010010 (ie. 146 in decimal), then the mask occurs 2 times in the sequence of bits.

Likewise, given a mask of 1111 (ie. F in hexadecimal) and a bitstream of 1111111 (ie. 127 in decimal), then the mask occurs 4 times in the sequence of bits.

Both of these examples are demonstrated below.

Unfortunately, since Tanner and Josh are CPEGs, software is not really their strong suit². Therefore, they want you to help them write a program that analyzes bitstreams and counts the number of times a mask appears in the sequence of bits.

Input¶

You will be given a series of masks and bitstreams in the form of a hexadecimal mask and integer bitstream:

Example Input¶

9 146
F 127

Output¶

For each pair of mask and bitstream, computer the number of times the mask appears in the bitstream and then output a message in the following format:

Example Output¶

1. 146 contains 0x9 2 times
2. 127 contains 0xF 4 times

Submission¶

To submit your work, follow the same procedure you used for Reading 01:

$ cd path/to/cse-30872-su23-assignments     # Go to assignments repository
$ git checkout master                       # Make sure we are on master
$ git pull --rebase                         # Pull any changes from GitHub

$ git checkout -b challenge08               # Create and checkout challenge08 branch

$ $EDITOR challenge08/program.cpp           # Edit your code

$ git add challenge08/program.cpp           # Stage your changes
$ git commit -m "challenge08: done"         # Commit your changes

$ git push -u origin challenge08            # Send changes to GitHub

To check your code, you can use the .scripts/check.py script or curl:

$ .scripts/check.py
Checking challenge08 program.c ...
  Result Success
    Time 0.41
   Score 6.00 / 6.00

$ curl -F source=@challenge08/program.c https://dredd.h4x0r.space/code/cse-30872-su23/challenge08
{"result": "Success", "score": 6, "time": 0.416405344009399414, "value": 6, "status": 0}