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With inspiration from other libraries
// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
/*
*******************************************************************************
* Copyright (C) 1996-2014, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*/
package com.ibm.icu.text;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import com.ibm.icu.impl.Norm2AllModes;
import com.ibm.icu.impl.Normalizer2Impl;
import com.ibm.icu.impl.Utility;
import com.ibm.icu.lang.UCharacter;
/**
* This class allows one to iterate through all the strings that are canonically equivalent to a given
* string. For example, here are some sample results:
* Results for: {A WITH RING ABOVE}{d}{DOT ABOVE}{CEDILLA}
*
1: {A}{RING ABOVE}{d}{DOT ABOVE}{CEDILLA}
2: {A}{RING ABOVE}{d}{CEDILLA}{DOT ABOVE}
3: {A}{RING ABOVE}{d WITH DOT ABOVE}{CEDILLA}
4: {A}{RING ABOVE}{d WITH CEDILLA}{DOT ABOVE}
5: {A WITH RING ABOVE}{d}{DOT ABOVE}{CEDILLA}
6: {A WITH RING ABOVE}{d}{CEDILLA}{DOT ABOVE}
7: {A WITH RING ABOVE}{d WITH DOT ABOVE}{CEDILLA}
8: {A WITH RING ABOVE}{d WITH CEDILLA}{DOT ABOVE}
9: {ANGSTROM SIGN}{d}{DOT ABOVE}{CEDILLA}
10: {ANGSTROM SIGN}{d}{CEDILLA}{DOT ABOVE}
11: {ANGSTROM SIGN}{d WITH DOT ABOVE}{CEDILLA}
12: {ANGSTROM SIGN}{d WITH CEDILLA}{DOT ABOVE}
*
*
Note: the code is intended for use with small strings, and is not suitable for larger ones,
* since it has not been optimized for that situation.
* @author M. Davis
* @stable ICU 2.4
*/
public final class CanonicalIterator {
/**
* Construct a CanonicalIterator object
* @param source string to get results for
* @stable ICU 2.4
*/
public CanonicalIterator(String source) {
Norm2AllModes allModes = Norm2AllModes.getNFCInstance();
nfd = allModes.decomp;
nfcImpl = allModes.impl.ensureCanonIterData();
setSource(source);
}
/**
* Gets the NFD form of the current source we are iterating over.
* @return gets the source: NOTE: it is the NFD form of the source originally passed in
* @stable ICU 2.4
*/
public String getSource() {
return source;
}
/**
* Resets the iterator so that one can start again from the beginning.
* @stable ICU 2.4
*/
public void reset() {
done = false;
for (int i = 0; i < current.length; ++i) {
current[i] = 0;
}
}
/**
* Get the next canonically equivalent string.
*
Warning: The strings are not guaranteed to be in any particular order.
* @return the next string that is canonically equivalent. The value null is returned when
* the iteration is done.
* @stable ICU 2.4
*/
public String next() {
if (done) return null;
// construct return value
buffer.setLength(0); // delete old contents
for (int i = 0; i < pieces.length; ++i) {
buffer.append(pieces[i][current[i]]);
}
String result = buffer.toString();
// find next value for next time
for (int i = current.length - 1; ; --i) {
if (i < 0) {
done = true;
break;
}
current[i]++;
if (current[i] < pieces[i].length) break; // got sequence
current[i] = 0;
}
return result;
}
/**
* Set a new source for this iterator. Allows object reuse.
* @param newSource the source string to iterate against. This allows the same iterator to be used
* while changing the source string, saving object creation.
* @stable ICU 2.4
*/
public void setSource(String newSource) {
source = nfd.normalize(newSource);
done = false;
// catch degenerate case
if (newSource.length() == 0) {
pieces = new String[1][];
current = new int[1];
pieces[0] = new String[]{""};
return;
}
// find the segments
List segmentList = new ArrayList();
int cp;
int start = 0;
// i should be the end of the first code point
// break up the string into segements
int i = UTF16.findOffsetFromCodePoint(source, 1);
for (; i < source.length(); i += Character.charCount(cp)) {
cp = source.codePointAt(i);
if (nfcImpl.isCanonSegmentStarter(cp)) {
segmentList.add(source.substring(start, i)); // add up to i
start = i;
}
}
segmentList.add(source.substring(start, i)); // add last one
// allocate the arrays, and find the strings that are CE to each segment
pieces = new String[segmentList.size()][];
current = new int[segmentList.size()];
for (i = 0; i < pieces.length; ++i) {
if (PROGRESS) System.out.println("SEGMENT");
pieces[i] = getEquivalents(segmentList.get(i));
}
}
/**
* Simple implementation of permutation.
