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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.email;
     18 
     19 import java.io.IOException;
     20 import java.io.InputStream;
     21 
     22 /**
     23  * A filtering InputStream that allows single byte "peeks" without consuming the byte. The
     24  * client of this stream can call peek() to see the next available byte in the stream
     25  * and a subsequent read will still return the peeked byte.
     26  */
     27 public class PeekableInputStream extends InputStream {
     28     private final InputStream mIn;
     29     private boolean mPeeked;
     30     private int mPeekedByte;
     31 
     32     public PeekableInputStream(InputStream in) {
     33         this.mIn = in;
     34     }
     35 
     36     @Override
     37     public int read() throws IOException {
     38         if (!mPeeked) {
     39             return mIn.read();
     40         } else {
     41             mPeeked = false;
     42             return mPeekedByte;
     43         }
     44     }
     45 
     46     public int peek() throws IOException {
     47         if (!mPeeked) {
     48             mPeekedByte = read();
     49             mPeeked = true;
     50         }
     51         return mPeekedByte;
     52     }
     53 
     54     @Override
     55     public int read(byte[] b, int offset, int length) throws IOException {
     56         if (!mPeeked) {
     57             return mIn.read(b, offset, length);
     58         } else {
     59             b[0] = (byte)mPeekedByte;
     60             mPeeked = false;
     61             int r = mIn.read(b, offset + 1, length - 1);
     62             if (r == -1) {
     63                 return 1;
     64             } else {
     65                 return r + 1;
     66             }
     67         }
     68     }
     69 
     70     @Override
     71     public int read(byte[] b) throws IOException {
     72         return read(b, 0, b.length);
     73     }
     74 
     75     @Override
     76     public String toString() {
     77         return String.format("PeekableInputStream(in=%s, peeked=%b, peekedByte=%d)",
     78                 mIn.toString(), mPeeked, mPeekedByte);
     79     }
     80 }
     81