JDK8/Java8源码在线阅读
/*
* Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/*
*
* (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
* (C) Copyright IBM Corp. 1996 - 2002 - All Rights Reserved
*
* The original version of this source code and documentation
* is copyrighted and owned by Taligent, Inc., a wholly-owned
* subsidiary of IBM. These materials are provided under terms
* of a License Agreement between Taligent and Sun. This technology
* is protected by multiple US and International patents.
*
* This notice and attribution to Taligent may not be removed.
* Taligent is a registered trademark of Taligent, Inc.
*/
package sun.util.locale.provider;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.text.BreakIterator;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.util.MissingResourceException;
import sun.text.CompactByteArray;
import sun.text.SupplementaryCharacterData;
/**
* <p>A subclass of BreakIterator whose behavior is specified using a list of rules.</p>
*
* <p>There are two kinds of rules, which are separated by semicolons: <i>substitutions</i>
* and <i>regular expressions.</i></p>
*
* <p>A substitution rule defines a name that can be used in place of an expression. It
* consists of a name, which is a string of characters contained in angle brackets, an equals
* sign, and an expression. (There can be no whitespace on either side of the equals sign.)
* To keep its syntactic meaning intact, the expression must be enclosed in parentheses or
* square brackets. A substitution is visible after its definition, and is filled in using
* simple textual substitution. Substitution definitions can contain other substitutions, as
* long as those substitutions have been defined first. Substitutions are generally used to
* make the regular expressions (which can get quite complex) shorted and easier to read.
* They typically define either character categories or commonly-used subexpressions.</p>
*
* <p>There is one special substitution. If the description defines a substitution
* called "<ignore>", the expression must be a [] expression, and the
* expression defines a set of characters (the "<em>ignore characters</em>") that
* will be transparent to the BreakIterator. A sequence of characters will break the
* same way it would if any ignore characters it contains are taken out. Break
* positions never occur befoer ignore characters.</p>
*
* <p>A regular expression uses a subset of the normal Unix regular-expression syntax, and
* defines a sequence of characters to be kept together. With one significant exception, the
* iterator uses a longest-possible-match algorithm when matching text to regular
* expressions. The iterator also treats descriptions containing multiple regular expressions
* as if they were ORed together (i.e., as if they were separated by |).</p>
*
* <p>The special characters recognized by the regular-expression parser are as follows:</p>
*
* <blockquote>
* <table border="1" width="100%">
* <tr>
* <td width="6%">*</td>
* <td width="94%">Specifies that the expression preceding the asterisk may occur any number
* of times (including not at all).</td>
* </tr>
* <tr>
* <td width="6%">{}</td>
* <td width="94%">Encloses a sequence of characters that is optional.</td>
* </tr>
* <tr>
* <td width="6%">()</td>
* <td width="94%">Encloses a sequence of characters. If followed by *, the sequence
* repeats. Otherwise, the parentheses are just a grouping device and a way to delimit
* the ends of expressions containing |.</td>
* </tr>
* <tr>
* <td width="6%">|</td>
* <td width="94%">Separates two alternative sequences of characters. Either one
* sequence or the other, but not both, matches this expression. The | character can
* only occur inside ().</td>
* </tr>
* <tr>
* <td width="6%">.</td>
* <td width="94%">Matches any character.</td>
* </tr>
* <tr>
* <td width="6%">*?</td>
* <td width="94%">Specifies a non-greedy asterisk. *? works the same way as *, except
* when there is overlap between the last group of characters in the expression preceding the
* * and the first group of characters following the *. When there is this kind of
* overlap, * will match the longest sequence of characters that match the expression before
* the *, and *? will match the shortest sequence of characters matching the expression
* before the *?. For example, if you have "xxyxyyyxyxyxxyxyxyy" in the text,
* "x[xy]*x" will match through to the last x (i.e., "<strong>xxyxyyyxyxyxxyxyx</strong>yy",
* but "x[xy]*?x" will only match the first two xes ("<strong>xx</strong>yxyyyxyxyxxyxyxyy").</td>
