Transliterator is an abstract class that transliterates text from one format to another. The most common
* kind of transliterator is a script, or alphabet, transliterator. For example, a Russian to Latin transliterator
* changes Russian text written in Cyrillic characters to phonetically equivalent Latin characters. It does not
* translate Russian to English! Transliteration, unlike translation, operates on characters, without reference
* to the meanings of words and sentences.
*
*
* Although script conversion is its most common use, a transliterator can actually perform a more general class of
* tasks. In fact, Transliterator defines a very general API which specifies only that a segment of the
* input text is replaced by new text. The particulars of this conversion are determined entirely by subclasses of
* Transliterator.
*
*
* Transliterators are stateless * *
* Transliterator objects are stateless; they retain no information between calls to
* transliterate(). As a result, threads may share transliterators without synchronizing them. This might
* seem to limit the complexity of the transliteration operation. In practice, subclasses perform complex
* transliterations by delaying the replacement of text until it is known that no other replacements are possible. In
* other words, although the Transliterator objects are stateless, the source text itself embodies all the
* needed information, and delayed operation allows arbitrary complexity.
*
*
* Batch transliteration * *
* The simplest way to perform transliteration is all at once, on a string of existing text. This is referred to as
* batch transliteration. For example, given a string input and a transliterator t,
* the call
*
*
String result = t.transliterate(input);
* * Keyboard transliteration * *
* Somewhat more involved is keyboard, or incremental transliteration. This is the transliteration of text that * is arriving from some source (typically the user's keyboard) one character at a time, or in some other piecemeal * fashion. * *
* In keyboard transliteration, a Replaceable buffer stores the text. As text is inserted, as much as
* possible is transliterated on the fly. This means a GUI that displays the contents of the buffer may show text being
* modified as each new character arrives.
*
*
* Consider the simple rule-based Transliterator: * *
* th>{theta}
* t>{tau}
*
* t>|{tau}
* {tau}h>{theta}
* transliterate(). Typically, the cursor will be coincident with the insertion point, but in a
* case like the one above, it will precede the insertion point.
*
*
* Keyboard transliteration methods maintain a set of three indices that are updated with each call to
* transliterate(), including the cursor, start, and limit. These indices are changed by the method, and
* they are passed in and out via a Position object. The start index marks the beginning of the substring
* that the transliterator will look at. It is advanced as text becomes committed (but it is not the committed index;
* that's the cursor). The cursor index, described above, marks the point at which the
* transliterator last stopped, either because it reached the end, or because it required more characters to
* disambiguate between possible inputs. The cursor can also be explicitly set by rules.
* Any characters before the cursor index are frozen; future keyboard
* transliteration calls within this input sequence will not change them. New text is inserted at the limit
* index, which marks the end of the substring that the transliterator looks at.
*
*
* Because keyboard transliteration assumes that more characters are to arrive, it is conservative in its operation. It
* only transliterates when it can do so unambiguously. Otherwise it waits for more characters to arrive. When the
* client code knows that no more characters are forthcoming, perhaps because the user has performed some input
* termination operation, then it should call finishTransliteration() to complete any pending
* transliterations.
*
*
* Inverses * *
* Pairs of transliterators may be inverses of one another. For example, if transliterator A transliterates
* characters by incrementing their Unicode value (so "abc" -> "def"), and transliterator B decrements character
* values, then A is an inverse of B and vice versa. If we compose A with B in a compound
* transliterator, the result is the identity transliterator, that is, a transliterator that does not change its input
* text.
*
* The Transliterator method getInverse() returns a transliterator's inverse, if one exists,
* or null otherwise. However, the result of getInverse() usually will not be a true
* mathematical inverse. This is because true inverse transliterators are difficult to formulate. For example, consider
* two transliterators: AB, which transliterates the character 'A' to 'B', and BA, which transliterates
* 'B' to 'A'. It might seem that these are exact inverses, since
*
*
"A" x AB -> "B"* * where 'x' represents transliteration. However, * *
* "B" x BA -> "A"
"ABCD" x AB -> "BBCD"* * so AB composed with BA is not the identity. Nonetheless, BA may be usefully considered to be * AB's inverse, and it is on this basis that AB
* "BBCD" x BA -> "AACD"
.getInverse() could legitimately return
* BA.
