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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.functions;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.ZeroOrOne;
import net.sf.saxon.serialize.charcode.UTF8CharacterSet;
import net.sf.saxon.trans.Err;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.util.FastStringBuffer;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.StringValue;
/**
* This class supports the function fn:encode-for-uri()
*/
public class EncodeForUri extends ScalarSystemFunction {
@Override
public AtomicValue evaluate(Item arg, XPathContext context) throws XPathException {
final CharSequence s = arg.getStringValueCS();
return StringValue.makeStringValue(escape(s, "-_.~"));
}
@Override
public ZeroOrOne resultWhenEmpty() {
return ZERO_LENGTH_STRING;
}
/**
* Escape special characters in a URI. The characters that are %HH-encoded are
* all non-ASCII characters, plus all ASCII characters except (a) letter A-Z
* and a-z, (b) digits 0-9, and (c) characters listed in the allowedPunctuation
* argument
*
* @param s the URI to be escaped
* @param allowedPunctuation ASCII characters other than letters and digits that
* should NOT be %HH-encoded
* @return the %HH-encoded string
*/
public static CharSequence escape(CharSequence s, String allowedPunctuation) {
FastStringBuffer sb = new FastStringBuffer(s.length());
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9')) {
sb.append(c);
} else if (c <= 0x20 || c >= 0x7f) {
escapeChar(c, (i + 1) < s.length() ? s.charAt(i + 1) : ' ', sb);
} else if (allowedPunctuation.indexOf(c) >= 0) {
sb.append(c);
} else {
escapeChar(c, ' ', sb);
}
}
return sb;
}
private static final String hex = "0123456789ABCDEF";
/**
* Escape a single character in %HH representation, or a pair of two chars representing
* a surrogate pair
*
* @param c the character to be escaped, or the first character of a surrogate pair
* @param c2 the second character of a surrogate pair
* @param sb the buffer to contain the escaped result
*/
private static void escapeChar(char c, char c2, FastStringBuffer sb) {
byte[] array = new byte[4];
int used = UTF8CharacterSet.getUTF8Encoding(c, c2, array);
for (int b = 0; b < used; b++) {
int v = (int) array[b] & 0xff;
sb.append('%');
sb.append(hex.charAt(v / 16));
sb.append(hex.charAt(v % 16));
}
}
/**
* Check that any percent-encoding within a URI is well-formed. The method assumes that a percent
* sign followed by two hex digits represents an octet of the UTF-8 representation of a character;
* any other percent sign is assumed to represent itself.
*
* @param uri the string to be checked for validity
* @throws XPathException if the string is not validly percent-encoded
*/
public static void checkPercentEncoding(String uri) throws XPathException {
final String hexDigits = "0123456789abcdefABCDEF";
for (int i = 0; i < uri.length(); ) {
char c = uri.charAt(i);
byte[] bytes;
// Note: we're translating the UTF-8 byte sequence but then not using the value
int expectedOctets;
if (c == '%') {
if (i + 2 >= uri.length()) {
throw new XPathException("% sign in URI must be followed by two hex digits" +
Err.wrap(uri));
}
int h1 = hexDigits.indexOf(uri.charAt(i + 1));
if (h1 > 15) {
h1 -= 6;
}
int h2 = hexDigits.indexOf(uri.charAt(i + 2));
if (h2 > 15) {
h2 -= 6;
}
if (h1 >= 0 && h2 >= 0) {
int b = h1 << 4 | h2;
expectedOctets = UTF8RepresentationLength[h1];
if (expectedOctets == -1) {
throw new XPathException("First %-encoded octet in URI is not valid as the start of a UTF-8 " +
"character: first two bits must not be '10'" +
Err.wrap(uri));
}
bytes = new byte[expectedOctets];
bytes[0] = (byte) b;
i += 3;
for (int q = 1; q < expectedOctets; q++) {
if (i + 2 > uri.length() || uri.charAt(i) != '%') {
throw new XPathException("Incomplete %-encoded UTF-8 octet sequence in URI " +
Err.wrap(uri));
}
h1 = hexDigits.indexOf(uri.charAt(i + 1));
if (h1 > 15) {
h1 -= 6;
}
h2 = hexDigits.indexOf(uri.charAt(i + 2));
if (h2 > 15) {
h2 -= 6;
}
if (h1 < 0 || h2 < 0) {
throw new XPathException("Invalid %-encoded UTF-8 octet sequence in URI" +
Err.wrap(uri));
}
if (UTF8RepresentationLength[h1] != -1) {
throw new XPathException("In a URI, a %-encoded UTF-8 octet after the first " +
"must have '10' as the first two bits" +
Err.wrap(uri));
}
b = h1 << 4 | h2;
bytes[q] = (byte) b;
i += 3;
}
} else {
throw new XPathException("% sign in URI must be followed by two hex digits" +
Err.wrap(uri));
}
} else {
i++;
}
}
}
// Length of a UTF8 byte sequence, as a function of the first nibble
private static int[] UTF8RepresentationLength = {1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, 2, 2, 3, 4};
}
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