* </tr>
* <tr>
* <td width="6%">[]</td>
* <td width="94%">Specifies a group of alternative characters. A [] expression will
* match any single character that is specified in the [] expression. For more on the
* syntax of [] expressions, see below.</td>
* </tr>
* <tr>
* <td width="6%">/</td>
* <td width="94%">Specifies where the break position should go if text matches this
* expression. (e.g., "[a-z]*/[:Zs:]*[1-0]" will match if the iterator sees a run
* of letters, followed by a run of whitespace, followed by a digit, but the break position
* will actually go before the whitespace). Expressions that don't contain / put the
* break position at the end of the matching text.</td>
* </tr>
* <tr>
* <td width="6%">\</td>
* <td width="94%">Escape character. The \ itself is ignored, but causes the next
* character to be treated as literal character. This has no effect for many
* characters, but for the characters listed above, this deprives them of their special
* meaning. (There are no special escape sequences for Unicode characters, or tabs and
* newlines; these are all handled by a higher-level protocol. In a Java string,
* "\n" will be converted to a literal newline character by the time the
* regular-expression parser sees it. Of course, this means that \ sequences that are
* visible to the regexp parser must be written as \\ when inside a Java string.) All
* characters in the ASCII range except for letters, digits, and control characters are
* reserved characters to the parser and must be preceded by \ even if they currently don't
* mean anything.</td>
* </tr>
* <tr>
* <td width="6%">!</td>
* <td width="94%">If ! appears at the beginning of a regular expression, it tells the regexp
* parser that this expression specifies the backwards-iteration behavior of the iterator,
* and not its normal iteration behavior. This is generally only used in situations
* where the automatically-generated backwards-iteration brhavior doesn't produce
* satisfactory results and must be supplemented with extra client-specified rules.</td>
* </tr>
* <tr>
* <td width="6%"><em>(all others)</em></td>
* <td width="94%">All other characters are treated as literal characters, which must match
* the corresponding character(s) in the text exactly.</td>
* </tr>
* </table>
* </blockquote>
*
* <p>Within a [] expression, a number of other special characters can be used to specify
* groups of characters:</p>
*
* <blockquote>
* <table border="1" width="100%">
* <tr>
* <td width="6%">-</td>
* <td width="94%">Specifies a range of matching characters. For example
* "[a-p]" matches all lowercase Latin letters from a to p (inclusive). The -
* sign specifies ranges of continuous Unicode numeric values, not ranges of characters in a
* language's alphabetical order: "[a-z]" doesn't include capital letters, nor does
* it include accented letters such as a-umlaut.</td>
* </tr>
* <tr>
* <td width="6%">::</td>
* <td width="94%">A pair of colons containing a one- or two-letter code matches all
* characters in the corresponding Unicode category. The two-letter codes are the same
* as the two-letter codes in the Unicode database (for example, "[:Sc::Sm:]"
* matches all currency symbols and all math symbols). Specifying a one-letter code is
* the same as specifying all two-letter codes that begin with that letter (for example,
* "[:L:]" matches all letters, and is equivalent to
* "[:Lu::Ll::Lo::Lm::Lt:]"). Anything other than a valid two-letter Unicode
* category code or a single letter that begins a Unicode category code is illegal within
* colons.</td>
* </tr>
* <tr>
* <td width="6%">[]</td>
* <td width="94%">[] expressions can nest. This has no effect, except when used in
* conjunction with the ^ token.</td>
* </tr>
* <tr>
* <td width="6%">^</td>
* <td width="94%">Excludes the character (or the characters in the [] expression) following
* it from the group of characters. For example, "[a-z^p]" matches all Latin
* lowercase letters except p. "[:L:^[\u4e00-\u9fff]]" matches all letters
* except the Han ideographs.</td>
* </tr>
* <tr>
* <td width="6%"><em>(all others)</em></td>
* <td width="94%">All other characters are treated as literal characters. (For
* example, "[aeiou]" specifies just the letters a, e, i, o, and u.)</td>
* </tr>
* </table>
* </blockquote>
*
* <p>For a more complete explanation, see <a
* href="http://www.ibm.com/java/education/boundaries/boundaries.html">http://www.ibm.com/java/education/boundaries/boundaries.html</a>.
