1 /* 2 * Copyright (C) 2010 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 android.util; 18 19 import java.io.FilterOutputStream; 20 import java.io.IOException; 21 import java.io.OutputStream; 22 23 /** 24 * An OutputStream that does Base64 encoding on the data written to 25 * it, writing the resulting data to another OutputStream. 26 */ 27 public class Base64OutputStream extends FilterOutputStream { 28 private final Base64.Coder coder; 29 private final int flags; 30 31 private byte[] buffer = null; 32 private int bpos = 0; 33 34 private static byte[] EMPTY = new byte[0]; 35 36 /** 37 * Performs Base64 encoding on the data written to the stream, 38 * writing the encoded data to another OutputStream. 39 * 40 * @param out the OutputStream to write the encoded data to 41 * @param flags bit flags for controlling the encoder; see the 42 * constants in {@link Base64} 43 */ Base64OutputStream(OutputStream out, int flags)44 public Base64OutputStream(OutputStream out, int flags) { 45 this(out, flags, true); 46 } 47 48 /** 49 * Performs Base64 encoding or decoding on the data written to the 50 * stream, writing the encoded/decoded data to another 51 * OutputStream. 52 * 53 * @param out the OutputStream to write the encoded data to 54 * @param flags bit flags for controlling the encoder; see the 55 * constants in {@link Base64} 56 * @param encode true to encode, false to decode 57 * 58 * @hide 59 */ Base64OutputStream(OutputStream out, int flags, boolean encode)60 public Base64OutputStream(OutputStream out, int flags, boolean encode) { 61 super(out); 62 this.flags = flags; 63 if (encode) { 64 coder = new Base64.Encoder(flags, null); 65 } else { 66 coder = new Base64.Decoder(flags, null); 67 } 68 } 69 write(int b)70 public void write(int b) throws IOException { 71 // To avoid invoking the encoder/decoder routines for single 72 // bytes, we buffer up calls to write(int) in an internal 73 // byte array to transform them into writes of decently-sized 74 // arrays. 75 76 if (buffer == null) { 77 buffer = new byte[1024]; 78 } 79 if (bpos >= buffer.length) { 80 // internal buffer full; write it out. 81 internalWrite(buffer, 0, bpos, false); 82 bpos = 0; 83 } 84 buffer[bpos++] = (byte) b; 85 } 86 87 /** 88 * Flush any buffered data from calls to write(int). Needed 89 * before doing a write(byte[], int, int) or a close(). 90 */ flushBuffer()91 private void flushBuffer() throws IOException { 92 if (bpos > 0) { 93 internalWrite(buffer, 0, bpos, false); 94 bpos = 0; 95 } 96 } 97 write(byte[] b, int off, int len)98 public void write(byte[] b, int off, int len) throws IOException { 99 if (len <= 0) return; 100 flushBuffer(); 101 internalWrite(b, off, len, false); 102 } 103 close()104 public void close() throws IOException { 105 IOException thrown = null; 106 try { 107 flushBuffer(); 108 internalWrite(EMPTY, 0, 0, true); 109 } catch (IOException e) { 110 thrown = e; 111 } 112 113 try { 114 if ((flags & Base64.NO_CLOSE) == 0) { 115 out.close(); 116 } else { 117 out.flush(); 118 } 119 } catch (IOException e) { 120 if (thrown != null) { 121 thrown = e; 122 } 123 } 124 125 if (thrown != null) { 126 throw thrown; 127 } 128 } 129 130 /** 131 * Write the given bytes to the encoder/decoder. 132 * 133 * @param finish true if this is the last batch of input, to cause 134 * encoder/decoder state to be finalized. 135 */ internalWrite(byte[] b, int off, int len, boolean finish)136 private void internalWrite(byte[] b, int off, int len, boolean finish) throws IOException { 137 coder.output = embiggen(coder.output, coder.maxOutputSize(len)); 138 if (!coder.process(b, off, len, finish)) { 139 throw new Base64DataException("bad base-64"); 140 } 141 out.write(coder.output, 0, coder.op); 142 } 143 144 /** 145 * If b.length is at least len, return b. Otherwise return a new 146 * byte array of length len. 147 */ embiggen(byte[] b, int len)148 private byte[] embiggen(byte[] b, int len) { 149 if (b == null || b.length < len) { 150 return new byte[len]; 151 } else { 152 return b; 153 } 154 } 155 } 156