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| 1 | +/* |
| 2 | + * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved. |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | + * |
| 5 | + * This code is free software; you can redistribute it and/or modify it |
| 6 | + * under the terms of the GNU General Public License version 2 only, as |
| 7 | + * published by the Free Software Foundation. |
| 8 | + * |
| 9 | + * This code is distributed in the hope that it will be useful, but WITHOUT |
| 10 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 11 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 12 | + * version 2 for more details (a copy is included in the LICENSE file that |
| 13 | + * accompanied this code). |
| 14 | + * |
| 15 | + * You should have received a copy of the GNU General Public License version |
| 16 | + * 2 along with this work; if not, write to the Free Software Foundation, |
| 17 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 18 | + * |
| 19 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| 20 | + * or visit www.oracle.com if you need additional information or have any |
| 21 | + * questions. |
| 22 | + */ |
| 23 | + |
| 24 | + |
| 25 | +import java.io.BufferedReader; |
| 26 | +import java.io.IOException; |
| 27 | +import java.io.InputStream; |
| 28 | +import java.io.InputStreamReader; |
| 29 | + |
| 30 | +/** |
| 31 | + * HumanInputStream tries to act like a human sitting in front of a computer |
| 32 | + * terminal typing on the keyboard while a program is running. |
| 33 | + * <p> |
| 34 | + * The program may call InputStream.read() and BufferedReader.readLine() in |
| 35 | + * various places. a call to B.readLine() will try to buffer as much input as |
| 36 | + * possible. Thus, a trivial InputStream will find it impossible to feed |
| 37 | + * anything to I.read() after a B.readLine() call. |
| 38 | + * <p> |
| 39 | + * This is why HumanInputStream was created, which will only send a single line |
| 40 | + * to B.readLine(), no more, no less, and the next I.read() can have a chance |
| 41 | + * to read the exact character right after "\n". |
| 42 | + * |
| 43 | + */ |
| 44 | + |
| 45 | +public class HumanInputStream extends InputStream { |
| 46 | + byte[] src; |
| 47 | + int pos; |
| 48 | + int length; |
| 49 | + boolean inLine; |
| 50 | + int stopIt; |
| 51 | + |
| 52 | + public HumanInputStream(String input) { |
| 53 | + src = input.getBytes(); |
| 54 | + pos = 0; |
| 55 | + length = src.length; |
| 56 | + stopIt = 0; |
| 57 | + inLine = false; |
| 58 | + } |
| 59 | + |
| 60 | + // the trick: when called through read(byte[], int, int), |
| 61 | + // return -1 twice after "\n" |
| 62 | + |
| 63 | + @Override public int read() throws IOException { |
| 64 | + int re; |
| 65 | + if(pos < length) { |
| 66 | + re = src[pos]; |
| 67 | + if(inLine) { |
| 68 | + if(stopIt > 0) { |
| 69 | + stopIt--; |
| 70 | + re = -1; |
| 71 | + } else { |
| 72 | + if(re == '\n') { |
| 73 | + stopIt = 2; |
| 74 | + } |
| 75 | + pos++; |
| 76 | + } |
| 77 | + } else { |
| 78 | + pos++; |
| 79 | + } |
| 80 | + } else { |
| 81 | + re = -1; //throws new IOException("NO MORE TO READ"); |
| 82 | + } |
| 83 | + return re; |
| 84 | + } |
| 85 | + @Override public int read(byte[] buffer, int offset, int len) { |
| 86 | + inLine = true; |
| 87 | + try { |
| 88 | + return super.read(buffer, offset, len); |
| 89 | + } catch(Exception e) { |
| 90 | + throw new RuntimeException("HumanInputStream error"); |
| 91 | + } finally { |
| 92 | + inLine = false; |
| 93 | + } |
| 94 | + } |
| 95 | + @Override public int available() { |
| 96 | + if (pos < length) return 1; |
| 97 | + return 0; |
| 98 | + } |
| 99 | + |
