| /* |
| ********************************************************************** |
| * Copyright (C) 1999 Alan Liu and others. All rights reserved. |
| ********************************************************************** |
| * Date Name Description |
| * 10/22/99 alan Creation. |
| ********************************************************************** |
| */ |
| |
| #include "rbbi.h" |
| #include "rbbi_bld.h" |
| |
| //======================================================================= |
| // RuleBasedBreakIterator.Builder |
| //======================================================================= |
| /** |
| * The Builder class has the job of constructing a RuleBasedBreakIterator from a |
| * textual description. A Builder is constructed by RuleBasedBreakIterator's |
| * constructor, which uses it to construct the iterator itself and then throws it |
| * away. |
| * <p>The construction logic is separated out into its own class for two primary |
| * reasons: |
| * <ul><li>The construction logic is quite complicated and large. Separating it |
| * out into its own class means the code must only be loaded into memory while a |
| * RuleBasedBreakIterator is being constructed, and can be purged after that. |
| * <li>There is a fair amount of state that must be maintained throughout the |
| * construction process that is not needed by the iterator after construction. |
| * Separating this state out into another class prevents all of the functions that |
| * construct the iterator from having to have really long parameter lists, |
| * (hopefully) contributing to readability and maintainability.</ul> |
| * <p>It'd be really nice if this could be an independent class rather than an |
| * inner class, because that would shorten the source file considerably, but |
| * making Builder an inner class of RuleBasedBreakIterator allows it direct access |
| * to RuleBasedBreakIterator's private members, which saves us from having to |
| * provide some kind of "back door" to the Builder class that could then also be |
| * used by other classes. |
| */ |
| |
| /** |
| * No special construction is required for the Builder. |
| */ |
| RuleBasedBreakIteratorBuilder::RuleBasedBreakIteratorBuilder() { |
| } |
| |
| /** |
| * This is the main function for setting up the BreakIterator's tables. It |
| * just vectors different parts of the job off to other functions. |
| */ |
| void RuleBasedBreakIteratorBuilder::buildBreakIterator() { |
| Vector tempRuleList = buildRuleList(description); |
| buildCharCategories(tempRuleList); |
| buildStateTable(tempRuleList); |
| buildBackwardsStateTable(tempRuleList); |
| } |
| |
| /** |
| * Thus function has three main purposes: |
| * <ul><li>Perform general syntax checking on the description, so the rest of the |
| * build code can assume that it's parsing a legal description. |
| * <li>Split the description into separate rules |
| * <li>Perform variable-name substitutions (so that no one else sees variable names) |
| * </ul> |
| */ |
| Vector RuleBasedBreakIteratorBuilder::buildRuleList(UnicodeString description) { |
| // invariants: |
| // - parentheses must be balanced: ()[]{}<> |
| // - nothing can be nested inside <> |
| // - nothing can be nested inside [] except more []s |
| // - pairs of ()[]{}<> must not be empty |
| // - ; can only occur at the outer level |
| // - | can only appear inside () |
| // - only one = or / can occur in a single rule |
| // - = and / cannot both occur in the same rule |
| // - <> can only occur on the left side of a = expression |
| // (because we'll perform substitutions to eliminate them from other places) |
| // - the left-hand side of a = expression can only be a single character |
| // (possibly with \) or text inside <> |
| // - the right-hand side of a = expression must be enclosed in [] or () |
| // - * may not occur at the beginning of a rule, nor may it follow |
| // =, /, (, (, |, }, ;, or * |
| // - ? may only follow * |
| // - the rule list must contain at least one / rule |
| // - no rule may be empty |
| // - all printing characters in the ASCII range except letters and digits |
| // are reserved and must be preceded by \ |
| // - ! may only occur at the beginning of a rule |
| |
| // set up a vector to contain the broken-up description (each entry in the |
| // vector is a separate rule) and a stack for keeping track of opening |
| // punctuation |
| Vector tempRuleList = new Vector(); |
| Stack parenStack = new Stack(); |
| |
| int32_t p = 0; |
| int32_t ruleStart = 0; |
| UChar c = '\u0000'; |
| UChar lastC = '\u0000'; |
| UChar lastOpen = '\u0000'; |
| bool_t haveEquals = FALSE; |
| bool_t havePipe = FALSE; |
| bool_t sawVarName = FALSE; |
| final UnicodeString UCharsThatCantPrecedeAsterisk = "=/{(|}*;\u0000"; |
| |
| // if the description doesn't end with a semicolon, tack a semicolon onto the end |
| if (description.length() != 0 && description.UCharAt(description.length() - 1) != ';') |
| description = description + ";"; |
| |
| // for each character, do... |
| while (p < description.length()) { |
| c = description.UCharAt(p); |
| switch (c) { |
| // if the character is opening punctuation, verify that no nesting |
| // rules are broken, and push the character onto the stack |
| case '{': |
| case '<': |
| case '[': |
| case '(': |
| if (lastOpen == '<') |
| error("Can't nest brackets inside <>", p, description); |
| if (lastOpen == '[' && c != '[') |
| error("Can't nest anything in [] but []", p, description); |
| |
| // if we see < anywhere except on the left-hand side of =, |
| // we must be seeing a variable name that was never defined |
| if (c == '<' && (haveEquals || havePipe)) |
| error("Unknown variable name", p, description); |
| |
| lastOpen = c; |
| parenStack.push(new Character(c)); |
| if (c == '<') |
| sawVarName = TRUE; |
| break; |
| |
| // if the character is closing punctuation, verify that it matches the |
| // last opening punctuation we saw, and that the brackets contain |
| // something, then pop the stack |
| case '}': |
| case '>': |
| case ']': |
| case ')': |
| UChar expectedClose = '\u0000'; |
| switch (lastOpen) { |
| case '{': |
| expectedClose = '}'; |
| break; |
| case '[': |
| expectedClose = ']'; |
| break; |
| case '(': |
| expectedClose = ')'; |
| break; |
| case '<': |
| expectedClose = '>'; |
| break; |
| } |
| if (c != expectedClose) |
| error("Unbalanced parentheses", p, description); |
| if (lastC == lastOpen) |
| error("Parens don't contain anything", p, description); |
| parenStack.pop(); |
| if (!parenStack.empty()) |
| lastOpen = ((Character)(parenStack.peek())).UCharValue(); |
| else |
| lastOpen = '\u0000'; |
| |
| break; |
| |
| // if the character is an asterisk, make sure it occurs in a place |
| // where an asterisk can legally go |
| case '*': |
| if (UCharsThatCantPrecedeAsterisk.indexOf(lastC) != -1) |
| error("Misplaced asterisk", p, description); |
| break; |
| |
| // if the character is a question mark, make sure it follows an asterisk |
| case '?': |
| if (lastC != '*') |
| error("Misplaced ?", p, description); |
| break; |
| |
| // if the character is an equals sign, make sure we haven't seen another |
| // equals sign or a slash yet |
| case '=': |
| if (havePipe || haveEquals) |
| error("More than one = or / in rule", p, description); |
| haveEquals = TRUE; |
| break; |
| |
| // if the character is a slash, make sure we haven't seen another slash |
| // or an equals sign yet |
| case '/': |
| if (havePipe || haveEquals) |
| error("More than one = or / in rule", p, description); |
| if (sawVarName) |
| error("Unknown variable name", p, description); |
| havePipe = TRUE; |
| break; |
| |
| // if the character is an exclamation point, make sure it occurs only |
| // at the beginning of a rule |
| case '!': |
| if (lastC != ';' && lastC != '\u0000') |
| error("! can only occur at the beginning of a rule", p, description); |
| break; |
| |
| // if the character is a backslash, skip the character that follows it |
| // (it'll get treated as a literal character) |
| case '\\': |
| ++p; |
| break; |
| |
| // we don't have to do anything special on a period |
| case '.': |
| break; |
| |
| // if the character is a syntax character that can only occur |
| // inside [], make sure that it does in fact only occur inside []. |
| case '^': |
| case '-': |
| case ':': |
| if (lastOpen != '[' && lastOpen != '<') |
| error("Illegal character", p, description); |
| break; |
| |
| // if the character is a semicolon, do the following... |
| case ';': |
| // make sure the rule contains something and that there are no |
| // unbalanced parentheses or brackets |
| if (lastC == ';' || lastC == '\u0000') |
| error("Empty rule", p, description); |
| if (!parenStack.empty()) |
| error("Unbalanced parenheses", p, description); |
| |
| if (parenStack.empty()) { |
| // if the rule contained an = sign, call processSubstitution() |
