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International Component for Unicode for Java (ICU4J) is a mature, widely used Java library
providing Unicode and Globalization support
/*
******************************************************************************
* Copyright (C) 1996-2010, International Business Machines Corporation and
* others. All Rights Reserved.
******************************************************************************
*/
package com.ibm.icu.impl;
import java.util.NoSuchElementException;
import com.ibm.icu.lang.UCharacter;
import com.ibm.icu.text.UTF16;
import com.ibm.icu.util.RangeValueIterator;
/**
* Class enabling iteration of the values in a Trie.
* Result of each iteration contains the interval of codepoints that have
* the same value type and the value type itself.
* The comparison of each codepoint value is done via extract(), which the
* default implementation is to return the value as it is.
* Method extract() can be overwritten to perform manipulations on
* codepoint values in order to perform specialized comparison.
* TrieIterator is designed to be a generic iterator for the CharTrie
* and the IntTrie, hence to accommodate both types of data, the return
* result will be in terms of int (32 bit) values.
* See com.ibm.icu.text.UCharacterTypeIterator for examples of use.
* Notes for porting utrie_enum from icu4c to icu4j:
* Internally, icu4c's utrie_enum performs all iterations in its body. In Java
* sense, the caller will have to pass a object with a callback function
* UTrieEnumRange(const void *context, UChar32 start, UChar32 limit,
* uint32_t value) into utrie_enum. utrie_enum will then find ranges of
* codepoints with the same value as determined by
* UTrieEnumValue(const void *context, uint32_t value). for each range,
* utrie_enum calls the callback function to perform a task. In this way,
* icu4c performs the iteration within utrie_enum.
* To follow the JDK model, icu4j is slightly different from icu4c.
* Instead of requesting the caller to implement an object for a callback.
* The caller will have to implement a subclass of TrieIterator, fleshing out
* the method extract(int) (equivalent to UTrieEnumValue). Independent of icu4j,
* the caller will have to code his own iteration and flesh out the task
* (equivalent to UTrieEnumRange) to be performed in the iteration loop.
*
* There are basically 3 usage scenarios for porting:
* 1) UTrieEnumValue is the only implemented callback then just implement a
* subclass of TrieIterator and override the extract(int) method. The
* extract(int) method is analogus to UTrieEnumValue callback.
*
* 2) UTrieEnumValue and UTrieEnumRange both are implemented then implement
* a subclass of TrieIterator, override the extract method and iterate, e.g
*
* utrie_enum(&normTrie, _enumPropertyStartsValue, _enumPropertyStartsRange,
* set);
* In Java :
*
* class TrieIteratorImpl extends TrieIterator{
* public TrieIteratorImpl(Trie data){
* super(data);
* }
* public int extract(int value){
* // port the implementation of _enumPropertyStartsValue here
* }
* }
* ....
* TrieIterator fcdIter = new TrieIteratorImpl(fcdTrieImpl.fcdTrie);
* while(fcdIter.next(result)) {
* // port the implementation of _enumPropertyStartsRange
* }
*
*
* 3) UTrieEnumRange is the only implemented callback then just implement
* the while loop, when utrie_enum is called
*
* // utrie_enum(&fcdTrie, NULL, _enumPropertyStartsRange, set);
* TrieIterator fcdIter = new TrieIterator(fcdTrieImpl.fcdTrie);
* while(fcdIter.next(result)){
* set.add(result.start);
* }
*
* @author synwee
* @see com.ibm.icu.impl.Trie
* @since release 2.1, Jan 17 2002
*/
public class TrieIterator implements RangeValueIterator
{
// public constructor ---------------------------------------------
/**
* TrieEnumeration constructor
* @param trie to be used
* @exception IllegalArgumentException throw when argument is null.
*/
public TrieIterator(Trie trie)
{
if (trie == null) {
throw new IllegalArgumentException(
"Argument trie cannot be null");
}
m_trie_ = trie;
// synwee: check that extract belongs to the child class
m_initialValue_ = extract(m_trie_.getInitialValue());
reset();
}
// public methods -------------------------------------------------
/**
* Returns true if we are not at the end of the iteration, false
* otherwise.
* The next set of codepoints with the same value type will be
* calculated during this call and returned in the arguement element.
* @param element return result
* @return true if we are not at the end of the iteration, false otherwise.
* @exception NoSuchElementException - if no more elements exist.
