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      1 /*
      2  * Copyright (C) 2015 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.voicemail.impl.mail;
     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 client of
     24  * this stream can call peek() to see the next available byte in the stream and a subsequent read
     25  * will still return the peeked byte.
     26  */
     27 public class PeekableInputStream extends InputStream {
     28   private final InputStream in;
     29   private boolean peeked;
     30   private int peekedByte;
     31 
     32   public PeekableInputStream(InputStream in) {
     33     this.in = in;
     34   }
     35 
     36   @Override
     37   public int read() throws IOException {
     38     if (!peeked) {
     39       return in.read();
     40     } else {
     41       peeked = false;
     42       return peekedByte;
     43     }
     44   }
     45 
     46   public int peek() throws IOException {
     47     if (!peeked) {
     48       peekedByte = read();
     49       peeked = true;
     50     }
     51     return peekedByte;
     52   }
     53 
     54   @Override
     55   public int read(byte[] b, int offset, int length) throws IOException {
     56     if (!peeked) {
     57       return in.read(b, offset, length);
     58     } else {
     59       b[0] = (byte) peekedByte;
     60       peeked = false;
     61       int r = in.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(
     78         "PeekableInputStream(in=%s, peeked=%b, peekedByte=%d)", in.toString(), peeked, peekedByte);
     79   }
     80 }
     81