A circular buffer, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
A circular buffer first starts empty and of some predefined length. For example, this is a 7-element buffer:
[ ][ ][ ][ ][ ][ ][ ]
Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer):
[ ][ ][ ][ ][ ][ ]
Then assume that two more elements are added — 2 & 3 — which get appended after the 1:
[ ][ ][ ][ ]
If two elements are then removed from the buffer, the oldest values inside the buffer are removed. The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3:
[ ][ ][ ][ ][ ][ ]
If the buffer has 7 elements then it is completely full:
When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free.
When the buffer is full, the client can opt to overwrite the oldest data with a forced write. In this case, two more elements — A & B — are added and they overwrite the 3 & 4:
3 & 4 have been replaced by A & B making 5 now the oldest data in the buffer. Finally, if two elements are removed then what would be returned is 5 & 6 yielding the buffer:
[ ][A][B][ ]
Because there is space available, if the client again uses overwrite to store C & D then the space where 5 & 6 were stored previously will be used not the location of 7 & 8. 7 is still the oldest element and the buffer is once again full.
Refer to the exercism help page for Rust installation and learning resources.
Writing the Code
Execute the tests with:
$ cargo test
All but the first test have been ignored. After you get the first test to
pass, open the tests source file which is located in the
and remove the
#[ignore] flag from the next test and get the tests to pass
again. Each separate test is a function with
#[test] flag above it.
Continue, until you pass every test.
If you wish to run all tests without editing the tests source file, use:
$ cargo test -- --ignored
To run a specific test, for example
some_test, you can use:
$ cargo test some_test
If the specific test is ignored use:
$ cargo test some_test -- --ignored
To learn more about Rust tests refer to the online test documentation
Make sure to read the Modules chapter if you haven't already, it will help you with organizing your files.
After you have solved the exercise, please consider using the additional utilities, described in the installation guide, to further refine your final solution.
To format your solution, inside the solution directory use
To see, if your solution contains some common ineffective use cases, inside the solution directory use
cargo clippy --all-targets
Feedback, Issues, Pull Requests
The exercism/rust repository on GitHub is the home for all of the Rust exercises. If you have feedback about an exercise, or want to help implement new exercises, head over there and create an issue. Members of the rust track team are happy to help!
If you want to know more about Exercism, take a look at the contribution guide.
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.