* For examples, see the resource data (which is annotated).</p>
*
* @author Richard Gillam
*/
class RuleBasedBreakIterator extends BreakIterator {
/**
* A token used as a character-category value to identify ignore characters
*/
protected static final byte IGNORE = -1;
/**
* The state number of the starting state
*/
private static final short START_STATE = 1;
/**
* The state-transition value indicating "stop"
*/
private static final short STOP_STATE = 0;
/**
* Magic number for the BreakIterator data file format.
*/
static final byte[] LABEL = {
(byte)'B', (byte)'I', (byte)'d', (byte)'a', (byte)'t', (byte)'a',
(byte)'\0'
};
static final int LABEL_LENGTH = LABEL.length;
/**
* Version number of the dictionary that was read in.
*/
static final byte supportedVersion = 1;
/**
* Header size in byte count
*/
private static final int HEADER_LENGTH = 36;
/**
* An array length of indices for BMP characters
*/
private static final int BMP_INDICES_LENGTH = 512;
/**
* Tables that indexes from character values to character category numbers
*/
private CompactByteArray charCategoryTable = null;
private SupplementaryCharacterData supplementaryCharCategoryTable = null;
/**
* The table of state transitions used for forward iteration
*/
private short[] stateTable = null;
/**
* The table of state transitions used to sync up the iterator with the
* text in backwards and random-access iteration
*/
private short[] backwardsStateTable = null;
/**
* A list of flags indicating which states in the state table are accepting
* ("end") states
*/
private boolean[] endStates = null;
/**
* A list of flags indicating which states in the state table are
* lookahead states (states which turn lookahead on and off)
*/
private boolean[] lookaheadStates = null;
/**
* A table for additional data. May be used by a subclass of
* RuleBasedBreakIterator.
*/
private byte[] additionalData = null;
/**
* The number of character categories (and, thus, the number of columns in
* the state tables)
*/
private int numCategories;
/**
* The character iterator through which this BreakIterator accesses the text
*/
private CharacterIterator text = null;
/**
* A CRC32 value of all data in datafile
*/
private long checksum;
//=======================================================================
// constructors
//=======================================================================
/**
* Constructs a RuleBasedBreakIterator according to the datafile
* provided.
*/
RuleBasedBreakIterator(String datafile)
throws IOException, MissingResourceException {
readTables(datafile);
}
/**
* Read datafile. The datafile's format is as follows:
* <pre>
* BreakIteratorData {
* u1 magic[7];
* u1 version;
* u4 totalDataSize;
* header_info header;
* body value;
* }
* </pre>
* <code>totalDataSize</code> is the summation of the size of
* <code>header_info</code> and <code>body</code> in byte count.
* <p>
* In <code>header</code>, each field except for checksum implies the
* length of each field. Since <code>BMPdataLength</code> is a fixed-length
* data(512 entries), its length isn't included in <code>header</code>.
* <code>checksum</code> is a CRC32 value of all in <code>body</code>.
* <pre>
* header_info {
* u4 stateTableLength;
* u4 backwardsStateTableLength;
* u4 endStatesLength;
* u4 lookaheadStatesLength;
* u4 BMPdataLength;
* u4 nonBMPdataLength;
* u4 additionalDataLength;
* u8 checksum;
* }
* </pre>
* <p>
*
* Finally, <code>BMPindices</code> and <code>BMPdata</code> are set to
* <code>charCategoryTable</code>. <code>nonBMPdata</code> is set to
* <code>supplementaryCharCategoryTable</code>.
