118 lines
3.5 KiB
Java
118 lines
3.5 KiB
Java
/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.io;
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import java.io.IOException;
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/**
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* Package-protected abstract class that implements the line reading algorithm
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* used by {@link LineReader}. Line separators are per
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* {@link java.io.BufferedReader}: line feed, carriage return, or carriage
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* return followed immediately by a linefeed.
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*
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* <p>
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* Subclasses must implement {@link #handleLine}, call {@link #add} to pass
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* character data, and call {@link #finish} at the end of stream.
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*
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* @author Chris Nokleberg
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* @since 1.0
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*/
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abstract class LineBuffer {
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/** Holds partial line contents. */
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private StringBuilder line = new StringBuilder();
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/** Whether a line ending with a CR is pending processing. */
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private boolean sawReturn;
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/**
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* Process additional characters from the stream. When a line separator is found
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* the contents of the line and the line separator itself are passed to the
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* abstract {@link #handleLine} method.
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*
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* @param cbuf the character buffer to process
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* @param off the offset into the buffer
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* @param len the number of characters to process
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* @throws IOException if an I/O error occurs
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* @see #finish
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*/
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protected void add(char[] cbuf, int off, int len) throws IOException {
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int pos = off;
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if (sawReturn && len > 0) {
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// Last call to add ended with a CR; we can handle the line now.
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if (finishLine(cbuf[pos] == '\n')) {
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pos++;
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}
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}
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int start = pos;
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for (int end = off + len; pos < end; pos++) {
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switch (cbuf[pos]) {
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case '\r':
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line.append(cbuf, start, pos - start);
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sawReturn = true;
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if (pos + 1 < end) {
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if (finishLine(cbuf[pos + 1] == '\n')) {
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pos++;
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}
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}
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start = pos + 1;
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break;
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case '\n':
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line.append(cbuf, start, pos - start);
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finishLine(true);
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start = pos + 1;
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break;
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default:
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// do nothing
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}
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}
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line.append(cbuf, start, off + len - start);
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}
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/** Called when a line is complete. */
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private boolean finishLine(boolean sawNewline) throws IOException {
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handleLine(line.toString(), sawReturn ? (sawNewline ? "\r\n" : "\r") : (sawNewline ? "\n" : ""));
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line = new StringBuilder();
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sawReturn = false;
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return sawNewline;
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}
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/**
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* Subclasses must call this method after finishing character processing, in
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* order to ensure that any unterminated line in the buffer is passed to
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* {@link #handleLine}.
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*
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* @throws IOException if an I/O error occurs
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*/
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protected void finish() throws IOException {
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if (sawReturn || line.length() > 0) {
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finishLine(false);
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}
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}
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/**
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* Called for each line found in the character data passed to {@link #add}.
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*
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* @param line a line of text (possibly empty), without any line separators
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* @param end the line separator; one of {@code "\r"}, {@code "\n"},
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* {@code "\r\n"}, or {@code ""}
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* @throws IOException if an I/O error occurs
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*/
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protected abstract void handleLine(String line, String end) throws IOException;
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}
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