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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) 1996-2010, International Business Machines Corporation and *
* others. All Rights Reserved. *
******************************************************************************
*/
package com.ibm.icu.impl;
import java.util.Arrays;
import com.ibm.icu.lang.UCharacter;
/**
* Builder class to manipulate and generate a trie.
* This is useful for ICU data in primitive types.
* Provides a compact way to store information that is indexed by Unicode
* values, such as character properties, types, keyboard values, etc. This is
* very useful when you have a block of Unicode data that contains significant
* values while the rest of the Unicode data is unused in the application or
* when you have a lot of redundance, such as where all 21,000 Han ideographs
* have the same value. However, lookup is much faster than a hash table.
* A trie of any primitive data type serves two purposes:
*
* - Fast access of the indexed values.
*
- Smaller memory footprint.
*
* This is a direct port from the ICU4C version
* @author Syn Wee Quek
*/
public class TrieBuilder
{
// public data member ----------------------------------------------
/**
* Number of data values in a stage 2 (data array) block. 2, 4, 8, ..,
* 0x200
*/
public static final int DATA_BLOCK_LENGTH = 1 << Trie.INDEX_STAGE_1_SHIFT_;
// public class declaration ----------------------------------------
/**
* Character data in com.ibm.impl.Trie have different user-specified format
* for different purposes.
* This interface specifies methods to be implemented in order for
* com.ibm.impl.Trie, to surrogate offset information encapsulated within
* the data.
*/
public static interface DataManipulate
{
/**
* Build-time trie callback function, used with serialize().
* This function calculates a lead surrogate's value including a
* folding offset from the 1024 supplementary code points
* [start..start+1024[ .
* It is U+10000 <= start <= U+10fc00 and (start&0x3ff)==0.
* The folding offset is provided by the caller.
* It is offset=UTRIE_BMP_INDEX_LENGTH+n*UTRIE_SURROGATE_BLOCK_COUNT
* with n=0..1023.
* Instead of the offset itself, n can be stored in 10 bits - or fewer
* if it can be assumed that few lead surrogates have associated data.
* The returned value must be
* - not zero if and only if there is relevant data for the
* corresponding 1024 supplementary code points
* - such that UTrie.getFoldingOffset(UNewTrieGetFoldedValue(...,
* offset))==offset
* @return a folded value, or 0 if there is no relevant data for the
* lead surrogate.
*/
public int getFoldedValue(int start, int offset);
}
// public methods ----------------------------------------------------
/**
* Checks if the character belongs to a zero block in the trie
* @param ch codepoint which data is to be retrieved
* @return true if ch is in the zero block
*/
public boolean isInZeroBlock(int ch)
{
// valid, uncompacted trie and valid c?
if (m_isCompacted_ || ch > UCharacter.MAX_VALUE
|| ch < UCharacter.MIN_VALUE) {
return true;
}
return m_index_[ch >> SHIFT_] == 0;
}
// package private method -----------------------------------------------
// protected data member -----------------------------------------------
/**
* Index values at build-time are 32 bits wide for easier processing.
* Bit 31 is set if the data block is used by multiple index values
* (from setRange()).
*/
protected int m_index_[];
protected int m_indexLength_;
protected int m_dataCapacity_;
protected int m_dataLength_;
protected boolean m_isLatin1Linear_;
protected boolean m_isCompacted_;
/**
* Map of adjusted indexes, used in utrie_compact().
* Maps from original indexes to new ones.
*/
protected int m_map_[];
/**
* Shift size for shifting right the input index. 1..9
*/
protected static final int SHIFT_ = Trie.INDEX_STAGE_1_SHIFT_;
/**
* Length of the index (stage 1) array before folding.
* Maximum number of Unicode code points (0x110000) shifted right by
* SHIFT.
*/
protected static final int MAX_INDEX_LENGTH_ = (0x110000 >> SHIFT_);
/**
* Length of the BMP portion of the index (stage 1) array.
*/
protected static final int BMP_INDEX_LENGTH_ = 0x10000 >> SHIFT_;
/**
* Number of index (stage 1) entries per lead surrogate.
* Same as number of indexe entries for 1024 trail surrogates,
* ==0x400>>UTRIE_SHIFT
* 10 - SHIFT == Number of bits of a trail surrogate that are used in
* index table lookups.
*/
protected static final int SURROGATE_BLOCK_COUNT_ = 1 << (10 - SHIFT_);
/**
* Mask for getting the lower bits from the input index.