*
Warning: The strings are not guaranteed to be in any particular order.
* @param source the string to find permutations for
* @param skipZeros set to true to skip characters with canonical combining class zero
* @param output the set to add the results to
* @internal
* @deprecated This API is ICU internal only.
*/
@Deprecated
public static void permute(String source, boolean skipZeros, Set output) {
// TODO: optimize
//if (PROGRESS) System.out.println("Permute: " + source);
// optimization:
// if zero or one character, just return a set with it
// we check for length < 2 to keep from counting code points all the time
if (source.length() <= 2 && UTF16.countCodePoint(source) <= 1) {
output.add(source);
return;
}
// otherwise iterate through the string, and recursively permute all the other characters
Set subpermute = new HashSet();
int cp;
for (int i = 0; i < source.length(); i += UTF16.getCharCount(cp)) {
cp = UTF16.charAt(source, i);
// optimization:
// if the character is canonical combining class zero,
// don't permute it
if (skipZeros && i != 0 && UCharacter.getCombiningClass(cp) == 0) {
//System.out.println("Skipping " + Utility.hex(UTF16.valueOf(source, i)));
continue;
}
// see what the permutations of the characters before and after this one are
subpermute.clear();
permute(source.substring(0,i)
+ source.substring(i + UTF16.getCharCount(cp)), skipZeros, subpermute);
// prefix this character to all of them
String chStr = UTF16.valueOf(source, i);
for (String s : subpermute) {
String piece = chStr + s;
//if (PROGRESS) System.out.println(" Piece: " + piece);
output.add(piece);
}
}
}
// FOR TESTING
/*
*@return the set of "safe starts", characters that are class zero AND are never non-initial in a decomposition.
*
public static UnicodeSet getSafeStart() {
return (UnicodeSet) SAFE_START.clone();
}
*/
/*
*@return the set of characters whose decompositions start with the given character
*
public static UnicodeSet getStarts(int cp) {
UnicodeSet result = AT_START.get(cp);
if (result == null) result = EMPTY;
return (UnicodeSet) result.clone();
}
*/
// ===================== PRIVATES ==============================
// debug
private static boolean PROGRESS = false; // debug progress
//private static Transliterator NAME = PROGRESS ? Transliterator.getInstance("name") : null;
private static boolean SKIP_ZEROS = true;
// fields
private final Normalizer2 nfd;
private final Normalizer2Impl nfcImpl;
private String source;
private boolean done;
private String[][] pieces;
private int[] current;
// Note: C will need two more fields, since arrays there don't have lengths
// int pieces_length;
// int[] pieces_lengths;
// transient fields
private transient StringBuilder buffer = new StringBuilder();
// we have a segment, in NFD. Find all the strings that are canonically equivalent to it.
private String[] getEquivalents(String segment) {
Set result = new HashSet();
Set basic = getEquivalents2(segment);
Set permutations = new HashSet();
// now get all the permutations
// add only the ones that are canonically equivalent
// TODO: optimize by not permuting any class zero.
