Add circular-buffer exercise

Author: ErikSchierboom

config.json

@@ -65,14 +65,6 @@
         "prerequisites": [],
         "difficulty": 1
       },
-      {
-        "slug": "isbn-verifier",
-        "name": "ISBN Verifier",
-        "uuid": "c4e3ea2f-8648-49ba-a9a5-54ba11b5c27e",
-        "practices": [],
-        "prerequisites": [],
-        "difficulty": 3
-      },
       {
         "slug": "leap",
         "name": "Leap",
@@ -129,6 +121,14 @@
         "prerequisites": [],
         "difficulty": 3
       },
+      {
+        "slug": "isbn-verifier",
+        "name": "ISBN Verifier",
+        "uuid": "c4e3ea2f-8648-49ba-a9a5-54ba11b5c27e",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "line-up",
         "name": "Line Up",
@@ -240,6 +240,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 5
+      },
+      {
+        "slug": "circular-buffer",
+        "name": "Circular Buffer",
+        "uuid": "ed824c1e-cc70-43f7-86d9-0d767cf2845e",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 6
       }
     ]
   },

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": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "solution.jai"
+    ],
+    "test": [
+      "tests.jai"
+    ],
+    "example": [
+      ".meta/example.jai"
+    ]
+  },
+  "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.jai

@@ -0,0 +1,48 @@
+// Unfortunately, there is a limitation right now, with the interaction of polymorph variables
+// in the type slot, and parameter auto-bakes, which is that they need to all
+// be solved in one step, thus they can't depend on each other in the same
+// procedure declaration. We thus can't parameterize the Circular_Buffer type by the element type
+// and its capacity, and instead have to hardcode them.
+
+Circular_Buffer :: struct {
+    data: [] int;
+    read_index: int;
+    write_index: int;
+    count: int;
+}
+
+new_circular_buffer :: (capacity: int) -> Circular_Buffer {
+    return Circular_Buffer.{ data = NewArray(capacity, int, initialized=true) };
+}
+
+read :: (circular_buffer: *Circular_Buffer) -> bool, int {
+    if circular_buffer.count == 0 return false, 0;
+    value := circular_buffer.data[circular_buffer.read_index];
+    circular_buffer.read_index = (circular_buffer.read_index + 1) % circular_buffer.data.count;
+    circular_buffer.count -= 1;
+    return true, value;
+}
+
+write :: (circular_buffer: *Circular_Buffer, value: int) -> bool {
+    if circular_buffer.count == circular_buffer.data.count return false;
+    circular_buffer.data[circular_buffer.write_index] = value;
+    circular_buffer.write_index = (circular_buffer.write_index + 1) % circular_buffer.data.count;
+    circular_buffer.count += 1;
+    return true;
+}
+
+clear :: (circular_buffer: *Circular_Buffer) {
+    circular_buffer.read_index = 0;
+    circular_buffer.write_index = 0;
+    circular_buffer.count = 0;
+}
+
+overwrite :: (circular_buffer: *Circular_Buffer, value: int) {
+    circular_buffer.data[circular_buffer.write_index] = value;
+    circular_buffer.write_index = (circular_buffer.write_index + 1) % circular_buffer.data.count;
+    if circular_buffer.count < circular_buffer.data.count {
+        circular_buffer.count += 1;
+    } else {
+        circular_buffer.read_index = (circular_buffer.read_index + 1) % circular_buffer.data.count;
+    }
+}

exercises/practice/circular-buffer/.meta/generator.jai

@@ -0,0 +1,50 @@
+to_test_case :: (canonical_case: CanonicalCase) -> Test {
+    using test: Test;
+    name = to_test_name(canonical_case.description);
+    skip = canonical_case.index > 0;
+    _, capacity := get_property(canonical_case.input, "capacity");
+    _, operations := get_array_property(canonical_case.input, "operations");
+
+    lines: [..]string;
+    array_add(*lines, tprint("CAPACITY :: %;", to_code(capacity)));
+    array_add(*lines, "circular_buffer := new_circular_buffer(CAPACITY);");
+
+    write_idx, read_idx: int = 1;
+
+    for operation: operations {
+        _, operation_name := get_string_property(*operation, "operation");
+        _, should_succeed := get_boolean_property(*operation, "should_succeed");
+
+        if operation_name == {
+            case "write";
+                _, item := get_number_property(*operation, "item");
+                array_add(*lines, tprint("write_successful_% := write(*circular_buffer, %);", write_idx, to_code(item)));
+                array_add(*lines, tprint("assert_equal(%, write_successful_%);", to_code(should_succeed), write_idx));
+                write_idx += 1;
+            case "read";
+                array_add(*lines, tprint("read_successful_%, read_value_% := read(*circular_buffer);", read_idx, read_idx));
+                array_add(*lines, tprint("assert_equal(%, read_successful_%);", to_code(should_succeed), read_idx));
+                if should_succeed {
+                    _, expected := get_number_property(*operation, "expected");
+                    array_add(*lines, tprint("assert_equal(%, read_value_%);", to_code(expected), read_idx));
+                }
+                read_idx += 1;
+            case "clear";
+                array_add(*lines, "clear(*circular_buffer);");
+            case "overwrite";
+                _, item := get_number_property(*operation, "item");
+                array_add(*lines, tprint("overwrite(*circular_buffer, %);", to_code(item)));
+            case;
+                assert(false, tprint("Unexpected operation: %", operation_name));
+        }
+    }
+
+    test.multiline_body = lines;
+
+    return test;
+}
+
+#run run_generator("circular-buffer", to_test_case);
+
+#import "Basic";
+#import,dir "../../../shared/generator";

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"