From de6b742f8a71b3a88efe9205061595545dc605ce Mon Sep 17 00:00:00 2001 From: Kevin Marker Date: Tue, 11 Jun 2024 08:57:25 -0500 Subject: [PATCH] add circular-buffer, part of 48 in 24 --- config.json | 8 ++ .../circular-buffer/.docs/instructions.md | 58 ++++++++ .../circular-buffer/.meta/config.json | 19 +++ .../practice/circular-buffer/.meta/example.el | 69 ++++++++++ .../practice/circular-buffer/.meta/tests.toml | 52 +++++++ .../circular-buffer/circular-buffer-test.el | 130 ++++++++++++++++++ .../circular-buffer/circular-buffer.el | 13 ++ 7 files changed, 349 insertions(+) create mode 100644 exercises/practice/circular-buffer/.docs/instructions.md create mode 100644 exercises/practice/circular-buffer/.meta/config.json create mode 100644 exercises/practice/circular-buffer/.meta/example.el create mode 100644 exercises/practice/circular-buffer/.meta/tests.toml create mode 100644 exercises/practice/circular-buffer/circular-buffer-test.el create mode 100644 exercises/practice/circular-buffer/circular-buffer.el diff --git a/config.json b/config.json index 1a2f8f7a..5bcde78c 100644 --- a/config.json +++ b/config.json @@ -814,6 +814,14 @@ "practices": [], "prerequisites": [], "difficulty": 5 + }, + { + "slug": "circular-buffer", + "name": "Circular Buffer", + "uuid": "d2eaa3fa-42b3-4287-9b87-714a73ac0c65", + "practices": [], + "prerequisites": [], + "difficulty": 5 } ] }, diff --git a/exercises/practice/circular-buffer/.docs/instructions.md b/exercises/practice/circular-buffer/.docs/instructions.md new file mode 100644 index 00000000..2ba1fda2 --- /dev/null +++ b/exercises/practice/circular-buffer/.docs/instructions.md @@ -0,0 +1,58 @@ +# Instructions + +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: + +```text +[ ][ ][ ][ ][ ][ ][ ] +``` + +Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer): + +```text +[ ][ ][ ][1][ ][ ][ ] +``` + +Then assume that two more elements are added — 2 & 3 — which get appended after the 1: + +```text +[ ][ ][ ][1][2][3][ ] +``` + +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: + +```text +[ ][ ][ ][ ][ ][3][ ] +``` + +If the buffer has 7 elements then it is completely full: + +```text +[5][6][7][8][9][3][4] +``` + +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: + +```text +[5][6][7][8][9][A][B] +``` + +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: + +```text +[ ][ ][7][8][9][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. + +```text +[C][D][7][8][9][A][B] +``` diff --git a/exercises/practice/circular-buffer/.meta/config.json b/exercises/practice/circular-buffer/.meta/config.json new file mode 100644 index 00000000..b840c6a0 --- /dev/null +++ b/exercises/practice/circular-buffer/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "kmarker1101" + ], + "files": { + "solution": [ + "circular-buffer.el" + ], + "test": [ + "circular-buffer-test.el" + ], + "example": [ + ".meta/example.el" + ] + }, + "blurb": "A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.", + "source": "Wikipedia", + "source_url": "https://en.wikipedia.org/wiki/Circular_buffer" +} diff --git a/exercises/practice/circular-buffer/.meta/example.el b/exercises/practice/circular-buffer/.meta/example.el new file mode 100644 index 00000000..f44aa2d8 --- /dev/null +++ b/exercises/practice/circular-buffer/.meta/example.el @@ -0,0 +1,69 @@ +;;; circular-buffer.el --- Circular Buffer (exercism) -*- lexical-binding: t; -*- + +;;; Commentary: + +;;; Code: + + +(defclass circular-buffer () + ((capacity :initarg :capacity :initform 10) + (buf-modulus :initform 20) + (data :initform nil) + (front :initform 0) + (back :initform 0)) + :documentation "Circular buffer class") + +(cl-defmethod initialize-instance :after ((buf circular-buffer) &rest _) + (with-slots (capacity buf-modulus data) buf + (setf buf-modulus (* 2 capacity) + data (make-vector