1 /* 2 * Copyright (C) 2008 Google Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.io; 18 19 import com.google.common.base.Preconditions; 20 21 import java.io.Reader; 22 import java.io.IOException; 23 import java.util.Iterator; 24 25 /** 26 * A {@link Reader} that will concatenates multiple readers 27 * 28 * @author Bin Zhu 29 * @since 2009.09.15 <b>tentative</b> 30 */ 31 class MultiReader extends Reader { 32 private final Iterator<? extends InputSupplier<? extends Reader>> it; 33 private Reader current; 34 MultiReader(Iterator<? extends InputSupplier<? extends Reader>> readers)35 MultiReader(Iterator<? extends InputSupplier<? extends Reader>> readers) 36 throws IOException { 37 this.it = readers; 38 advance(); 39 } 40 41 /** 42 * Closes the current reader and opens the next one, if any. 43 */ advance()44 private void advance() throws IOException { 45 close(); 46 if (it.hasNext()) { 47 current = it.next().getInput(); 48 } 49 } 50 read(char cbuf[], int off, int len)51 @Override public int read(char cbuf[], int off, int len) throws IOException { 52 if (current == null) { 53 return -1; 54 } 55 int result = current.read(cbuf, off, len); 56 if (result == -1) { 57 advance(); 58 return read(cbuf, off, len); 59 } 60 return result; 61 } 62 skip(long n)63 @Override public long skip(long n) throws IOException { 64 Preconditions.checkArgument(n >= 0, "n is negative"); 65 if (n > 0) { 66 while (current != null) { 67 long result = current.skip(n); 68 if (result > 0) { 69 return result; 70 } 71 advance(); 72 } 73 } 74 return 0; 75 } 76 ready()77 @Override public boolean ready() throws IOException { 78 return (current != null) && current.ready(); 79 } 80 close()81 @Override public void close() throws IOException { 82 if (current != null) { 83 try { 84 current.close(); 85 } finally { 86 current = null; 87 } 88 } 89 } 90 } 91