| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.iapi.services.io.InputStreamUtil |
| 4 | |
| 5 | Copyright 1998, 2004 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.iapi.services.io; |
| 22 | |
| 23 | import java.io.*; |
| 24 | |
| 25 | /** |
| 26 | Utility methods for InputStream that are stand-ins for |
| 27 | a small subset of DataInput methods. This avoids pushing |
| 28 | a DataInputStream just to get this functionality. |
| 29 | */ |
| 30 | public final class InputStreamUtil { |
| 31 | |
| 32 | /** |
| 33 | Read an unsigned byte from an InputStream, throwing an EOFException |
| 34 | if the end of the input is reached. |
| 35 | |
| 36 | @exception IOException if an I/O error occurs. |
| 37 | @exception EOFException if the end of the stream is reached |
| 38 | |
| 39 | @see DataInput#readUnsignedByte |
| 40 | |
| 41 | */ |
| 42 | public static int readUnsignedByte(InputStream in) throws IOException { |
| 43 | int b = in.read(); |
| 44 | if (b < 0) |
| 45 | throw new EOFException(); |
| 46 | |
| 47 | return b; |
| 48 | } |
| 49 | |
| 50 | /** |
| 51 | Read a number of bytes into an array. |
| 52 | |
| 53 | @exception IOException if an I/O error occurs. |
| 54 | @exception EOFException if the end of the stream is reached |
| 55 | |
| 56 | @see DataInput#readFully |
| 57 | |
| 58 | */ |
| 59 | public static void readFully(InputStream in, byte b[], |
| 60 | int offset, |
| 61 | int len) throws IOException |
| 62 | { |
| 63 | do { |
| 64 | int bytesRead = in.read(b, offset, len); |
| 65 | if (bytesRead < 0) |
| 66 | throw new EOFException(); |
| 67 | len -= bytesRead; |
| 68 | offset += bytesRead; |
| 69 | } while (len != 0); |
| 70 | } |
| 71 | |
| 72 | |
| 73 | /** |
| 74 | Read a number of bytes into an array. |
| 75 | Keep reading in a loop until len bytes are read or EOF is reached or |
| 76 | an exception is thrown. Return the number of bytes read. |
| 77 | (InputStream.read(byte[],int,int) does not guarantee to read len bytes |
| 78 | even if it can do so without reaching EOF or raising an exception.) |
| 79 | |
| 80 | @exception IOException if an I/O error occurs. |
| 81 | */ |
| 82 | public static int readLoop(InputStream in, |
| 83 | byte b[], |
| 84 | int offset, |
| 85 | int len) |
| 86 | throws IOException |
| 87 | { |
| 88 | int firstOffset = offset; |
| 89 | do { |
| 90 | int bytesRead = in.read(b, offset, len); |
| 91 | if (bytesRead <= 0) |
| 92 | break; |
| 93 | len -= bytesRead; |
| 94 | offset += bytesRead; |
| 95 | } while (len != 0); |
| 96 | return offset - firstOffset; |
| 97 | } |
| 98 | |
| 99 | |
| 100 | /** |
| 101 | Skip a number of bytes in the stream. Note that this version takes and returns |
| 102 | a long instead of the int used by skipBytes. |
| 103 | |
| 104 | @exception IOException if an I/O error occurs. |
| 105 | @exception EOFException if the end of the stream is reached |
| 106 | |
| 107 | @see DataInput#skipBytes |
| 108 | */ |
| 109 | public static long skipBytes(InputStream in, long n) throws IOException { |
| 110 | |
| 111 | while (n > 0) { |
| 112 | //System.out.println(" skip n = " + n); |
| 113 | long delta = in.skip(n); |
| 114 | //System.out.println(" skipped = " + delta); |
| 115 | if (delta < 0) |
| 116 | throw new EOFException(); |
| 117 | n -= delta; |
| 118 | } |
| 119 | |
| 120 | return n; |
| 121 | } |
| 122 | } |