Android example source code file (UrlQuerySanitizer.java)
The UrlQuerySanitizer.java Android example source code/*
* Copyright (C) 2007 The Android Open Source Project
*
* 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 android.net;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Set;
import java.util.StringTokenizer;
/**
*
* Sanitizes the Query portion of a URL. Simple example:
* <code>
* UrlQuerySanitizer sanitizer = new UrlQuerySanitizer();
* sanitizer.setAllowUnregisteredParamaters(true);
* sanitizer.parseUrl("http://example.com/?name=Joe+User");
* String name = sanitizer.getValue("name"));
* // name now contains "Joe_User"
* </code>
*
* Register ValueSanitizers to customize the way individual
* parameters are sanitized:
* <code>
* UrlQuerySanitizer sanitizer = new UrlQuerySanitizer();
* sanitizer.registerParamater("name", UrlQuerySanitizer.createSpaceLegal());
* sanitizer.parseUrl("http://example.com/?name=Joe+User");
* String name = sanitizer.getValue("name"));
* // name now contains "Joe User". (The string is first decoded, which
* // converts the '+' to a ' '. Then the string is sanitized, which
* // converts the ' ' to an '_'. (The ' ' is converted because the default
* unregistered parameter sanitizer does not allow any special characters,
* and ' ' is a special character.)
* </code>
*
* There are several ways to create ValueSanitizers. In order of increasing
* sophistication:
* <ol>
* <li>Call one of the UrlQuerySanitizer.createXXX() methods.
* <li>Construct your own instance of
* UrlQuerySanitizer.IllegalCharacterValueSanitizer.
* <li>Subclass UrlQuerySanitizer.ValueSanitizer to define your own value
* sanitizer.
* </ol>
*
*/
public class UrlQuerySanitizer {
/**
* A simple tuple that holds parameter-value pairs.
*
*/
public class ParameterValuePair {
/**
* Construct a parameter-value tuple.
* @param parameter an unencoded parameter
* @param value an unencoded value
*/
public ParameterValuePair(String parameter,
String value) {
mParameter = parameter;
mValue = value;
}
/**
* The unencoded parameter
*/
public String mParameter;
/**
* The unencoded value
*/
public String mValue;
}
final private HashMap<String, ValueSanitizer> mSanitizers =
new HashMap<String, ValueSanitizer>();
final private HashMap<String, String> mEntries =
new HashMap<String, String>();
final private ArrayList<ParameterValuePair> mEntriesList =
new ArrayList<ParameterValuePair>();
private boolean mAllowUnregisteredParamaters;
private boolean mPreferFirstRepeatedParameter;
private ValueSanitizer mUnregisteredParameterValueSanitizer =
getAllIllegal();
/**
* A functor used to sanitize a single query value.
*
*/
public static interface ValueSanitizer {
/**
* Sanitize an unencoded value.
* @param value
* @return the sanitized unencoded value
*/
public String sanitize(String value);
}
/**
* Sanitize values based on which characters they contain. Illegal
* characters are replaced with either space or '_', depending upon
* whether space is a legal character or not.
*/
public static class IllegalCharacterValueSanitizer implements
ValueSanitizer {
private int mFlags;
/**
* Allow space (' ') characters.
*/
public final static int SPACE_OK = 1 << 0;
/**
* Allow whitespace characters other than space. The
* other whitespace characters are
* '\t' '\f' '\n' '\r' and '\0x000b' (vertical tab)
*/
public final static int OTHER_WHITESPACE_OK = 1 << 1;
/**
* Allow characters with character codes 128 to 255.
*/
public final static int NON_7_BIT_ASCII_OK = 1 << 2;
/**
* Allow double quote characters. ('"')
*/
public final static int DQUOTE_OK = 1 << 3;
/**
* Allow single quote characters. ('\'')
*/
public final static int SQUOTE_OK = 1 << 4;
/**
* Allow less-than characters. ('<')
*/
public final static int LT_OK = 1 << 5;
/**
* Allow greater-than characters. ('>')
*/
public final static int GT_OK = 1 << 6;
/**
* Allow ampersand characters ('&')
*/
public final static int AMP_OK = 1 << 7;
/**
* Allow percent-sign characters ('%')
*/
public final static int PCT_OK = 1 << 8;
/**
* Allow nul characters ('\0')
*/
public final static int NUL_OK = 1 << 9;
/**
* Allow text to start with a script URL
* such as "javascript:" or "vbscript:"
*/
public final static int SCRIPT_URL_OK = 1 << 10;
/**
* Mask with all fields set to OK
*/
public final static int ALL_OK = 0x7ff;
/**
* Mask with both regular space and other whitespace OK
*/
public final static int ALL_WHITESPACE_OK =
SPACE_OK | OTHER_WHITESPACE_OK;
// Common flag combinations:
/**
* <ul>
* <li>Deny all special characters.
