1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.io;
16
17 import com.google.common.annotations.GwtIncompatible;
18 import com.google.errorprone.annotations.CanIgnoreReturnValue;
19 import java.io.IOException;
20
21 /**
22 * Package-protected abstract class that implements the line reading algorithm used by {@link
23 * LineReader}. Line separators are per {@link java.io.BufferedReader}: line feed, carriage return,
24 * or carriage return followed immediately by a linefeed.
25 *
26 * <p>Subclasses must implement {@link #handleLine}, call {@link #add} to pass character data, and
27 * call {@link #finish} at the end of stream.
28 *
29 * @author Chris Nokleberg
30 * @since 1.0
31 */
32 @GwtIncompatible
33 @ElementTypesAreNonnullByDefault
34 abstract class LineBuffer {
35 /** Holds partial line contents. */
36 private StringBuilder line = new StringBuilder();
37 /** Whether a line ending with a CR is pending processing. */
38 private boolean sawReturn;
39
40 /**
41 * Process additional characters from the stream. When a line separator is found the contents of
42 * the line and the line separator itself are passed to the abstract {@link #handleLine} method.
43 *
44 * @param cbuf the character buffer to process
45 * @param off the offset into the buffer
46 * @param len the number of characters to process
47 * @throws IOException if an I/O error occurs
48 * @see #finish
49 */
50 protected void add(char[] cbuf, int off, int len) throws IOException {
51 int pos = off;
52 if (sawReturn && len > 0) {
53 // Last call to add ended with a CR; we can handle the line now.
54 if (finishLine(cbuf[pos] == '\n')) {
55 pos++;
56 }
57 }
58
59 int start = pos;
60 for (int end = off + len; pos < end; pos++) {
61 switch (cbuf[pos]) {
62 case '\r':
63 line.append(cbuf, start, pos - start);
64 sawReturn = true;
65 if (pos + 1 < end) {
66 if (finishLine(cbuf[pos + 1] == '\n')) {
67 pos++;
68 }
69 }
70 start = pos + 1;
71 break;
72
73 case '\n':
74 line.append(cbuf, start, pos - start);
75 finishLine(true);
76 start = pos + 1;
77 break;
78
79 default:
80 // do nothing
81 }
82 }
83 line.append(cbuf, start, off + len - start);
84 }
85
86 /** Called when a line is complete. */
87 @CanIgnoreReturnValue
88 private boolean finishLine(boolean sawNewline) throws IOException {
89 String separator = sawReturn ? (sawNewline ? "\r\n" : "\r") : (sawNewline ? "\n" : "");
90 handleLine(line.toString(), separator);
91 line = new StringBuilder();
92 sawReturn = false;
93 return sawNewline;
94 }
95
96 /**
97 * Subclasses must call this method after finishing character processing, in order to ensure that
98 * any unterminated line in the buffer is passed to {@link #handleLine}.
99 *
100 * @throws IOException if an I/O error occurs
101 */
102 protected void finish() throws IOException {
103 if (sawReturn || line.length() > 0) {
104 finishLine(false);
105 }
106 }
107
108 /**
109 * Called for each line found in the character data passed to {@link #add}.
110 *
111 * @param line a line of text (possibly empty), without any line separators
112 * @param end the line separator; one of {@code "\r"}, {@code "\n"}, {@code "\r\n"}, or {@code ""}
113 * @throws IOException if an I/O error occurs
114 */
115 protected abstract void handleLine(String line, String end) throws IOException;
116 }