* @see com.ibm.icu.util.RangeValueIterator.Element
*/
public final boolean next(Element element)
{
if (m_nextCodepoint_ > UCharacter.MAX_VALUE) {
return false;
}
if (m_nextCodepoint_ < UCharacter.SUPPLEMENTARY_MIN_VALUE &&
calculateNextBMPElement(element)) {
return true;
}
calculateNextSupplementaryElement(element);
return true;
}
/**
* Resets the iterator to the beginning of the iteration
*/
public final void reset()
{
m_currentCodepoint_ = 0;
m_nextCodepoint_ = 0;
m_nextIndex_ = 0;
m_nextBlock_ = m_trie_.m_index_[0] << Trie.INDEX_STAGE_2_SHIFT_;
if (m_nextBlock_ == m_trie_.m_dataOffset_) {
m_nextValue_ = m_initialValue_;
}
else {
m_nextValue_ = extract(m_trie_.getValue(m_nextBlock_));
}
m_nextBlockIndex_ = 0;
m_nextTrailIndexOffset_ = TRAIL_SURROGATE_INDEX_BLOCK_LENGTH_;
}
// protected methods ----------------------------------------------
/**
* Called by next() to extracts a 32 bit value from a trie value
* used for comparison.
* This method is to be overwritten if special manipulation is to be done
* to retrieve a relevant comparison.
* The default function is to return the value as it is.
* @param value a value from the trie
* @return extracted value
*/
protected int extract(int value)
{
return value;
}
// private methods ------------------------------------------------
/**
* Set the result values
* @param element return result object
* @param start codepoint of range
* @param limit (end + 1) codepoint of range
* @param value common value of range
*/
private final void setResult(Element element, int start, int limit,
int value)
{
element.start = start;
element.limit = limit;
element.value = value;
}
/**
* Finding the next element.
* This method is called just before returning the result of
* next().
* We always store the next element before it is requested.
* In the case that we have to continue calculations into the
* supplementary planes, a false will be returned.
* @param element return result object
* @return true if the next range is found, false if we have to proceed to
* the supplementary range.
*/
private final boolean calculateNextBMPElement(Element element)
{
int currentValue = m_nextValue_;
m_currentCodepoint_ = m_nextCodepoint_;
m_nextCodepoint_ ++;
m_nextBlockIndex_ ++;
if (!checkBlockDetail(currentValue)) {
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
return true;
}
// synwee check that next block index == 0 here
// enumerate BMP - the main loop enumerates data blocks
while (m_nextCodepoint_ < UCharacter.SUPPLEMENTARY_MIN_VALUE) {
// because of the way the character is split to form the index
// the lead surrogate and trail surrogate can not be in the
// mid of a block
if (m_nextCodepoint_ == LEAD_SURROGATE_MIN_VALUE_) {
// skip lead surrogate code units,
// go to lead surrogate codepoints
m_nextIndex_ = BMP_INDEX_LENGTH_;
}
else if (m_nextCodepoint_ == TRAIL_SURROGATE_MIN_VALUE_) {
// go back to regular BMP code points
m_nextIndex_ = m_nextCodepoint_ >> Trie.INDEX_STAGE_1_SHIFT_;
} else {
m_nextIndex_ ++;
}
m_nextBlockIndex_ = 0;
if (!checkBlock(currentValue)) {
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
return true;
}
}
m_nextCodepoint_ --; // step one back since this value has not been
m_nextBlockIndex_ --; // retrieved yet.
return false;
}
/**
* Finds the next supplementary element.
* For each entry in the trie, the value to be delivered is passed through
* extract().
* We always store the next element before it is requested.
* Called after calculateNextBMP() completes its round of BMP characters.
* There is a slight difference in the usage of m_currentCodepoint_
* here as compared to calculateNextBMP(). Though both represents the
* lower bound of the next element, in calculateNextBMP() it gets set
* at the start of any loop, where-else, in calculateNextSupplementary()
* since m_currentCodepoint_ already contains the lower bound of the
* next element (passed down from calculateNextBMP()), we keep it till
* the end before resetting it to the new value.
* Note, if there are no more iterations, it will never get to here.
* Blocked out by next().
