/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.value;
import java.nio.charset.Charset;
import java.text.Collator;
import java.util.Comparator;
import java.util.Locale;
import java.util.Objects;
import org.h2.util.StringUtils;
/**
* Instances of this class can compare strings. Case sensitive and case
* insensitive comparison is supported, and comparison using a collator.
*/
public class CompareMode implements Comparator<Value> {
/**
* This constant means there is no collator set, and the default string
* comparison is to be used.
*/
public static final String OFF = "OFF";
/**
* This constant means the default collator should be used, even if ICU4J is
* in the classpath.
*/
public static final String DEFAULT = "DEFAULT_";
/**
* This constant means ICU4J should be used (this will fail if it is not in
* the classpath).
*/
public static final String ICU4J = "ICU4J_";
/**
* This constant means the charset specified should be used.
* This will fail if the specified charset does not exist.
*/
public static final String CHARSET = "CHARSET_";
private static Locale[] LOCALES;
private static volatile CompareMode lastUsed;
private static final boolean CAN_USE_ICU4J;
static {
boolean b = false;
try {
Class.forName("com.ibm.icu.text.Collator");
b = true;
} catch (Exception e) {
// ignore
}
CAN_USE_ICU4J = b;
}
private final String name;
private final int strength;
protected CompareMode(String name, int strength) {
this.name = name;
this.strength = strength;
}
/**
* Create a new compare mode with the given collator and strength. If
* required, a new CompareMode is created, or if possible the last one is
* returned. A cache is used to speed up comparison when using a collator;
* CollationKey objects are cached.
*
* @param name the collation name or null
* @param strength the collation strength
* @return the compare mode
*/
public static CompareMode getInstance(String name, int strength) {
CompareMode last = lastUsed;
if (last != null && Objects.equals(last.name, name) && last.strength == strength) {
return last;
}
if (name == null || name.equals(OFF)) {
last = new CompareMode(name, strength);
} else {
boolean useICU4J;
if (name.startsWith(ICU4J)) {
useICU4J = true;
name = name.substring(ICU4J.length());
} else if (name.startsWith(DEFAULT)) {
useICU4J = false;
name = name.substring(DEFAULT.length());
} else if (name.startsWith(CHARSET)) {
useICU4J = false;
} else {
useICU4J = CAN_USE_ICU4J;
}
if (useICU4J) {
last = new CompareModeIcu4J(name, strength);
} else {
last = new CompareModeDefault(name, strength);
}
}
lastUsed = last;
return last;
}
/**
* Returns available locales for collations.
*
* @param onlyIfInitialized
* if {@code true}, returns {@code null} when locales are not yet
* initialized
* @return available locales for collations.
*/
public static Locale[] getCollationLocales(boolean onlyIfInitialized) {
Locale[] locales = LOCALES;
if (locales == null && !onlyIfInitialized) {
LOCALES = locales = Collator.getAvailableLocales();
}
return locales;
}
/**
* Compare two characters in a string.
*
* @param a the first string
* @param ai the character index in the first string
* @param b the second string
* @param bi the character index in the second string
* @param ignoreCase true if a case-insensitive comparison should be made
* @return true if the characters are equals
*/
public boolean equalsChars(String a, int ai, String b, int bi, boolean ignoreCase) {
char ca = a.charAt(ai);
char cb = b.charAt(bi);
if (ca == cb) {
return true;
}
if (ignoreCase) {
if (Character.toUpperCase(ca) == Character.toUpperCase(cb)
|| Character.toLowerCase(ca) == Character.toLowerCase(cb)) {
return true;
}
}
return false;
}
/**
* Compare two strings.
*
* @param a the first string
* @param b the second string
* @param ignoreCase true if a case-insensitive comparison should be made
* @return -1 if the first string is 'smaller', 1 if the second string is
* smaller, and 0 if they are equal
*/
public int compareString(String a, String b, boolean ignoreCase) {
if (ignoreCase) {
return a.compareToIgnoreCase(b);
}
return a.compareTo(b);
}
/**
* Get the collation name.
*
* @param l the locale
* @return the name of the collation
*/
public static String getName(Locale l) {
Locale english = Locale.ENGLISH;
String name = l.getDisplayLanguage(english) + ' ' +
l.getDisplayCountry(english) + ' ' + l.getVariant();
name = StringUtils.toUpperEnglish(name.trim().replace(' ', '_'));
return name;
}
/**
* Compare name of the locale with the given name. The case of the name
* is ignored.
*
* @param locale the locale
* @param name the name
* @return true if they match
*/
static boolean compareLocaleNames(Locale locale, String name) {
return name.equalsIgnoreCase(locale.toString()) || name.equalsIgnoreCase(locale.toLanguageTag()) ||
name.equalsIgnoreCase(getName(locale));
}
/**
* Get the collator object for the given language name or language / country
* combination.
*
* @param name the language name
* @return the collator
*/
public static Collator getCollator(String name) {
Collator result = null;
if (name.startsWith(ICU4J)) {
name = name.substring(ICU4J.length());
} else if (name.startsWith(DEFAULT)) {
name = name.substring(DEFAULT.length());
} else if (name.startsWith(CHARSET)) {
return new CharsetCollator(Charset.forName(name.substring(CHARSET.length())));
}
int length = name.length();
if (length == 2) {
Locale locale = new Locale(StringUtils.toLowerEnglish(name), "");
if (compareLocaleNames(locale, name)) {
result = Collator.getInstance(locale);
}
} else if (length == 5) {
// LL_CC (language_country)
int idx = name.indexOf('_');
if (idx >= 0) {
String language = StringUtils.toLowerEnglish(name.substring(0, idx));
String country = name.substring(idx + 1);
Locale locale = new Locale(language, country);
if (compareLocaleNames(locale, name)) {
result = Collator.getInstance(locale);
}
}
} else if (name.indexOf('-') > 0) {
Locale locale = Locale.forLanguageTag(name);
if (!locale.getLanguage().isEmpty()) {
return Collator.getInstance(locale);
}
}
if (result == null) {
for (Locale locale : getCollationLocales(false)) {
if (compareLocaleNames(locale, name)) {
result = Collator.getInstance(locale);
break;
}
}
}
return result;
}
public String getName() {
return name == null ? OFF : name;
}
public int getStrength() {
return strength;
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
} else if (!(obj instanceof CompareMode)) {
return false;
}
CompareMode o = (CompareMode) obj;
if (!getName().equals(o.getName())) {
return false;
}
if (strength != o.strength) {
return false;
}
return true;
}
@Override
public int hashCode() {
int result = 1;
result = 31 * result + getName().hashCode();
result = 31 * result + strength;
return result;
}
@Override
public int compare(Value o1, Value o2) {
return o1.compareTo(o2, null, this);
}
}