| /* |
| |
| Derby - Class org.apache.derby.iapi.services.io.InputStreamUtil |
| |
| Licensed to the Apache Software Foundation (ASF) under one or more |
| contributor license agreements. See the NOTICE file distributed with |
| this work for additional information regarding copyright ownership. |
| The ASF licenses this file to you 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 org.apache.derby.iapi.services.io; |
| |
| import java.io.*; |
| |
| /** |
| Utility methods for InputStream that are stand-ins for |
| a small subset of DataInput methods. This avoids pushing |
| a DataInputStream just to get this functionality. |
| */ |
| public final class InputStreamUtil { |
| private static final int SKIP_FRAGMENT_SIZE = Integer.MAX_VALUE; |
| |
| /** |
| Read an unsigned byte from an InputStream, throwing an EOFException |
| if the end of the input is reached. |
| |
| @exception IOException if an I/O error occurs. |
| @exception EOFException if the end of the stream is reached |
| |
| @see DataInput#readUnsignedByte |
| |
| */ |
| public static int readUnsignedByte(InputStream in) throws IOException { |
| int b = in.read(); |
| if (b < 0) |
| throw new EOFException(); |
| |
| return b; |
| } |
| |
| /** |
| Read a number of bytes into an array. |
| |
| @exception IOException if an I/O error occurs. |
| @exception EOFException if the end of the stream is reached |
| |
| @see DataInput#readFully |
| |
| */ |
| public static void readFully(InputStream in, byte b[], |
| int offset, |
| int len) throws IOException |
| { |
| do { |
| int bytesRead = in.read(b, offset, len); |
| if (bytesRead < 0) |
| throw new EOFException(); |
| len -= bytesRead; |
| offset += bytesRead; |
| } while (len != 0); |
| } |
| |
| |
| /** |
| Read a number of bytes into an array. |
| Keep reading in a loop until len bytes are read or EOF is reached or |
| an exception is thrown. Return the number of bytes read. |
| (InputStream.read(byte[],int,int) does not guarantee to read len bytes |
| even if it can do so without reaching EOF or raising an exception.) |
| |
| @exception IOException if an I/O error occurs. |
| */ |
| public static int readLoop(InputStream in, |
| byte b[], |
| int offset, |
| int len) |
| throws IOException |
| { |
| int firstOffset = offset; |
| do { |
| int bytesRead = in.read(b, offset, len); |
| if (bytesRead <= 0) |
| break; |
| len -= bytesRead; |
| offset += bytesRead; |
| } while (len != 0); |
| return offset - firstOffset; |
| } |
| |
| /** |
| * Skips until EOF, returns number of bytes skipped. |
| * @param is |
| * InputStream to be skipped. |
| * @return |
| * number of bytes skipped in fact. |
| * @throws IOException |
| * if IOException occurs. It doesn't contain EOFException. |
| * @throws NullPointerException |
| * if the param 'is' equals null. |
| */ |
| public static long skipUntilEOF(InputStream is) throws IOException { |
| if(is == null) |
| throw new NullPointerException(); |
| |
| long bytes = 0; |
| while(true){ |
| long r = skipPersistent(is, SKIP_FRAGMENT_SIZE); |
| bytes += r; |
| if(r < SKIP_FRAGMENT_SIZE) |
| return bytes; |
| } |
| } |
| |
| /** |
| * Skips requested number of bytes, |
| * throws EOFException if there is too few bytes in the stream. |
| * @param is |
| * InputStream to be skipped. |
| * @param skippedBytes |
| * number of bytes to skip. if skippedBytes ≷= zero, do nothing. |
| * @throws EOFException |
| * if EOF meets before requested number of bytes are skipped. |
| * @throws IOException |
| * if IOException occurs. It doesn't contain EOFException. |
| * @throws NullPointerException |
| * if the param 'is' equals null. |
| */ |
| public static void skipFully(InputStream is, long skippedBytes) |
| throws IOException { |
| if(is == null) |
| throw new NullPointerException(); |
| |
| if(skippedBytes <= 0) |
| return; |
| |
| long bytes = skipPersistent(is, skippedBytes); |
| |
| if(bytes < skippedBytes) |
| throw new EOFException(); |
| } |
| |
| /** |
| * Tries harder to skip the requested number of bytes. |
| * <p> |
| * Note that even if the method fails to skip the requested number of bytes, |
| * it will not throw an exception. If this happens, the caller can be sure |
| * that end-of-stream has been reached. |
| * |
| * @param in byte stream |
| * @param bytesToSkip the number of bytes to skip |
| * @return The number of bytes skipped. |
| * @throws IOException if reading from the stream fails |
| */ |
| public static final long skipPersistent(InputStream in, long bytesToSkip) |
| throws IOException { |
| long skipped = 0; |
| while (skipped < bytesToSkip) { |
| long skippedNow = in.skip(bytesToSkip - skipped); |
| if (skippedNow == 0) { |
| if (in.read() == -1) { |
| // EOF, return what we have and leave it up to caller to |
| // decide what to do about it. |
| break; |
| } else { |
| skippedNow = 1; // Added to count below. |
| } |
| } |
| skipped += skippedNow; |
| } |
| return skipped; |
| } |
| } |