* @param element return result object
*/
private final void calculateNextSupplementaryElement(Element element)
{
int currentValue = m_nextValue_;
m_nextCodepoint_ ++;
m_nextBlockIndex_ ++;
if (UTF16.getTrailSurrogate(m_nextCodepoint_)
!= UTF16.TRAIL_SURROGATE_MIN_VALUE) {
// this piece is only called when we are in the middle of a lead
// surrogate block
if (!checkNullNextTrailIndex() && !checkBlockDetail(currentValue)) {
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
m_currentCodepoint_ = m_nextCodepoint_;
return;
}
// we have cleared one block
m_nextIndex_ ++;
m_nextTrailIndexOffset_ ++;
if (!checkTrailBlock(currentValue)) {
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
m_currentCodepoint_ = m_nextCodepoint_;
return;
}
}
int nextLead = UTF16.getLeadSurrogate(m_nextCodepoint_);
// enumerate supplementary code points
while (nextLead < TRAIL_SURROGATE_MIN_VALUE_) {
// lead surrogate access
final int leadBlock =
m_trie_.m_index_[nextLead >> Trie.INDEX_STAGE_1_SHIFT_] <<
Trie.INDEX_STAGE_2_SHIFT_;
if (leadBlock == m_trie_.m_dataOffset_) {
// no entries for a whole block of lead surrogates
if (currentValue != m_initialValue_) {
m_nextValue_ = m_initialValue_;
m_nextBlock_ = leadBlock; // == m_trie_.m_dataOffset_
m_nextBlockIndex_ = 0;
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
m_currentCodepoint_ = m_nextCodepoint_;
return;
}
nextLead += DATA_BLOCK_LENGTH_;
// number of total affected supplementary codepoints in one
// block
// this is not a simple addition of
// DATA_BLOCK_SUPPLEMENTARY_LENGTH since we need to consider
// that we might have moved some of the codepoints
m_nextCodepoint_ = UCharacterProperty.getRawSupplementary(
(char)nextLead,
(char)UTF16.TRAIL_SURROGATE_MIN_VALUE);
continue;
}
if (m_trie_.m_dataManipulate_ == null) {
throw new NullPointerException(
"The field DataManipulate in this Trie is null");
}
// enumerate trail surrogates for this lead surrogate
m_nextIndex_ = m_trie_.m_dataManipulate_.getFoldingOffset(
m_trie_.getValue(leadBlock +
(nextLead & Trie.INDEX_STAGE_3_MASK_)));
if (m_nextIndex_ <= 0) {
// no data for this lead surrogate
if (currentValue != m_initialValue_) {
m_nextValue_ = m_initialValue_;
m_nextBlock_ = m_trie_.m_dataOffset_;
m_nextBlockIndex_ = 0;
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
m_currentCodepoint_ = m_nextCodepoint_;
return;
}
m_nextCodepoint_ += TRAIL_SURROGATE_COUNT_;
} else {
m_nextTrailIndexOffset_ = 0;
if (!checkTrailBlock(currentValue)) {
setResult(element, m_currentCodepoint_, m_nextCodepoint_,
currentValue);
m_currentCodepoint_ = m_nextCodepoint_;
return;
}
}
nextLead ++;
}
// deliver last range
setResult(element, m_currentCodepoint_, UCharacter.MAX_VALUE + 1,
currentValue);
}
/**
* Internal block value calculations
* Performs calculations on a data block to find codepoints in m_nextBlock_
* after the index m_nextBlockIndex_ that has the same value.
* Note m_*_ variables at this point is the next codepoint whose value
* has not been calculated.
* But when returned with false, it will be the last codepoint whose
* value has been calculated.
* @param currentValue the value which other codepoints are tested against
* @return true if the whole block has the same value as currentValue or if
* the whole block has been calculated, false otherwise.
*/
private final boolean checkBlockDetail(int currentValue)
{
while (m_nextBlockIndex_ < DATA_BLOCK_LENGTH_) {
m_nextValue_ = extract(m_trie_.getValue(m_nextBlock_ +
m_nextBlockIndex_));
if (m_nextValue_ != currentValue) {
return false;
}
++ m_nextBlockIndex_;
++ m_nextCodepoint_;
}
return true;
}
/**
* Internal block value calculations
* Performs calculations on a data block to find codepoints in m_nextBlock_
* that has the same value.
* Will call checkBlockDetail() if highlevel check fails.
* Note m_*_ variables at this point is the next codepoint whose value
* has not been calculated.
* @param currentBlock the initial block containing all currentValue
* @param currentValue the value which other codepoints are tested against
* @return true if the whole block has the same value as currentValue or if
* the whole block has been calculated, false otherwise.
*/
private final boolean checkBlock(int currentValue)
{
int currentBlock = m_nextBlock_;
m_nextBlock_ = m_trie_.m_index_[m_nextIndex_] <<
Trie.INDEX_STAGE_2_SHIFT_;
if (m_nextBlock_ == currentBlock &&
(m_nextCodepoint_ - m_currentCodepoint_) >= DATA_BLOCK_LENGTH_) {
// the block is the same as the previous one, filled with
// currentValue
m_nextCodepoint_ += DATA_BLOCK_LENGTH_;
}
else if (m_nextBlock_ == m_trie_.m_dataOffset_) {
// this is the all-initial-value block
if (currentValue != m_initialValue_) {
m_nextValue_ = m_initialValue_;
m_nextBlockIndex_ = 0;
return false;
}
m_nextCodepoint_ += DATA_BLOCK_LENGTH_;
}
else {
if (!checkBlockDetail(currentValue)) {
return false;
}
}
return true;
}
/**
* Internal block value calculations
* Performs calculations on multiple data blocks for a set of trail
* surrogates to find codepoints in m_nextBlock_ that has the same value.