| // to replace the substitution name with the substitution text |
| // wherever it appears in the description |
| if (haveEquals) |
| description = processSubstitution(description.substring(ruleStart, |
| p), description, p + 1); |
| else { |
| // otherwise, check to make sure the rule doesn't reference |
| // any undefined substitutions |
| if (sawVarName) |
| error("Unknown variable name", p, description); |
| |
| // then add it to tempRuleList |
| tempRuleList.addElement(description.substring(ruleStart, p)); |
| } |
| |
| // and reset everything to process the next rule |
| ruleStart = p + 1; |
| haveEquals = havePipe = sawVarName = FALSE; |
| } |
| break; |
| |
| // if the character is a vertical bar, check to make sure that it |
| // occurs inside a () expression and that the character that precedes |
| // it isn't also a vertical bar |
| case '|': |
| if (lastC == '|') |
| error("Empty alternative", p, description); |
| if (parenStack.empty() || lastOpen != '(') |
| error("Misplaced |", p, description); |
| break; |
| |
| // if the character is anything else (escaped characters are |
| // skipped and don't make it here), it's an error |
| default: |
| if (c >= ' ' && c < '\u007f' && !Character.isLetter(c) && |
| !Character.isDigit(c)) |
| error("Illegal character", p, description); |
| break; |
| } |
| lastC = c; |
| ++p; |
| } |
| if (tempRuleList.size() == 0) |
| error("No valid rules in description", p, description); |
| return tempRuleList; |
| } |
| |
| /** |
| * This function performs variable-name substitutions. First it does syntax |
| * checking on the variable-name definition. If it's syntactically valid, it |
| * then goes through the remainder of the description and does a simple |
| * find-and-replace of the variable name with its text. (The variable text |
| * must be enclosed in either [] or () for this to work.) |
| */ |
| UnicodeString RuleBasedBreakIteratorBuilder::processSubstitution(UnicodeString substitutionRule, UnicodeString description, |
| int32_t startPos) { |
| // isolate out the text on either side of the equals sign |
| UnicodeString replace; |
| UnicodeString replaceWith; |
| int32_t equalPos = substitutionRule.indexOf('='); |
| replace = substitutionRule.substring(0, equalPos); |
| replaceWith = substitutionRule.substring(equalPos + 1); |
| |
| // check to see whether the substitution name is something we've declared |
| // to be "special". For RuleBasedBreakIterator itself, this is "<ignore>". |
| // This function takes care of any extra processing that has to be done |
| // with "special" substitution names. |
| handleSpecialSubstitution(replace, replaceWith, startPos, description); |
| |
| // perform various other syntax checks on the rule |
| if (replaceWith.length() == 0) |
| error("Nothing on right-hand side of =", startPos, description); |
| if (replace.length() == 0) |
| error("Nothing on left-hand side of =", startPos, description); |
| if (replace.length() == 2 && replace.UCharAt(0) != '\\') |
| error("Illegal left-hand side for =", startPos, description); |
| if (replace.length() >= 3 && replace.UCharAt(0) != '<' && replace.UCharAt(equalPos - 1) |
| != '>') |
| error("Illegal left-hand side for =", startPos, description); |
| if (!(replaceWith.UCharAt(0) == '[' && replaceWith.UCharAt(replaceWith.length() - 1) |
| == ']') && !(replaceWith.UCharAt(0) == '(' && replaceWith.UCharAt( |
| replaceWith.length() - 1) == ')')) |
| error("Illegal right-hand side for =", startPos, description); |
| |
| // now go through the rest of the description (which hasn't been broken up |
| // into separate rules yet) and replace every occurrence of the |
| // substitution name with the substitution body |
| UnicodeString result = new UnicodeString(); |
| result.append(description.substring(0, startPos)); |
| int32_t lastPos = startPos; |
| int32_t pos = description.indexOf(replace, startPos); |
| while (pos != -1) { |
| result.append(description.substring(lastPos, pos)); |
| result.append(replaceWith); |
| lastPos = pos + replace.length(); |
| pos = description.indexOf(replace, lastPos); |
| } |
| result.append(description.substring(lastPos)); |
| return result.toString(); |
| } |
| |
| /** |
| * This function defines a protocol for handling substitution names that |
| * are "special," i.e., that have some property beyond just being |
| * substitutions. At the RuleBasedBreakIterator level, we have one |
| * special substitution name, "<ignore>". Subclasses can override this |
| * function to add more. Any special processing that has to go on beyond |
| * that which is done by the normal substitution-processing code is done |
| * here. |
| */ |
| void RuleBasedBreakIteratorBuilder::handleSpecialSubstitution(UnicodeString replace, UnicodeString replaceWith, |
| int32_t startPos, UnicodeString description) { |
| // if we get a definition for a substitution called "ignore", it defines |
| // the ignore characters for the iterator. Check to make sure the expression |
| // is a [] expression, and if it is, parse it and store the characters off |
| // to the side. |
| if (replace.equals("<ignore>")) { |
| if (replaceWith.UCharAt(0) == '(') |
| error("Ignore group can't be enclosed in (", startPos, description); |
| ignoreChars = CharSet.parseString(replaceWith); |
| } |
| } |
| |
| /** |
| * This function builds the character category table. On entry, |
| * tempRuleList is a vector of break rules that has had variable names substituted. |
| * On exit, the charCategoryTable data member has been initialized to hold the |
| * character category table, and tempRuleList's rules have been munged to contain |
| * character category numbers everywhere a literal character or a [] expression |
| * originally occurred. |
| */ |
| void RuleBasedBreakIteratorBuilder::buildCharCategories(Vector tempRuleList) { |
| int32_t bracketLevel = 0; |
| int32_t p = 0; |
| int32_t lineNum = 0; |
| |
| // build hash table of every literal character or [] expression in the rule list |
| // and use CharSet.parseString() to derive a CharSet object representing the |
| // characters each refers to |
| expressions = new Hashtable(); |
| while (lineNum < tempRuleList.size()) { |
| UnicodeString line = (UnicodeString)(tempRuleList.elementAt(lineNum)); |
| p = 0; |
| while (p < line.length()) { |
| UChar c = line.UCharAt(p); |
| switch (c) { |
| // skip over all syntax characters except [ |
| case '{': case '}': case '(': case ')': case '*': case '.': |
| case '/': case '|': case ';': case '?': case '!': |
| break; |
| |
| // for [, find the matching ] (taking nested [] pairs into account) |
| // and add the whole expression to the expression list |
| case '[': |
| int32_t q = p + 1; |
| ++bracketLevel; |
| while (q < line.length() && bracketLevel != 0) { |
| c = line.UCharAt(q); |
| if (c == '[') |
| ++bracketLevel; |
| else if (c == ']') |
| --bracketLevel; |
| ++q; |
| } |
| if (expressions.get(line.substring(p, q)) == 0) { |
| expressions.put(line.substring(p, q), CharSet.parseString(line. |
| substring(p, q))); |
| } |
| p = q - 1; |
| break; |
| |
| // for \ sequences, just move to the next character and treat |
| // it as a single character |
| case '\\': |
| ++p; |
| c = line.UCharAt(p); |
| // DON'T break; fall through into "default" clause |
| |
| // for an isolated single character, add it to the expression list |
| default: |
| expressions.put(line.substring(p, p + 1), CharSet.parseString(line. |
| substring(p, p + 1))); |
| break; |
| } |
| ++p; |
| } |
| ++lineNum; |
| } |
| // dump CharSet's internal expression cache |
| CharSet.releaseExpressionCache(); |
| |
| // create the temporary category table (which is a vector of CharSet objects) |
| categories = new Vector(); |
| if (ignoreChars != 0) |
| categories.addElement(ignoreChars); |
| else |
| categories.addElement(new CharSet()); |
| ignoreChars = 0; |
| |
| // Derive the character categories. Go through the existing character categories |
| // looking for overlap. Any time there's overlap, we create a new character |
| // category for the characters that overlapped and remove them from their original |
| // category. At the end, any characters that are left in the expression haven't |
| // been mentioned in any category, so another new category is created for them. |
| // For example, if the first expression is [abc], then a, b, and c will be placed |
| // into a single character category. If the next expression is [bcd], we will first |
| // remove b and c from their existing category (leaving a behind), create a new |
| // category for b and c, and then create another new category for d (which hadn't |
| // been mentioned in the previous expression). |
| // At no time should a character ever occur in more than one character category. |
| |
| // for each expression in the expressions list, do... |
| Enumeration iter = expressions.elements(); |