* <pre>
* body {
* u2 stateTable[stateTableLength];
* u2 backwardsStateTable[backwardsStateTableLength];
* u1 endStates[endStatesLength];
* u1 lookaheadStates[lookaheadStatesLength];
* u2 BMPindices[512];
* u1 BMPdata[BMPdataLength];
* u4 nonBMPdata[numNonBMPdataLength];
* u1 additionalData[additionalDataLength];
* }
* </pre>
*/
protected final void readTables(String datafile)
throws IOException, MissingResourceException {
byte[] buffer = readFile(datafile);
/* Read header_info. */
int stateTableLength = getInt(buffer, 0);
int backwardsStateTableLength = getInt(buffer, 4);
int endStatesLength = getInt(buffer, 8);
int lookaheadStatesLength = getInt(buffer, 12);
int BMPdataLength = getInt(buffer, 16);
int nonBMPdataLength = getInt(buffer, 20);
int additionalDataLength = getInt(buffer, 24);
checksum = getLong(buffer, 28);
/* Read stateTable[numCategories * numRows] */
stateTable = new short[stateTableLength];
int offset = HEADER_LENGTH;
for (int i = 0; i < stateTableLength; i++, offset+=2) {
stateTable[i] = getShort(buffer, offset);
}
/* Read backwardsStateTable[numCategories * numRows] */
backwardsStateTable = new short[backwardsStateTableLength];
for (int i = 0; i < backwardsStateTableLength; i++, offset+=2) {
backwardsStateTable[i] = getShort(buffer, offset);
}
/* Read endStates[numRows] */
endStates = new boolean[endStatesLength];
for (int i = 0; i < endStatesLength; i++, offset++) {
endStates[i] = buffer[offset] == 1;
}
/* Read lookaheadStates[numRows] */
lookaheadStates = new boolean[lookaheadStatesLength];
for (int i = 0; i < lookaheadStatesLength; i++, offset++) {
lookaheadStates[i] = buffer[offset] == 1;
}
/* Read a category table and indices for BMP characters. */
short[] temp1 = new short[BMP_INDICES_LENGTH]; // BMPindices
for (int i = 0; i < BMP_INDICES_LENGTH; i++, offset+=2) {
temp1[i] = getShort(buffer, offset);
}
byte[] temp2 = new byte[BMPdataLength]; // BMPdata
System.arraycopy(buffer, offset, temp2, 0, BMPdataLength);
offset += BMPdataLength;
charCategoryTable = new CompactByteArray(temp1, temp2);
/* Read a category table for non-BMP characters. */
int[] temp3 = new int[nonBMPdataLength];
for (int i = 0; i < nonBMPdataLength; i++, offset+=4) {
temp3[i] = getInt(buffer, offset);
}
supplementaryCharCategoryTable = new SupplementaryCharacterData(temp3);
/* Read additional data */
if (additionalDataLength > 0) {
additionalData = new byte[additionalDataLength];
System.arraycopy(buffer, offset, additionalData, 0, additionalDataLength);
}
/* Set numCategories */
numCategories = stateTable.length / endStates.length;
}
protected byte[] readFile(final String datafile)
throws IOException, MissingResourceException {
BufferedInputStream is;
try {
is = AccessController.doPrivileged(
new PrivilegedExceptionAction<BufferedInputStream>() {
@Override
public BufferedInputStream run() throws Exception {
return new BufferedInputStream(getClass().getResourceAsStream("/sun/text/resources/" + datafile));
}
}
);
}
catch (PrivilegedActionException e) {
throw new InternalError(e.toString(), e);
}
int offset = 0;
/* First, read magic, version, and header_info. */
int len = LABEL_LENGTH + 5;
byte[] buf = new byte[len];
if (is.read(buf) != len) {
throw new MissingResourceException("Wrong header length",
datafile, "");
}
/* Validate the magic number. */
for (int i = 0; i < LABEL_LENGTH; i++, offset++) {
if (buf[offset] != LABEL[offset]) {
throw new MissingResourceException("Wrong magic number",
datafile, "");
}
}
/* Validate the version number. */
if (buf[offset] != supportedVersion) {
throw new MissingResourceException("Unsupported version(" + buf[offset] + ")",
datafile, "");
}
/* Read data: totalDataSize + 8(for checksum) */
len = getInt(buf, ++offset);
buf = new byte[len];
if (is.read(buf) != len) {
throw new MissingResourceException("Wrong data length",
datafile, "");
}
is.close();
return buf;
}
byte[] getAdditionalData() {
return additionalData;
}
void setAdditionalData(byte[] b) {
additionalData = b;
}
//=======================================================================
// boilerplate
//=======================================================================
/**
* Clones this iterator.
* @return A newly-constructed RuleBasedBreakIterator with the same
* behavior as this one.
*/
@Override
public Object clone() {
RuleBasedBreakIterator result = (RuleBasedBreakIterator) super.clone();
if (text != null) {
result.text = (CharacterIterator) text.clone();
}
return result;
}
/**
* Returns true if both BreakIterators are of the same class, have the same
* rules, and iterate over the same text.
