function CircularBuffer(capacity) {

var readPoint = 0;

var writePoint = 0;

var buffer = new Array(capacity);

return {

read: function() {

if (isBufferEmpty()) { throw new BufferEmptyException(); }

var data = buffer[readPoint];

buffer[readPoint] = null;

updateReadPoint();

return data;

},

write: function(data) {

updateBuffer(data, function() {

if (isBufferFull()) { throw new BufferFullException(); }

buffer[writePoint] = data;

});

},

forceWrite: function(data) {

updateBuffer(data, function(){

buffer[writePoint] = data;

if (isBufferFull()) { updateReadPoint(); }

});

},

clear: function() {

readPoint = 0;

writePoint = 0;

buffer = new Array(capacity);

},

isFull: function() {

return isBufferFull();

},

isEmpty: function() {

return isBufferEmpty();

}

};

function isBufferEmpty() {

return buffer.every(isEmpty);

};

function isBufferFull() {

return buffer.filter(isFull).length === capacity;

};

function updateBuffer(data, callback) {

if (isEmpty(data)) { return; }

callback();

updateWritePoint();

};

function updateWritePoint() {

writePoint = (writePoint + 1) % capacity;

};

function updateReadPoint() {

readPoint = (readPoint + 1) % capacity;

};

function isFull(data) {

return !isEmpty(data);

};

function isEmpty(data) {

return data === null || data === undefined;

};

};

function BufferEmptyException() {

this.name = 'BufferEmptyException';

this.message = 'Buffer is empty.';

};

function BufferFullException() {

this.name = 'BufferFullException';

this.message = 'Buffer is full.';

};

module.exports = {

circularBuffer: function(capacity) {

return new CircularBuffer(capacity);

},

bufferEmptyException: function() {

return new BufferEmptyException();

},

bufferFullException: function() {

return new BufferFullException();

}

};