overlog/lib/CircularBuffer.js

Simple logs collection and retrieval.

function CircularBuffer(n) {
  this.xs = new Array(n || 100);
  this.empty = true;
  this.begin = 0;
  this.end = 0;
};

CircularBuffer.prototype.push = function(x) {
  this.xs[this.end] = x;
  if (!this.empty && this.begin === this.end) {
    this.end = (this.end + 1) % this.xs.length;
    this.begin = this.end;
  } else {
    this.end = (this.end + 1) % this.xs.length;
  }
  this.empty = false;
};

CircularBuffer.prototype.dump = function() {
  var result = [];
  if (!this.empty) {
    var first = true;
    for (var i = this.begin; first || i != this.end; i = (i + 1) % this.xs.length) {
      result.push(this.xs[i]);
      first = false;
    }
  }
  return result;
};

CircularBuffer.prototype.size = function() {
  if (this.empty) {
    return 0;
  } else if (this.begin === this.end) {
    return this.xs.length;
  } else {
    return this.end;
  }
};

CircularBuffer.prototype.peek_least_recent = function() {
  if (this.empty) {
    throw new Error('Called peek_least_recent() on empty CircularBuffer.');
  } else {
    return this.xs[this.begin];
  }
};

CircularBuffer.prototype.peek_most_recent = function() {
  if (this.empty) {
    throw new Error('Called peek_most_recent() on empty CircularBuffer.');
  } else {
    return this.xs[(this.end + this.xs.length - 1) % this.xs.length];
  }
};

module.exports = CircularBuffer;