com.google.common.escape.Escapers Maven / Gradle / Ivy
/*
* Copyright (C) 2009 The Guava Authors
*
* 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 com.google.common.escape;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.HashMap;
import java.util.Map;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Static utility methods pertaining to {@link Escaper} instances.
*
* @author Sven Mawson
* @author David Beaumont
* @since 15.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class Escapers {
private Escapers() {}
/**
* Returns an {@link Escaper} that does no escaping, passing all character data through unchanged.
*/
public static Escaper nullEscaper() {
return NULL_ESCAPER;
}
// An Escaper that efficiently performs no escaping.
// Extending CharEscaper (instead of Escaper) makes Escapers.compose() easier.
private static final Escaper NULL_ESCAPER =
new CharEscaper() {
@Override
public String escape(String string) {
return checkNotNull(string);
}
@Override
@CheckForNull
protected char[] escape(char c) {
// TODO: Fix tests not to call this directly and make it throw an error.
return null;
}
};
/**
* Returns a builder for creating simple, fast escapers. A builder instance can be reused and each
* escaper that is created will be a snapshot of the current builder state. Builders are not
* thread safe.
*
* The initial state of the builder is such that:
*
*
* - There are no replacement mappings
*
- {@code safeMin == Character.MIN_VALUE}
*
- {@code safeMax == Character.MAX_VALUE}
*
- {@code unsafeReplacement == null}
*
*
* For performance reasons escapers created by this builder are not Unicode aware and will not
* validate the well-formedness of their input.
*/
public static Builder builder() {
return new Builder();
}
/**
* A builder for simple, fast escapers.
*
*
Typically an escaper needs to deal with the escaping of high valued characters or code
* points. In these cases it is necessary to extend either {@link ArrayBasedCharEscaper} or {@link
* ArrayBasedUnicodeEscaper} to provide the desired behavior. However this builder is suitable for
* creating escapers that replace a relative small set of characters.
*
* @author David Beaumont
* @since 15.0
*/
public static final class Builder {
private final Map replacementMap = new HashMap<>();
private char safeMin = Character.MIN_VALUE;
private char safeMax = Character.MAX_VALUE;
@CheckForNull private String unsafeReplacement = null;
// The constructor is exposed via the builder() method above.
private Builder() {}
/**
* Sets the safe range of characters for the escaper. Characters in this range that have no
* explicit replacement are considered 'safe' and remain unescaped in the output. If {@code
* safeMax < safeMin} then the safe range is empty.
*
* @param safeMin the lowest 'safe' character
* @param safeMax the highest 'safe' character
* @return the builder instance
*/
@CanIgnoreReturnValue
public Builder setSafeRange(char safeMin, char safeMax) {
this.safeMin = safeMin;
this.safeMax = safeMax;
return this;
}
/**
* Sets the replacement string for any characters outside the 'safe' range that have no explicit
* replacement. If {@code unsafeReplacement} is {@code null} then no replacement will occur, if
* it is {@code ""} then the unsafe characters are removed from the output.
*
* @param unsafeReplacement the string to replace unsafe characters
* @return the builder instance
*/
@CanIgnoreReturnValue
public Builder setUnsafeReplacement( String unsafeReplacement) {
this.unsafeReplacement = unsafeReplacement;
return this;
}
/**
* Adds a replacement string for the given input character. The specified character will be
* replaced by the given string whenever it occurs in the input, irrespective of whether it lies
* inside or outside the 'safe' range.
*
* @param c the character to be replaced
* @param replacement the string to replace the given character
* @return the builder instance
* @throws NullPointerException if {@code replacement} is null
*/
@CanIgnoreReturnValue
public Builder addEscape(char c, String replacement) {
checkNotNull(replacement);
// This can replace an existing character (the builder is re-usable).
replacementMap.put(c, replacement);
return this;
}
/** Returns a new escaper based on the current state of the builder. */
public Escaper build() {
return new ArrayBasedCharEscaper(replacementMap, safeMin, safeMax) {
@CheckForNull
private final char[] replacementChars =
unsafeReplacement != null ? unsafeReplacement.toCharArray() : null;
@Override
@CheckForNull
protected char[] escapeUnsafe(char c) {
return replacementChars;
}
};
}
}
/**
* Returns a string that would replace the given character in the specified escaper, or {@code
* null} if no replacement should be made. This method is intended for use in tests through the
* {@code EscaperAsserts} class; production users of {@link CharEscaper} should limit themselves
* to its public interface.
*
* @param c the character to escape if necessary
* @return the replacement string, or {@code null} if no escaping was needed
*/
@CheckForNull
public static String computeReplacement(CharEscaper escaper, char c) {
return stringOrNull(escaper.escape(c));
}
/**
* Returns a string that would replace the given character in the specified escaper, or {@code
* null} if no replacement should be made. This method is intended for use in tests through the
* {@code EscaperAsserts} class; production users of {@link UnicodeEscaper} should limit
* themselves to its public interface.
*
* @param cp the Unicode code point to escape if necessary
* @return the replacement string, or {@code null} if no escaping was needed
*/
@CheckForNull
public static String computeReplacement(UnicodeEscaper escaper, int cp) {
return stringOrNull(escaper.escape(cp));
}
@CheckForNull
private static String stringOrNull(@CheckForNull char[] in) {
return (in == null) ? null : new String(in);
}
}