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.IOException; 022import java.io.InputStream; 023import java.util.Objects; 024 025import org.apache.commons.io.IOUtils; 026 027/** 028 * Implements a buffered input stream, which is internally based on a {@link CircularByteBuffer}. Unlike the 029 * {@link java.io.BufferedInputStream}, this one doesn't need to reallocate byte arrays internally. 030 */ 031public class CircularBufferInputStream extends InputStream { 032 033 /** What we are streaming, used to fill the internal buffer. */ 034 protected final InputStream in; 035 036 /** Internal buffer. */ 037 protected final CircularByteBuffer buffer; 038 039 /** Internal buffer size. */ 040 protected final int bufferSize; 041 042 /** Whether we've see the input stream EOF. */ 043 private boolean eof; 044 045 /** 046 * Creates a new instance, which filters the given input stream, and uses the given buffer size. 047 * 048 * @param inputStream The input stream, which is being buffered. 049 * @param bufferSize The size of the {@link CircularByteBuffer}, which is used internally. 050 */ 051 public CircularBufferInputStream(final InputStream inputStream, final int bufferSize) { 052 if (bufferSize <= 0) { 053 throw new IllegalArgumentException("Invalid bufferSize: " + bufferSize); 054 } 055 this.in = Objects.requireNonNull(inputStream, "inputStream"); 056 this.buffer = new CircularByteBuffer(bufferSize); 057 this.bufferSize = bufferSize; 058 this.eof = false; 059 } 060 061 /** 062 * Creates a new instance, which filters the given input stream, and uses a reasonable default buffer size 063 * ({@link IOUtils#DEFAULT_BUFFER_SIZE}). 064 * 065 * @param inputStream The input stream, which is being buffered. 066 */ 067 public CircularBufferInputStream(final InputStream inputStream) { 068 this(inputStream, IOUtils.DEFAULT_BUFFER_SIZE); 069 } 070 071 /** 072 * Fills the buffer with the contents of the input stream. 073 * 074 * @throws IOException in case of an error while reading from the input stream. 075 */ 076 protected void fillBuffer() throws IOException { 077 if (eof) { 078 return; 079 } 080 int space = buffer.getSpace(); 081 final byte[] buf = IOUtils.byteArray(space); 082 while (space > 0) { 083 final int res = in.read(buf, 0, space); 084 if (res == EOF) { 085 eof = true; 086 return; 087 } 088 if (res > 0) { 089 buffer.add(buf, 0, res); 090 space -= res; 091 } 092 } 093 } 094 095 /** 096 * Fills the buffer from the input stream until the given number of bytes have been added to the buffer. 097 * 098 * @param count number of byte to fill into the buffer 099 * @return true if the buffer has bytes 100 * @throws IOException in case of an error while reading from the input stream. 101 */ 102 protected boolean haveBytes(final int count) throws IOException { 103 if (buffer.getCurrentNumberOfBytes() < count) { 104 fillBuffer(); 105 } 106 return buffer.hasBytes(); 107 } 108 109 @Override 110 public int read() throws IOException { 111 if (!haveBytes(1)) { 112 return EOF; 113 } 114 return buffer.read() & 0xFF; // return unsigned byte 115 } 116 117 @Override 118 public int read(final byte[] buffer) throws IOException { 119 return read(buffer, 0, buffer.length); 120 } 121 122 @Override 123 public int read(final byte[] targetBuffer, final int offset, final int length) throws IOException { 124 Objects.requireNonNull(targetBuffer, "targetBuffer"); 125 if (offset < 0) { 126 throw new IllegalArgumentException("Offset must not be negative"); 127 } 128 if (length < 0) { 129 throw new IllegalArgumentException("Length must not be negative"); 130 } 131 if (!haveBytes(length)) { 132 return EOF; 133 } 134 final int result = Math.min(length, buffer.getCurrentNumberOfBytes()); 135 for (int i = 0; i < result; i++) { 136 targetBuffer[offset + i] = buffer.read(); 137 } 138 return result; 139 } 140 141 @Override 142 public void close() throws IOException { 143 in.close(); 144 eof = true; 145 buffer.clear(); 146 } 147}