* <li>Deny script URLs.
* </ul>
*/
public final static int ALL_ILLEGAL =
0;
/**
* <ul>
* <li>Allow all special characters except Nul. ('\0').
* <li>Allow script URLs.
* </ul>
*/
public final static int ALL_BUT_NUL_LEGAL =
ALL_OK & ~NUL_OK;
/**
* <ul>
* <li>Allow all special characters except for:
* <ul>
* <li>whitespace characters
* <li>Nul ('\0')
* </ul>
* <li>Allow script URLs.
* </ul>
*/
public final static int ALL_BUT_WHITESPACE_LEGAL =
ALL_OK & ~(ALL_WHITESPACE_OK | NUL_OK);
/**
* <ul>
* <li>Allow characters used by encoded URLs.
* <li>Deny script URLs.
* </ul>
*/
public final static int URL_LEGAL =
NON_7_BIT_ASCII_OK | SQUOTE_OK | AMP_OK | PCT_OK;
/**
* <ul>
* <li>Allow characters used by encoded URLs.
* <li>Allow spaces.
* <li>Deny script URLs.
* </ul>
*/
public final static int URL_AND_SPACE_LEGAL =
URL_LEGAL | SPACE_OK;
/**
* <ul>
* <li>Allow ampersand.
* <li>Deny script URLs.
* </ul>
*/
public final static int AMP_LEGAL =
AMP_OK;
/**
* <ul>
* <li>Allow ampersand.
* <li>Allow space.
* <li>Deny script URLs.
* </ul>
*/
public final static int AMP_AND_SPACE_LEGAL =
AMP_OK | SPACE_OK;
/**
* <ul>
* <li>Allow space.
* <li>Deny script URLs.
* </ul>
*/
public final static int SPACE_LEGAL =
SPACE_OK;
/**
* <ul>
* <li>Allow all but.
* <ul>
* <li>Nul ('\0')
* <li>Angle brackets ('<', '>')
* </ul>
* <li>Deny script URLs.
* </ul>
*/
public final static int ALL_BUT_NUL_AND_ANGLE_BRACKETS_LEGAL =
ALL_OK & ~(NUL_OK | LT_OK | GT_OK);
/**
* Script URL definitions
*/
private final static String JAVASCRIPT_PREFIX = "javascript:";
private final static String VBSCRIPT_PREFIX = "vbscript:";
private final static int MIN_SCRIPT_PREFIX_LENGTH = Math.min(
JAVASCRIPT_PREFIX.length(), VBSCRIPT_PREFIX.length());
/**
* Construct a sanitizer. The parameters set the behavior of the
* sanitizer.
* @param flags some combination of the XXX_OK flags.
*/
public IllegalCharacterValueSanitizer(
int flags) {
mFlags = flags;
}
/**
* Sanitize a value.
* <ol>
* <li>If script URLs are not OK, the will be removed.
* <li>If neither spaces nor other white space is OK, then
* white space will be trimmed from the beginning and end of
* the URL. (Just the actual white space characters are trimmed, not
* other control codes.)
* <li> Illegal characters will be replaced with
* either ' ' or '_', depending on whether a space is itself a
* legal character.