*
* * Filtering *
Each transliterator has a filter, which restricts changes to those characters selected by the filter. The * filter affects just the characters that are changed -- the characters outside of the filter are still part of the * context for the filter. For example, in the following even though 'x' is filtered out, and doesn't convert to y, it does affect the conversion of 'a'. * *
* String rules = "x > y; x{a} > b; ";
* Transliterator tempTrans = Transliterator.createFromRules("temp", rules, Transliterator.FORWARD);
* tempTrans.setFilter(new UnicodeSet("[a]"));
* String tempResult = tempTrans.transform("xa");
* // results in "xb"
*
* * IDs and display names * *
* A transliterator is designated by a short identifier string or ID. IDs follow the format * source-destination, where source describes the entity being replaced, and destination * describes the entity replacing source. The entities may be the names of scripts, particular sequences of * characters, or whatever else it is that the transliterator converts to or from. For example, a transliterator from * Russian to Latin might be named "Russian-Latin". A transliterator from keyboard escape sequences to Latin-1 * characters might be named "KeyboardEscape-Latin1". By convention, system entity names are in English, with the * initial letters of words capitalized; user entity names may follow any format so long as they do not contain dashes. * *
* In addition to programmatic IDs, transliterator objects have display names for presentation in user interfaces, * returned by {@link #getDisplayName}. * *
* Composed transliterators * *
* In addition to built-in system transliterators like "Latin-Greek", there are also built-in composed * transliterators. These are implemented by composing two or more component transliterators. For example, if we have * scripts "A", "B", "C", and "D", and we want to transliterate between all pairs of them, then we need to write 12 * transliterators: "A-B", "A-C", "A-D", "B-A",..., "D-A", "D-B", "D-C". If it is possible to convert all scripts to an * intermediate script "M", then instead of writing 12 rule sets, we only need to write 8: "A~M", "B~M", "C~M", "D~M", * "M~A", "M~B", "M~C", "M~D". (This might not seem like a big win, but it's really 2n vs. n * 2 - n, so as n gets larger the gain becomes significant. With 9 scripts, it's 18 vs. 72 * rule sets, a big difference.) Note the use of "~" rather than "-" for the script separator here; this indicates that * the given transliterator is intended to be composed with others, rather than be used as is. * *
* Composed transliterators can be instantiated as usual. For example, the system transliterator "Devanagari-Gujarati" * is a composed transliterator built internally as "Devanagari~InterIndic;InterIndic~Gujarati". When this * transliterator is instantiated, it appears externally to be a standard transliterator (e.g., getID() returns * "Devanagari-Gujarati"). * *
Rule syntax * *
A set of rules determines how to perform translations. * Rules within a rule set are separated by semicolons (';'). * To include a literal semicolon, prefix it with a backslash ('\'). * Unicode Pattern_White_Space is ignored. * If the first non-blank character on a line is '#', * the entire line is ignored as a comment. * *
Each set of rules consists of two groups, one forward, and one * reverse. This is a convention that is not enforced; rules for one * direction may be omitted, with the result that translations in * that direction will not modify the source text. In addition, * bidirectional forward-reverse rules may be specified for * symmetrical transformations. * *
Note: Another description of the Transliterator rule syntax is available in * section * Transform Rules Syntax of UTS #35: Unicode LDML. * The rules are shown there using arrow symbols ← and → and ↔. * ICU supports both those and the equivalent ASCII symbols < and > and <>. * *
Rule statements take one of the following forms: * *
$alefmadda=\\u0622;$alefmadda", will be replaced by
* the Unicode character U+0622. Variable names must begin
* with a letter and consist only of letters, digits, and
* underscores. Case is significant. Duplicate names cause
* an exception to be thrown, that is, variables cannot be
* redefined. The right hand side may contain well-formed
* text of any length, including no text at all ("$empty=;").