| 100 | + // test part |
| 101 | + static void assertTrue(boolean bool) { |
| 102 | + if (!bool) |
| 103 | + throw new RuntimeException(); |
| 104 | + } |
| 105 | + |
| 106 | + public static void test() throws Exception { |
| 107 | + class Tester { |
| 108 | + HumanInputStream is; |
| 109 | + BufferedReader reader; |
| 110 | + Tester(String s) { |
| 111 | + is = new HumanInputStream(s); |
| 112 | + reader = new BufferedReader(new InputStreamReader(is)); |
| 113 | + } |
| 114 | + |
| 115 | + // three kinds of test method |
| 116 | + // 1. read byte by byte from InputStream |
| 117 | + void testStreamReadOnce(int expection) throws Exception { |
| 118 | + assertTrue(is.read() == expection); |
| 119 | + } |
| 120 | + void testStreamReadMany(String expectation) throws Exception { |
| 121 | + char[] keys = expectation.toCharArray(); |
| 122 | + for (char key : keys) { |
| 123 | + assertTrue(is.read() == key); |
| 124 | + } |
| 125 | + } |
| 126 | + // 2. read a line with a newly created Reader |
| 127 | + void testReaderReadline(String expectation) throws Exception { |
| 128 | + String s = new BufferedReader(new InputStreamReader(is)).readLine(); |
| 129 | + if(s == null) assertTrue(expectation == null); |
| 130 | + else assertTrue(s.equals(expectation)); |
| 131 | + } |
| 132 | + // 3. read a line with the old Reader |
| 133 | + void testReaderReadline2(String expectation) throws Exception { |
| 134 | + String s = reader.readLine(); |
| 135 | + if(s == null) assertTrue(expectation == null); |
| 136 | + else assertTrue(s.equals(expectation)); |
| 137 | + } |
| 138 | + } |
| 139 | + |
| 140 | + Tester test; |
| 141 | + |
| 142 | + test = new Tester("111\n222\n\n444\n\n"); |
| 143 | + test.testReaderReadline("111"); |
| 144 | + test.testReaderReadline("222"); |
| 145 | + test.testReaderReadline(""); |
| 146 | + test.testReaderReadline("444"); |
| 147 | + test.testReaderReadline(""); |
| 148 | + test.testReaderReadline(null); |
| 149 | + |
| 150 | + test = new Tester("111\n222\n\n444\n\n"); |
| 151 | + test.testReaderReadline2("111"); |
| 152 | + test.testReaderReadline2("222"); |
| 153 | + test.testReaderReadline2(""); |
| 154 | + test.testReaderReadline2("444"); |
| 155 | + test.testReaderReadline2(""); |
| 156 | + test.testReaderReadline2(null); |
| 157 | + |
| 158 | + test = new Tester("111\n222\n\n444\n\n"); |
| 159 | + test.testReaderReadline2("111"); |
| 160 | + test.testReaderReadline("222"); |
| 161 | + test.testReaderReadline2(""); |
| 162 | + test.testReaderReadline2("444"); |
| 163 | + test.testReaderReadline(""); |
| 164 | + test.testReaderReadline2(null); |
| 165 | + |
| 166 | + test = new Tester("1\n2"); |
| 167 | + test.testStreamReadMany("1\n2"); |
| 168 | + test.testStreamReadOnce(-1); |
| 169 | + |
| 170 | + test = new Tester("12\n234"); |
| 171 | + test.testStreamReadOnce('1'); |
| 172 | + test.testReaderReadline("2"); |
| 173 | + test.testStreamReadOnce('2'); |
| 174 | + test.testReaderReadline2("34"); |
| 175 | + test.testReaderReadline2(null); |
| 176 | + |
| 177 | + test = new Tester("changeit\n"); |
| 178 | + test.testStreamReadMany("changeit\n"); |
| 179 | + test.testReaderReadline(null); |
| 180 | + |
| 181 | + test = new Tester("changeit\nName\nCountry\nYes\n"); |
| 182 | + test.testStreamReadMany("changeit\n"); |
| 183 | + test.testReaderReadline("Name"); |
| 184 | + test.testReaderReadline("Country"); |
| 185 | + test.testReaderReadline("Yes"); |
| 186 | + test.testReaderReadline(null); |
| 187 | + |
| 188 | + test = new Tester("Me\nHere\n"); |
| 189 | + test.testReaderReadline2("Me"); |
| 190 | + test.testReaderReadline2("Here"); |
| 191 | + } |
| 192 | +} |
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