* </ol>
* @param value
* @return the sanitized value
*/
public String sanitize(String value) {
if (value == null) {
return null;
}
int length = value.length();
if ((mFlags & SCRIPT_URL_OK) != 0) {
if (length >= MIN_SCRIPT_PREFIX_LENGTH) {
String asLower = value.toLowerCase();
if (asLower.startsWith(JAVASCRIPT_PREFIX) ||
asLower.startsWith(VBSCRIPT_PREFIX)) {
return "";
}
}
}
// If whitespace isn't OK, get rid of whitespace at beginning
// and end of value.
if ( (mFlags & ALL_WHITESPACE_OK) == 0) {
value = trimWhitespace(value);
// The length could have changed, so we need to correct
// the length variable.
length = value.length();
}
StringBuilder stringBuilder = new StringBuilder(length);
for(int i = 0; i < length; i++) {
char c = value.charAt(i);
if (!characterIsLegal(c)) {
if ((mFlags & SPACE_OK) != 0) {
c = ' ';
}
else {
c = '_';
}
}
stringBuilder.append(c);
}
return stringBuilder.toString();
}
/**
* Trim whitespace from the beginning and end of a string.
* <p>
* Note: can't use {@link String#trim} because {@link String#trim} has a
* different definition of whitespace than we want.
* @param value the string to trim
* @return the trimmed string
*/
private String trimWhitespace(String value) {
int start = 0;
int last = value.length() - 1;
int end = last;
while (start <= end && isWhitespace(value.charAt(start))) {
start++;
}
while (end >= start && isWhitespace(value.charAt(end))) {
end--;
}
if (start == 0 && end == last) {
return value;
}
return value.substring(start, end + 1);
}
/**
* Check if c is whitespace.
* @param c character to test
* @return true if c is a whitespace character
*/
private boolean isWhitespace(char c) {
switch(c) {
case ' ':
case '\t':
case '\f':
case '\n':
case '\r':
case 11: /* VT */
return true;
default:
return false;
}
}
/**
* Check whether an individual character is legal. Uses the
* flag bit-set passed into the constructor.
* @param c
* @return true if c is a legal character
*/
private boolean characterIsLegal(char c) {
switch(c) {
case ' ' : return (mFlags & SPACE_OK) != 0;
case '\t': case '\f': case '\n': case '\r': case 11: /* VT */
return (mFlags & OTHER_WHITESPACE_OK) != 0;
case '\"': return (mFlags & DQUOTE_OK) != 0;
case '\'': return (mFlags & SQUOTE_OK) != 0;
case '<' : return (mFlags & LT_OK) != 0;
case '>' : return (mFlags & GT_OK) != 0;
case '&' : return (mFlags & AMP_OK) != 0;
case '%' : return (mFlags & PCT_OK) != 0;
case '\0': return (mFlags & NUL_OK) != 0;
default : return (c >= 32 && c < 127) ||
((c >= 128) && ((mFlags & NON_7_BIT_ASCII_OK) != 0));
}
}
}
/**
* Get the current value sanitizer used when processing
* unregistered parameter values.
* <p>
* <b>Note: The default unregistered parameter value sanitizer is
* one that doesn't allow any special characters, similar to what
* is returned by calling createAllIllegal.
*
* @return the current ValueSanitizer used to sanitize unregistered
* parameter values.
*/
public ValueSanitizer getUnregisteredParameterValueSanitizer() {
return mUnregisteredParameterValueSanitizer;
}
/**
* Set the value sanitizer used when processing unregistered
* parameter values.
* @param sanitizer set the ValueSanitizer used to sanitize unregistered
* parameter values.
*/
public void setUnregisteredParameterValueSanitizer(
ValueSanitizer sanitizer) {
mUnregisteredParameterValueSanitizer = sanitizer;
}
// Private fields for singleton sanitizers:
private static final ValueSanitizer sAllIllegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.ALL_ILLEGAL);
private static final ValueSanitizer sAllButNulLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.ALL_BUT_NUL_LEGAL);
private static final ValueSanitizer sAllButWhitespaceLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.ALL_BUT_WHITESPACE_LEGAL);
private static final ValueSanitizer sURLLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.URL_LEGAL);
private static final ValueSanitizer sUrlAndSpaceLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.URL_AND_SPACE_LEGAL);
private static final ValueSanitizer sAmpLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.AMP_LEGAL);
private static final ValueSanitizer sAmpAndSpaceLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.AMP_AND_SPACE_LEGAL);
private static final ValueSanitizer sSpaceLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.SPACE_LEGAL);
private static final ValueSanitizer sAllButNulAndAngleBracketsLegal =
new IllegalCharacterValueSanitizer(
IllegalCharacterValueSanitizer.ALL_BUT_NUL_AND_ANGLE_BRACKETS_LEGAL);
/**
* Return a value sanitizer that does not allow any special characters,
* and also does not allow script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getAllIllegal() {
return sAllIllegal;
}
/**
* Return a value sanitizer that allows everything except Nul ('\0')
* characters. Script URLs are allowed.
* @return a value sanitizer
*/
public static final ValueSanitizer getAllButNulLegal() {
return sAllButNulLegal;
}
/**
* Return a value sanitizer that allows everything except Nul ('\0')
* characters, space (' '), and other whitespace characters.
* Script URLs are allowed.
* @return a value sanitizer
*/
public static final ValueSanitizer getAllButWhitespaceLegal() {
return sAllButWhitespaceLegal;
}
/**
* Return a value sanitizer that allows all the characters used by
* encoded URLs. Does not allow script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getUrlLegal() {
return sURLLegal;
}
/**
* Return a value sanitizer that allows all the characters used by
* encoded URLs and allows spaces, which are not technically legal
* in encoded URLs, but commonly appear anyway.
* Does not allow script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getUrlAndSpaceLegal() {
return sUrlAndSpaceLegal;
}
/**
* Return a value sanitizer that does not allow any special characters
* except ampersand ('&'). Does not allow script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getAmpLegal() {
return sAmpLegal;
}
/**
* Return a value sanitizer that does not allow any special characters
* except ampersand ('&') and space (' '). Does not allow script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getAmpAndSpaceLegal() {
return sAmpAndSpaceLegal;
}
/**
* Return a value sanitizer that does not allow any special characters
* except space (' '). Does not allow script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getSpaceLegal() {
return sSpaceLegal;
}
/**
* Return a value sanitizer that allows any special characters
* except angle brackets ('<' and '>') and Nul ('\0').
* Allows script URLs.
* @return a value sanitizer
*/
public static final ValueSanitizer getAllButNulAndAngleBracketsLegal() {
return sAllButNulAndAngleBracketsLegal;
}
/**
* Constructs a UrlQuerySanitizer.
* <p>
* Defaults:
* <ul>
* <li>unregistered parameters are not allowed.
* <li>the last instance of a repeated parameter is preferred.
* <li>The default value sanitizer is an AllIllegal value sanitizer.
* <ul>
*/
public UrlQuerySanitizer() {
}
/**
* Constructs a UrlQuerySanitizer and parse a URL.
* This constructor is provided for convenience when the
* default parsing behavior is acceptable.
* <p>
* Because the URL is parsed before the constructor returns, there isn't
* a chance to configure the sanitizer to change the parsing behavior.
* <p>
* <code>
* UrlQuerySanitizer sanitizer = new UrlQuerySanitizer(myUrl);
* String name = sanitizer.getValue("name");
* </code>
* <p>
* Defaults:
* <ul>
* <li>unregistered parameters are allowed.
* <li>the last instance of a repeated parameter is preferred.
* <li>The default value sanitizer is an AllIllegal value sanitizer.
* <ul>
*/
public UrlQuerySanitizer(String url) {
setAllowUnregisteredParamaters(true);
parseUrl(url);
}
/**
* Parse the query parameters out of an encoded URL.
* Works by extracting the query portion from the URL and then
* calling parseQuery(). If there is no query portion it is
* treated as if the query portion is an empty string.
* @param url the encoded URL to parse.
*/
public void parseUrl(String url) {
int queryIndex = url.indexOf('?');
String query;
if (queryIndex >= 0) {
query = url.substring(queryIndex + 1);
}
else {
query = "";
}
parseQuery(query);
}
/**
* Parse a query. A query string is any number of parameter-value clauses
* separated by any non-zero number of ampersands. A parameter-value clause
* is a parameter followed by an equal sign, followed by a value. If the
* equal sign is missing, the value is assumed to be the empty string.
* @param query the query to parse.
*/
public void parseQuery(String query) {
clear();
// Split by '&'
StringTokenizer tokenizer = new StringTokenizer(query, "&");
while(tokenizer.hasMoreElements()) {
String attributeValuePair = tokenizer.nextToken();
if (attributeValuePair.length() > 0) {
int assignmentIndex = attributeValuePair.indexOf('=');
if (assignmentIndex < 0) {
// No assignment found, treat as if empty value
parseEntry(attributeValuePair, "");
}
else {
parseEntry(attributeValuePair.substring(0, assignmentIndex),
attributeValuePair.substring(assignmentIndex + 1));
}
}
}
}
/**
* Get a set of all of the parameters found in the sanitized query.
