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// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.server.fixes;
import static com.google.common.base.Preconditions.checkNotNull;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* An identifier of lines in a string. Lines are sequences of characters which are separated by any
* Unicode linebreak sequence as defined by the regular expression {@code \R}. If data for several
* lines is requested, calls which are ordered according to ascending line numbers are the most
* efficient.
*/
class LineIdentifier {
private static final Pattern LINE_SEPARATOR_PATTERN = Pattern.compile("\\R");
private final Matcher lineSeparatorMatcher;
private int nextLineNumber;
private int nextLineStartIndex;
private int currentLineStartIndex;
private int currentLineEndIndex;
LineIdentifier(String string) {
checkNotNull(string);
lineSeparatorMatcher = LINE_SEPARATOR_PATTERN.matcher(string);
reset();
}
/**
* Returns the start index of the indicated line within the given string. Start indices are
* zero-based while line numbers are one-based.
*
* <p><b>Note:</b> Requesting data for several lines is more efficient if those calls occur with
* increasing line number.
*
* @param lineNumber the line whose start index should be determined
* @return the start index of the line
* @throws StringIndexOutOfBoundsException if the line number is negative, zero or greater than
* the identified number of lines
*/
public int getStartIndexOfLine(int lineNumber) {
findLine(lineNumber);
return currentLineStartIndex;
}
/**
* Returns the length of the indicated line in the given string. The character(s) used to separate
* lines aren't included in the count. Line numbers are one-based.
*
* <p><b>Note:</b> Requesting data for several lines is more efficient if those calls occur with
* increasing line number.
*
* @param lineNumber the line whose length should be determined
* @return the length of the line
* @throws StringIndexOutOfBoundsException if the line number is negative, zero or greater than
* the identified number of lines
*/
public int getLengthOfLine(int lineNumber) {
findLine(lineNumber);
return currentLineEndIndex - currentLineStartIndex;
}
private void findLine(int targetLineNumber) {
if (targetLineNumber <= 0) {
throw new StringIndexOutOfBoundsException("Line number must be positive");
}
if (targetLineNumber < nextLineNumber) {
reset();
}
while (nextLineNumber < targetLineNumber + 1 && lineSeparatorMatcher.find()) {
currentLineStartIndex = nextLineStartIndex;
currentLineEndIndex = lineSeparatorMatcher.start();
nextLineStartIndex = lineSeparatorMatcher.end();
nextLineNumber++;
}
// End of string
if (nextLineNumber == targetLineNumber) {
currentLineStartIndex = nextLineStartIndex;
currentLineEndIndex = lineSeparatorMatcher.regionEnd();
}
if (nextLineNumber < targetLineNumber) {
throw new StringIndexOutOfBoundsException(
String.format("Line %d isn't available", targetLineNumber));
}
}
private void reset() {
nextLineNumber = 1;
nextLineStartIndex = 0;
currentLineStartIndex = 0;
currentLineEndIndex = 0;
lineSeparatorMatcher.reset();
}
}
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