capacity nil)))) + +(cl-defmethod buf-empty-p ((buf circular-buffer)) + (with-slots (front back) buf + (= front back))) + +(cl-defmethod buf-full-p ((buf circular-buffer)) + (with-slots (front back buf-modulus capacity) buf + (= (mod (- back front) buf-modulus) capacity))) + +(cl-defmethod next-spot ((buf circular-buffer) s) + (with-slots (buf-modulus) buf + (mod (1+ s) buf-modulus))) + +(cl-defmethod advance-front ((buf circular-buffer)) + (with-slots (front) buf + (setf front (next-spot buf front)))) + +(cl-defmethod advance-back ((buf circular-buffer)) + (with-slots (back) buf + (setf back (next-spot buf back)))) + +(cl-defmethod clear ((buf circular-buffer)) + (with-slots (front back) buf + (setf front back))) + +(cl-defmethod read-buff ((buf circular-buffer)) + (with-slots (front data capacity) buf + (if (buf-empty-p buf) + (error "buffer is empty") + (let ((v (aref data (mod front capacity)))) + (advance-front buf) + v)))) + +(cl-defmethod write ((buf circular-buffer) v) + (with-slots (back data capacity) buf + (if (buf-full-p buf) + (error "buffer is full") + (progn + (aset data (mod back capacity) v) + (advance-back buf))))) + +(cl-defmethod overwrite ((buf circular-buffer) v) + (with-slots (front) buf + (when (buf-full-p buf) + (advance-front buf)) + (write buf v))) + +(provide 'circular-buffer) +;;; circular-buffer.el ends here + diff --git a/exercises/practice/circular-buffer/.meta/tests.toml b/exercises/practice/circular-buffer/.meta/tests.toml new file mode 100644 index 00000000..0fb3143d --- /dev/null +++ b/exercises/practice/circular-buffer/.meta/tests.toml @@ -0,0 +1,52 @@ +# This is an auto-generated file. +# +# Regenerating this file via `configlet sync` will: +# - Recreate every `description` key/value pair +# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications +# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion) +# - Preserve any other key/value pair +# +# As user-added comments (using the # character) will be removed when this file +# is regenerated, comments can be added via a `comment` key. + +[28268ed4-4ff3-45f3-820e-895b44d53dfa] +description = "reading empty buffer should fail" + +[2e6db04a-58a1-425d-ade8-ac30b5f318f3] +description = "can read an item just written" + +[90741fe8-a448-45ce-be2b-de009a24c144] +description = "each item may only be read once" + +[be0e62d5-da9c-47a8-b037-5db21827baa7] +description = "items are read in the order they are written" + +[2af22046-3e44-4235-bfe6-05ba60439d38] +description = "full buffer can't be written to" + +[547d192c-bbf0-4369-b8fa-fc37e71f2393] +description = "a read frees up capacity for another write" + +[04a56659-3a81-4113-816b-6ecb659b4471] +description = "read position is maintained even across multiple writes" + +[60c3a19a-81a7-43d7-bb0a-f07242b1111f] +description = "items cleared out of buffer can't be read" + +[45f3ae89-3470-49f3-b50e-362e4b330a59] +description = "clear frees up capacity for another write" + +[e1ac5170-a026-4725-bfbe-0cf332eddecd] +description = "clear does nothing on empty buffer" + +[9c2d4f26-3ec7-453f-a895-7e7ff8ae7b5b] +description = "overwrite acts like write on non-full buffer" + +[880f916b-5039-475c-bd5c-83463c36a147] +description = "overwrite replaces the oldest item on full buffer" + +[bfecab5b-aca1-4fab-a2b0-cd4af2b053c3] +description = "overwrite replaces the oldest item remaining in buffer following a read" + +[9cebe63a-c405-437b-8b62-e3fdc1ecec5a] +description = "initial clear does not affect wrapping around" diff --git a/exercises/practice/circular-buffer/circular-buffer-test.el b/exercises/practice/circular-buffer/circular-buffer-test.el new file mode 100644 index 00000000..985e5446 --- /dev/null +++ b/exercises/practice/circular-buffer/circular-buffer-test.el @@ -0,0 +1,130 @@ +;;; circular-buffer-test.el --- Circular Buffer (exercism) -*- lexical-binding: t; -*- + +;;; Commentary: + +;;; Code: + + +(load-file "circular-buffer.el") + +(defun create-test-buffer (capacity) + "Helper function to create a circular buffer with the given capacity." + (circular-buffer :capacity capacity)) + +(ert-deftest reading-empty-buffer-should-fail () + (let ((buf (create-test-buffer 1))) + (should-error (read-buff buf) :type 'error))) + + +(ert-deftest can-read-an-item-just-written () + (let ((buf (create-test-buffer 1))) + (write buf 1) + (should (equal (read-buff buf) 1)))) + + +(ert-deftest each-item-may-only-be-read-once () + (let ((buf (create-test-buffer 1))) + (write buf 1) + (should (equal (read-buff buf) 1)) + (should-error (read-buff buf) :type 'error))) + + +(ert-deftest items-are-read-in-the-order-they-are-written () + (let ((buf (create-test-buffer 2))) + (write buf 1) + (write buf 2) + (should (equal (read-buff buf) 1)) + (should (equal (read-buff buf) 2)))) + + +(ert-deftest full-buffer-cant-be-written-to () + (let ((buf (create-test-buffer 1))) + (write buf 1) + (should-error (write buf 2) :type 'error))) + + +(ert-deftest a-read-frees-up-capacity-for-another-write () + (let ((buf (create-test-buffer 1))) + (write buf 1) + (should (equal (read-buff buf) 1)) + (write buf 2) + (should (equal (read-buff buf) 2)))) + + +(ert-deftest read-position-is-maintained-even-across-multiple-writes () + (let ((buf (create-test-buffer 3))) + (write buf 1) + (write buf 2) + (should (equal (read-buff buf) 1)) + (write buf 3) + (should (equal (read-buff buf) 2)) + (should (equal (read-buff buf) 3)))) + + +(ert-deftest items-cleared-out-of-buffer-cant-be-read () + (let ((buf (create-test-buffer 1))) + (write buf 1) + (clear buf) + (should-error (read-buff buf) :type 'error))) + + +(ert-deftest clear-frees-up-capacity-for-another-write () + (let ((buf (create-test-buffer 1))) + (write buf 1) + (clear buf) + (write buf 2) + (should (equal (read-buff buf) 2)))) + + +(ert-deftest clear-does-nothing-on-empty-buffer () + (let ((buf (create-test-buffer 1))) + (clear buf) + (write buf 1) + (should (equal (read-buff buf) 1)))) + + +(ert-deftest overwrite-acts-like-write-on-non-full-buffer () + (let ((buf (create-test-buffer 2))) + (write buf 1) + (overwrite buf 2) + (should (equal (read-buff buf) 1)) + (should (equal (read-buff buf) 2)))) + + +(ert-deftest overwrite-replaces-the-oldest-item-on-full-buffer () + (let ((buf (create-test-buffer 2))) + (write buf 1) + (write buf 2) + (overwrite buf 3) + (should (equal (read-buff buf) 2)) + (should (equal (read-buff buf) 3)))) + + +(ert-deftest overwrite-replaces-the-oldest-item-remaining-in-buffer-following-a-read () + (let ((buf (create-test-buffer 3))) + (write buf 1) + (write buf 2) + (write buf 3) + (should (equal (read-buff buf) 1)) + (write buf 4) + (overwrite buf 5) + (should (equal (read-buff buf) 3)) + (should (equal (read-buff buf) 4)) + (should (equal (read-buff buf) 5)))) + + +(ert-deftest initial-clear-does-not-affect-wrapping-around () + (let ((buf (create-test-buffer 2))) + (clear buf) + (write buf 1) + (write buf 2) + (overwrite buf 3) + (overwrite buf 4) + (should (equal (read-buff buf) 3)) + (should (equal (read-buff buf) 4)) + (should-error (read-buff buf) :type 'error))) + + +(provide 'circular-buffer-test) +;;; circular-buffer-test.el ends here + diff --git a/exercises/practice/circular-buffer/circular-buffer.el b/exercises/practice/circular-buffer/circular-buffer.el new file mode 100644 index 00000000..b694273e --- /dev/null +++ b/exercises/practice/circular-buffer/circular-buffer.el @@ -0,0 +1,13 @@ +;;; circular-buffer.el --- Circular Buffer (exercism) -*- lexical-binding: t; -*- + +;;; Commentary: + +;;; Code: + + +(defclass circular-buffer () + (error "Delete this S-Expression and write your own implementation")) + +(provide 'circular-buffer) +;;; circular-buffer.el ends here +