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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.node.admin.task.util.text;
import java.util.Objects;
/**
* Cursor is a mutable offset into a fixed String, and useful for String parsing.
*
* @author hakonhall
*/
// @Mutable
public class Cursor {
private final String text;
private int offset;
private TextLocation locationCache;
/** Creates a pointer to the first char of {@code text}, which is EOT if {@code text} is empty. */
public Cursor(String text) { this(text, 0, new TextLocation()); }
public Cursor(Cursor that) { this(that.text, that.offset, that.locationCache); }
private Cursor(String text, int offset, TextLocation location) {
this.text = Objects.requireNonNull(text);
this.offset = offset;
this.locationCache = Objects.requireNonNull(location);
}
/** Returns the substring of {@code text} starting at {@link #offset()} (to EOT). */
@Override
public String toString() { return text.substring(offset); }
public int offset() { return offset; }
public boolean bot() { return offset == 0; }
public boolean eot() { return offset == text.length(); }
public boolean startsWith(char c) { return offset < text.length() && text.charAt(offset) == c; }
public boolean startsWith(String prefix) { return text.startsWith(prefix, offset); }
public char getChar() { return text.charAt(offset); }
/** The number of chars between pointer and EOT. */
public int length() { return text.length() - offset; }
public String fullText() { return text; }
/** Calculate the current text location in O(length(text)). */
public TextLocation calculateLocation() {
if (offset < locationCache.offset()) {
locationCache = new TextLocation();
} else if (offset == locationCache.offset()) {
return locationCache;
}
int lineIndex = locationCache.lineIndex();
int columnIndex = locationCache.columnIndex();
for (int i = locationCache.offset(); i < offset; ++i) {
if (text.charAt(i) == '\n') {
++lineIndex;
columnIndex = 0;
} else {
++columnIndex;
}
}
locationCache = new TextLocation(offset, lineIndex, columnIndex);
return locationCache;
}
public void set(Cursor that) {
if (that.text != text) {
throw new IllegalArgumentException("'that' doesn't refer to the same text");
}
this.offset = that.offset;
}
/** If the next substring.length() chars of matches substring pointing at Advance pointer past substring if pointer Returns true if pointing at string. */
public boolean skip(String substring) {
if (startsWith(substring)) {
offset += substring.length();
return true;
} else {
return false;
}
}
public boolean skip(char c) {
if (startsWith(c)) {
++offset;
return true;
} else {
return false;
}
}
public boolean skipBackwards(String substring) {
int newOffset = offset - substring.length();
if (newOffset < 0) return false;
if (text.startsWith(substring, newOffset)) {
offset = newOffset;
return true;
} else {
return false;
}
}
/** If the current char is a whitespace, skip it and return true. */
public boolean skipWhitespace() {
if (!eot() && Character.isWhitespace(getChar())) {
++offset;
return true;
} else {
return false;
}
}
/** Returns true if at least one whitespace was skipped. */
public boolean skipWhitespaces() {
if (skipWhitespace()) {
while (skipWhitespace())
++offset;
return true;
} else {
return false;
}
}
/** Return false if eot(), otherwise advance to the next char and return true. */
public boolean increment() {
if (eot()) return false;
++offset;
return true;
}
/** Return false if bot(), otherwise retreat to the previous char and return true. */
public boolean decrement() {
if (bot()) return false;
--offset;
return true;
}
/**
* Advance {@code distance} chars until bot() or eot() is reached (distance may be negative),
* and return true if this cursor moved the full distance.
*/
public boolean advance(int distance) {
int newOffset = offset + distance;
if (newOffset < 0) {
this.offset = 0;
return false;
} else if (newOffset > text.length()) {
this.offset = text.length();
return false;
} else {
this.offset = newOffset;
return true;
}
}
/** Advance pointer until start of needle is found (and return true), or EOT is reached (and return false). */
public boolean advanceTo(String needle) {
int index = text.indexOf(needle, offset);
if (index == -1) {
offset = text.length();
return false; // and eot() is true
} else {
offset = index;
return true; // and eot() is false
}
}
/** Advance pointer until start of needle is found (and return true), or EOT is reached (and return false). */
public boolean advanceTo(char needle) {
int index = text.indexOf(needle, offset);
if (index == -1) {
offset = text.length();
return false; // and eot() is true
} else {
offset = index;
return true; // and eot() is false
}
}
/** Advance pointer past needle (and return true), or to EOT (and return false). */
public boolean advancePast(String needle) {
if (advanceTo(needle)) {
offset += needle.length();
return true; // and eot() may or may not be true
} else {
return false; // and eot() is true
}
}
/** Advance pointer past needle (and return true), or to EOT (and return false). */
public boolean advancePast(char needle) {
if (advanceTo(needle)) {
++offset;
return true; // and eot() may or may not be true
} else {
return false; // and eot() is true
}
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Cursor cursor = (Cursor) o;
return offset == cursor.offset && text.equals(cursor.text);
}
@Override
public int hashCode() {
return Objects.hash(text, offset);
}
private void throwIfEot() { if (eot()) throw new StringIndexOutOfBoundsException(offset); }
}
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