Merge pull request exercism#52 from ekse/exercise-circular-buffer

add exercise circular-buffer

circular-buffer/Cargo.toml

@@ -0,0 +1,3 @@
+[package]
+name = "circular-buffer"
+version = "0.0.0"

circular-buffer/example.rs

@@ -0,0 +1,69 @@
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    EmptyBuffer,
+    FullBuffer,
+}
+
+pub struct CircularBuffer {
+    buffer: Vec<char>,
+    size: usize,
+    start: usize,
+    end: usize,
+}
+
+impl CircularBuffer {
+    // this circular buffer keeps an unallocated slot between the start and the end
+    // when the buffer is full. 
+    pub fn new(size: usize) -> CircularBuffer {
+        let mut v = Vec::new();
+        v.reserve(size + 1);
+
+        // initialize the buffer
+        for _ in 0..(size + 1) {
+            v.push('0');
+        }
+
+        let buffer = CircularBuffer { 
+                buffer: v, 
+                size: size + 1, 
+                start: 0, 
+                end: 0 
+        };
+
+        buffer
+    }
+
+    pub fn read(&mut self) -> Result<char, Error> {
+        if self.start == self.end {
+            return Err(Error::EmptyBuffer);
+        }
+
+        let v = *self.buffer.get(self.start).unwrap();
+        self.start = (self.start + 1) % self.size;
+
+        Ok(v)
+    }
+
+    pub fn write(&mut self, byte: char) -> Result<(), Error> {
+        if (self.end + 1) % self.size == self.start {
+            return Err(Error::FullBuffer);
+        } else {
+            self.buffer[self.end] = byte;
+            self.end = (self.end + 1) % self.size;
+            return Ok(());
+        }
+    }
+
+    pub fn overwrite(&mut self, byte: char) {
+        self.buffer[self.end] = byte;
+        self.end = (self.end + 1) % self.size;
+        if self.start == self.end {
+            self.start = (self.start + 1) % self.size;
+        }
+    }
+
+    pub fn clear(&mut self) {
+        self.start = 0;
+        self.end = 0;
+    }
+}

circular-buffer/tests/circular-buffer.rs

@@ -0,0 +1,90 @@
+extern crate circular_buffer;
+
+#[allow(unused_must_use)]
+mod tests {
+
+    use circular_buffer::{CircularBuffer, Error};
+
+    #[test]
+    fn error_on_read_empty_buffer() {
+        let mut buffer = CircularBuffer::new(1);
+        assert_eq!(Err(Error::EmptyBuffer), buffer.read());
+    }
+
+    #[test]
+    #[ignore]
+    fn write_and_read_back_item() {
+        let mut buffer = CircularBuffer::new(1);
+        buffer.write('1');
+        assert_eq!('1', buffer.read().unwrap());
+        assert_eq!(Err(Error::EmptyBuffer), buffer.read());
+    }
+
+    #[test]
+    #[ignore]
+    fn write_and_read_back_multiple_items() {
+        let mut buffer = CircularBuffer::new(2);
+        buffer.write('1');
+        buffer.write('2');
+        assert_eq!('1', buffer.read().unwrap());
+        assert_eq!('2', buffer.read().unwrap());
+        assert_eq!(Err(Error::EmptyBuffer), buffer.read());
+    }
+
+    #[test]
+    #[ignore]
+    fn alternate_write_and_read() {
+        let mut buffer = CircularBuffer::new(2);
+        buffer.write('1');
+        assert_eq!('1', buffer.read().unwrap());
+        buffer.write('2');
+        assert_eq!('2', buffer.read().unwrap());
+    }
+
+    #[test]
+    #[ignore]
+    fn clear_buffer() {
+        let mut buffer = CircularBuffer::new(3);
+        buffer.write('1');
+        buffer.write('2');
+        buffer.write('3');
+        buffer.clear();
+        assert_eq!(Err(Error::EmptyBuffer), buffer.read());
+        buffer.write('1');
+        buffer.write('2');
+        assert_eq!('1', buffer.read().unwrap());
+        buffer.write('3');
+        assert_eq!('2', buffer.read().unwrap());
+    }
+
+    #[test]
+    #[ignore]
+    fn full_buffer_error() {
+        let mut buffer = CircularBuffer::new(2);
+        buffer.write('1');
+        buffer.write('2');
+        assert_eq!(Err(Error::FullBuffer), buffer.write('3'));
+    }
+
+    #[test]
+    #[ignore]
+    fn overwrite_item_in_non_full_buffer() {
+        let mut buffer = CircularBuffer::new(2);
+        buffer.write('1');
+        buffer.overwrite('2');
+        assert_eq!('1', buffer.read().unwrap());
+        assert_eq!('2', buffer.read().unwrap());
+        assert_eq!(Err(Error::EmptyBuffer), buffer.read());
+    }
+
+    #[test]
+    #[ignore]
+    fn overwrite_item_in_full_buffer() {
+        let mut buffer = CircularBuffer::new(2);
+        buffer.write('1');
+        buffer.write('2');
+        buffer.overwrite('A');
+        assert_eq!('2', buffer.read().unwrap());
+        assert_eq!('A', buffer.read().unwrap());
+    }
+}

config.json

@@ -27,7 +27,8 @@
     "custom-set",
     "tournament",
     "rectangles",
-    "forth"
+    "forth",
+    "circular-buffer"
   ],
   "deprecated": [