* The right hand side may contain embedded UnicodeSet
* patterns, for example, "$softvowel=[eiyEIY]".ai>$alefmadda;ai<$alefmadda;ai<>$alefmadda;Translation rules consist of a match pattern and an output
* string. The match pattern consists of literal characters,
* optionally preceded by context, and optionally followed by
* context. Context characters, like literal pattern characters,
* must be matched in the text being transliterated. However, unlike
* literal pattern characters, they are not replaced by the output
* text. For example, the pattern "abc{def}"
* indicates the characters "def" must be
* preceded by "abc" for a successful match.
* If there is a successful match, "def" will
* be replaced, but not "abc". The final '}'
* is optional, so "abc{def" is equivalent to
* "abc{def}". Another example is "{123}456"
* (or "123}456") in which the literal
* pattern "123" must be followed by "456".
*
*
The output string of a forward or reverse rule consists of
* characters to replace the literal pattern characters. If the
* output string contains the character '|', this is
* taken to indicate the location of the cursor after
* replacement. The cursor is the point in the text at which the
* next replacement, if any, will be applied. The cursor is usually
* placed within the replacement text; however, it can actually be
* placed into the precending or following context by using the
* special character '@'. Examples:
*
*
* a {foo} z > | @ bar; # foo -> bar, move cursor before a
* {foo} xyz > bar @@|; # foo -> bar, cursor between y and z
*
*
* UnicodeSet * *
UnicodeSet patterns may appear anywhere that
* makes sense. They may appear in variable definitions.
* Contrariwise, UnicodeSet patterns may themselves
* contain variable references, such as "$a=[a-z];$not_a=[^$a]",
* or "$range=a-z;$ll=[$range]".
*
*
UnicodeSet patterns may also be embedded directly
* into rule strings. Thus, the following two rules are equivalent:
*
*
* $vowel=[aeiou]; $vowel>'*'; # One way to do this * [aeiou]>'*'; # Another way ** *
See {@link UnicodeSet} for more documentation and examples. * *
Segments * *
Segments of the input string can be matched and copied to the * output string. This makes certain sets of rules simpler and more * general, and makes reordering possible. For example: * *
* ([a-z]) > $1 $1; # double lowercase letters * ([:Lu:]) ([:Ll:]) > $2 $1; # reverse order of Lu-Ll pairs ** *
The segment of the input string to be copied is delimited by
* "(" and ")". Up to
* nine segments may be defined. Segments may not overlap. In the
* output string, "$1" through "$9"
* represent the input string segments, in left-to-right order of
* definition.
*
*
Anchors * *
Patterns can be anchored to the beginning or the end of the text. This is done with the
* special characters '^' and '$'. For example:
*
*
* ^ a > 'BEG_A'; # match 'a' at start of text * a > 'A'; # match other instances of 'a' * z $ > 'END_Z'; # match 'z' at end of text * z > 'Z'; # match other instances of 'z' ** *
It is also possible to match the beginning or the end of the text using a UnicodeSet.
* This is done by including a virtual anchor character '$' at the end of the
* set pattern. Although this is usually the match character for the end anchor, the set will
* match either the beginning or the end of the text, depending on its placement. For
* example:
*
*
* $x = [a-z$]; # match 'a' through 'z' OR anchor * $x 1 > 2; # match '1' after a-z or at the start * 3 $x > 4; # match '3' before a-z or at the end ** *
Example * *
The following example rules illustrate many of the features of * the rule language. * *
| Rule 1. | *abc{def}>x|y |
*
| Rule 2. | *xyz>r |
*
| Rule 3. | *yz>q |
*
Applying these rules to the string "adefabcdefz"
* yields the following results:
*
*
|adefabcdefz |
* Initial state, no rules match. Advance * cursor. | *
a|defabcdefz |
* Still no match. Rule 1 does not match * because the preceding context is not present. | *
ad|efabcdefz |
* Still no match. Keep advancing until * there is a match... | *
ade|fabcdefz |
* ... | *
adef|abcdefz |
* ... | *
adefa|bcdefz |
* ... | *
adefab|cdefz |
* ... | *
adefabc|defz |
* Rule 1 matches; replace "def"
* with "xy" and back up the cursor
* to before the 'y'. |
*
adefabcx|yz |
* Although "xyz" is
* present, rule 2 does not match because the cursor is
* before the 'y', not before the 'x'.
* Rule 3 does match. Replace "yz"
* with "q". |
*
adefabcxq| |
* The cursor is at the end; * transliteration is complete. | *
The order of rules is significant. If multiple rules may match * at some point, the first matching rule is applied. * *
Forward and reverse rules may have an empty output string. * Otherwise, an empty left or right hand side of any statement is a * syntax error. * *
Single quotes are used to quote any character other than a
* digit or letter. To specify a single quote itself, inside or
* outside of quotes, use two single quotes in a row. For example,
* the rule "'>'>o''clock" changes the
* string ">" to the string "o'clock".
*
*
Notes * *
While a Transliterator is being built from rules, it checks that * the rules are added in proper order. For example, if the rule * "a>x" is followed by the rule "ab>y", * then the second rule will throw an exception. The reason is that * the second rule can never be triggered, since the first rule * always matches anything it matches. In other words, the first * rule masks the second rule. * * @author Alan Liu */ public abstract class Transliterator implements StringTransform { /** * Direction constant indicating the forward direction in a transliterator, * e.g., the forward rules of a rule-based Transliterator. An "A-B" * transliterator transliterates A to B when operating in the forward * direction, and B to A when operating in the reverse direction. */ public static final int FORWARD = 0; /** * Direction constant indicating the reverse direction in a transliterator, * e.g., the reverse rules of a rule-based Transliterator. An "A-B" * transliterator transliterates A to B when operating in the forward * direction, and B to A when operating in the reverse direction. */ public static final int REVERSE = 1; /** * Position structure for incremental transliteration. This data * structure defines two substrings of the text being * transliterated. The first region, [contextStart, * contextLimit), defines what characters the transliterator will * read as context. The second region, [start, limit), defines * what characters will actually be transliterated. The second * region should be a subset of the first. * *
After a transliteration operation, some of the indices in this * structure will be modified. See the field descriptions for * details. * *
contextStart <= start <= limit <= contextLimit * *
Note: All index values in this structure must be at code point
* boundaries. That is, none of them may occur between two code units
* of a surrogate pair. If any index does split a surrogate pair,
* results are unspecified.
*/
public static class Position {
/**
* Beginning index, inclusive, of the context to be considered for
* a transliteration operation. The transliterator will ignore
* anything before this index. INPUT/OUTPUT parameter: This parameter
* is updated by a transliteration operation to reflect the maximum
* amount of antecontext needed by a transliterator.
*/
public int contextStart;
/**
* Ending index, exclusive, of the context to be considered for a
* transliteration operation. The transliterator will ignore
* anything at or after this index. INPUT/OUTPUT parameter: This
* parameter is updated to reflect changes in the length of the
* text, but points to the same logical position in the text.
*/
public int contextLimit;
/**
* Beginning index, inclusive, of the text to be transliteratd.
* INPUT/OUTPUT parameter: This parameter is advanced past
* characters that have already been transliterated by a
* transliteration operation.
*/
public int start;
/**
* Ending index, exclusive, of the text to be transliteratd.
* INPUT/OUTPUT parameter: This parameter is updated to reflect
* changes in the length of the text, but points to the same
* logical position in the text.
*/
public int limit;
/**
* Constructs a Position object with start, limit,
* contextStart, and contextLimit all equal to zero.
*/
public Position() {
this(0, 0, 0, 0);
}
/**
* Constructs a Position object with the given start,
* contextStart, and contextLimit. The limit is set to the
* contextLimit.
*/
public Position(int contextStart, int contextLimit, int start) {
this(contextStart, contextLimit, start, contextLimit);
}
/**
* Constructs a Position object with the given start, limit,
* contextStart, and contextLimit.
*/
public Position(int contextStart, int contextLimit,
int start, int limit) {
this.contextStart = contextStart;
this.contextLimit = contextLimit;
this.start = start;
this.limit = limit;
}
/**
* Constructs a Position object that is a copy of another.
*/
public Position(Position pos) {
set(pos);
}
/**
* Copies the indices of this position from another.
*/
public void set(Position pos) {
contextStart = pos.contextStart;
contextLimit = pos.contextLimit;
start = pos.start;
limit = pos.limit;
}
/**
* Returns true if this Position is equal to the given object.
