A subclass of BreakIterator whose behavior is specified using a list of rules.
* *There are two kinds of rules, which are separated by semicolons: substitutions * and regular expressions.
* *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.
* *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 "ignore characters") 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.
* *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 |).
* *The special characters recognized by the regular-expression parser are as follows:
* *** **
** ** *Specifies that the expression preceding the asterisk may occur any number * of times (including not at all). ** *{} *Encloses a sequence of characters that is optional. ** *() *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 |. ** *| *Separates two alternative sequences of characters. Either one * sequence or the other, but not both, matches this expression. The | character can * only occur inside (). ** *. *Matches any character. ** **? *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., "xxyxyyyxyxyxxyxyxyy", * but "x[xy]*?x" will only match the first two xes ("xxyxyyyxyxyxxyxyxyy"). ** *[] *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. ** */ *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. ** *\ *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. ** *! *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. ** *(all others) *All other characters are treated as literal characters, which must match * the corresponding character(s) in the text exactly. *
Within a [] expression, a number of other special characters can be used to specify * groups of characters:
* *** **
** *- *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. ** *:: *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. ** *[] *[] expressions can nest. This has no effect, except when used in * conjunction with the ^ token. ** *^ *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. ** *(all others) *All other characters are treated as literal characters. (For * example, "[aeiou]" specifies just the letters a, e, i, o, and u.) *
For a more complete explanation, see http://www.ibm.com/java/education/boundaries/boundaries.html. * For examples, see the resource data (which is annotated).
* * @author Richard Gillam */ public 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; /** * 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 using the given rule data. * * @throws MissingResourceException if the rule data is invalid or corrupted */ public RuleBasedBreakIterator(String ruleFile, byte[] ruleData) { ByteBuffer bb = ByteBuffer.wrap(ruleData); try { validateRuleData(ruleFile, bb); setupTables(ruleFile, bb); } catch (BufferUnderflowException bue) { MissingResourceException e; e = new MissingResourceException("Corrupted rule data file", ruleFile, ""); e.initCause(bue); throw e; } } /** * Initializes the fields with the given rule data. * The data format is as follows: *
* BreakIteratorData {
* u1 magic[7];
* u1 version;
* u4 totalDataSize;
* header_info header;
* body value;
* }
*
* totalDataSize is the summation of the size of
* header_info and body in byte count.
*
* In header, each field except for checksum implies the
* length of each field. Since BMPdataLength is a fixed-length
* data(512 entries), its length isn't included in header.
* checksum is a CRC32 value of all in body.
*
* header_info {
* u4 stateTableLength;
* u4 backwardsStateTableLength;
* u4 endStatesLength;
* u4 lookaheadStatesLength;
* u4 BMPdataLength;
* u4 nonBMPdataLength;
* u4 additionalDataLength;
* u8 checksum;
* }
*
*
*
* Finally, BMPindices and BMPdata are set to
* charCategoryTable. nonBMPdata is set to
* supplementaryCharCategoryTable.
*
* 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];
* }
*
*
* @throws BufferUnderflowException if the end-of-data is reached before
* setting up all the tables
*/
private void setupTables(String ruleFile, ByteBuffer bb) {
/* Read header_info. */
int stateTableLength = bb.getInt();
int backwardsStateTableLength = bb.getInt();
int endStatesLength = bb.getInt();
int lookaheadStatesLength = bb.getInt();
int BMPdataLength = bb.getInt();
int nonBMPdataLength = bb.getInt();
int additionalDataLength = bb.getInt();
checksum = bb.getLong();
/* Read stateTable[numCategories * numRows] */
stateTable = new short[stateTableLength];
for (int i = 0; i < stateTableLength; i++) {
stateTable[i] = bb.getShort();
}
/* Read backwardsStateTable[numCategories * numRows] */
backwardsStateTable = new short[backwardsStateTableLength];
for (int i = 0; i < backwardsStateTableLength; i++) {
backwardsStateTable[i] = bb.getShort();
}
/* Read endStates[numRows] */
endStates = new boolean[endStatesLength];
for (int i = 0; i < endStatesLength; i++) {
endStates[i] = bb.get() == 1;
}
/* Read lookaheadStates[numRows] */
lookaheadStates = new boolean[lookaheadStatesLength];
for (int i = 0; i < lookaheadStatesLength; i++) {
lookaheadStates[i] = bb.get() == 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++) {
temp1[i] = bb.getShort();
}
byte[] temp2 = new byte[BMPdataLength]; // BMPdata
bb.get(temp2);
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++) {
temp3[i] = bb.getInt();
}
supplementaryCharCategoryTable = new SupplementaryCharacterData(temp3);
/* Read additional data */
if (additionalDataLength > 0) {
additionalData = new byte[additionalDataLength];
bb.get(additionalData);
}
assert bb.position() == bb.limit();
/* Set numCategories */
numCategories = stateTable.length / endStates.length;
}
/**
* Validates the magic number, version, and the length of the given data.
