PercentEscaper.java
/*
* Copyright (c) 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package org.yaml.snakeyaml.external.com.google.gdata.util.common.base;
/**
* A {@code UnicodeEscaper} that escapes some set of Java characters using the URI percent encoding
* scheme. The set of safe characters (those which remain unescaped) can be specified on
* construction.
*
* <p>
* For details on escaping URIs for use in web pages, see section 2.4 of
* <a href="http://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>.
*
* <p>
* In most cases this class should not need to be used directly. If you have no special requirements
* for escaping your URIs, you should use either {@link CharEscapers#uriEscaper()} or
* {@link CharEscapers#uriEscaper(boolean)}.
*
* <p>
* When encoding a String, the following rules apply:
* <ul>
* <li>The alphanumeric characters "a" through "z", "A" through "Z" and "0" through "9" remain the
* same.
* <li>Any additionally specified safe characters remain the same.
* <li>If {@code plusForSpace} was specified, the space character " " is converted into a plus sign
* "+".
* <li>All other characters are converted into one or more bytes using UTF-8 encoding and each byte
* is then represented by the 3-character string "%XY", where "XY" is the two-digit, uppercase,
* hexadecimal representation of the byte value.
* </ul>
*
* <p>
* RFC 2396 specifies the set of unreserved characters as "-", "_", ".", "!", "~", "*", "'", "(" and
* ")". It goes on to state:
*
* <p>
* <i>Unreserved characters can be escaped without changing the semantics of the URI, but this
* should not be done unless the URI is being used in a context that does not allow the unescaped
* character to appear.</i>
*
* <p>
* For performance reasons the only currently supported character encoding of this class is UTF-8.
*
* <p>
* <b>Note</b>: This escaper produces uppercase hexidecimal sequences. From
* <a href="http://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>:<br>
* <i>"URI producers and normalizers should use uppercase hexadecimal digits for all
* percent-encodings."</i>
*/
public class PercentEscaper extends UnicodeEscaper {
/**
* A string of safe characters that mimics the behavior of {@link java.net.URLEncoder}.
*/
public static final String SAFECHARS_URLENCODER = "-_.*";
/**
* A string of characters that do not need to be encoded when used in URI path segments, as
* specified in RFC 3986. Note that some of these characters do need to be escaped when used in
* other parts of the URI.
*/
public static final String SAFEPATHCHARS_URLENCODER = "-_.!~*'()@:$&,;=";
/**
* A string of characters that do not need to be encoded when used in URI query strings, as
* specified in RFC 3986. Note that some of these characters do need to be escaped when used in
* other parts of the URI.
*/
public static final String SAFEQUERYSTRINGCHARS_URLENCODER = "-_.!~*'()@:$,;/?:";
// In some uri escapers spaces are escaped to '+'
private static final char[] URI_ESCAPED_SPACE = {'+'};
private static final char[] UPPER_HEX_DIGITS = "0123456789ABCDEF".toCharArray();
/**
* If true we should convert space to the {@code +} character.
*/
private final boolean plusForSpace;
/**
* An array of flags where for any {@code char c} if {@code safeOctets[c]} is true then {@code c}
* should remain unmodified in the output. If {@code c > safeOctets.length} then it should be
* escaped.
*/
private final boolean[] safeOctets;
/**
* Constructs a URI escaper with the specified safe characters and optional handling of the space
* character.
*
* @param safeChars a non null string specifying additional safe characters for this escaper (the
* ranges 0..9, a..z and A..Z are always safe and should not be specified here)
* @param plusForSpace true if ASCII space should be escaped to {@code +} rather than {@code %20}
* @throws IllegalArgumentException if any of the parameters were invalid
*/
public PercentEscaper(String safeChars, boolean plusForSpace) {
// Avoid any misunderstandings about the behavior of this escaper
if (safeChars.matches(".*[0-9A-Za-z].*")) {
throw new IllegalArgumentException(
"Alphanumeric characters are always 'safe' and should not be " + "explicitly specified");
}
// Avoid ambiguous parameters. Safe characters are never modified so if
// space is a safe character then setting plusForSpace is meaningless.
if (plusForSpace && safeChars.contains(" ")) {
throw new IllegalArgumentException(
"plusForSpace cannot be specified when space is a 'safe' character");
}
if (safeChars.contains("%")) {
throw new IllegalArgumentException("The '%' character cannot be specified as 'safe'");
}
this.plusForSpace = plusForSpace;
this.safeOctets = createSafeOctets(safeChars);
}
/**
* Creates a boolean[] with entries corresponding to the character values for 0-9, A-Z, a-z and
* those specified in safeChars set to true. The array is as small as is required to hold the
* given character information.