| while (iter.hasMoreElements()) { |
| // initialize the working char set to the chars in the current expression |
| CharSet e = (CharSet)iter.nextElement(); |
| |
| // for each category in the category list, do... |
| for (int32_t j = categories.size() - 1; !e.empty() && j > 0; j--) { |
| |
| // if there's overlap between the current working set of chars |
| // and the current category... |
| CharSet that = (CharSet)(categories.elementAt(j)); |
| if (!that.intersection(e).empty()) { |
| |
| // add a new category for the characters that were in the |
| // current category but not in the working char set |
| CharSet temp = that.difference(e); |
| if (!temp.empty()) |
| categories.addElement(temp); |
| |
| // remove those characters from the working char set and replace |
| // the current category with the characters that it did |
| // have in common with the current working char set |
| temp = e.intersection(that); |
| e = e.difference(that); |
| if (!temp.equals(that)) |
| categories.setElementAt(temp, j); |
| } |
| } |
| |
| // if there are still characters left in the working char set, |
| // add a new category containing them |
| if (!e.empty()) |
| categories.addElement(e); |
| } |
| |
| // we have the ignore characters stored in position 0. Make an extra pass through |
| // the character category list and remove anything from the ignore list that shows |
| // up in some other category |
| CharSet allChars = new CharSet(); |
| for (int32_t i = 1; i < categories.size(); i++) |
| allChars = allChars.union((CharSet)(categories.elementAt(i))); |
| CharSet ignoreChars = (CharSet)(categories.elementAt(0)); |
| ignoreChars = ignoreChars.difference(allChars); |
| categories.setElementAt(ignoreChars, 0); |
| |
| // now that we've derived the character categories, go back through the expression |
| // list and replace each CharSet object with a String that represents the |
| // character categories that expression refers to. The String is encoded: each |
| // character is a character category number (plus 0x100 to avoid confusing them |
| // with syntax characters in the rule grammar) |
| iter = expressions.keys(); |
| while (iter.hasMoreElements()) { |
| UnicodeString key = (UnicodeString)iter.nextElement(); |
| CharSet cs = (CharSet)expressions.get(key); |
| UnicodeString cats = new UnicodeString(); |
| |
| // for each category... |
| for (int32_t j = 0; j < categories.size(); j++) { |
| |
| // if the current expression contains characters in that category... |
| CharSet temp = cs.intersection((CharSet)(categories.elementAt(j))); |
| if (!temp.empty()) { |
| |
| // then add the encoded category number to the String for this |
| // expression |
| cats.append((UChar)(0x100 + j)); |
| if (temp.equals(cs)) |
| break; |
| } |
| } |
| |
| // once we've finished building the encoded String for this expression, |
| // replace the CharSet object with it |
| expressions.put(key, cats.toString()); |
| } |
| |
| // and finally, we turn the temporary category table into a permanent category |
| // table, which is a CompactByteArray. (we skip category 0, which by definition |
| // refers to all characters not mentioned specifically in the rules) |
| UCharCategoryTable = new CompactByteArray((int8_t)0); |
| |
| // for each category... |
| for (int32_t i = 0; i < categories.size(); i++) { |
| CharSet UChars = (CharSet)(categories.elementAt(i)); |
| |
| // go through the character ranges in the category one by one... |
| Enumeration enum = UChars.getChars(); |
| while (enum.hasMoreElements()) { |
| UChar* range = (UChar*)(enum.nextElement()); |
| |
| // and set the corresponding elements in the CompactArray accordingly |
| if (i != 0) |
| UCharCategoryTable.setElementAt(range[0], range[1], (int8_t)i); |
| |
| // (category 0 is special-- it's the hiding place for the ignore |
| // characters, whose real category number in the CompactArray is |
| // -1 [this is because category 0 contains all characters not |
| // specifically mentioned anywhere in the rules] ) |
| else |
| UCharCategoryTable.setElementAt(range[0], range[1], IGNORE); |
| } |
| } |
| |
| // once we've populated the CompactArray, compact it |
| UCharCategoryTable.compact(); |
| // initialize numCategories |
| numCategories = categories.size(); |
| } |
| |
| /** |
| * This is the function that builds the forward state table. Most of the real |
| * work is done in parseRule(), which is called once for each rule in the |
| * description. |
| */ |
| void RuleBasedBreakIteratorBuilder::buildStateTable(Vector tempRuleList) { |
| // initialize our temporary state table, and fill it with two states: |
| // state 0 is a dummy state that allows state 1 to be the starting state |
| // and 0 to represent "stop". State 1 is added here to seed things |
| // before we start parsing |
| tempStateTable = new Vector(); |
| tempStateTable.addElement(new int16_t[numCategories + 1]); |
| tempStateTable.addElement(new int16_t[numCategories + 1]); |
| |
| // call parseRule() for every rule in the rule list (except those which |
| // start with !, which are actually backwards-iteration rules) |
| for (int32_t i = 0; i < tempRuleList.size(); i++) { |
| UnicodeString rule = (UnicodeString)tempRuleList.elementAt(i); |
| if (rule.UCharAt(0) != '!') |
| parseRule(rule, TRUE); |
| } |
| |
| // finally, use finishBuildingStateTable() to minimize the number of |
| // states in the table and perform some other cleanup work |
| finishBuildingStateTable(TRUE); |
| } |
| |
| /** |
| * This is where most of the work really happens. This routine parses a single |
| * rule in the rule description, adding and modifying states in the state |
| * table according to the new expression. The state table is kept deterministic |
| * throughout the whole operation, although some ugly postprocessing is needed |
| * to handle the *? token. |
| */ |
| void RuleBasedBreakIteratorBuilder::parseRule(UnicodeString rule, bool_t forward) { |
| // algorithm notes: |
| // - The basic idea here is to read successive character-category groups |
| // from the input string. For each group, you create a state and point |
| // the appropriate entries in the previous state to it. This produces a |
| // straight line from the start state to the end state. The {}, *, and (|) |
| // idioms produce branches in this straight line. These branches (states |
| // that can transition to more than one other state) are called "decision |
| // points." A list of decision points is kept. This contains a list of |
| // all states that can transition to the next state to be created. For a |
| // straight line progression, the only thing in the decision-point list is |
| // the current state. But if there's a branch, the decision-point list |
| // will contain all of the beginning points of the branch when the next |
| // state to be created represents the end point of the branch. A stack is |
| // used to save decision point lists in the presence of nested parentheses |
| // and the like. For example, when a { is encountered, the current decision |
| // point list is saved on the stack and restored when the corresponding } |
| // is encountered. This way, after the } is read, the decision point list |
| // will contain both the state right before the } _and_ the state before |
| // the whole {} expression. Both of these states can transition to the next |
| // state after the {} expression. |
| // - one complication arises when we have to stamp a transition value into |
| // an array cell that already contains one. The updateStateTable() and |
| // mergeStates() functions handle this case. Their basic approach is to |
| // create a new state that combines the two states that conflict and point |
| // at it when necessary. This happens recursively, so if the merged states |
| // also conflict, they're resolved in the same way, and so on. There are |
| // a number of tests aimed at preventing infinite recursion. |
| // - another complication arises with repeating characters. It's somewhat |
| // ambiguous whether the user wants a greedy or non-greedy match in these cases. |
| // (e.g., whether "[a-z]*abc" means the SHORTEST sequence of letters ending in |
| // "abc" or the LONGEST sequence of letters ending in "abc". We've adopted |
| // the *? to mean "shortest" and * by itself to mean "longest". (You get the |
| // same result with both if there's no overlap between the repeating character |
| // group and the group immediately following it.) Handling the *? token is |
| // rather complicated and involves keeping track of whether a state needs to |
| // be merged (as described above) or merely overwritten when you update one of |
| // its cells, and copying the contents of a state that loops with a *? token |
| // into some of the states that follow it after the rest of the table-building |
| // process is complete ("backfilling"). |
| // implementation notes: |
