Add circular-buffer

config.json

@@ -543,6 +543,14 @@
           "strings"
         ]
       },
+      {
+        "slug": "circular-buffer",
+        "name": "Circular Buffer",
+        "uuid": "75477d21-a1cb-4ed8-8be9-0c9260cbecf9",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "custom-set",
         "name": "Custom Set",
@@ -571,7 +579,7 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 4
-      },  
+      },
       {
         "slug": "nucleotide-count",
         "name": "Nucleotide Count",

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+3 & 4 have been replaced by A & B making 5 now the oldest data in the buffer.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]
+```

exercises/practice/circular-buffer/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "circular_buffer.vim"
+    ],
+    "test": [
+      "circular_buffer.vader"
+    ],
+    "example": [
+      ".meta/example.vim"
+    ]
+  },
+  "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"
+}

exercises/practice/circular-buffer/.meta/example.vim

@@ -0,0 +1,54 @@
+"
+" Returns a dictionary representing a circular buffer with a set capacity
+"
+function! CircularBuffer(capacity) abort
+  return {
+  \  'capacity': a:capacity,
+  \  'size': 0,
+  \  'data': repeat([v:null], a:capacity),
+  \  'readIndex': 0,
+  \  'writeIndex': 0,
+  \  'Read': funcref('s:Read'),
+  \  'Write': funcref('s:Write'),
+  \  'Overwrite': funcref('s:Overwrite'),
+  \  'Clear': funcref('s:Clear')
+  \  }
+endfunction
+
+function! s:Read() dict
+  if self.size == 0
+    throw 'Empty buffer'
+  endif
+
+  let l:value = self.data[self.readIndex]
+  let self.readIndex = (self.readIndex + 1) % self.capacity
+  let self.size -= 1
+
+  return l:value
+endfunction
+
+function! s:Write(value) dict
+  if self.size >= self.capacity
+    throw 'Full buffer'
+  endif
+
+  let self.data[self.writeIndex] = a:value
+  let self.writeIndex = (self.writeIndex + 1) % self.capacity
+  let self.size += 1
+endfunction
+
+function! s:Overwrite(value) dict
+  if self.size == self.capacity
+    call self.Read()
+  endif
+
+  call self.Write(a:value)
+endfunction
+
+function! s:Clear() dict
+  let l:capacity = len(self.data)
+  let self.data = repeat([v:null], l:capacity)
+  let self.readIndex = 0
+  let self.writeIndex = 0
+  let self.size = 0
+endfunction

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"

exercises/practice/circular-buffer/circular_buffer.vader

@@ -0,0 +1,106 @@
+
+Execute (reading empty buffer should fail):
+  let g:buffer = CircularBuffer(1)
+  AssertThrows call g:buffer.Read()
+  AssertEqual "Empty buffer", g:vader_exception
+
+Execute (can read an item just written):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Write(1)
+  AssertEqual g:buffer.Read(), 1
+
+Execute (each item may only be read once):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Write(1)
+  AssertEqual g:buffer.Read(), 1
+  AssertThrows call g:buffer.Read()
+  AssertEqual "Empty buffer", g:vader_exception
+
+Execute (items are read in the order they are written):
+  let g:buffer = CircularBuffer(2)
+  call g:buffer.Write(1)
+  call g:buffer.Write(2)
+  AssertEqual g:buffer.Read(), 1
+  AssertEqual g:buffer.Read(), 2
+
+Execute (full buffer can't be written to):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Write(1)
+  AssertThrows call g:buffer.Write(2)
+  AssertEqual "Full buffer", g:vader_exception
+
+Execute (a read frees up capacity for another write):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Write(1)
+  AssertEqual g:buffer.Read(), 1
+  call g:buffer.Write(2)
+  AssertEqual g:buffer.Read(), 2
+
+Execute (read position is maintained even across multiple writes):
+  let g:buffer = CircularBuffer(3)
+  call g:buffer.Write(1)
+  call g:buffer.Write(2)
+  AssertEqual g:buffer.Read(), 1
+  call g:buffer.Write(3)
+  AssertEqual g:buffer.Read(), 2
+  AssertEqual g:buffer.Read(), 3
+
+Execute (items cleared out of buffer can't be read):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Write(1)
+  call g:buffer.Clear()
+  AssertThrows call g:buffer.Read()
+  AssertEqual "Empty buffer", g:vader_exception
+
+Execute (clear frees up capacity for another write):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Write(1)
+  call g:buffer.Clear()
+  call g:buffer.Write(2)
+  AssertEqual g:buffer.Read(), 2
+
+Execute (clear does nothing on empty buffer):
+  let g:buffer = CircularBuffer(1)
+  call g:buffer.Clear()
+  call g:buffer.Write(1)
+  AssertEqual g:buffer.Read(), 1
+
+Execute (overwrite acts like write on non-full buffer):
+  let g:buffer = CircularBuffer(2)
+  call g:buffer.Write(1)
+  call g:buffer.Overwrite(2)
+  AssertEqual g:buffer.Read(), 1
+  AssertEqual g:buffer.Read(), 2
+
+Execute (overwrite replaces the oldest item on full buffer):
+  let g:buffer = CircularBuffer(2)
+  call g:buffer.Write(1)
+  call g:buffer.Write(2)
+  call g:buffer.Overwrite(3)
+  AssertEqual g:buffer.Read(), 2
+  AssertEqual g:buffer.Read(), 3
+
+Execute (overwrite replaces the oldest item remaining in buffer following a read):
+  let g:buffer = CircularBuffer(3)
+  call g:buffer.Write(1)
+  call g:buffer.Write(2)
+  call g:buffer.Write(3)
+  AssertEqual g:buffer.Read(), 1
+  call g:buffer.Write(4)
+  call g:buffer.Overwrite(5)
+  AssertEqual g:buffer.Read(), 3
+  AssertEqual g:buffer.Read(), 4
+  AssertEqual g:buffer.Read(), 5
+
+Execute (initial clear does not affect wrapping around):
+  let g:buffer = CircularBuffer(2)
+  call g:buffer.Clear()
+  call g:buffer.Write(1)
+  call g:buffer.Write(2)
+  call g:buffer.Overwrite(3)
+  call g:buffer.Overwrite(4)
+  AssertEqual g:buffer.Read(), 3
+  AssertEqual g:buffer.Read(), 4
+  AssertThrows call g:buffer.Read()
+  AssertEqual "Empty buffer", g:vader_exception
+

exercises/practice/circular-buffer/circular_buffer.vim

@@ -0,0 +1,6 @@
+"
+" Returns a dictionary representing a circular buffer with a set capacity
+"
+function! CircularBuffer(capacity) abort
+  " your code goes here
+endfunction