*/
private static boolean[] createSafeOctets(String safeChars) {
int maxChar = 'z';
char[] safeCharArray = safeChars.toCharArray();
for (char c : safeCharArray) {
maxChar = Math.max(c, maxChar);
}
boolean[] octets = new boolean[maxChar + 1];
for (int c = '0'; c <= '9'; c++) {
octets[c] = true;
}
for (int c = 'A'; c <= 'Z'; c++) {
octets[c] = true;
}
for (int c = 'a'; c <= 'z'; c++) {
octets[c] = true;
}
for (char c : safeCharArray) {
octets[c] = true;
}
return octets;
}
/*
* Overridden for performance. For unescaped strings this improved the performance of the uri
* escaper from ~760ns to ~400ns as measured by {@link CharEscapersBenchmark}.
*/
@Override
protected int nextEscapeIndex(CharSequence csq, int index, int end) {
for (; index < end; index++) {
char c = csq.charAt(index);
if (c >= safeOctets.length || !safeOctets[c]) {
break;
}
}
return index;
}
/*
* Overridden for performance. For unescaped strings this improved the performance of the uri
* escaper from ~400ns to ~170ns as measured by {@link CharEscapersBenchmark}.
*/
@Override
public String escape(String s) {
int slen = s.length();
for (int index = 0; index < slen; index++) {
char c = s.charAt(index);
if (c >= safeOctets.length || !safeOctets[c]) {
return escapeSlow(s, index);
}
}
return s;
}
/**
* Escapes the given Unicode code point in UTF-8.
*/
@Override
protected char[] escape(int cp) {
// We should never get negative values here but if we do it will throw
// an
// IndexOutOfBoundsException, so at least it will get spotted.
if (cp < safeOctets.length && safeOctets[cp]) {
return null;
} else if (cp == ' ' && plusForSpace) {
return URI_ESCAPED_SPACE;
} else if (cp <= 0x7F) {
// Single byte UTF-8 characters
// Start with "%--" and fill in the blanks
char[] dest = new char[3];
dest[0] = '%';
dest[2] = UPPER_HEX_DIGITS[cp & 0xF];
dest[1] = UPPER_HEX_DIGITS[cp >>> 4];
return dest;
} else if (cp <= 0x7ff) {
// Two byte UTF-8 characters [cp >= 0x80 && cp <= 0x7ff]
// Start with "%--%--" and fill in the blanks
char[] dest = new char[6];
dest[0] = '%';
dest[3] = '%';
dest[5] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[4] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
cp >>>= 2;
dest[2] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[1] = UPPER_HEX_DIGITS[0xC | cp];
return dest;
} else if (cp <= 0xffff) {
// Three byte UTF-8 characters [cp >= 0x800 && cp <= 0xffff]
// Start with "%E-%--%--" and fill in the blanks
char[] dest = new char[9];
dest[0] = '%';
dest[1] = 'E';
dest[3] = '%';
dest[6] = '%';
dest[8] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[7] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
cp >>>= 2;
dest[5] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[4] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
cp >>>= 2;
dest[2] = UPPER_HEX_DIGITS[cp];
return dest;
} else if (cp <= 0x10ffff) {
char[] dest = new char[12];
// Four byte UTF-8 characters [cp >= 0xffff && cp <= 0x10ffff]
// Start with "%F-%--%--%--" and fill in the blanks
dest[0] = '%';
dest[1] = 'F';
dest[3] = '%';
dest[6] = '%';
dest[9] = '%';
dest[11] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[10] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
cp >>>= 2;
dest[8] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[7] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
cp >>>= 2;
dest[5] = UPPER_HEX_DIGITS[cp & 0xF];
cp >>>= 4;
dest[4] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
cp >>>= 2;
dest[2] = UPPER_HEX_DIGITS[cp & 0x7];
return dest;
} else {
// If this ever happens it is due to bug in UnicodeEscaper, not bad
// input.
throw new IllegalArgumentException("Invalid unicode character value " + cp);
}
}
}