| // - This function assumes syntax checking has been performed on the input string |
| // prior to its being passed in here. It assumes that parentheses are |
| // balanced, all literal characters are enclosed in [] and turned into category |
| // numbers, that there are no illegal characters or character sequences, and so |
| // on. Violation of these invariants will lead to undefined behavior. |
| // - It'd probably be better to use linked lists rather than Vector and Stack |
| // to maintain the decision point list and stack. I went for simplicity in |
| // this initial implementation. If performance is critical enough, we can go |
| // back and fix this later. |
| // -There are a number of important limitations on the *? token. It does not work |
| // right when followed by a repeating character sequence (e.g., ".*?(abc)*") |
| // (although it does work right when followed by a single repeating character). |
| // It will not always work right when nested in parentheses or braces (although |
| // sometimes it will). It also will not work right if the group of repeating |
| // characters and the group of characters that follows overlap partially |
| // (e.g., "[a-g]*?[e-j]"). None of these capabilites was deemed necessary for |
| // describing breaking rules we know about, so we left them out for |
| // expeditiousness. |
| // - The / token is not fully general: There are cases where it will put the |
| // break in the wrong place. In particular, rule sets such as "?; cat/alog;" |
| // will put a break after "cat" instead of after "c" ANY time it sees "cat", |
| // regardless of whether the text matches "catalog" or not. Also, rules such |
| // as "[a-z]*?abc;" will be treated the same as "[a-z]*?aa*bc;"-- that is, |
| // if the string ends in "aaaabc", the break will go before the first "a" |
| // rather than the last one. Both of these are limitations in the design |
| // of RuleBasedBreakIterator and not limitations of the rule parser. |
| |
| int32_t p = 0; |
| int32_t currentState = 1; // don't use state number 0; 0 means "stop" |
| int32_t lastState = currentState; |
| UnicodeString pendingChars = ""; |
| |
| decisionPointStack = new Stack(); |
| decisionPointList = new Vector(); |
| loopingStates = new Vector(); |
| statesToBackfill = new Vector(); |
| |
| int16_t* state; |
| bool_t sawEarlyBreak = FALSE; |
| |
| // if we're adding rules to the backward state table, mark the initial state |
| // as a looping state |
| if (!forward) |
| loopingStates.addElement(new Integer(1)); |
| |
| // put the current state on the decision point list before we start |
| decisionPointList.addElement(new Integer(currentState)); // we want currentState to |
| // be 1 here... |
| currentState = tempStateTable.size() - 1; // but after that, we want it to be |
| // 1 less than the state number of the next state |
| while (p < rule.length()) { |
| UChar c = rule.UCharAt(p); |
| clearLoopingStates = FALSE; |
| |
| // this section handles literal characters, escaped character (which are |
| // effectively literal characters too), the . token, and [] expressions |
| if (c == '[' || c == '\\' || Character.isLetter(c) || Character.isDigit(c) |
| || c < ' ' || c == '.' || c >= '\u007f') { |
| |
| // if we're not on a period, isolate the expression and look up |
| // the corresponding category list |
| if (c != '.') { |
| int32_t q = p; |
| |
| // if we're on a backslash, the expression is the character |
| // after the backslash |
| if (c == '\\') { |
| q = p + 2; |
| ++p; |
| } |
| |
| // if we're on an opening bracket, scan to the closing bracket |
| // to isolate the expression |
| else if (c == '[') { |
| int32_t bracketLevel = 1; |
| while (bracketLevel > 0) { |
| ++q; |
| c = rule.UCharAt(q); |
| if (c == '[') |
| ++bracketLevel; |
| else if (c == ']') |
| --bracketLevel; |
| else if (c == '\\') |
| ++q; |
| } |
| ++q; |
| } |
| |
| // otherwise, the expression is just the character itself |
| else |
| q = p + 1; |
| |
| // look up the category list for the expression and store it |
| // in pendingChars |
| pendingChars = (UnicodeString)expressions.get(rule.substring(p, q)); |
| |
| // advance the current position past the expression |
| p = q - 1; |
| } |
| |
| // if the character we're on is a period, we end up down here |
| else { |
| int32_t rowNum = ((Integer)decisionPointList.lastElement()).intValue(); |
| state = (int16_t*)tempStateTable.elementAt(rowNum); |
| |
| // if the period is followed by an asterisk, then just set the current |
| // state to loop back on itself |
| if (p + 1 < rule.length() && rule.UCharAt(p + 1) == '*' && state[0] != 0) { |
| decisionPointList.addElement(new Integer(state[0])); |
| pendingChars = ""; |
| ++p; |
| } |
| |
| // otherwise, fabricate a category list ("pendingChars") with |
| // every category in it |
| else { |
| UnicodeString temp = new UnicodeString(); |
| for (int32_t i = 0; i < numCategories; i++) |
| temp.append((UChar)(i + 0x100)); |
| pendingChars = temp.toString(); |
| } |
| } |
| |
| // we'll end up in here for all expressions except for .*, which is |
| // special-cased above |
| if (pendingChars.length() != 0) { |
| |
| // if the expression is followed by an asterisk, then push a copy |
| // of the current desicion point list onto the stack (this is |
| // the same thing we do on an opening brace) |
| if (p + 1 < rule.length() && rule.UCharAt(p + 1) == '*') |
| decisionPointStack.push(decisionPointList.clone()); |
| |
| // create a new state, add it to the list of states to backfill |
| // if we have looping states to worry about, set its "don't make |
| // me an accepting state" flag if we've seen a slash, and add |
| // it to the end of the state table |
| int32_t newState = tempStateTable.size(); |
| if (loopingStates.size() != 0) |
| statesToBackfill.addElement(new Integer(newState)); |
| state = new int16_t[numCategories + 1]; |
| if (sawEarlyBreak) |
| state[numCategories] = 0x4000; |
| tempStateTable.addElement(state); |
| |
| // update everybody in the decision point list to point to |
| // the new state (this also performs all the reconciliation |
| // needed to make the table deterministic), then clear the |
| // decision point list |
| updateStateTable(decisionPointList, pendingChars, (int16_t)newState); |
| decisionPointList.removeAllElements(); |
| |
| // add all states created since the last literal character we've |
| // seen to the decision point list |
| lastState = currentState; |
| do { |
| ++currentState; |
| decisionPointList.addElement(new Integer(currentState)); |
| } while (currentState + 1 < tempStateTable.size()); |
| } |
| } |
| |
| // a { marks the beginning of an optional run of characters. Push a |
| // copy of the current decision point list onto the stack. This saves |
| // it, preventing it from being affected by whatever's inside the parentheses. |
| // This decision point list is restored when a } is encountered. |
| else if (c == '{') { |
| decisionPointStack.push(decisionPointList.clone()); |
| } |
| |
| // a } marks the end of an optional run of characters. Pop the last decision |
| // point list off the stack and merge it with the current decision point list. |
| // a * denotes a repeating character or group (* after () is handled separately |
| // below). In addition to restoring the decision point list, modify the |
| // current state to point to itself on the appropriate character categories. |
| else if (c == '}' || c == '*') { |
| // when there's a *, update the current state to loop back on itself |
| // on the character categories that caused us to enter this state |
| if (c == '*') { |
| for (int32_t i = lastState + 1; i < tempStateTable.size(); i++) { |
| Vector temp = new Vector(); |
| temp.addElement(new Integer(i)); |
| updateStateTable(temp, pendingChars, (int16_t)(lastState + 1)); |
| } |
| } |
| |
| // pop the top element off the decision point stack and merge |
| // it with the current decision point list (this causes the divergent |
| // paths through the state table to come together again on the next |
| // new state) |
| Vector temp = (Vector)decisionPointStack.pop(); |
| for (int32_t i = 0; i < decisionPointList.size(); i++) |
| temp.addElement(decisionPointList.elementAt(i)); |
| decisionPointList = temp; |
| } |
| |
| // a ? after a * modifies the behavior of * in cases where there is overlap |
| // between the set of characters that repeat and the characters which follow. |
| // Without the ?, all states following the repeating state, up to a state which |
| // is reached by a character that doesn't overlap, will loop back into the |
| // repeating state. With the ?, the mark states following the *? DON'T loop |
| // back into the repeating state. Thus, "[a-z]*xyz" will match the longest |
| // sequence of letters that ends in "xyz," while "[a-z]*? will match the |
| // _shortest_ sequence of letters that ends in "xyz". |
