lru cache

lib/bcoin/lru.js

@@ -4,6 +4,14 @@
  * https://github.com/indutny/bcoin
  */
 
+var bcoin = require('../bcoin');
+var utils = bcoin.utils;
+var assert = utils.assert;
+
+/**
+ * LRU
+ */
+
 function LRU(maxSize) {
   if (!(this instanceof LRU))
     return new LRU(maxSize);
@@ -37,11 +45,12 @@ LRU.prototype._getSize = function _getSize(value) {
 LRU.prototype._compact = function _compact() {
   var item;
 
-  if (this.size < this.maxSize)
+  if (this.size <= this.maxSize)
     return;
 
   for (item = this.head; item; item = item.next) {
-    if (this.size <= this.maxSize / 2 | 0)
+    // if (this.size <= this.maxSize / 2 | 0)
+    if (this.size < this.maxSize)
       break;
     this.size -= this._getSize(item.value);
     delete this.data[item.key];
@@ -63,7 +72,8 @@ LRU.prototype.set = function set(key, value) {
     this.size -= this._getSize(item.value);
     this.size += this._getSize(value);
     item.value = value;
-    this.get(key);
+    this._remove(item);
+    this._append(item);
     this._compact();
     return;
   }
@@ -72,14 +82,7 @@ LRU.prototype.set = function set(key, value) {
 
   this.data[key] = item;
 
-  if (!this.head) {
-    this.head = item;
-    this.tail = item;
-  } else {
-    this.tail.next = item;
-    item.prev = this.tail;
-    this.tail = item;
-  }
+  this._append(item);
 
   this.size += this._getSize(value);
 
@@ -93,26 +96,8 @@ LRU.prototype.get = function get(key) {
   if (!item)
     return;
 
-  if (this.tail === item)
-    return item.value;
-
-  prev = item.prev;
-  next = item.next;
-  tail = this.tail;
-
-  this.tail = item;
-
-  if (this.head === item)
-    this.head = next || item;
-
-  if (prev)
-    prev.next = next;
-
-  if (next)
-    next.prev = prev;
-
-  item.next = null;
-  item.prev = tail;
+  this._remove(item);
+  this._append(item);
 
   return item.value;
 };
@@ -132,24 +117,116 @@ LRU.prototype.remove = function remove(key) {
 
   delete this.data[key];
 
-  prev = item.prev;
-  next = item.next;
-
-  if (prev)
-    prev.next = next;
-
-  if (next)
-    next.prev = prev;
-
-  if (this.tail === item)
-    this.tail = prev || null;
-
-  if (this.head === item)
-    this.head = next || null;
+  this._remove(item);
 
   return true;
 };
 
+LRU.prototype._prepend = function prepend(item) {
+  this._insert(null, item);
+};
+
+LRU.prototype._append = function prepend(item) {
+  this._insert(this.tail, item);
+};
+
+LRU.prototype._insert = function insert(ref, item) {
+  assert(!item.next);
+  assert(!item.prev);
+  if (ref == null) {
+    if (!this.head) {
+      this.head = item;
+      this.tail = item;
+    } else {
+      this.head.prev = item;
+      item.next = this.head;
+      this.head = item;
+    }
+    return;
+  }
+  item.next = ref.next;
+  item.prev = ref;
+  ref.next = item;
+  if (ref === this.tail)
+    this.tail = item;
+};
+
+LRU.prototype._remove = function insert(item) {
+  if (item.prev)
+    item.prev.next = item.next;
+
+  if (item.next)
+    item.next.prev = item.prev;
+
+  if (this.head === item)
+    this.head = item.next;
+
+  if (this.tail === item)
+    this.tail = item.prev;
+
+  item.prev = null;
+  item.next = null;
+};
+
+LRU.prototype._keys = function _keys() {
+  var keys = [];
+  var item;
+  for (item = this.head; item; item = item.next) {
+    if (item === this.head)
+      assert(!item.prev);
+    if (!item.prev)
+      assert(item === this.head);
+    if (!item.next)
+      assert(item === this.tail);
+    keys.push(item.key);
+  }
+  return keys;
+};
+
+var a1 = '1';
+var a2 = '2';
+var a3 = '3';
+var a4 = '4';
+var a5 = '5';
+var lru = new LRU(5);
+lru.set('a1', a1);
+assert(lru.get('a1') === '1');
+assert(lru.size === 1);
+assert(lru.head.key === 'a1' && lru.tail.key === 'a1' && !lru.head.prev && !lru.head.next);
+console.log(lru._keys());
+lru.set('a2', a2);
+assert(lru.get('a2') === '2');
+assert(lru.size === 2);
+assert(lru.head.key === 'a1' && lru.tail.key === 'a2'
+  && !lru.head.prev && lru.head.next.key === 'a2'
+  && !lru.tail.next && lru.tail.prev.key === 'a1');
+console.log(lru._keys());
+lru.set('a3', a3);
+assert(lru.get('a3') === '3');
+assert(lru.size === 3);
+console.log(lru._keys());
+lru.set('a3', a3);
+assert(lru.get('a3') === '3');
+assert(lru.size === 3);
+console.log(lru._keys());
+lru.set('a4', a4);
+assert(lru.get('a4') === '4');
+assert(lru.size === 4);
+console.log(lru._keys());
+// lru.set('a5', a5);
+// assert(lru.get('a5') === '5');
+// assert(lru.size === 4);
+// assert(!lru.get('a1'));
+assert(lru.get('a1'));
+lru.remove('a1');
+console.log(lru._keys());
+var _a3 = lru.head.next;
+assert(_a3.key === 'a3');
+assert(_a3.prev === lru.head && _a3.next === lru.tail);
+assert(lru.head.key === 'a2' && lru.tail.key === 'a4'
+  && !lru.head.prev && lru.head.next.key === 'a3'
+  && !lru.tail.next && lru.tail.prev.key === 'a3');
+
 /**
  * Expose
  */