*
* @throws BufferUnderflowException if the end-of-data is reached while
* validating data
* @throws MissingResourceException if valification failed
*/
void validateRuleData(String ruleFile, ByteBuffer bb) {
/* Verify the magic number. */
for (int i = 0; i < LABEL_LENGTH; i++) {
if (bb.get() != LABEL[i]) {
throw new MissingResourceException("Wrong magic number",
ruleFile, "");
}
}
/* Verify the version number. */
byte version = bb.get();
if (version != supportedVersion) {
throw new MissingResourceException("Unsupported version(" + version + ")",
ruleFile, "");
}
// Check the length of the rest of data
int len = bb.getInt();
if (bb.position() + len != bb.limit()) {
throw new MissingResourceException("Wrong data length",
ruleFile, "");
}
}
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() {
return "[checksum=0x" + Long.toHexString(checksum) + ']';
}
/**
* 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) {
return charCategoryTable.elementAt((char)c);
} else {
return supplementaryCharCategoryTable.getValue(c);
}
}
/**
* Given a current state and a character category, looks up the
* next state to transition to in the state table.
*/
protected int lookupState(int state, int category) {
return stateTable[state * numCategories + category];
}
/**
* Given a current state and a character category, looks up the
* next state to transition to in the backwards state table.
*/
protected int lookupBackwardState(int state, int category) {
return backwardsStateTable[state * numCategories + category];
}
/*
* This class exists to work around a bug in incorrect implementations
* of CharacterIterator, which incorrectly handle setIndex(endIndex).
* This iterator relies only on base.setIndex(n) where n is less than
* endIndex.
*
* One caveat: if the base iterator's begin and end indices change
* the change will not be reflected by this wrapper. Does that matter?
*/
// TODO: Review this class to see if it's still required.
private static final class SafeCharIterator implements CharacterIterator,
Cloneable {
private CharacterIterator base;
private int rangeStart;
private int rangeLimit;
private int currentIndex;
SafeCharIterator(CharacterIterator base) {
this.base = base;
this.rangeStart = base.getBeginIndex();
this.rangeLimit = base.getEndIndex();
this.currentIndex = base.getIndex();
}
@Override
public char first() {
return setIndex(rangeStart);
}
@Override
public char last() {
return setIndex(rangeLimit - 1);
}
@Override
public char current() {
if (currentIndex < rangeStart || currentIndex >= rangeLimit) {
return DONE;
}
else {
return base.setIndex(currentIndex);
}
}
@Override
public char next() {
currentIndex++;
if (currentIndex >= rangeLimit) {
currentIndex = rangeLimit;
return DONE;
}
else {
return base.setIndex(currentIndex);
}
}
@Override
public char previous() {
currentIndex--;
if (currentIndex < rangeStart) {
currentIndex = rangeStart;
return DONE;
}
else {
return base.setIndex(currentIndex);
}
}
@Override
public char setIndex(int i) {
if (i < rangeStart || i > rangeLimit) {
throw new IllegalArgumentException("Invalid position");
}
currentIndex = i;
return current();
}
@Override
public int getBeginIndex() {
return rangeStart;
}
@Override
public int getEndIndex() {
return rangeLimit;
}
@Override
public int getIndex() {
return currentIndex;
}
@Override
public Object clone() {
SafeCharIterator copy = null;
try {
copy = (SafeCharIterator) super.clone();
}
catch(CloneNotSupportedException e) {
throw new Error("Clone not supported: " + e);
}
CharacterIterator copyOfBase = (CharacterIterator) base.clone();
copy.base = copyOfBase;
return copy;
}
}
}