| // We use extra bookkeeping to achieve this effect, since everything else works |
| // according to the "longest possible match" principle. The basic principle |
| // is that transitions out of a looping state are written in over the looping |
| // value instead of being reconciled, and that we copy the contents of the |
| // looping state into empty cells of all non-terminal states that follow the |
| // looping state. |
| else if (c == '?') { |
| setLoopingStates(decisionPointList, decisionPointList); |
| } |
| |
| // a ( marks the beginning of a sequence of characters. Parentheses can either |
| // contain several alternative character sequences (i.e., "(ab|cd|ef)"), or |
| // they can contain a sequence of characters that can repeat (i.e., "(abc)*"). Thus, |
| // A () group can have multiple entry and exit points. To keep track of this, |
| // we reserve TWO spots on the decision-point stack. The top of the stack is |
| // the list of exit points, which becomes the current decision point list when |
| // the ) is reached. The next entry down is the decision point list at the |
| // beginning of the (), which becomes the current decision point list at every |
| // entry point. |
| // In addition to keeping track of the exit points and the active decision |
| // points before the ( (i.e., the places from which the () can be entered), |
| // we need to keep track of the entry points in case the expression loops |
| // (i.e., is followed by *). We do that by creating a dummy state in the |
| // state table and adding it to the decision point list (BEFORE it's duplicated |
| // on the stack). Nobody points to this state, so it'll get optimized out |
| // at the end. It exists only to hold the entry points in case the () |
| // expression loops. |
| else if (c == '(') { |
| |
| // add a new state to the state table to hold the entry points into |
| // the () expression |
| tempStateTable.addElement(new int16_t[numCategories + 1]); |
| |
| // we have to adjust lastState and currentState to account for the |
| // new dummy state |
| lastState = currentState; |
| ++currentState; |
| |
| // add the current state to the decision point list (add it at the |
| // BEGINNING so we can find it later) |
| decisionPointList.insertElementAt(new Integer(currentState), 0); |
| |
| // finally, push a copy of the current decision point list onto the |
| // stack (this keeps track of the active decision point list before |
| // the () expression), followed by an empty decision point list |
| // (this will hold the exit points) |
| decisionPointStack.push(decisionPointList.clone()); |
| decisionPointStack.push(new Vector()); |
| } |
| |
| // a | separates alternative character sequences in a () expression. When |
| // a | is encountered, we add the current decision point list to the exit-point |
| // list, and restore the decision point list to its state prior to the (. |
| else if (c == '|') { |
| |
| // pick out the top two decision point lists on the stack |
| Vector oneDown = (Vector)decisionPointStack.pop(); |
| Vector twoDown = (Vector)decisionPointStack.peek(); |
| decisionPointStack.push(oneDown); |
| |
| // append the current decision point list to the list below it |
| // on the stack (the list of exit points), and restore the |
| // current decision point list to its state before the () expression |
| for (int32_t i = 0; i < decisionPointList.size(); i++) |
| oneDown.addElement(decisionPointList.elementAt(i)); |
| decisionPointList = (Vector)twoDown.clone(); |
| } |
| |
| // a ) marks the end of a sequence of characters. We do one of two things |
| // depending on whether the sequence repeats (i.e., whether the ) is followed |
| // by *): If the sequence doesn't repeat, then the exit-point list is merged |
| // with the current decision point list and the decision point list from before |
| // the () is thrown away. If the sequence does repeat, then we fish out the |
| // state we were in before the ( and copy all of its forward transitions |
| // (i.e., every transition added by the () expression) into every state in the |
| // exit-point list and the current decision point list. The current decision |
| // point list is then merged with both the exit-point list AND the saved version |
| // of the decision point list from before the (). Then we throw out the *. |
| else if (c == ')') { |
| |
| // pull the exit point list off the stack, merge it with the current |
| // decision point list, and make the merged version the current |
| // decision point list |
| Vector exitPoints = (Vector)decisionPointStack.pop(); |
| for (int32_t i = 0; i < decisionPointList.size(); i++) |
| exitPoints.addElement(decisionPointList.elementAt(i)); |
| decisionPointList = exitPoints; |
| |
| // if the ) isn't followed by a *, then all we have to do is throw |
| // away the other list on the decision point stack, and we're done |
| if (p + 1 >= rule.length() || rule.UCharAt(p + 1) != '*') |
| decisionPointStack.pop(); |
| |
| // but if the sequence repeats, we have a lot more work to do... |
| else { |
| |
| // now exitPoints and decisionPointList have to point to equivalent |
| // vectors, but not the SAME vector |
| exitPoints = (Vector)decisionPointList.clone(); |
| |
| // pop the original decision point list off the stack |
| Vector temp = (Vector)decisionPointStack.pop(); |
| |
| // we squirreled away the row number of our entry point list |
| // at the beginning of the original decision point list. Fish |
| // that state number out and retrieve the entry point list |
| int32_t tempStateNum = ((Integer)temp.firstElement()).intValue(); |
| int16_t* tempState = (int16_t*)tempStateTable.elementAt(tempStateNum); |
| |
| // merge the original decision point list with the current |
| // decision point list |
| for (int32_t i = 0; i < decisionPointList.size(); i++) |
| temp.addElement(decisionPointList.elementAt(i)); |
| decisionPointList = temp; |
| |
| // finally, copy every forward reference from the entry point |
| // list into every state in the new decision point list |
| for (int32_t i = 0; i < tempState.length; i++) { |
| if (tempState[i] > tempStateNum) |
| updateStateTable(exitPoints, |
| new Character((UChar)(i + 0x100)).toString(), |
| tempState[i]); |
| } |
| |
| // update lastState and currentState, and throw away the * |
| lastState = currentState; |
| currentState = tempStateTable.size() - 1; |
| ++p; |
| } |
| } |
| |
| // a / marks the position where the break is to go if the character sequence |
| // matches this rule. We update the flag word of every state on the decision |
| // point list to mark them as ending states, and take note of the fact that |
| // we've seen the slash |
| else if (c == '/') { |
| sawEarlyBreak = TRUE; |
| for (int32_t i = 0; i < decisionPointList.size(); i++) { |
| state = (int16_t*)tempStateTable.elementAt(((Integer)decisionPointList. |
| elementAt(i)).intValue()); |
| state[numCategories] |= 0x8000; |
| } |
| } |
| |
| // if we get here without executing any of the above clauses, we have a |
| // syntax error. However, for now we just ignore the offending character |
| // and move on |
| |
| // clearLoopingStates is a signal back from updateStateTable() that we've |
| // transitioned to a state that won't loop back to the current looping |
| // state. (In other words, we've gotten to a point where we can no longer |
| // go back into a *? we saw earlier.) Clear out the list of looping states |
| // and backfill any states that need to be backfilled. |
| if (clearLoopingStates) |
| setLoopingStates(0, decisionPointList); |
| |
| // advance to the next character, now that we've processed the current |
| // character |
| ++p; |
| } |
| |
| // this takes care of backfilling any states that still need to be backfilled |
| setLoopingStates(0, decisionPointList); |
| |
| // when we reach the end of the string, we do a postprocessing step to mark the |
| // end states. If we didn't see the / token, then the decision point list |
| // contains every state that can transition to the end state-- that is, every |
| // state that is the last state in a sequence that matches the rule. All of |
| // these states are considered "mark states"-- that is, states that cause the |
| // position returned from next() to be updated. A mark state represents a possible |
| // break position. This allows us to look ahead and remember how far the rule |
| // matched before following the new branch (see next() for more information). |
| // The temporary state table has an extra "flag column" at the end where this |
| // information is stored. We mark the end states by setting a flag in their |
| // flag column. |
| // (If we did see the /, we've already marked the end states.) |
| if (!sawEarlyBreak) { |
| for (int32_t i = 0; i < decisionPointList.size(); i++) { |
| int32_t rowNum = ((Integer)decisionPointList.elementAt(i)).intValue(); |