*/
@Override
public boolean equals(Object that) {
try {
if (that == null) {
return false;
}
RuleBasedBreakIterator other = (RuleBasedBreakIterator) that;
if (checksum != other.checksum) {
return false;
}
if (text == null) {
return other.text == null;
} else {
return text.equals(other.text);
}
}
catch(ClassCastException e) {
return false;
}
}
/**
* Returns text
*/
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append('[');
sb.append("checksum=0x");
sb.append(Long.toHexString(checksum));
sb.append(']');
return sb.toString();
}
/**
* Compute a hashcode for this BreakIterator
* @return A hash code
*/
@Override
public int hashCode() {
return (int)checksum;
}
//=======================================================================
// BreakIterator overrides
//=======================================================================
/**
* Sets the current iteration position to the beginning of the text.
* (i.e., the CharacterIterator's starting offset).
* @return The offset of the beginning of the text.
*/
@Override
public int first() {
CharacterIterator t = getText();
t.first();
return t.getIndex();
}
/**
* Sets the current iteration position to the end of the text.
* (i.e., the CharacterIterator's ending offset).
* @return The text's past-the-end offset.
*/
@Override
public int last() {
CharacterIterator t = getText();
// I'm not sure why, but t.last() returns the offset of the last character,
// rather than the past-the-end offset
t.setIndex(t.getEndIndex());
return t.getIndex();
}
/**
* Advances the iterator either forward or backward the specified number of steps.
* Negative values move backward, and positive values move forward. This is
* equivalent to repeatedly calling next() or previous().
* @param n The number of steps to move. The sign indicates the direction
* (negative is backwards, and positive is forwards).
* @return The character offset of the boundary position n boundaries away from
* the current one.
*/
@Override
public int next(int n) {
int result = current();
while (n > 0) {
result = handleNext();
--n;
}
while (n < 0) {
result = previous();
++n;
}
return result;
}
/**
* Advances the iterator to the next boundary position.
* @return The position of the first boundary after this one.
*/
@Override
public int next() {
return handleNext();
}
private int cachedLastKnownBreak = BreakIterator.DONE;
/**
* Advances the iterator backwards, to the last boundary preceding this one.
* @return The position of the last boundary position preceding this one.
*/
@Override
public int previous() {
// if we're already sitting at the beginning of the text, return DONE
CharacterIterator text = getText();
if (current() == text.getBeginIndex()) {
return BreakIterator.DONE;
}
// set things up. handlePrevious() will back us up to some valid
// break position before the current position (we back our internal
// iterator up one step to prevent handlePrevious() from returning
// the current position), but not necessarily the last one before
// where we started
int start = current();
int lastResult = cachedLastKnownBreak;
if (lastResult >= start || lastResult <= BreakIterator.DONE) {
getPrevious();
lastResult = handlePrevious();
} else {
//it might be better to check if handlePrevious() give us closer
//safe value but handlePrevious() is slow too
//So, this has to be done carefully
text.setIndex(lastResult);
}
int result = lastResult;
// iterate forward from the known break position until we pass our
// starting point. The last break position before the starting
// point is our return value
while (result != BreakIterator.DONE && result < start) {
lastResult = result;
result = handleNext();
}
// set the current iteration position to be the last break position
// before where we started, and then return that value
text.setIndex(lastResult);
cachedLastKnownBreak = lastResult;
return lastResult;
}
/**
* Returns previous character
*/
private int getPrevious() {
char c2 = text.previous();
if (Character.isLowSurrogate(c2) &&
text.getIndex() > text.getBeginIndex()) {
char c1 = text.previous();
if (Character.isHighSurrogate(c1)) {
return Character.toCodePoint(c1, c2);
} else {
text.next();
}
}
return (int)c2;
}
/**
* Returns current character
*/
int getCurrent() {
char c1 = text.current();
if (Character.isHighSurrogate(c1) &&
text.getIndex() < text.getEndIndex()) {
char c2 = text.next();
text.previous();
if (Character.isLowSurrogate(c2)) {
return Character.toCodePoint(c1, c2);
}
}
return (int)c1;
}
/**
* Returns the count of next character.
