Merge pull request #249 from danfickle/font_metrics_cache

Cache PDF font metrics across runs to avoid loading fallback fonts

openhtmltopdf-core/src/main/java/com/openhtmltopdf/extend/FSCacheEx.java

@@ -0,0 +1,9 @@
+package com.openhtmltopdf.extend;
+
+import java.util.concurrent.Callable;
+
+public interface FSCacheEx<K, V> {
+    public void put(K key, V value);
+    public V get(K key, Callable<? extends V> loader);
+    public V get(K key);
+}

openhtmltopdf-core/src/main/java/com/openhtmltopdf/extend/FSCacheValue.java

@@ -0,0 +1,11 @@
+package com.openhtmltopdf.extend;
+
+/**
+ * Note: Classes implementing this interface should be thread safe as we document the cache being useable accross threads.
+ */
+public interface FSCacheValue {
+    /**
+     * @return the (very) approximate weight of a cache value in bytes if known or -1 otherwise.
+     */
+    public int weight();
+}

openhtmltopdf-core/src/main/java/com/openhtmltopdf/extend/impl/FSDefaultCacheStore.java

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+package com.openhtmltopdf.extend.impl;
+
+import java.util.Map;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.logging.Level;
+
+import com.openhtmltopdf.extend.FSCacheEx;
+import com.openhtmltopdf.extend.FSCacheValue;
+import com.openhtmltopdf.util.XRLog;
+
+
+/**
+ * A simple default cache implementation, mainly for testing. For production you will probably want to wrap Guava's cache implementation
+ * or something similar. This implementation does not use synchronisation beyond using a <code>ConcurrentHashMap<code> internally.
+ * Specifically, the {@link #get(String, Callable)} may call the loader multiple times if called in close succession.
+ */
+public class FSDefaultCacheStore implements FSCacheEx<String, FSCacheValue> {
+    private final Map<String, FSCacheValue> _store = new ConcurrentHashMap<String, FSCacheValue>();
+
+    @Override
+    public void put(String key, FSCacheValue value) {
+        XRLog.load(Level.INFO, "Putting key(" + key + ") in cache.");
+        _store.put(key, value);
+    }
+
+    @Override
+    public FSCacheValue get(String key, Callable<? extends FSCacheValue> loader) {
+        if (_store.containsKey(key)) {
+            return this.get(key);
+        }
+
+        FSCacheValue value;
+        try {
+            value = loader.call();
+
+            if (value != null) {
+                _store.put(key, value);
+            }
+        } catch (Exception e) {
+            XRLog.exception("Could not load cache value for key(" + key + ")", e);
+            value = null;
+        }
+
+        XRLog.load(Level.INFO, (value == null ? "Missed" : "Hit") + " key(" + key + ") from cache.");
+        return value;
+    }
+
+    @Override
+    public FSCacheValue get(String key) {
+        FSCacheValue value = _store.get(key);
+        XRLog.load(Level.INFO, (value == null ? "Missed" : "Hit") + " key(" + key + ") from cache.");
+        return value;
+    }
+}

openhtmltopdf-core/src/main/java/com/openhtmltopdf/extend/impl/FSNoOpCacheStore.java

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+package com.openhtmltopdf.extend.impl;
+
+import java.util.concurrent.Callable;
+
+import com.openhtmltopdf.extend.FSCacheEx;
+import com.openhtmltopdf.extend.FSCacheValue;
+
+public class FSNoOpCacheStore implements FSCacheEx<String, FSCacheValue> {
+    public final static FSNoOpCacheStore INSTANCE = new FSNoOpCacheStore();
+
+    @Override
+    public void put(String key, FSCacheValue value) {
+    }
+
+    @Override
+    public FSCacheValue get(String key, Callable<? extends FSCacheValue> loader) {
+        return null;
+    }
+
+    @Override
+    public FSCacheValue get(String key) {
+        return null;
+    }
+}