| state = (int16_t*)tempStateTable.elementAt(rowNum); |
| state[numCategories] |= 0x8000; |
| } |
| } |
| } |
| |
| /** |
| * Update entries in the state table, and merge states when necessary to keep |
| * the table deterministic. |
| * @param rows The list of rows that need updating (the decision point list) |
| * @param pendingChars A character category list, encoded in a String. This is the |
| * list of the columns that need updating. |
| * @param newValue Update the cells specfied above to contain this value |
| */ |
| void RuleBasedBreakIteratorBuilder::updateStateTable(Vector rows, |
| UnicodeString pendingChars, |
| int16_t newValue) { |
| // create a dummy state that has the specified row number (newValue) in |
| // the cells that need to be updated (those specified by pendingChars) |
| // and 0 in the other cells |
| int16_t* newValues = new int16_t[numCategories + 1]; |
| for (int32_t i = 0; i < pendingChars.length(); i++) |
| newValues[(int32_t)(pendingChars.UCharAt(i)) - 0x100] = newValue; |
| |
| // go through the list of rows to update, and update them by calling |
| // mergeStates() to merge them the the dummy state we created |
| for (int32_t i = 0; i < rows.size(); i++) { |
| mergeStates(((Integer)rows.elementAt(i)).intValue(), newValues, rows); |
| } |
| } |
| |
| /** |
| * The real work of making the state table deterministic happens here. This function |
| * merges a state in the state table (specified by rowNum) with a state that is |
| * passed in (newValues). The basic process is to copy the nonzero cells in newStates |
| * into the state in the state table (we'll call that oldValues). If there's a |
| * collision (i.e., if the same cell has a nonzero value in both states, and it's |
| * not the SAME value), then we have to reconcile the collision. We do this by |
| * creating a new state, adding it to the end of the state table, and using this |
| * function recursively to merge the original two states into a single, combined |
| * state. This process may happen recursively (i.e., each successive level may |
| * involve collisions). To prevent infinite recursion, we keep a log of merge |
| * operations. Any time we're merging two states we've merged before, we can just |
| * supply the row number for the result of that merge operation rather than creating |
| * a new state just like it. |
| * @param rowNum The row number in the state table of the state to be updated |
| * @param newValues The state to merge it with. |
| * @param rowsBeingUpdated A copy of the list of rows passed to updateStateTable() |
| * (itself a copy of the decision point list from parseRule()). Newly-created |
| * states get added to the decision point list if their "parents" were on it. |
| */ |
| void RuleBasedBreakIteratorBuilder::mergeStates(int32_t rowNum, |
| int16_t* newValues, |
| Vector rowsBeingUpdated) { |
| int16_t* oldValues = (int16_t*)(tempStateTable.elementAt(rowNum)); |
| bool_t isLoopingState = loopingStates.contains(new Integer(rowNum)); |
| |
| // for each of the cells in the rows we're reconciling, do... |
| for (int32_t i = 0; i < oldValues.length; i++) { |
| |
| // if they contain the same value, we don't have to do anything |
| if (oldValues[i] == newValues[i]) |
| continue; |
| |
| // if oldValues is a looping state and the state the current cell points to |
| // is too, then we can just stomp over the current value of that cell (and |
| // set the clear-looping-states flag if necessaru) |
| else if (isLoopingState && loopingStates.contains(new Integer(oldValues[i]))) { |
| if (newValues[i] != 0) { |
| if (oldValues[i] == 0) |
| clearLoopingStates = TRUE; |
| oldValues[i] = newValues[i]; |
| } |
| } |
| |
| // if the current cell in oldValues is 0, copy in the corresponding value |
| // from newValues |
| else if (oldValues[i] == 0) |
| oldValues[i] = newValues[i]; |
| |
| // the last column of each row is the flag column. Take care to merge the |
| // flag words correctly |
| else if (i == numCategories) { |
| oldValues[i] = (int16_t)((newValues[i] & 0xc000) | oldValues[i]); |
| } |
| |
| // if both newValues and oldValues have a nonzero value in the current |
| // cell, and it isn't the same value both places... |
| else if (oldValues[i] != 0 && newValues[i] != 0) { |
| |
| // look up this pair of cell values in the merge list. If it's |
| // found, update the cell in oldValues to point to the merged state |
| int32_t combinedRowNum = searchMergeList(oldValues[i], newValues[i]); |
| if (combinedRowNum != 0) |
| oldValues[i] = (int16_t)combinedRowNum; |
| |
| // otherwise, we have to reconcile them... |
| else { |
| // copy our row numbers into variables to make things easier |
| int32_t oldRowNum = oldValues[i]; |
| int32_t newRowNum = newValues[i]; |
| combinedRowNum = tempStateTable.size(); |
| |
| // add this pair of row numbers to the merge list (create it first |
| // if we haven't created the merge list yet) |
| if (mergeList == 0) |
| mergeList = new Vector(); |
| mergeList.addElement(new int32_t* { oldRowNum, newRowNum, combinedRowNum }); |
| |
| // create a new row to represent the merged state, and copy the |
| // contents of oldRow into it, then add it to the end of the |
| // state table and update the original row (oldValues) to point |
| // to the new, merged, state |
| int16_t* newRow = new int16_t[numCategories + 1]; |
| int16_t* oldRow = (int16_t*)(tempStateTable.elementAt(oldRowNum)); |
| System.arraycopy(oldRow, 0, newRow, 0, numCategories + 1); |
| tempStateTable.addElement(newRow); |
| oldValues[i] = (int16_t)combinedRowNum; |
| |
| // if the decision point list contains either of the parent rows, |
| // update it to include the new row as well |
| if ((decisionPointList.contains(new Integer(oldRowNum)) || |
| decisionPointList.contains(new Integer(newRowNum))) && |
| !decisionPointList.contains(new Integer(combinedRowNum))) |
| decisionPointList.addElement(new Integer(combinedRowNum)); |
| |
| // do the same thing with the list of rows being updated |
| if ((rowsBeingUpdated.contains(new Integer(oldRowNum)) || |
| rowsBeingUpdated.contains(new Integer(newRowNum))) && |
| !rowsBeingUpdated.contains(new Integer(combinedRowNum))) |
| decisionPointList.addElement(new Integer(combinedRowNum)); |
| // now (groan) do the same thing for all the entries on the |
| // decision point stack |
| for (int32_t k = 0; k < decisionPointStack.size(); k++) { |
| Vector dpl = (Vector)decisionPointStack.elementAt(k); |
| if ((dpl.contains(new Integer(oldRowNum)) || |
| dpl.contains(new Integer(newRowNum))) && !dpl.contains( |
| new Integer(combinedRowNum))) |
| dpl.addElement(new Integer(combinedRowNum)); |
| } |
| |
| // FINALLY (puff puff puff), call mergeStates() recursively to copy |
| // the row referred to by newValues into the new row and resolve any |
| // conflicts that come up at that level |
| mergeStates(combinedRowNum, (int16_t*)(tempStateTable.elementAt( |
| newValues[i])), rowsBeingUpdated); |
| } |
| } |
| } |
| return; |
| } |
| |
| /** |
| * The merge list is a list of pairs of rows that have been merged somewhere in |
| * the process of building this state table, along with the row number of the |
| * row containing the merged state. This function looks up a pair of row numbers |
| * and returns the row number of the row they combine into. (It returns 0 if |
| * this pair of rows isn't in the merge list.) |
| */ |
| int32_t RuleBasedBreakIteratorBuilder::searchMergeList(int32_t a, int32_t b) { |
| // if there is no merge list, there obviously isn't anything in it |
| if (mergeList == 0) |
| return 0; |
| |
| // otherwise, for each element in the merge list... |
| else { |
| int32_t* entry; |
| for (int32_t i = 0; i < mergeList.size(); i++) { |
| entry = (int32_t*)(mergeList.elementAt(i)); |
| |
| // we have a hit if the two row numbers match the two row numbers |
| // in the beginning of the entry (the two that combine), in either |
| // order |
| if ((entry[0] == a && entry[1] == b) || (entry[0] == b && entry[1] == a)) |
| return entry[2]; |
| |
| // we also have a hit if one of the two row numbers matches the marged |
| // row number and the other one matches one of the original row numbers |
| if ((entry[2] == a && (entry[0] == b || entry[1] == b))) |
| return entry[2]; |
| if ((entry[2] == b && (entry[0] == a || entry[1] == a))) |
| return entry[2]; |
| } |
| return 0; |
| } |
| } |
| |
| /** |
| * This function is used to update the list of current loooping states (i.e., |
| * states that are controlled by a *? construct). It backfills values from |
| * the looping states into unpopulated cells of the states that are currently |
| * marked for backfilling, and then updates the list of looping states to be |
| * the new list |
| * @param newLoopingStates The list of new looping states |
| * @param endStates The list of states to treat as end states (states that |