*/
private int getCurrentCodePointCount() {
char c1 = text.current();
if (Character.isHighSurrogate(c1) &&
text.getIndex() < text.getEndIndex()) {
char c2 = text.next();
text.previous();
if (Character.isLowSurrogate(c2)) {
return 2;
}
}
return 1;
}
/**
* Returns next character
*/
int getNext() {
int index = text.getIndex();
int endIndex = text.getEndIndex();
if (index == endIndex ||
(index += getCurrentCodePointCount()) >= endIndex) {
return CharacterIterator.DONE;
}
text.setIndex(index);
return getCurrent();
}
/**
* Returns the position of next character.
*/
private int getNextIndex() {
int index = text.getIndex() + getCurrentCodePointCount();
int endIndex = text.getEndIndex();
if (index > endIndex) {
return endIndex;
} else {
return index;
}
}
/**
* Throw IllegalArgumentException unless begin <= offset < end.
*/
protected static final void checkOffset(int offset, CharacterIterator text) {
if (offset < text.getBeginIndex() || offset > text.getEndIndex()) {
throw new IllegalArgumentException("offset out of bounds");
}
}
/**
* Sets the iterator to refer to the first boundary position following
* the specified position.
* @offset The position from which to begin searching for a break position.
* @return The position of the first break after the current position.
*/
@Override
public int following(int offset) {
CharacterIterator text = getText();
checkOffset(offset, text);
// Set our internal iteration position (temporarily)
// to the position passed in. If this is the _beginning_ position,
// then we can just use next() to get our return value
text.setIndex(offset);
if (offset == text.getBeginIndex()) {
cachedLastKnownBreak = handleNext();
return cachedLastKnownBreak;
}
// otherwise, we have to sync up first. Use handlePrevious() to back
// us up to a known break position before the specified position (if
// we can determine that the specified position is a break position,
// we don't back up at all). This may or may not be the last break
// position at or before our starting position. Advance forward
// from here until we've passed the starting position. The position
// we stop on will be the first break position after the specified one.
int result = cachedLastKnownBreak;
if (result >= offset || result <= BreakIterator.DONE) {
result = handlePrevious();
} else {
//it might be better to check if handlePrevious() give us closer
//safe value but handlePrevious() is slow too
//So, this has to be done carefully
text.setIndex(result);
}
while (result != BreakIterator.DONE && result <= offset) {
result = handleNext();
}
cachedLastKnownBreak = result;
return result;
}
/**
* Sets the iterator to refer to the last boundary position before the
* specified position.
* @offset The position to begin searching for a break from.
* @return The position of the last boundary before the starting position.
*/
@Override
public int preceding(int offset) {
// if we start by updating the current iteration position to the
// position specified by the caller, we can just use previous()
// to carry out this operation
CharacterIterator text = getText();
checkOffset(offset, text);
text.setIndex(offset);
return previous();
}
/**
* Returns true if the specified position is a boundary position. As a side
* effect, leaves the iterator pointing to the first boundary position at
* or after "offset".
* @param offset the offset to check.
* @return True if "offset" is a boundary position.
*/
@Override
public boolean isBoundary(int offset) {
CharacterIterator text = getText();
checkOffset(offset, text);
if (offset == text.getBeginIndex()) {
return true;
}
// to check whether this is a boundary, we can use following() on the
// position before the specified one and return true if the position we
// get back is the one the user specified
else {
return following(offset - 1) == offset;
}
}
/**
* Returns the current iteration position.
* @return The current iteration position.
*/
@Override
public int current() {
return getText().getIndex();
}
/**
* Return a CharacterIterator over the text being analyzed. This version
* of this method returns the actual CharacterIterator we're using internally.
* Changing the state of this iterator can have undefined consequences. If
* you need to change it, clone it first.
* @return An iterator over the text being analyzed.
*/
@Override
public CharacterIterator getText() {
// The iterator is initialized pointing to no text at all, so if this
// function is called while we're in that state, we have to fudge an
// iterator to return.
if (text == null) {
text = new StringCharacterIterator("");
}
return text;
}
/**
* Set the iterator to analyze a new piece of text. This function resets
* the current iteration position to the beginning of the text.
