net.sf.saxon.tree.tiny.CompressedWhitespace Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of Saxon-HE Show documentation
Show all versions of Saxon-HE Show documentation
The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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 net.sf.saxon.tree.util.FastStringBuffer;
import java.io.OutputStream;
import java.io.Writer;
/**
* This class provides a compressed representation of a sequence of whitespace characters. The representation
* is a sequence of bytes: in each byte the top two bits indicate which whitespace character is used
* (x9, xA, xD, or x20) and the bottom six bits indicate the number of such characters. A zero byte is a filler.
* We don't compress the sequence if it would occupy more than 8 bytes, because that's the space we've got available
* in the TinyTree arrays.
*/
public class CompressedWhitespace implements CharSequence {
/*@NotNull*/ private static char[] WHITE_CHARS = {0x09, 0x0A, 0x0D, 0x20};
/*@NotNull*/ private static int[] CODES =
{-1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, -1, -1, 2, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
3};
private long value;
public CompressedWhitespace(long compressedValue) {
value = compressedValue;
}
/**
* Attempt to compress a CharSequence
*
* @param in the CharSequence to be compressed
* @return the compressed sequence if it can be compressed; or the original CharSequence otherwise
*/
/*@NotNull*/
public static CharSequence compress(/*@NotNull*/ CharSequence in) {
final int inlen = in.length();
if (inlen == 0) {
return in;
}
int runlength = 1;
int outlength = 0;
for (int i = 0; i < inlen; i++) {
final char c = in.charAt(i);
if (c <= 32 && CODES[c] > 0) {
if (i == inlen - 1 || c != in.charAt(i + 1) || runlength == 63) {
runlength = 1;
outlength++;
if (outlength > 8) {
return in;
}
} else {
runlength++;
}
} else {
return in;
}
}
int ix = 0;
runlength = 1;
int[] out = new int[outlength];
for (int i = 0; i < inlen; i++) {
final char c = in.charAt(i);
if (i == inlen - 1 || c != in.charAt(i + 1) || runlength == 63) {
out[ix++] = (CODES[c] << 6) | runlength;
runlength = 1;
} else {
runlength++;
}
}
long value = 0;
for (int i = 0; i < outlength; i++) {
value = (value << 8) | out[i];
}
value <<= (8 * (8 - outlength));
return new CompressedWhitespace(value);
}
/**
* Uncompress the whitespace to a FastStringBuffer
*
* @param buffer the buffer to which the whitespace is to be appended. The parameter may be
* null, in which case a new buffer is created.
* @return the FastStringBuffer to which the whitespace has been appended. If a buffer was
* supplied in the argument, this will be the same buffer.
*/
public FastStringBuffer uncompress(/*@Nullable*/ FastStringBuffer buffer) {
if (buffer == null) {
buffer = new FastStringBuffer(length());
}
uncompress(value, buffer);
return buffer;
}
public static void uncompress(long value, /*@NotNull*/ FastStringBuffer buffer) {
for (int s = 56; s >= 0; s -= 8) {
byte b = (byte) ((value >>> s) & 0xff);
if (b == 0) {
break;
}
char c = WHITE_CHARS[b >>> 6 & 0x3];
int len = (b & 0x3f);
buffer.ensureCapacity(len);
for (int j = 0; j < len; j++) {
buffer.append(c);
}
}
}
public long getCompressedValue() {
return value;
}
public int length() {
int count = 0;
long val = value;
for (int s = 56; s >= 0; s -= 8) {
int c = (int) ((val >>> s) & 0x3f);
if (c == 0) {
break;
}
count += c;
}
return count;
}
/**
* Returns the char value at the specified index. An index ranges from zero
* to length() - 1. The first char value of the sequence is at
* index zero, the next at index one, and so on, as for array
* indexing.
*
* If the char value specified by the index is a
* surrogate, the surrogate
* value is returned.