| * can exit the loop). |
| */ |
| void RuleBasedBreakIteratorBuilder::setLoopingStates(Vector newLoopingStates, Vector endStates) { |
| |
| // if the current list of looping states isn't empty, we have to backfill |
| // values from the looping states into the states that are waiting to be |
| // backfilled |
| if (!loopingStates.isEmpty()) { |
| int32_t loopingState = ((Integer)loopingStates.lastElement()).intValue(); |
| int32_t rowNum; |
| |
| // don't backfill into an end state OR any state reachable from an end state |
| // (since the search for reachable states is recursive, it's split out into |
| // a separate function, eliminateBackfillStates(), below) |
| for (int32_t i = 0; i < endStates.size(); i++) { |
| eliminateBackfillStates(((Integer)endStates.elementAt(i)).intValue()); |
| } |
| |
| // we DON'T actually backfill the states that need to be backfilled here. |
| // Instead, we MARK them for backfilling. The reason for this is that if |
| // there are multiple rules in the state-table description, the looping |
| // states may have some of their values changed by a succeeding rule, and |
| // this wouldn't be reflected in the backfilled states. We mark a state |
| // for backfilling by putting the row number of the state to copy from |
| // into the flag cell at the end of the row |
| for (int32_t i = 0; i < statesToBackfill.size(); i++) { |
| rowNum = ((Integer)statesToBackfill.elementAt(i)).intValue(); |
| int16_t* state = (int16_t*)tempStateTable.elementAt(rowNum); |
| state[numCategories] = (int16_t)((state[numCategories] & 0xc000) | |
| loopingState); |
| } |
| statesToBackfill.removeAllElements(); |
| loopingStates.removeAllElements(); |
| } |
| |
| if (newLoopingStates != 0) |
| loopingStates = (Vector)newLoopingStates.clone(); |
| } |
| |
| /** |
| * This removes "ending states" and states reachable from them from the |
| * list of states to backfill. |
| * @param The row number of the state to remove from the backfill list |
| */ |
| void RuleBasedBreakIteratorBuilder::eliminateBackfillStates(int32_t baseState) { |
| |
| // don't do anything unless this state is actually in the backfill list... |
| if (statesToBackfill.contains(new Integer(baseState))) { |
| |
| // if it is, take it out |
| statesToBackfill.removeElement(new Integer(baseState)); |
| |
| // then go through and recursively call this function for every |
| // state that the base state points to |
| int16_t* state = (int16_t*)tempStateTable.elementAt(baseState); |
| for (int32_t i = 0; i < numCategories; i++) { |
| if (state[i] != 0) |
| eliminateBackfillStates(state[i]); |
| } |
| } |
| } |
| |
| /** |
| * This function completes the backfilling process by actually doing the |
| * backfilling on the states that are marked for it |
| */ |
| void RuleBasedBreakIteratorBuilder::backfillLoopingStates() { |
| int16_t* state; |
| int16_t* loopingState = 0; |
| int32_t loopingStateRowNum = 0; |
| int32_t fromState; |
| |
| // for each state in the state table... |
| for (int32_t i = 0; i < tempStateTable.size(); i++) { |
| state = (int16_t*)tempStateTable.elementAt(i); |
| |
| // check the state's flag word to see if it's marked for backfilling |
| // (it's marked for backfilling if any bits other than the two high-order |
| // bits are set-- if they are, then the flag word, minus the two high bits, |
| // is the row number to copy from) |
| fromState = state[numCategories] & 0x3fff; |
| if (fromState > 0) { |
| |
| // load up the state to copy from (if we haven't already) |
| if (fromState != loopingStateRowNum) { |
| loopingStateRowNum = fromState; |
| loopingState = (int16_t*)tempStateTable.elementAt(loopingStateRowNum); |
| } |
| |
| // clear out the backfill part of the flag word |
| state[numCategories] &= 0xc000; |
| |
| // then fill all zero cells in the current state with values |
| // from the corresponding cells of the fromState |
| for (int32_t j = 0; j < state.length; j++) { |
| if (state[j] == 0) |
| state[j] = loopingState[j]; |
| else if (state[j] == 0x4000) |
| state[j] = 0; |
| } |
| } |
| } |
| } |
| |
| /** |
| * This function completes the state-table-building process by doing several |
| * postprocessing steps and copying everything into its final resting place |
| * in the iterator itself |
| * @param forward True if we're working on the forward state table |
| */ |
| void RuleBasedBreakIteratorBuilder::finishBuildingStateTable(bool_t forward) { |
| // start by backfilling the looping states |
| backfillLoopingStates(); |
| |
| int32_t* rowNumMap = new int32_t[tempStateTable.size()]; |
| Stack rowsToFollow = new Stack(); |
| rowsToFollow.push(new Integer(1)); |
| rowNumMap[1] = 1; |
| |
| // determine which states are no longer reachable from the start state |
| // (the reachable states will have their row numbers in the row number |
| // map, and the nonreachable states will have zero in the row number map) |
| while (rowsToFollow.size() != 0) { |
| int32_t rowNum = ((Integer)rowsToFollow.pop()).intValue(); |
| int16_t* row = (int16_t*)(tempStateTable.elementAt(rowNum)); |
| |
| for (int32_t i = 0; i < numCategories; i++) { |
| if (row[i] != 0) { |
| if (rowNumMap[row[i]] == 0) { |
| rowNumMap[row[i]] = row[i]; |
| rowsToFollow.push(new Integer(row[i])); |
| } |
| } |
| } |
| } |
| |
| bool_t madeChange; |
| int32_t newRowNum; |
| |
| // algorithm for minimizing the number of states in the table adapted from |
| // Aho & Ullman, "Principles of Compiler Design" |
| // The basic idea here is to organize the states into classes. When we're done, |
| // all states in the same class can be considered identical and all but one eliminated. |
| |
| // initially assign states to classes based on the number of populated cells they |
| // contain (the class number is the number of populated cells) |
| int32_t* stateClasses = new int32_t[tempStateTable.size()]; |
| int32_t nextClass = numCategories + 1; |
| int16_t* state1, state2; |
| for (int32_t i = 1; i < stateClasses.length; i++) { |
| if (rowNumMap[i] == 0) |
| continue; |
| state1 = (int16_t*)tempStateTable.elementAt(i); |
| for (int32_t j = 0; j < numCategories; j++) |
| if (state1[j] != 0) |
| ++stateClasses[i]; |
| if (stateClasses[i] == 0) |
| stateClasses[i] = nextClass; |
| } |
| ++nextClass; |
| |
| // then, for each class, elect the first member of that class as that class's |
| // "representative". For each member of the class, compare it to the "representative." |
| // If there's a column position where the state being tested transitions to a |
| // state in a DIFFERENT class from the class where the "representative" transitions, |
| // then move the state into a new class. Repeat this process until no new classes |
| // are created. |
| int32_t currentClass; |
| int32_t lastClass; |
| bool_t split; |
| |
| do { |
| currentClass = 1; |
| lastClass = nextClass; |
| while (currentClass < nextClass) { |
| split = FALSE; |
| state1 = state2 = 0; |
| for (int32_t i = 0; i < stateClasses.length; i++) { |
| if (stateClasses[i] == currentClass) { |
| if (state1 == 0) { |
| state1 = (int16_t*)tempStateTable.elementAt(i); |
| } |
| else { |
| state2 = (int16_t*)tempStateTable.elementAt(i); |
| for (int32_t j = 0; j < state2.length; j++) |
| if ((j == numCategories && state1[j] != state2[j] && forward) |
| || (j != numCategories && stateClasses[state1[j]] |
| != stateClasses[state2[j]])) { |
| stateClasses[i] = nextClass; |
| split = TRUE; |
| break; |
| } |
| } |
| } |
| } |
| if (split) |
| ++nextClass; |
| ++currentClass; |
| } |
| } while (lastClass != nextClass); |
| |
| // at this point, all of the states in a class except the first one (the |
| //"representative") can be eliminated, so update the row-number map accordingly |
| int32_t* representatives = new int32_t[nextClass]; |
| for (int32_t i = 1; i < stateClasses.length; i++) |
| if (representatives[stateClasses[i]] == 0) |
| representatives[stateClasses[i]] = i; |
| else |
| rowNumMap[i] = representatives[stateClasses[i]]; |
| |
| // renumber all remaining rows... |
| // first drop all that are either unreferenced or not a class representative |
| for (int32_t i = 1; i < rowNumMap.length; i++) |
| if (rowNumMap[i] != i) |
| tempStateTable.setElementAt(0, i); |
| |
| // then calculate everybody's new row number and update the row |
| // number map appropriately (the first pass updates the row numbers |
| // of all the class representatives [the rows we're keeping], and the |
| // second pass updates the cross references for all the rows that |
| // are being deleted) |
| newRowNum = 1; |
| for (int32_t i = 1; i < rowNumMap.length; i++) |
| if (tempStateTable.elementAt(i) != 0) |
| rowNumMap[i] = newRowNum++; |
| for (int32_t i = 1; i < rowNumMap.length; i++) |
| if (tempStateTable.elementAt(i) == 0) |
| rowNumMap[i] = rowNumMap[rowNumMap[i]]; |
| |
| // allocate the permanent state table, and copy the remaining rows into it |
| // (adjusting all the cell values, of course) |
| |
| // this section does that for the forward state table |
| if (forward) { |
| endStates = new bool_t[newRowNum]; |
| stateTable = new int16_t[newRowNum * numCategories]; |
| int32_t p = 0; |
| int32_t p2 = 0; |
| for (int32_t i = 0; i < tempStateTable.size(); i++) { |
| int16_t* row = (int16_t*)(tempStateTable.elementAt(i)); |
| if (row == 0) |
| continue; |
| for (int32_t j = 0; j < numCategories; j++) { |
| stateTable[p] = (int16_t)(rowNumMap[row[j]]); |
| ++p; |
| } |
| endStates[p2++] = ((row[numCategories] & 0x8000) != 0); |
| } |
| } |
| |
| // and this section does it for the backward state table |
| else { |
| backwardsStateTable = new int16_t[newRowNum * numCategories]; |
| int32_t p = 0; |
| for (int32_t i = 0; i < tempStateTable.size(); i++) { |
| int16_t* row = (int16_t*)(tempStateTable.elementAt(i)); |
| if (row == 0) |
| continue; |
| for (int32_t j = 0; j < numCategories; j++) { |
| backwardsStateTable[p] = (int16_t)(rowNumMap[row[j]]); |
| ++p; |
| } |
| } |
| } |
| } |
| |
| /** |
| * This function builds the backward state table from the forward state |
| * table and any additional rules (identified by the ! on the front) |
| * supplied in the description |
| */ |
| void RuleBasedBreakIteratorBuilder::buildBackwardsStateTable(Vector tempRuleList) { |
| |
| // create the temporary state table and seed it with two rows (row 0 |
| // isn't used for anything, and we have to create row 1 (the initial |
| // state) before we can do anything else |
| tempStateTable = new Vector(); |
| tempStateTable.addElement(new int16_t[numCategories + 1]); |
| tempStateTable.addElement(new int16_t[numCategories + 1]); |
| |
| // although the backwards state table is built automatically from the forward |
| // state table, there are some situations (the default sentence-break rules, |
| // for example) where this doesn't yield enough stop states, causing a dramatic |
| // drop in performance. To help with these cases, the user may supply |
| // supplemental rules that are added to the backward state table. These have |
| // the same syntax as the normal break rules, but begin with '!' to distinguish |
| // them from normal break rules |
| for (int32_t i = 0; i < tempRuleList.size(); i++) { |
| UnicodeString rule = (UnicodeString)tempRuleList.elementAt(i); |
| if (rule.UCharAt(0) == '!') { |
| parseRule(rule.substring(1), FALSE); |
| } |
| } |
| backfillLoopingStates(); |
| |
| // Backwards iteration is qualitatively different from forwards iteration. |
| // This is because backwards iteration has to be made to operate from no context |
| // at all-- the user should be able to ask BreakIterator for the break position |
| // immediately on either side of some arbitrary offset in the text. The |
| // forward iteration table doesn't let us do that-- it assumes complete |
| // information on the context, which means starting from the beginning of the |
| // document. |
| // The way we do backward and random-access iteration is to back up from the |
| // current (or user-specified) position until we see something we're sure is |
| // a break position (it may not be the last break position immediately |
| // preceding our starting point, however). Then we roll forward from there to |
| // locate the actual break position we're after. |
| // This means that the backwards state table doesn't have to identify every |
| // break position, allowing the building algorithm to be much simpler. Here, |
| // we use a "pairs" approach, scanning the forward-iteration state table for |
| // pairs of character categories we ALWAYS break between, and building a state |
| // table from that information. No context is required-- all this state table |
| // looks at is a pair of adjacent characters. |
| |
| // It's possible that the user has supplied supplementary rules (see above). |
| // This has to be done first to keep parseRule() and friends from becoming |
| // EVEN MORE complicated. The automatically-generated states are appended |
| // onto the end of the state table, and then the two sets of rules are |
| // stitched together at the end. Take note of the row number of the |
| // first row of the auromatically-generated part. |
| int32_t backTableOffset = tempStateTable.size(); |
| if (backTableOffset > 2) |
| ++backTableOffset; |
| |
| // the automatically-generated part of the table models a two-dimensional |
| // array where the two dimensions represent the two characters we're currently |
| // looking at. To model this as a state table, we actually need one additional |
| // row to represent the initial state. It gets populated with the row numbers |
| // of the other rows (in order). |
| for (int32_t i = 0; i < numCategories + 1; i++) |
| tempStateTable.addElement(new int16_t[numCategories + 1]); |
| int16_t* state = (int16_t*)tempStateTable.elementAt(backTableOffset - 1); |
| for (int32_t i = 0; i < numCategories; i++) |
| state[i] = (int16_t)(i + backTableOffset); |
| |
| // scavenge the forward state table for pairs of character categories |
| // that always have a break between them. The algorithm is as follows: |
| // Look down each column in the state table. For each nonzero cell in |
| // that column, look up the row it points to. For each nonzero cell in |
| // that row, populate a cell in the backwards state table: the row number |
| // of that cell is the number of the column we were scanning (plus the |
| // offset that locates this sub-table), and the column number of that cell |
| // is the column number of the nonzero cell we just found. This cell is |
| // populated with its own column number (adjusted according to the actual |
| // location of the sub-table). This process will produce a state table |
| // whose behavior is the same as looking up successive pairs of characters |
| // in an array of Booleans to determine whether there is a break. |
| int32_t numRows = stateTable.length / numCategories; |
| for (int32_t column = 0; column < numCategories; column++) { |
| for (int32_t row = 0; row < numRows; row++) { |
| int32_t nextRow = lookupState(row, column); |
| if (nextRow != 0) { |
| for (int32_t nextColumn = 0; nextColumn < numCategories; nextColumn++) { |
| int32_t cellValue = lookupState(nextRow, nextColumn); |
| if (cellValue != 0) { |
| state = (int16_t*)tempStateTable.elementAt(nextColumn + |
| backTableOffset); |
| state[column] = (int16_t)(column + backTableOffset); |
| } |
| } |
| } |
| } |
| } |
| |
| // if the user specified some backward-iteration rules with the ! token, |
| // we have to merge the resulting state table with the auto-generated one |
| // above. First copy the populated cells from row 1 over the populated |
| // cells in the auto-generated table. Then copy values from row 1 of the |
| // auto-generated table into all of the the unpopulated cells of the |
| // rule-based table. |
| if (backTableOffset > 1) { |
| |
| // for every row in the auto-generated sub-table, if a cell is |
| // populated that is also populated in row 1 of the rule-based |
| // sub-table, copy the value from row 1 over the value in the |
| // auto-generated sub-table |
| state = (int16_t*)tempStateTable.elementAt(1); |
| for (int32_t i = backTableOffset - 1; i < tempStateTable.size(); i++) { |
| int16_t* state2 = (int16_t*)tempStateTable.elementAt(i); |
| for (int32_t j = 0; j < numCategories; j++) { |
| if (state[j] != 0 && state2[j] != 0) |
| state2[j] = state[j]; |
| } |
| } |
| |
| // now, for every row in the rule-based sub-table that is not |
| // an end state, fill in all unpopulated cells with the values |
| // of the corresponding cells in the first row of the auto- |
| // generated sub-table. |
| state = (int16_t*)tempStateTable.elementAt(backTableOffset - 1); |
| for (int32_t i = 1; i < backTableOffset - 1; i++) { |
| int16_t* state2 = (int16_t*)tempStateTable.elementAt(i); |
| if ((state2[numCategories] & 0x8000) == 0) { |
| for (int32_t j = 0; j < numCategories; j++) { |
| if (state2[j] == 0) |
| state2[j] = state[j]; |
| } |
| } |
| } |
| } |
| |
| // finally, clean everything up and copy it into the actual BreakIterator |
| // by calling finishBuildingStateTable() |
| finishBuildingStateTable(FALSE); |
| } |
| |
| /** |
| * Throws an IllegalArgumentException representing a syntax error in the rule |
| * description. The exception's message contains some debugging information. |
| * @param message A message describing the problem |
| * @param position The position in the description where the problem was |
| * discovered |
| * @param context The string containing the error |
| */ |
| void RuleBasedBreakIteratorBuilder::error(UnicodeString message, int32_t position, UnicodeString context) { |
| throw new IllegalArgumentException("Parse error: " + message + " at " + position |
| + " in " + context); |
| } |
