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; 018 019import static org.apache.commons.io.IOUtils.EOF; 020 021import java.io.FilterReader; 022import java.io.IOException; 023import java.io.Reader; 024import java.util.function.IntPredicate; 025 026/** 027 * A filter reader that filters out characters where subclasses decide which characters to filter out. 028 */ 029public abstract class AbstractCharacterFilterReader extends FilterReader { 030 031 /** 032 * Skips nothing. 033 * 034 * @since 2.9.0 035 */ 036 protected static final IntPredicate SKIP_NONE = ch -> false; 037 038 private final IntPredicate skip; 039 040 /** 041 * Constructs a new reader. 042 * 043 * @param reader the reader to filter 044 */ 045 protected AbstractCharacterFilterReader(final Reader reader) { 046 this(reader, SKIP_NONE); 047 } 048 049 /** 050 * Constructs a new reader. 051 * 052 * @param reader the reader to filter. 053 * @param skip Skip test. 054 * @since 2.9.0 055 */ 056 protected AbstractCharacterFilterReader(final Reader reader, final IntPredicate skip) { 057 super(reader); 058 this.skip = skip == null ? SKIP_NONE : skip; 059 } 060 061 /** 062 * Returns true if the given character should be filtered out, false to keep the character. 063 * 064 * @param ch the character to test. 065 * @return true if the given character should be filtered out, false to keep the character. 066 */ 067 protected boolean filter(final int ch) { 068 return skip.test(ch); 069 } 070 071 @Override 072 public int read() throws IOException { 073 int ch; 074 do { 075 ch = in.read(); 076 } while (ch != EOF && filter(ch)); 077 return ch; 078 } 079 080 @Override 081 public int read(final char[] cbuf, final int off, final int len) throws IOException { 082 final int read = super.read(cbuf, off, len); 083 if (read == EOF) { 084 return EOF; 085 } 086 int pos = off - 1; 087 for (int readPos = off; readPos < off + read; readPos++) { 088 if (filter(cbuf[readPos])) { 089 continue; 090 } 091 pos++; 092 if (pos < readPos) { 093 cbuf[pos] = cbuf[readPos]; 094 } 095 } 096 return pos - off + 1; 097 } 098}