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Android example source code file (Base64InputStream.java)

This example Android source code file (Base64InputStream.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

base64inputstream, buffer_size, empty, filterinputstream, io, ioexception, unsupportedoperationexception

The Base64InputStream.java Android example source code

/*
 * 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 android.util;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * An InputStream that does Base64 decoding on the data read through
 * it.
 */
public class Base64InputStream extends FilterInputStream {
    private final Base64.Coder coder;

    private static byte[] EMPTY = new byte[0];

    private static final int BUFFER_SIZE = 2048;
    private boolean eof;
    private byte[] inputBuffer;
    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 in, int flags) {
        this(in, 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
     *
     * @hide
     */
    public Base64InputStream(InputStream in, int flags, boolean encode) {
        super(in);
        eof = false;
        inputBuffer = new byte[BUFFER_SIZE];
        if (encode) {
            coder = new Base64.Encoder(flags, null);
        } else {
            coder = new Base64.Decoder(flags, null);
        }
        coder.output = new byte[coder.maxOutputSize(BUFFER_SIZE)];
        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 coder.output[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(coder.output, outputStart, b, off, bytes);
        outputStart += bytes;
        return bytes;
    }

    /**
     * Read data from the input stream into inputBuffer, then
     * decode/encode it into the empty coder.output, and reset the
     * outputStart and outputEnd pointers.
     */
    private void refill() throws IOException {
        if (eof) return;
        int bytesRead = in.read(inputBuffer);
        boolean success;
        if (bytesRead == -1) {
            eof = true;
            success = coder.process(EMPTY, 0, 0, true);
        } else {
            success = coder.process(inputBuffer, 0, bytesRead, false);
        }
        if (!success) {
            throw new IOException("bad base-64");
        }
        outputEnd = coder.op;
        outputStart = 0;
    }
}

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