8318756: Create better internal buffer for AEADs

Reviewed-by: djelinski

src/java.base/share/classes/com/sun/crypto/provider/AEADBufferedStream.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.crypto.provider;
+
+import jdk.internal.util.ArraysSupport;
+
+import java.io.ByteArrayOutputStream;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.HexFormat;
+
+/**
+ * This class extends ByteArrayOutputStream by optimizing internal buffering.
+ * It skips bounds checking, as the buffers are known and input previously
+ * checked.  toByteArray() returns the internal buffer to avoid an extra copy.
+ *
+ * This uses `count` to determine the state of `buf`.  `buf` can still
+ * point to an array while `count` equals zero.
+ */
+final class AEADBufferedStream extends ByteArrayOutputStream {
+
+    /**
+     * Create an instance with the specified buffer
+     */
+
+    public AEADBufferedStream(int len) {
+        super(len);
+    }
+
+    /**
+     * This method saves memory by returning the internal buffer. The calling
+     * method must use {@code size()} for the relevant data length as the
+     * returning byte[] maybe larger.
+     *
+     * @return internal buffer.
+     */
+    public byte[] getBuffer() {
+        return buf;
+    }
+
+    /**
+     * This method with expand the buffer if {@code count} + {@code len}
+     * is larger than the buffer byte[] length.
+     * @param len length to add to the current buffer
+     */
+    private void checkCapacity(int len) {
+        int blen = buf.length;
+        // Create a new larger buffer and append the new data
+        if (blen < count + len) {
+            buf = Arrays.copyOf(buf, ArraysSupport.newLength(blen, len, blen));
+        }
+    }
+
+    /**
+     * Takes a ByteBuffer writing non-blocksize data directly to the internal
+     * buffer.
+     * @param src remaining non-blocksize ByteBuffer
+     */
+    public void write(ByteBuffer src) {
+        int pos = src.position();
+        int len = src.remaining();
+
+        if (src.hasArray()) {
+            write(src.array(), pos + src.arrayOffset(), len);
+            src.position(pos + len);
+            return;
+        }
+
+        checkCapacity(len);
+        src.get(buf, count, len);
+        count += len;
+    }
+
+    @Override
+    public void write(byte[] in, int offset, int len) {
+        checkCapacity(len);
+        System.arraycopy(in, offset, buf, count, len);
+        count += len;
+    }
+
+    @Override
+    public String toString() {
+        return (count == 0 ? "null" : HexFormat.of().formatHex(buf));
+    }
+}