*
* @param index the index of the char value to be returned
* @return the specified char value
* @throws IndexOutOfBoundsException if the index argument is negative or not less than
* length()
*/
public char charAt(int index) {
int count = 0;
final long val = value;
for (int s = 56; s >= 0; s -= 8) {
byte b = (byte) ((val >>> s) & 0xff);
if (b == 0) {
break;
}
count += (b & 0x3f);
if (count > index) {
return WHITE_CHARS[b >>> 6 & 0x3];
}
}
throw new IndexOutOfBoundsException(index + "");
}
/**
* Returns a new CharSequence that is a subsequence of this sequence.
* The subsequence starts with the char value at the specified index and
* ends with the char value at index end - 1. The length
* (in chars) 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 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 uncompress(null).subSequence(start, end);
}
/**
* Indicates whether some other object is "equal to" this one.
*/
public boolean equals(/*@NotNull*/ Object obj) {
if (obj instanceof CompressedWhitespace) {
return value == ((CompressedWhitespace) obj).value;
}
return uncompress(null).equals(obj);
}
/**
* Returns a hash code value for the object.
*/
public int hashCode() {
return uncompress(null).hashCode();
}
/**
* Returns a string representation of the object.
*/
public String toString() {
return uncompress(null).toString();
}
/**
* Write the value to a Writer
*
* @param writer the writer to write to
* @throws java.io.IOException if an error occurs downstream
*/
public void write(/*@NotNull*/ Writer writer) throws java.io.IOException {
final long val = value;
for (int s = 56; s >= 0; s -= 8) {
final byte b = (byte) ((val >>> s) & 0xff);
if (b == 0) {
break;
}
final char c = WHITE_CHARS[b >>> 6 & 0x3];
final int len = (b & 0x3f);
for (int j = 0; j < len; j++) {
writer.write(c);
}
}
}
/**
* Write the value to a Writer with escaping of special characters
*
* @param specialChars identifies which characters are considered special
* @param writer the writer to write to
* @throws java.io.IOException if an error occurs downstream
*/
public void writeEscape(boolean[] specialChars, /*@NotNull*/ Writer writer) throws java.io.IOException {
final long val = value;
for (int s = 56; s >= 0; s -= 8) {
final byte b = (byte) ((val >>> s) & 0xff);
if (b == 0) {
break;
}
final char c = WHITE_CHARS[b >>> 6 & 0x3];
final int len = (b & 0x3f);
if (specialChars[c]) {
String e = "";
if (c == '\n') {
e = "
";
} else if (c == '\r') {
e = "
";
} else if (c == '\t') {
e = " ";
}
for (int j = 0; j < len; j++) {
writer.write(e);
}
} else {
for (int j = 0; j < len; j++) {
writer.write(c);
}
}
}
}
/**
* Write the value to a UTF-8 OutputStream with escaping of special characters
*
* @param specialChars array of booleans indicating which characters need to be XML-escaped
* @param stream the output stream to write to
* @throws java.io.IOException if an error occurs downstream
*/
public void writeEscape(boolean[] specialChars, /*@NotNull*/ OutputStream stream) throws java.io.IOException {
final long val = value;
for (int s = 56; s >= 0; s -= 8) {
final byte b = (byte) ((val >>> s) & 0xff);
if (b == 0) {
break;
}
final char c = WHITE_CHARS[b >>> 6 & 0x3];
final int len = (b & 0x3f);
if (specialChars[c]) {
byte[] e;
if (c == '\n') {
e = ESCAPE_N;
} else if (c == '\r') {
e = ESCAPE_R;
} else {
e = ESCAPE_T;
}
for (int j = 0; j < len; j++) {
stream.write(e);
}
} else {
for (int j = 0; j < len; j++) {
stream.write(c);
}
}
}
}
/*@NotNull*/ private static byte[] ESCAPE_N = {'&', '#', 'x', 'A', ';'};
/*@NotNull*/ private static byte[] ESCAPE_R = {'&', '#', 'x', 'D', ';'};
/*@NotNull*/ private static byte[] ESCAPE_T = {'&', '#', 'x', '9', ';'};
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy