001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.io.input.buffer; 018 019import static org.apache.commons.io.IOUtils.EOF; 020 021import java.io.FilterInputStream; 022import java.io.IOException; 023import java.io.InputStream; 024import java.util.Objects; 025 026import org.apache.commons.io.IOUtils; 027 028/** 029 * Implements a buffered input stream, which is internally based on a {@link CircularByteBuffer}. Unlike the 030 * {@link java.io.BufferedInputStream}, this one doesn't need to reallocate byte arrays internally. 031 */ 032public class CircularBufferInputStream extends FilterInputStream { 033 034 /** Internal buffer. */ 035 protected final CircularByteBuffer buffer; 036 037 /** Internal buffer size. */ 038 protected final int bufferSize; 039 040 /** Whether we've seen the input stream EOF. */ 041 private boolean eof; 042 043 /** 044 * Constructs a new instance, which filters the given input stream, and uses a reasonable default buffer size 045 * ({@link IOUtils#DEFAULT_BUFFER_SIZE}). 046 * 047 * @param inputStream The input stream, which is being buffered. 048 */ 049 public CircularBufferInputStream(final InputStream inputStream) { 050 this(inputStream, IOUtils.DEFAULT_BUFFER_SIZE); 051 } 052 053 /** 054 * Constructs a new instance, which filters the given input stream, and uses the given buffer size. 055 * 056 * @param inputStream The input stream, which is being buffered. 057 * @param bufferSize The size of the {@link CircularByteBuffer}, which is used internally. 058 */ 059 @SuppressWarnings("resource") // Caller closes InputStream 060 public CircularBufferInputStream(final InputStream inputStream, final int bufferSize) { 061 super(Objects.requireNonNull(inputStream, "inputStream")); 062 if (bufferSize <= 0) { 063 throw new IllegalArgumentException("Illegal bufferSize: " + bufferSize); 064 } 065 this.buffer = new CircularByteBuffer(bufferSize); 066 this.bufferSize = bufferSize; 067 this.eof = false; 068 } 069 070 @Override 071 public void close() throws IOException { 072 super.close(); 073 eof = true; 074 buffer.clear(); 075 } 076 077 /** 078 * Fills the buffer with the contents of the input stream. 079 * 080 * @throws IOException in case of an error while reading from the input stream. 081 */ 082 protected void fillBuffer() throws IOException { 083 if (eof) { 084 return; 085 } 086 int space = buffer.getSpace(); 087 final byte[] buf = IOUtils.byteArray(space); 088 while (space > 0) { 089 final int res = in.read(buf, 0, space); 090 if (res == EOF) { 091 eof = true; 092 return; 093 } 094 if (res > 0) { 095 buffer.add(buf, 0, res); 096 space -= res; 097 } 098 } 099 } 100 101 /** 102 * Fills the buffer from the input stream until the given number of bytes have been added to the buffer. 103 * 104 * @param count number of byte to fill into the buffer 105 * @return true if the buffer has bytes 106 * @throws IOException in case of an error while reading from the input stream. 107 */ 108 protected boolean haveBytes(final int count) throws IOException { 109 if (buffer.getCurrentNumberOfBytes() < count) { 110 fillBuffer(); 111 } 112 return buffer.hasBytes(); 113 } 114 115 @Override 116 public int read() throws IOException { 117 if (!haveBytes(1)) { 118 return EOF; 119 } 120 return buffer.read() & 0xFF; // return unsigned byte 121 } 122 123 @Override 124 public int read(final byte[] targetBuffer, final int offset, final int length) throws IOException { 125 Objects.requireNonNull(targetBuffer, "targetBuffer"); 126 if (offset < 0) { 127 throw new IllegalArgumentException("Offset must not be negative"); 128 } 129 if (length < 0) { 130 throw new IllegalArgumentException("Length must not be negative"); 131 } 132 if (!haveBytes(length)) { 133 return EOF; 134 } 135 final int result = Math.min(length, buffer.getCurrentNumberOfBytes()); 136 for (int i = 0; i < result; i++) { 137 targetBuffer[offset + i] = buffer.read(); 138 } 139 return result; 140 } 141}