* <p>
* Note: Do not modify this set. Treat it as a read-only set.
* @return all the parameters found in the current query.
*/
public Set<String> getParameterSet() {
return mEntries.keySet();
}
/**
* An array list of all of the parameter value pairs in the sanitized
* query, in the order they appeared in the query. May contain duplicate
* parameters.
* <p class="note">Note: Do not modify this list. Treat it as a read-only list.
*/
public List<ParameterValuePair> getParameterList() {
return mEntriesList;
}
/**
* Check if a parameter exists in the current sanitized query.
* @param parameter the unencoded name of a parameter.
* @return true if the paramater exists in the current sanitized queary.
*/
public boolean hasParameter(String parameter) {
return mEntries.containsKey(parameter);
}
/**
* Get the value for a parameter in the current sanitized query.
* Returns null if the parameter does not
* exit.
* @param parameter the unencoded name of a parameter.
* @return the sanitized unencoded value of the parameter,
* or null if the parameter does not exist.
*/
public String getValue(String parameter) {
return mEntries.get(parameter);
}
/**
* Register a value sanitizer for a particular parameter. Can also be used
* to replace or remove an already-set value sanitizer.
* <p>
* Registering a non-null value sanitizer for a particular parameter
* makes that parameter a registered parameter.
* @param parameter an unencoded parameter name
* @param valueSanitizer the value sanitizer to use for a particular
* parameter. May be null in order to unregister that parameter.
* @see #getAllowUnregisteredParamaters()
*/
public void registerParameter(String parameter,
ValueSanitizer valueSanitizer) {
if (valueSanitizer == null) {
mSanitizers.remove(parameter);
}
mSanitizers.put(parameter, valueSanitizer);
}
/**
* Register a value sanitizer for an array of parameters.
* @param parameters An array of unencoded parameter names.
* @param valueSanitizer
* @see #registerParameter
*/
public void registerParameters(String[] parameters,
ValueSanitizer valueSanitizer) {
int length = parameters.length;
for(int i = 0; i < length; i++) {
mSanitizers.put(parameters[i], valueSanitizer);
}
}
/**
* Set whether or not unregistered parameters are allowed. If they
* are not allowed, then they will be dropped when a query is sanitized.
* <p>
* Defaults to false.
* @param allowUnregisteredParamaters true to allow unregistered parameters.
* @see #getAllowUnregisteredParamaters()
*/
public void setAllowUnregisteredParamaters(
boolean allowUnregisteredParamaters) {
mAllowUnregisteredParamaters = allowUnregisteredParamaters;
}
/**
* Get whether or not unregistered parameters are allowed. If not
* allowed, they will be dropped when a query is parsed.
* @return true if unregistered parameters are allowed.
* @see #setAllowUnregisteredParamaters(boolean)
*/
public boolean getAllowUnregisteredParamaters() {
return mAllowUnregisteredParamaters;
}
/**
* Set whether or not the first occurrence of a repeated parameter is
* preferred. True means the first repeated parameter is preferred.
* False means that the last repeated parameter is preferred.
* <p>
* The preferred parameter is the one that is returned when getParameter
* is called.
* <p>
* defaults to false.
* @param preferFirstRepeatedParameter True if the first repeated
* parameter is preferred.
* @see #getPreferFirstRepeatedParameter()
*/
public void setPreferFirstRepeatedParameter(
boolean preferFirstRepeatedParameter) {
mPreferFirstRepeatedParameter = preferFirstRepeatedParameter;
}
/**
* Get whether or not the first occurrence of a repeated parameter is
* preferred.
* @return true if the first occurrence of a repeated parameter is
* preferred.
* @see #setPreferFirstRepeatedParameter(boolean)
*/
public boolean getPreferFirstRepeatedParameter() {
return mPreferFirstRepeatedParameter;
}
/**
* Parse an escaped parameter-value pair. The default implementation
* unescapes both the parameter and the value, then looks up the
* effective value sanitizer for the parameter and uses it to sanitize
* the value. If all goes well then addSanitizedValue is called with
* the unescaped parameter and the sanitized unescaped value.
