1 files changed, 76 insertions, 0 deletions
diff --git a/core/java/android/os/PooledStringWriter.java b/core/java/android/os/PooledStringWriter.java
new file mode 100644
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+++ b/core/java/android/os/PooledStringWriter.java
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+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.os;
+
+import java.util.HashMap;
+
+/**
+ * Helper class for writing pooled strings into a Parcel.  It must be used
+ * in conjunction with {@link android.os.PooledStringReader}.  This really needs
+ * to be pushed in to Parcel itself, but doing that is...  complicated.
+ * @hide
+ */
+public class PooledStringWriter {
+    private final Parcel mOut;
+
+    /**
+     * Book-keeping for writing pooled string objects, mapping strings we have
+     * written so far to their index in the pool.  We deliberately use HashMap
+     * here since performance is critical, we expect to be doing lots of adds to
+     * it, and it is only a temporary object so its overall memory footprint is
+     * not a signifciant issue.
+     */
+    private final HashMap<String, Integer> mPool;
+
+    /**
+     * Book-keeping for writing pooling string objects, indicating where we
+     * started writing the pool, which is where we need to ultimately store
+     * how many strings are in the pool.
+     */
+    private int mStart;
+
+    /**
+     * Next available index in the pool.
+     */
+    private int mNext;
+
+    public PooledStringWriter(Parcel out) {
+        mOut = out;
+        mPool = new HashMap<>();
+        mStart = out.dataPosition();
+        out.writeInt(0); // reserve space for final pool size.
+    }
+
+    public void writeString(String str) {
+        final Integer cur = mPool.get(str);
+        if (cur != null) {
+            mOut.writeInt(cur);
+        } else {
+            mPool.put(str, mNext);
+            mOut.writeInt(-(mNext+1));
+            mOut.writeString(str);
+            mNext++;
+        }
+    }
+
+    public void finish() {
+        final int pos = mOut.dataPosition();
+        mOut.setDataPosition(mStart);
+        mOut.writeInt(mNext);
+        mOut.setDataPosition(pos);
+    }
+}