JSONzip

zip/Keep.java

@@ -0,0 +1,84 @@
+package org.json.zip;
+
+
+/*
+ Copyright (c) 2013 JSON.org
+
+ Permission is hereby granted, free of charge, to any person obtaining a copy
+ of this software and associated documentation files (the "Software"), to deal
+ in the Software without restriction, including without limitation the rights
+ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ copies of the Software, and to permit persons to whom the Software is
+ furnished to do so, subject to the following conditions:
+
+ The above copyright notice and this permission notice shall be included in all
+ copies or substantial portions of the Software.
+
+ The Software shall be used for Good, not Evil.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ SOFTWARE.
+ */
+
+/**
+ * A keep is a data structure that associates strings (or substrings) with
+ * numbers. This allows the sending of small integers instead of strings.
+ *
+ * @author JSON.org
+ * @version 2013-04-18
+ */
+abstract class Keep implements None, PostMortem {
+    protected int capacity;
+    protected int length;
+    protected int power;
+    protected long[] uses;
+
+    public Keep(int bits) {
+        this.capacity = JSONzip.twos[bits];
+        this.length = 0;
+        this.power = 0;
+        this.uses = new long[this.capacity];
+    }
+
+    /**
+     * When an item ages, its use count is reduced by at least half.
+     *
+     * @param use
+     *            The current use count of an item.
+     * @return The new use count for that item.
+     */
+    public static long age(long use) {
+        return use >= 32 ? 16 : use / 2;
+    }
+
+    /**
+     * Return the number of bits required to contain an integer based on the
+     * current length of the keep. As the keep fills up, the number of bits
+     * required to identify one of its items goes up.
+     */
+    public int bitsize() {
+        while (JSONzip.twos[this.power] < this.length) {
+            this.power += 1;
+        }
+        return this.power;
+    }
+
+    /**
+     * Increase the usage count on an integer value.
+     */
+    public void tick(int integer) {
+        this.uses[integer] += 1;
+    }
+
+    /**
+     * Get the value associated with an integer.
+     * @param integer The number of an item in the keep.
+     * @return The value.
+     */
+    abstract public Object value(int integer);
+}