/*
*******************************************************************************
* Copyright (C) 2009-2010, International Business Machines Corporation and
* others. All Rights Reserved.
*******************************************************************************
*/
package com.ibm.icu.impl;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* @author aheninger
*
* A read-only Trie2, holding 16 bit data values.
*
* A Trie2 is a highly optimized data structure for mapping from Unicode code points (values ranging from 0 to 0x10ffff) to a 16 or
* 32 bit value.
*
* See class Trie2 for descriptions of the API for accessing the contents of a trie.
*
* The fundamental data access methods are declared final in this class, with the intent that applications might gain a little extra
* performance, when compared with calling the same methods via the abstract UTrie2 base class.
*/
public final class Trie2_16 extends Trie2 {
/**
* Internal constructor, not for general use.
*/
Trie2_16() {
}
/**
* Create a Trie2 from its serialized form. Inverse of utrie2_serialize(). The serialized format is identical between ICU4C and ICU4J,
* so this function will work with serialized Trie2s from either.
*
* The serialized Trie2 on the stream may be in either little or big endian byte order. This allows using serialized Tries from ICU4C
* without needing to consider the byte order of the system that created them.
*
* @param is
* an input stream to the serialized form of a UTrie2.
* @return An unserialized Trie_16, ready for use.
* @throws IllegalArgumentException
* if the stream does not contain a serialized Trie2.
* @throws IOException
* if a read error occurs on the InputStream.
* @throws ClassCastException
* if the stream contains a serialized Trie2_32
*/
public static Trie2_16 createFromSerialized(InputStream is) throws IOException {
return (Trie2_16) Trie2.createFromSerialized(is);
}
/**
* Get the value for a code point as stored in the Trie2.
*
* @param codePoint
* the code point
* @return the value
*/
@Override
public final int get(int codePoint) {
int value;
int ix;
if (codePoint >= 0) {
if (codePoint < 0x0d800 || (codePoint > 0x0dbff && codePoint <= 0x0ffff)) {
// Ordinary BMP code point, excluding leading surrogates.
// BMP uses a single level lookup. BMP index starts at offset 0 in the Trie2 index.
// 16 bit data is stored in the index array itself.
ix = index[codePoint >> UTRIE2_SHIFT_2];
ix = (ix << UTRIE2_INDEX_SHIFT) + (codePoint & UTRIE2_DATA_MASK);
value = index[ix];
return value;
}
if (codePoint <= 0xffff) {
// Lead Surrogate Code Point. A Separate index section is stored for
// lead surrogate code units and code points.
// The main index has the code unit data.
// For this function, we need the code point data.
// Note: this expression could be refactored for slightly improved efficiency, but
// surrogate code points will be so rare in practice that it's not worth it.
ix = index[UTRIE2_LSCP_INDEX_2_OFFSET + ((codePoint - 0xd800) >> UTRIE2_SHIFT_2)];
ix = (ix << UTRIE2_INDEX_SHIFT) + (codePoint & UTRIE2_DATA_MASK);
value = index[ix];
return value;
}
if (codePoint < highStart) {
// Supplemental code point, use two-level lookup.
ix = (UTRIE2_INDEX_1_OFFSET - UTRIE2_OMITTED_BMP_INDEX_1_LENGTH) + (codePoint >> UTRIE2_SHIFT_1);
ix = index[ix];
ix += (codePoint >> UTRIE2_SHIFT_2) & UTRIE2_INDEX_2_MASK;
ix = index[ix];
ix = (ix << UTRIE2_INDEX_SHIFT) + (codePoint & UTRIE2_DATA_MASK);
value = index[ix];
return value;
}
if (codePoint <= 0x10ffff) {
value = index[highValueIndex];
return value;
}
}
// Fall through. The code point is outside of the legal range of 0..0x10ffff.
return errorValue;
}
/**
* Get a Trie2 value for a UTF-16 code unit.
*
* This function returns the same value as get() if the input character is outside of the lead surrogate range
*
* There are two values stored in a Trie2 for inputs in the lead surrogate range. This function returns the alternate value, while
* Trie2.get() returns the main value.
*
* @param codeUnit
* a 16 bit code unit or lead surrogate value.
