add Base64InputStream

Change-Id: I777b54bd6d01c86105b473a6701a06d350cee8d1

common/java/com/android/common/Base64InputStream.java

@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2010 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 com.android.common;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * An OutputStream that does either Base64 encoding or decoding on the
+ * data written to it, writing the resulting data to another
+ * OutputStream.
+ */
+public class Base64InputStream extends FilterInputStream {
+    private final boolean encode;
+    private final Base64.EncoderState estate;
+    private final Base64.DecoderState dstate;
+
+    private static byte[] EMPTY = new byte[0];
+
+    private static final int BUFFER_SIZE = 2048;
+    private boolean eof;
+    private byte[] inputBuffer;
+    private byte[] outputBuffer;
+    private int outputStart;
+    private int outputEnd;
+
+    /**
+     * An InputStream that performs Base64 decoding on the data read
+     * from the wrapped stream.
+     *
+     * @param in the InputStream to read the source data from
+     * @param flags bit flags for controlling the decoder; see the
+     *        constants in {@link Base64}
+     */
+    public Base64InputStream(InputStream out, int flags) {
+        this(out, flags, false);
+    }
+
+    /**
+     * Performs Base64 encoding or decoding on the data read from the
+     * wrapped InputStream.
+     *
+     * @param in the InputStream to read the source data from
+     * @param flags bit flags for controlling the decoder; see the
+     *        constants in {@link Base64}
+     * @param encode true to encode, false to decode
+     */
+    public Base64InputStream(InputStream out, int flags, boolean encode) {
+        super(out);
+        this.encode = encode;
+        eof = false;
+        inputBuffer = new byte[BUFFER_SIZE];
+        if (encode) {
+            // len*8/5+10 is an overestimate of the most bytes the
+            // encoder can produce for len bytes of input.
+            outputBuffer = new byte[BUFFER_SIZE * 8/5 + 10];
+            estate = new Base64.EncoderState(flags, outputBuffer);
+            dstate = null;
+        } else {
+            // len*3/4+10 is an overestimate of the most bytes the
+            // decoder can produce for len bytes of input.
+            outputBuffer = new byte[BUFFER_SIZE * 3/4 + 10];
+            estate = null;
+            dstate = new Base64.DecoderState(flags, outputBuffer);
+        }
+        outputStart = 0;
+        outputEnd = 0;
+    }
+
+    public boolean markSupported() {
+        return false;
+    }
+
+    public void mark(int readlimit) {
+        throw new UnsupportedOperationException();
+    }
+
+    public void reset() {
+        throw new UnsupportedOperationException();
+    }
+
+    public void close() throws IOException {
+        in.close();
+        inputBuffer = null;
+    }
+
+    public int available() {
+        return outputEnd - outputStart;
+    }
+
+    public long skip(long n) throws IOException {
+        if (outputStart >= outputEnd) {
+            refill();
+        }
+        if (outputStart >= outputEnd) {
+            return 0;
+        }
+        long bytes = Math.min(n, outputEnd-outputStart);
+        outputStart += bytes;
+        return bytes;
+    }
+
+    public int read() throws IOException {
+        if (outputStart >= outputEnd) {
+            refill();
+        }
+        if (outputStart >= outputEnd) {
+            return -1;
+        } else {
+            return outputBuffer[outputStart++];
+        }
+    }
+
+    public int read(byte[] b, int off, int len) throws IOException {
+        if (outputStart >= outputEnd) {
+            refill();
+        }
+        if (outputStart >= outputEnd) {
+            return -1;
+        }
+        int bytes = Math.min(len, outputEnd-outputStart);
+        System.arraycopy(outputBuffer, outputStart, b, off, bytes);
+        outputStart += bytes;
+        return bytes;
+    }
+
+    /**
+     * Read data from the input stream into inputBuffer, then
+     * decode/encode it into the empty outputBuffer, and reset the
+     * outputStart and outputEnd pointers.
+     */
+    private void refill() throws IOException {
+        if (eof) return;
+        int bytesRead = in.read(inputBuffer);
+        if (encode) {
+            if (bytesRead == -1) {
+                eof = true;
+                Base64.encodeInternal(EMPTY, 0, 0, estate, true);
+            } else {
+                Base64.encodeInternal(inputBuffer, 0, bytesRead, estate, false);
+            }
+            outputEnd = estate.op;
+        } else {
+            if (bytesRead == -1) {
+                eof = true;
+                Base64.decodeInternal(EMPTY, 0, 0, dstate, true);
+            } else {
+                Base64.decodeInternal(inputBuffer, 0, bytesRead, dstate, false);
+            }
+            outputEnd = dstate.op;
+        }
+        outputStart = 0;
+    }
+}