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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.tree.tiny;
import java.io.Writer;
/**
* This is an implementation of the CharSequence interface: it implements
* a CharSequence as a view of an array. The implementation relies on the array
* being immutable: as a minimum, the caller is required to ensure that the array
* contents will not change so long as the CharSlice remains in existence.
*
* This class should be more efficient than String because it avoids copying the
* characters unnecessarily.
*
* The methods in the class don't check their arguments. Incorrect arguments will
* generally result in exceptions from lower-level classes.
*/
public final class CharSlice implements CharSequence {
private char[] array;
private int offset;
private int count;
/**
* Create a CharSlice that maps to the whole of a char[] array
*
* @param array the char[] array
*/
public CharSlice(char[] array) {
this.array = array;
offset = 0;
count = array.length;
}
/**
* Create a CharSlice that maps to a section of a char[] array
*
* @param array the char[] array
* @param start position of the first character to be included
* @param length number of characters to be included
*/
public CharSlice(char[] array, int start, int length) {
this.array = array;
offset = start;
count = length;
if (start + length > array.length) {
throw new IndexOutOfBoundsException("start(" + start +
") + length(" + length + ") > size(" + array.length + ')');
}
}
/**
* Returns the length of this character sequence. The length is the number
* of 16-bit Unicode characters in the sequence.
*
* @return the number of characters in this sequence
*/
public int length() {
return count;
}
/**
* Set the length of this character sequence, without changing the array and start offset
* to which it is bound
*
* @param length the new length of the CharSlice (which must be less than the existing length,
* though this is not enforced)
*/
public void setLength(int length) {
count = length;
}
/**
* Returns the character at the specified index. An index ranges from zero
* to length() - 1. The first character of the sequence is at
* index zero, the next at index one, and so on, as for array
* indexing.
*
* @param index the index of the character to be returned
* @return the specified character
* @throws java.lang.IndexOutOfBoundsException
* if the index argument is negative or not less than
* length()
*/
public char charAt(int index) {
return array[offset + index];
}
/**
* Returns a new character sequence that is a subsequence of this sequence.
* The subsequence starts with the character at the specified index and
* ends with the character at index end - 1. The length of the
* returned sequence is end - start, so if start == end
* then an empty sequence is returned.
*
* @param start the start index, inclusive
* @param end the end index, exclusive
* @return the specified subsequence
* @throws java.lang.IndexOutOfBoundsException
* if start or end are negative,
* if end is greater than length(),
* or if start is greater than end
*/
public CharSequence subSequence(int start, int end) {
return new CharSlice(array, offset + start, end - start);
}
/**
* Convert to a string
*/
public String toString() {
return new String(array, offset, count);
}
/**
* Compare equality
*/
public boolean equals(Object other) {
if (other instanceof CharSlice) {
CharSlice cs2 = (CharSlice) other;
if (count != cs2.count) {
return false;
}
int limit = offset + count;
for (int j = offset, k = cs2.offset; j < limit; ) {
if (array[j++] != cs2.array[k++]) {
return false;
}
}
return true;
} else if (other instanceof CharSequence) {
return count == ((CharSequence) other).length() && toString().equals(other.toString());
}
return false;
}
/**
* Generate a hash code
*/
public int hashCode() {
// Same algorithm as String#hashCode(), but not cached
int end = offset + count;
int h = 0;
for (int i = offset; i < end; i++) {
h = 31 * h + array[i];
}
return h;
}
/**
* Get the index of a specific character in the sequence. Returns -1 if not found.
* This method mimics {@link String#indexOf}
*
* @param c the character to be found
* @return the position of the first occurrence of that character, or -1 if not found.
*/
public int indexOf(char c) {
int end = offset + count;
for (int i = offset; i < end; i++) {
if (array[i] == c) {
return i - offset;
}
}
return -1;
}
/**
* Returns a new character sequence that is a subsequence of this sequence.
* Unlike subSequence, this is guaranteed to return a String.
*
* @param start position of the first character to be included (relative to the
* start of the CharSlice, not the underlying array)
* @param end position of the first character not to be included (relative
* to the start of the CharSlice)
* @return the substring, as a String object
*/
public String substring(int start, int end) {
return new String(array, offset + start, end - start);
}
/**
* Append the contents to another array at a given offset. The caller is responsible
* for ensuring that sufficient space is available.
*
* @param destination the array to which the characters will be copied
* @param destOffset the offset in the target array where the copy will start
*/
public void copyTo(char[] destination, int destOffset) {
System.arraycopy(array, offset, destination, destOffset, count);
}
/**
* Append the contents to another array at a given offset. The caller is responsible
* for ensuring that sufficient space is available. Otherwise this behaves like String.getChars()
*
* @param start offset of first character to be copied
* @param end offset of the first character that is not copied
* @param destination the array to which the characters will be copied
* @param destOffset the offset in the target array where the copy will start
*/
public void getChars(int start, int end, char[] destination, int destOffset) {
System.arraycopy(array, offset + start, destination, destOffset, end - start);
}
public char[] toCharArray() {
char[] chars = new char[count];
System.arraycopy(array, offset, chars, 0, count);
return chars;
}
/**
* Write the value to a writer
*
* @param writer the writer to be written to
* @throws java.io.IOException if writing fails
*/
public void write(/*@NotNull*/ Writer writer) throws java.io.IOException {
writer.write(array, offset, count);
}
}
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