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/*
* Copyright (c) 2013, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
package com.oracle.truffle.api.source;
import java.util.ArrayList;
/**
* A utility for converting between coordinate systems in a string of text interspersed with newline
* characters. The coordinate systems are:
*
* - 0-based character offset from the beginning of the text, where newline characters count as a
* single character and the first character in the text occupies position 0.
* - 1-based position in the 2D space of lines and columns, in which the first position in the
* text is at (1,1).
*
*
* This utility is based on positions occupied by characters, not text stream positions as in a text
* editor. The distinction shows up in editors where you can put the cursor just past the last
* character in a buffer; this is necessary, among other reasons, so that you can put the edit
* cursor in a new (empty) buffer. For the purposes of this utility, however, there are no character
* positions in an empty text string and there are no lines in an empty text string.
*
* A newline character designates the end of a line and occupies a column position.
*
* If the text ends with a character other than a newline, then the characters following the final
* newline character count as a line, even though not newline-terminated.
*
* Limitations:
*
* - Does not handle multiple character encodings correctly.
* - Treats tabs as occupying 1 column.
* - Does not handle multiple-character line termination sequences correctly.
*
*/
final class TextMap {
// 0-based offsets of newline characters in the text, with sentinel
private final int[] nlOffsets;
// The number of characters in the text, including newlines (which count as 1).
private final int textLength;
// Is the final text character a newline?
final boolean finalNL;
TextMap(int[] nlOffsets, int textLength, boolean finalNL) {
this.nlOffsets = nlOffsets;
this.textLength = textLength;
this.finalNL = finalNL;
}
/**
* Constructs map permitting translation between 0-based character offsets and 1-based
* lines/columns.
*/
public static TextMap fromString(String text) {
final int textLength = text.length();
final ArrayList lines = new ArrayList<>();
lines.add(0);
int offset = 0;
while (offset < text.length()) {
final int nlIndex = text.indexOf('\n', offset);
if (nlIndex >= 0) {
offset = nlIndex + 1;
lines.add(offset);
} else {
break;
}
}
lines.add(Integer.MAX_VALUE);
final int[] nlOffsets = new int[lines.size()];
for (int line = 0; line < lines.size(); line++) {
nlOffsets[line] = lines.get(line);
}
final boolean finalNL = textLength > 0 && (textLength == nlOffsets[nlOffsets.length - 2]);
return new TextMap(nlOffsets, textLength, finalNL);
}
/**
* Converts 0-based character offset to 1-based number of the line containing the character.
*
* @throws IllegalArgumentException if the offset is outside the string.
*/
public int offsetToLine(int offset) throws IllegalArgumentException {
if (offset < 0 || offset >= textLength) {
if (offset == 0 && textLength == 0) {
return 1;
}
throw new IllegalArgumentException("offset out of bounds");
}
int line = 1;
while (offset >= nlOffsets[line]) {
line++;
}
return line;
}
/**
* Converts 0-based character offset to 1-based number of the column occupied by the character.
*
* Tabs are not expanded; they occupy 1 column.
*
* @throws IllegalArgumentException if the offset is outside the string.
*/
public int offsetToCol(int offset) throws IllegalArgumentException {
return 1 + offset - nlOffsets[offsetToLine(offset) - 1];
}
/**
* The number of characters in the mapped text.
*/
public int length() {
return textLength;
}
/**
* The number of lines in the text; if characters appear after the final newline, then they also
* count as a line, even though not newline-terminated.
*/
public int lineCount() {
if (textLength == 0) {
return 0;
}
return finalNL ? nlOffsets.length - 2 : nlOffsets.length - 1;
}
/**
* Converts 1-based line number to the 0-based offset of the line's first character; this would
* be the offset of a newline if the line is empty.
*
* @throws IllegalArgumentException if there is no such line in the text.
*/
public int lineStartOffset(int line) throws IllegalArgumentException {
if (textLength == 0) {
return 0;
}
if (lineOutOfRange(line)) {
throw new IllegalArgumentException("line out of bounds");
}
return nlOffsets[line - 1];
}
/**
* Gets the number of characters in a line, identified by 1-based line number; does not
* include the final newline, if any.
*
* @throws IllegalArgumentException if there is no such line in the text.
*/
public int lineLength(int line) throws IllegalArgumentException {
if (textLength == 0) {
return 0;
}
if (lineOutOfRange(line)) {
throw new IllegalArgumentException("line out of bounds");
}
if (line == nlOffsets.length - 1 && !finalNL) {
return textLength - nlOffsets[line - 1];
}
return (nlOffsets[line] - nlOffsets[line - 1]) - 1;
}
/**
* Is the line number out of range.
*/
private boolean lineOutOfRange(int line) {
return line <= 0 || line >= nlOffsets.length || (line == nlOffsets.length - 1 && finalNL);
}
}