Iterator it = basic.iterator();
while (it.hasNext()) {
String item = it.next();
permutations.clear();
permute(item, SKIP_ZEROS, permutations);
Iterator it2 = permutations.iterator();
while (it2.hasNext()) {
String possible = it2.next();
/*
String attempt = Normalizer.normalize(possible, Normalizer.DECOMP, 0);
if (attempt.equals(segment)) {
*/
if (Normalizer.compare(possible, segment,0)==0) {
if (PROGRESS) System.out.println("Adding Permutation: " + Utility.hex(possible));
result.add(possible);
} else {
if (PROGRESS) System.out.println("-Skipping Permutation: " + Utility.hex(possible));
}
}
}
// convert into a String[] to clean up storage
String[] finalResult = new String[result.size()];
result.toArray(finalResult);
return finalResult;
}
private Set getEquivalents2(String segment) {
Set result = new HashSet();
if (PROGRESS) System.out.println("Adding: " + Utility.hex(segment));
result.add(segment);
StringBuffer workingBuffer = new StringBuffer();
UnicodeSet starts = new UnicodeSet();
// cycle through all the characters
int cp;
for (int i = 0; i < segment.length(); i += Character.charCount(cp)) {
// see if any character is at the start of some decomposition
cp = segment.codePointAt(i);
if (!nfcImpl.getCanonStartSet(cp, starts)) {
continue;
}
// if so, see which decompositions match
for(UnicodeSetIterator iter = new UnicodeSetIterator(starts); iter.next();) {
int cp2 = iter.codepoint;
Set remainder = extract(cp2, segment, i, workingBuffer);
if (remainder == null) {
continue;
}
// there were some matches, so add all the possibilities to the set.
String prefix= segment.substring(0,i);
prefix += UTF16.valueOf(cp2);
for (String item : remainder) {
result.add(prefix + item);
}
}
}
return result;
/*
Set result = new HashSet();
if (PROGRESS) System.out.println("Adding: " + NAME.transliterate(segment));
result.add(segment);
StringBuffer workingBuffer = new StringBuffer();
// cycle through all the characters
int cp;
for (int i = 0; i < segment.length(); i += UTF16.getCharCount(cp)) {
// see if any character is at the start of some decomposition
cp = UTF16.charAt(segment, i);
NormalizerImpl.getCanonStartSet(c,fillSet)
UnicodeSet starts = AT_START.get(cp);
if (starts == null) continue;
UnicodeSetIterator usi = new UnicodeSetIterator(starts);
// if so, see which decompositions match
while (usi.next()) {
int cp2 = usi.codepoint;
// we know that there are no strings in it
// so we don't have to check CharacterIterator.IS_STRING
Set remainder = extract(cp2, segment, i, workingBuffer);
if (remainder == null) continue;
// there were some matches, so add all the possibilities to the set.
String prefix = segment.substring(0, i) + UTF16.valueOf(cp2);
Iterator it = remainder.iterator();
while (it.hasNext()) {
String item = (String) it.next();
if (PROGRESS) System.out.println("Adding: " + NAME.transliterate(prefix + item));
result.add(prefix + item);
}
}
}
return result;
*/
}
/**
* See if the decomposition of cp2 is at segment starting at segmentPos
* (with canonical rearrangment!)
* If so, take the remainder, and return the equivalents
*/
private Set extract(int comp, String segment, int segmentPos, StringBuffer buf) {
if (PROGRESS) System.out.println(" extract: " + Utility.hex(UTF16.valueOf(comp))
+ ", " + Utility.hex(segment.substring(segmentPos)));
String decomp = nfcImpl.getDecomposition(comp);
if (decomp == null) {
decomp = UTF16.valueOf(comp);
}
// See if it matches the start of segment (at segmentPos)
boolean ok = false;
int cp;
int decompPos = 0;
int decompCp = UTF16.charAt(decomp,0);
decompPos += UTF16.getCharCount(decompCp); // adjust position to skip first char
//int decompClass = getClass(decompCp);
buf.setLength(0); // initialize working buffer, shared among callees
for (int i = segmentPos; i < segment.length(); i += UTF16.getCharCount(cp)) {
cp = UTF16.charAt(segment, i);
if (cp == decompCp) { // if equal, eat another cp from decomp
if (PROGRESS) System.out.println(" matches: " + Utility.hex(UTF16.valueOf(cp)));
if (decompPos == decomp.length()) { // done, have all decomp characters!