* @return the value
*/
@Override
public int getFromU16SingleLead(char codeUnit) {
int value;
int ix;
// Because the input is a 16 bit char, we can skip the tests for it being in
// the BMP range. It is.
ix = index[codeUnit >> UTRIE2_SHIFT_2];
ix = (ix << UTRIE2_INDEX_SHIFT) + (codeUnit & UTRIE2_DATA_MASK);
value = index[ix];
return value;
}
/**
* Serialize a Trie2_16 onto an OutputStream.
*
* A Trie2 can be serialized multiple times. The serialized data is compatible with ICU4C UTrie2 serialization. Trie2 serialization is
* unrelated to Java object serialization.
*
* @param os
* the stream to which the serialized Trie2 data will be written.
* @return the number of bytes written.
* @throw IOException on an error writing to the OutputStream.
*/
public int serialize(OutputStream os) throws IOException {
DataOutputStream dos = new DataOutputStream(os);
int bytesWritten = 0;
bytesWritten += serializeHeader(dos);
for (int i = 0; i < dataLength; i++) {
dos.writeChar(index[data16 + i]);
}
bytesWritten += dataLength * 2;
return bytesWritten;
}
/**
* @return the number of bytes of the serialized trie
*/
public int getSerializedLength() {
return 16 + (header.indexLength + dataLength) * 2;
}
/**
* Given a starting code point, find the last in a range of code points, all with the same value.
*
* This function is part of the implementation of iterating over the Trie2's contents.
*
* @param startingCP
* The code point at which to begin looking.
* @return The last code point with the same value as the starting code point.
*/
@Override
int rangeEnd(int startingCP, int limit, int value) {
int cp = startingCP;
int block = 0;
int index2Block = 0;
// Loop runs once for each of
// - a partial data block
// - a reference to the null (default) data block.
// - a reference to the index2 null block
outerLoop: for (;;) {
if (cp >= limit) {
break;
}
if (cp < 0x0d800 || (cp > 0x0dbff && cp <= 0x0ffff)) {
// Ordinary BMP code point, excluding leading surrogates.
// BMP uses a single level lookup. BMP index starts at offset 0 in the Trie2 index.
// 16 bit data is stored in the index array itself.
index2Block = 0;
block = index[cp >> UTRIE2_SHIFT_2] << UTRIE2_INDEX_SHIFT;
} else if (cp < 0xffff) {
// Lead Surrogate Code Point, 0xd800 <= cp < 0xdc00
index2Block = UTRIE2_LSCP_INDEX_2_OFFSET;
block = index[index2Block + ((cp - 0xd800) >> UTRIE2_SHIFT_2)] << UTRIE2_INDEX_SHIFT;
} else if (cp < highStart) {
// Supplemental code point, use two-level lookup.
int ix = (UTRIE2_INDEX_1_OFFSET - UTRIE2_OMITTED_BMP_INDEX_1_LENGTH) + (cp >> UTRIE2_SHIFT_1);
index2Block = index[ix];
block = index[index2Block + ((cp >> UTRIE2_SHIFT_2) & UTRIE2_INDEX_2_MASK)] << UTRIE2_INDEX_SHIFT;
} else {
// Code point above highStart.
if (value == index[highValueIndex]) {
cp = limit;
}
break;
}
if (index2Block == index2NullOffset) {
if (value != initialValue) {
break;
}
cp += UTRIE2_CP_PER_INDEX_1_ENTRY;
} else if (block == dataNullOffset) {
// The block at dataNullOffset has all values == initialValue.
// Because Trie2 iteration always proceeds in ascending order, we will always
// encounter a null block at its beginning, and can skip over
// a number of code points equal to the length of the block.
if (value != initialValue) {
break;
}
cp += UTRIE2_DATA_BLOCK_LENGTH;
} else {
// Current position refers to an ordinary data block.
// Walk over the data entries, checking the values.
int startIx = block + (cp & UTRIE2_DATA_MASK);
int limitIx = block + UTRIE2_DATA_BLOCK_LENGTH;
for (int ix = startIx; ix < limitIx; ix++) {
if (index[ix] != value) {
// We came to an entry with a different value.
// We are done.
cp += (ix - startIx);
break outerLoop;
}
}
// The ordinary data block contained our value until its end.
// Advance the current code point, and continue the outerloop.
cp += limitIx - startIx;
}
}
if (cp > limit) {
cp = limit;
}
return cp - 1;
}
}