* DATA_BLOCK_LENGTH - 1.
*/
protected static final int MASK_ = Trie.INDEX_STAGE_3_MASK_;
/**
* Shift size for shifting left the index array values.
* Increases possible data size with 16-bit index values at the cost
* of compactability.
* This requires blocks of stage 2 data to be aligned by UTRIE_DATA_GRANULARITY.
* 0..UTRIE_SHIFT
*/
protected static final int INDEX_SHIFT_ = Trie.INDEX_STAGE_2_SHIFT_;
/**
* Maximum length of the runtime data (stage 2) array.
* Limited by 16-bit index values that are left-shifted by INDEX_SHIFT_.
*/
protected static final int MAX_DATA_LENGTH_ = (0x10000 << INDEX_SHIFT_);
/**
* Shifting to position the index value in options
*/
protected static final int OPTIONS_INDEX_SHIFT_ = 4;
/**
* If set, then the data (stage 2) array is 32 bits wide.
*/
protected static final int OPTIONS_DATA_IS_32_BIT_ = 0x100;
/**
* If set, then Latin-1 data (for U+0000..U+00ff) is stored in the data
* (stage 2) array as a simple, linear array at data + DATA_BLOCK_LENGTH.
*/
protected static final int OPTIONS_LATIN1_IS_LINEAR_ = 0x200;
/**
* The alignment size of a stage 2 data block. Also the granularity for
* compaction.
*/
protected static final int DATA_GRANULARITY_ = 1 << INDEX_SHIFT_;
// protected constructor ----------------------------------------------
protected TrieBuilder()
{
m_index_ = new int[MAX_INDEX_LENGTH_];
m_map_ = new int[MAX_BUILD_TIME_DATA_LENGTH_ >> SHIFT_];
m_isLatin1Linear_ = false;
m_isCompacted_ = false;
m_indexLength_ = MAX_INDEX_LENGTH_;
}
protected TrieBuilder(TrieBuilder table)
{
m_index_ = new int[MAX_INDEX_LENGTH_];
m_indexLength_ = table.m_indexLength_;
System.arraycopy(table.m_index_, 0, m_index_, 0, m_indexLength_);
m_dataCapacity_ = table.m_dataCapacity_;
m_dataLength_ = table.m_dataLength_;
m_map_ = new int[table.m_map_.length];
System.arraycopy(table.m_map_, 0, m_map_, 0, m_map_.length);
m_isLatin1Linear_ = table.m_isLatin1Linear_;
m_isCompacted_ = table.m_isCompacted_;
}
// protected functions ------------------------------------------------
/**
* Compare two sections of an array for equality.
*/
protected static final boolean equal_int(int[] array, int start1, int start2, int length) {
while(length>0 && array[start1]==array[start2]) {
++start1;
++start2;
--length;
}
return length==0;
}
/**
* Set a value in the trie index map to indicate which data block
* is referenced and which one is not.
* utrie_compact() will remove data blocks that are not used at all.
* Set
* - 0 if it is used
* - -1 if it is not used
*/
protected void findUnusedBlocks()
{
// fill the entire map with "not used"
Arrays.fill(m_map_, 0xff);
// mark each block that _is_ used with 0
for (int i = 0; i < m_indexLength_; ++ i) {
m_map_[Math.abs(m_index_[i]) >> SHIFT_] = 0;
}
// never move the all-initial-value block 0
m_map_[0] = 0;
}
/**
* Finds the same index block as the otherBlock
* @param index array
* @param indexLength size of index
* @param otherBlock
* @return same index block
*/
protected static final int findSameIndexBlock(int index[], int indexLength,
int otherBlock)
{
for (int block = BMP_INDEX_LENGTH_; block < indexLength;
block += SURROGATE_BLOCK_COUNT_) {
if(equal_int(index, block, otherBlock, SURROGATE_BLOCK_COUNT_)) {
return block;
}
}
return indexLength;
}
// private data member ------------------------------------------------
/**
* Maximum length of the build-time data (stage 2) array.
* The maximum length is 0x110000 + DATA_BLOCK_LENGTH + 0x400.
* (Number of Unicode code points + one all-initial-value block +
* possible duplicate entries for 1024 lead surrogates.)
*/
private static final int MAX_BUILD_TIME_DATA_LENGTH_ =
0x110000 + DATA_BLOCK_LENGTH + 0x400;
}