* @param parameter an escaped parameter
* @param value an unsanitzied escaped value
*/
protected void parseEntry(String parameter, String value) {
String unescapedParameter = unescape(parameter);
ValueSanitizer valueSanitizer =
getEffectiveValueSanitizer(unescapedParameter);
if (valueSanitizer == null) {
return;
}
String unescapedValue = unescape(value);
String sanitizedValue = valueSanitizer.sanitize(unescapedValue);
addSanitizedEntry(unescapedParameter, sanitizedValue);
}
/**
* Record a sanitized parameter-value pair. Override if you want to
* do additional filtering or validation.
* @param parameter an unescaped parameter
* @param value a sanitized unescaped value
*/
protected void addSanitizedEntry(String parameter, String value) {
mEntriesList.add(
new ParameterValuePair(parameter, value));
if (mPreferFirstRepeatedParameter) {
if (mEntries.containsKey(parameter)) {
return;
}
}
mEntries.put(parameter, value);
}
/**
* Get the value sanitizer for a parameter. Returns null if there
* is no value sanitizer registered for the parameter.
* @param parameter the unescaped parameter
* @return the currently registered value sanitizer for this parameter.
* @see #registerParameter(String, android.net.UrlQuerySanitizer.ValueSanitizer)
*/
public ValueSanitizer getValueSanitizer(String parameter) {
return mSanitizers.get(parameter);
}
/**
* Get the effective value sanitizer for a parameter. Like getValueSanitizer,
* except if there is no value sanitizer registered for a parameter, and
* unregistered paramaters are allowed, then the default value sanitizer is
* returned.
* @param parameter an unescaped parameter
* @return the effective value sanitizer for a parameter.
*/
public ValueSanitizer getEffectiveValueSanitizer(String parameter) {
ValueSanitizer sanitizer = getValueSanitizer(parameter);
if (sanitizer == null && mAllowUnregisteredParamaters) {
sanitizer = getUnregisteredParameterValueSanitizer();
}
return sanitizer;
}
/**
* Unescape an escaped string.
* <ul>
* <li>'+' characters are replaced by
* ' ' characters.
* <li>Valid "%xx" escape sequences are replaced by the
* corresponding unescaped character.
* <li>Invalid escape sequences such as %1z", are passed through unchanged.
* <ol>
* @param string the escaped string
* @return the unescaped string.
*/
public String unescape(String string) {
// Early exit if no escaped characters.
int firstEscape = string.indexOf('%');
if ( firstEscape < 0) {
firstEscape = string.indexOf('+');
if (firstEscape < 0) {
return string;
}
}
int length = string.length();
StringBuilder stringBuilder = new StringBuilder(length);
stringBuilder.append(string.substring(0, firstEscape));
for (int i = firstEscape; i < length; i++) {
char c = string.charAt(i);
if (c == '+') {
c = ' ';
}
else if ( c == '%' && i + 2 < length) {
char c1 = string.charAt(i + 1);
char c2 = string.charAt(i + 2);
if (isHexDigit(c1) && isHexDigit(c2)) {
c = (char) (decodeHexDigit(c1) * 16 + decodeHexDigit(c2));
i += 2;
}
}
stringBuilder.append(c);
}
return stringBuilder.toString();
}
/**
* Test if a character is a hexidecimal digit. Both upper case and lower
* case hex digits are allowed.
* @param c the character to test
* @return true if c is a hex digit.
*/
protected boolean isHexDigit(char c) {
return decodeHexDigit(c) >= 0;
}
/**
* Convert a character that represents a hexidecimal digit into an integer.
* If the character is not a hexidecimal digit, then -1 is returned.
* Both upper case and lower case hex digits are allowed.
* @param c the hexidecimal digit.
* @return the integer value of the hexidecimal digit.
*/
protected int decodeHexDigit(char c) {
if (c >= '0' && c <= '9') {
return c - '0';
}
else if (c >= 'A' && c <= 'F') {
return c - 'A' + 10;
}
else if (c >= 'a' && c <= 'f') {
return c - 'a' + 10;
}
else {
return -1;
}
}
/**
* Clear the existing entries. Called to get ready to parse a new
* query string.
*/
protected void clear() {
mEntries.clear();
mEntriesList.clear();
}
}
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