* Will call checkBlock() for internal block checks.
* Note m_*_ variables at this point is the next codepoint whose value
* has not been calculated.
* @param currentValue the value which other codepoints are tested against
* @return true if the whole block has the same value as currentValue or if
* the whole block has been calculated, false otherwise.
*/
private final boolean checkTrailBlock(int currentValue)
{
// enumerate code points for this lead surrogate
while (m_nextTrailIndexOffset_ < TRAIL_SURROGATE_INDEX_BLOCK_LENGTH_)
{
// if we ever reach here, we are at the start of a new block
m_nextBlockIndex_ = 0;
// copy of most of the body of the BMP loop
if (!checkBlock(currentValue)) {
return false;
}
m_nextTrailIndexOffset_ ++;
m_nextIndex_ ++;
}
return true;
}
/**
* Checks if we are beginning at the start of a initial block.
* If we are then the rest of the codepoints in this initial block
* has the same values.
* We increment m_nextCodepoint_ and relevant data members if so.
* This is used only in for the supplementary codepoints because
* the offset to the trail indexes could be 0.
* @return true if we are at the start of a initial block.
*/
private final boolean checkNullNextTrailIndex()
{
if (m_nextIndex_ <= 0) {
m_nextCodepoint_ += TRAIL_SURROGATE_COUNT_ - 1;
int nextLead = UTF16.getLeadSurrogate(m_nextCodepoint_);
int leadBlock =
m_trie_.m_index_[nextLead >> Trie.INDEX_STAGE_1_SHIFT_] <<
Trie.INDEX_STAGE_2_SHIFT_;
if (m_trie_.m_dataManipulate_ == null) {
throw new NullPointerException(
"The field DataManipulate in this Trie is null");
}
m_nextIndex_ = m_trie_.m_dataManipulate_.getFoldingOffset(
m_trie_.getValue(leadBlock +
(nextLead & Trie.INDEX_STAGE_3_MASK_)));
m_nextIndex_ --;
m_nextBlockIndex_ = DATA_BLOCK_LENGTH_;
return true;
}
return false;
}
// private data members --------------------------------------------
/**
* Size of the stage 1 BMP indexes
*/
private static final int BMP_INDEX_LENGTH_ =
0x10000 >> Trie.INDEX_STAGE_1_SHIFT_;
/**
* Lead surrogate minimum value
*/
private static final int LEAD_SURROGATE_MIN_VALUE_ = 0xD800;
/**
* Trail surrogate minimum value
*/
private static final int TRAIL_SURROGATE_MIN_VALUE_ = 0xDC00;
/*
* Trail surrogate maximum value
*/
//private static final int TRAIL_SURROGATE_MAX_VALUE_ = 0xDFFF;
/**
* Number of trail surrogate
*/
private static final int TRAIL_SURROGATE_COUNT_ = 0x400;
/**
* Number of stage 1 indexes for supplementary calculations that maps to
* each lead surrogate character.
* See second pass into getRawOffset for the trail surrogate character.
* 10 for significant number of bits for trail surrogates, 5 for what we
* discard during shifting.
*/
private static final int TRAIL_SURROGATE_INDEX_BLOCK_LENGTH_ =
1 << (10 - Trie.INDEX_STAGE_1_SHIFT_);
/**
* Number of data values in a stage 2 (data array) block.
*/
private static final int DATA_BLOCK_LENGTH_ =
1 << Trie.INDEX_STAGE_1_SHIFT_;
// /**
// * Number of codepoints in a stage 2 block
// */
// private static final int DATA_BLOCK_SUPPLEMENTARY_LENGTH_ =
// DATA_BLOCK_LENGTH_ << 10;
/**
* Trie instance
*/
private Trie m_trie_;
/**
* Initial value for trie values
*/
private int m_initialValue_;
/**
* Next element results and data.
*/
private int m_currentCodepoint_;
private int m_nextCodepoint_;
private int m_nextValue_;
private int m_nextIndex_;
private int m_nextBlock_;
private int m_nextBlockIndex_;
private int m_nextTrailIndexOffset_;
}