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/*
* Copyright (C) 2008 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.os;
/**
* A simple pattern matcher, which is safe to use on untrusted data: it does
* not provide full reg-exp support, only simple globbing that can not be
* used maliciously.
*/
public class PatternMatcher implements Parcelable {
/**
* Pattern type: the given pattern must exactly match the string it is
* tested against.
*/
public static final int PATTERN_LITERAL = 0;
/**
* Pattern type: the given pattern must match the
* beginning of the string it is tested against.
*/
public static final int PATTERN_PREFIX = 1;
/**
* Pattern type: the given pattern is interpreted with a
* simple glob syntax for matching against the string it is tested against.
* In this syntax, you can use the '*' character to match against zero or
* more occurrences of the character immediately before. If the
* character before it is '.' it will match any character. The character
* '\' can be used as an escape. This essentially provides only the '*'
* wildcard part of a normal regexp.
*/
public static final int PATTERN_SIMPLE_GLOB = 2;
private final String mPattern;
private final int mType;
public PatternMatcher(String pattern, int type) {
mPattern = pattern;
mType = type;
}
public final String getPath() {
return mPattern;
}
public final int getType() {
return mType;
}
public boolean match(String str) {
return matchPattern(mPattern, str, mType);
}
public String toString() {
String type = "? ";
switch (mType) {
case PATTERN_LITERAL:
type = "LITERAL: ";
break;
case PATTERN_PREFIX:
type = "PREFIX: ";
break;
case PATTERN_SIMPLE_GLOB:
type = "GLOB: ";
break;
}
return "PatternMatcher{" + type + mPattern + "}";
}
public int describeContents() {
return 0;
}
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(mPattern);
dest.writeInt(mType);
}
public PatternMatcher(Parcel src) {
mPattern = src.readString();
mType = src.readInt();
}
public static final Parcelable.Creator<PatternMatcher> CREATOR
= new Parcelable.Creator<PatternMatcher>() {
public PatternMatcher createFromParcel(Parcel source) {
return new PatternMatcher(source);
}
public PatternMatcher[] newArray(int size) {
return new PatternMatcher[size];
}
};
static boolean matchPattern(String pattern, String match, int type) {
if (match == null) return false;
if (type == PATTERN_LITERAL) {
return pattern.equals(match);
} if (type == PATTERN_PREFIX) {
return match.startsWith(pattern);
} else if (type != PATTERN_SIMPLE_GLOB) {
return false;
}
final int NP = pattern.length();
if (NP <= 0) {
return match.length() <= 0;
}
final int NM = match.length();
int ip = 0, im = 0;
char nextChar = pattern.charAt(0);
while ((ip<NP) && (im<NM)) {
char c = nextChar;
ip++;
nextChar = ip < NP ? pattern.charAt(ip) : 0;
final boolean escaped = (c == '\\');
if (escaped) {
c = nextChar;
ip++;
nextChar = ip < NP ? pattern.charAt(ip) : 0;
}
if (nextChar == '*') {
if (!escaped && c == '.') {
if (ip >= (NP-1)) {
// at the end with a pattern match, so
// all is good without checking!
return true;
}
ip++;
nextChar = pattern.charAt(ip);
// Consume everything until the next character in the
// pattern is found.
if (nextChar == '\\') {
ip++;
nextChar = ip < NP ? pattern.charAt(ip) : 0;
}
do {
if (match.charAt(im) == nextChar) {
break;
}
im++;
} while (im < NM);
if (im == NM) {
// Whoops, the next character in the pattern didn't
// exist in the match.
return false;
}
ip++;
nextChar = ip < NP ? pattern.charAt(ip) : 0;
im++;
} else {
// Consume only characters matching the one before '*'.
do {
if (match.charAt(im) != c) {
break;
}
im++;
} while (im < NM);
ip++;
nextChar = ip < NP ? pattern.charAt(ip) : 0;
}
} else {
if (c != '.' && match.charAt(im) != c) return false;
im++;
}
}
if (ip >= NP && im >= NM) {
// Reached the end of both strings, all is good!
return true;
}
// One last check: we may have finished the match string, but still
// have a '.*' at the end of the pattern, which should still count
// as a match.
if (ip == NP-2 && pattern.charAt(ip) == '.'
&& pattern.charAt(ip+1) == '*') {
return true;
}
return false;
}
}
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