buf.append(segment.substring(i + UTF16.getCharCount(cp))); // add remaining segment chars
ok = true;
break;
}
decompCp = UTF16.charAt(decomp, decompPos);
decompPos += UTF16.getCharCount(decompCp);
//decompClass = getClass(decompCp);
} else {
if (PROGRESS) System.out.println(" buffer: " + Utility.hex(UTF16.valueOf(cp)));
// brute force approach
UTF16.append(buf, cp);
/* TODO: optimize
// since we know that the classes are monotonically increasing, after zero
// e.g. 0 5 7 9 0 3
// we can do an optimization
// there are only a few cases that work: zero, less, same, greater
// if both classes are the same, we fail
// if the decomp class < the segment class, we fail
segClass = getClass(cp);
if (decompClass <= segClass) return null;
*/
}
}
if (!ok) return null; // we failed, characters left over
if (PROGRESS) System.out.println("Matches");
if (buf.length() == 0) return SET_WITH_NULL_STRING; // succeed, but no remainder
String remainder = buf.toString();
// brute force approach
// to check to make sure result is canonically equivalent
/*
String trial = Normalizer.normalize(UTF16.valueOf(comp) + remainder, Normalizer.DECOMP, 0);
if (!segment.regionMatches(segmentPos, trial, 0, segment.length() - segmentPos)) return null;
*/
if (0!=Normalizer.compare(UTF16.valueOf(comp) + remainder, segment.substring(segmentPos), 0)) return null;
// get the remaining combinations
return getEquivalents2(remainder);
}
/*
// TODO: fix once we have a codepoint interface to get the canonical combining class
// TODO: Need public access to canonical combining class in UCharacter!
private static int getClass(int cp) {
return Normalizer.getClass((char)cp);
}
*/
// ================= BUILDER =========================
// TODO: Flatten this data so it doesn't have to be reconstructed each time!
//private static final UnicodeSet EMPTY = new UnicodeSet(); // constant, don't change
private static final Set SET_WITH_NULL_STRING = new HashSet(); // constant, don't change
static {
SET_WITH_NULL_STRING.add("");
}
// private static UnicodeSet SAFE_START = new UnicodeSet();
// private static CharMap AT_START = new CharMap();
// TODO: WARNING, NORMALIZER doesn't have supplementaries yet !!;
// Change FFFF to 10FFFF in C, and in Java when normalizer is upgraded.
// private static int LAST_UNICODE = 0x10FFFF;
/*
static {
buildData();
}
*/
/*
private static void buildData() {
if (PROGRESS) System.out.println("Getting Safe Start");
for (int cp = 0; cp <= LAST_UNICODE; ++cp) {
if (PROGRESS & (cp & 0x7FF) == 0) System.out.print('.');
int cc = UCharacter.getCombiningClass(cp);
if (cc == 0) SAFE_START.add(cp);
// will fix to be really safe below
}
if (PROGRESS) System.out.println();
if (PROGRESS) System.out.println("Getting Containment");
for (int cp = 0; cp <= LAST_UNICODE; ++cp) {
if (PROGRESS & (cp & 0x7FF) == 0) System.out.print('.');
if (Normalizer.isNormalized(cp, Normalizer.NFD)) continue;
//String istr = UTF16.valueOf(cp);
String decomp = Normalizer.normalize(cp, Normalizer.NFD);
//if (decomp.equals(istr)) continue;
// add each character in the decomposition to canBeIn
int component;
for (int i = 0; i < decomp.length(); i += UTF16.getCharCount(component)) {
component = UTF16.charAt(decomp, i);
if (i == 0) {
AT_START.add(component, cp);
} else if (UCharacter.getCombiningClass(component) == 0) {
SAFE_START.remove(component);
}
}
}
if (PROGRESS) System.out.println();
}
// the following is just for a map from characters to a set of characters
private static class CharMap {
Map storage = new HashMap();
MutableInt probe = new MutableInt();
boolean converted = false;
public void add(int cp, int whatItIsIn) {
UnicodeSet result = (UnicodeSet) storage.get(probe.set(cp));
if (result == null) {
result = new UnicodeSet();
storage.put(probe, result);
}
result.add(whatItIsIn);
}
public UnicodeSet get(int cp) {
return (UnicodeSet) storage.get(probe.set(cp));
}
}
private static class MutableInt {
public int contents;
public int hashCode() { return contents; }
public boolean equals(Object other) {
return ((MutableInt)other).contents == contents;
}
// allows chaining
public MutableInt set(int contents) {
this.contents = contents;
return this;
}
}
*/
}