* @param newText An iterator over the text to analyze.
*/
@Override
public void setText(CharacterIterator newText) {
// Test iterator to see if we need to wrap it in a SafeCharIterator.
// The correct behavior for CharacterIterators is to allow the
// position to be set to the endpoint of the iterator. Many
// CharacterIterators do not uphold this, so this is a workaround
// to permit them to use this class.
int end = newText.getEndIndex();
boolean goodIterator;
try {
newText.setIndex(end); // some buggy iterators throw an exception here
goodIterator = newText.getIndex() == end;
}
catch(IllegalArgumentException e) {
goodIterator = false;
}
if (goodIterator) {
text = newText;
}
else {
text = new SafeCharIterator(newText);
}
text.first();
cachedLastKnownBreak = BreakIterator.DONE;
}
//=======================================================================
// implementation
//=======================================================================
/**
* This method is the actual implementation of the next() method. All iteration
* vectors through here. This method initializes the state machine to state 1
* and advances through the text character by character until we reach the end
* of the text or the state machine transitions to state 0. We update our return
* value every time the state machine passes through a possible end state.
*/
protected int handleNext() {
// if we're already at the end of the text, return DONE.
CharacterIterator text = getText();
if (text.getIndex() == text.getEndIndex()) {
return BreakIterator.DONE;
}
// no matter what, we always advance at least one character forward
int result = getNextIndex();
int lookaheadResult = 0;
// begin in state 1
int state = START_STATE;
int category;
int c = getCurrent();
// loop until we reach the end of the text or transition to state 0
while (c != CharacterIterator.DONE && state != STOP_STATE) {
// look up the current character's character category (which tells us
// which column in the state table to look at)
category = lookupCategory(c);
// if the character isn't an ignore character, look up a state
// transition in the state table
if (category != IGNORE) {
state = lookupState(state, category);
}
// if the state we've just transitioned to is a lookahead state,
// (but not also an end state), save its position. If it's
// both a lookahead state and an end state, update the break position
// to the last saved lookup-state position
if (lookaheadStates[state]) {
if (endStates[state]) {
result = lookaheadResult;
}
else {
lookaheadResult = getNextIndex();
}
}
// otherwise, if the state we've just transitioned to is an accepting
// state, update the break position to be the current iteration position
else {
if (endStates[state]) {
result = getNextIndex();
}
}
c = getNext();
}
// if we've run off the end of the text, and the very last character took us into
// a lookahead state, advance the break position to the lookahead position
// (the theory here is that if there are no characters at all after the lookahead
// position, that always matches the lookahead criteria)
if (c == CharacterIterator.DONE && lookaheadResult == text.getEndIndex()) {
result = lookaheadResult;
}
text.setIndex(result);
return result;
}
/**
* This method backs the iterator back up to a "safe position" in the text.
* This is a position that we know, without any context, must be a break position.
* The various calling methods then iterate forward from this safe position to
* the appropriate position to return. (For more information, see the description
* of buildBackwardsStateTable() in RuleBasedBreakIterator.Builder.)
*/
protected int handlePrevious() {
CharacterIterator text = getText();
int state = START_STATE;
int category = 0;
int lastCategory = 0;
int c = getCurrent();
// loop until we reach the beginning of the text or transition to state 0
while (c != CharacterIterator.DONE && state != STOP_STATE) {
// save the last character's category and look up the current
// character's category
lastCategory = category;
category = lookupCategory(c);
// if the current character isn't an ignore character, look up a
// state transition in the backwards state table
if (category != IGNORE) {
state = lookupBackwardState(state, category);
}
// then advance one character backwards
c = getPrevious();
}
// if we didn't march off the beginning of the text, we're either one or two
// positions away from the real break position. (One because of the call to
// previous() at the end of the loop above, and another because the character
// that takes us into the stop state will always be the character BEFORE
// the break position.)
if (c != CharacterIterator.DONE) {
if (lastCategory != IGNORE) {
getNext();
getNext();
}
else {
getNext();
}
}
return text.getIndex();
}
/**
* Looks up a character's category (i.e., its category for breaking purposes,
* not its Unicode category)
*/
protected int lookupCategory(int c) {
if (c < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
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