*/
@Override
public boolean equals(Object obj) {
if (obj instanceof Position) {
Position pos = (Position) obj;
return contextStart == pos.contextStart &&
contextLimit == pos.contextLimit &&
start == pos.start &&
limit == pos.limit;
}
return false;
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
return Objects.hash(contextStart, contextLimit, start, limit);
}
/**
* Returns a string representation of this Position.
* @return a string representation of the object.
*/
@Override
public String toString() {
return "[cs=" + contextStart
+ ", s=" + start
+ ", l=" + limit
+ ", cl=" + contextLimit
+ "]";
}
/**
* Check all bounds. If they are invalid, throw an exception.
* @param length the length of the string this object applies to
* @exception IllegalArgumentException if any indices are out
* of bounds
*/
public final void validate(int length) {
if (contextStart < 0 ||
start < contextStart ||
limit < start ||
contextLimit < limit ||
length < contextLimit) {
throw new IllegalArgumentException("Invalid Position {cs=" +
contextStart + ", s=" +
start + ", l=" +
limit + ", cl=" +
contextLimit + "}, len=" +
length);
}
}
}
/**
* Programmatic name, e.g., "Latin-Arabic".
*/
private String ID;
/**
* This transliterator's filter. Any character for which
* filter.contains() returns false will not be
* altered by this transliterator. If filter is
* null then no filtering is applied.
*/
private UnicodeSet filter;
private int maximumContextLength = 0;
/**
* System transliterator registry.
*/
private static TransliteratorRegistry registry;
private static Map Upon return, values in Typical usage of this method begins with an initial call
* with This method assumes that future calls may be made that will
* insert new text into the buffer. As a result, it only performs
* unambiguous transliterations. After the last call to this
* method, there may be untransliterated text that is waiting for
* more input to resolve an ambiguity. In order to perform these
* pending transliterations, clients should call {@link
* #finishTransliteration} after the last call to this
* method has been made.
*
* @param text the buffer holding transliterated and untransliterated text
* @param index the start and limit of the text, the position
* of the cursor, and the start and limit of transliteration.
* @param insertion text to be inserted and possibly
* transliterated into the translation buffer at
* Implementations of this method should also obey the
* following invariants: Subclasses may safely assume that all characters in
* [ This method is not for public consumption. Calling
* this method directly will transliterate
* [
*
* @param text the buffer holding transliterated and
* untransliterated text
*
* @param pos the indices indicating the start, limit, context
* start, and context limit of the text.
*
* @param incremental if true, assume more text may be inserted at
* If this transliterator has a filter, break up the input text into runs
* of unfiltered characters. Pass each run to
* In incremental mode, if rollback is true, perform a special
* incremental procedure in which several passes are made over the input
* text, adding one character at a time, and committing successful
* transliterations as they occur. Unsuccessful transliterations are rolled
* back and retried with additional characters to give correct results.
*
* @param text the text to be transliterated
* @param index the position indices
* @param incremental if true, then assume more characters may be inserted
* at index.limit, and postpone processing to accommodate future incoming
* characters
* @param rollback if true and if incremental is true, then perform special
* incremental processing, as described above, and undo partial
* transliterations where necessary. If incremental is false then this
* parameter is ignored.
*/
private void filteredTransliterate(Replaceable text,
Position index,
boolean incremental,
boolean rollback) {
// Short circuit path for transliterators with no filter in
// non-incremental mode.
if (filter == null && !rollback) {
handleTransliterate(text, index, incremental);
return;
}
//----------------------------------------------------------------------
// This method processes text in two groupings:
//
// RUNS -- A run is a contiguous group of characters which are contained
// in the filter for this transliterator (filter.contains(ch) == true).
// Text outside of runs may appear as context but it is not modified.
// The start and limit Position values are narrowed to each run.
//
// PASSES (incremental only) -- To make incremental mode work correctly,
// each run is broken up into n passes, where n is the length (in code
// points) of the run. Each pass contains the first n characters. If a
// pass is completely transliterated, it is committed, and further passes
// include characters after the committed text. If a pass is blocked,
// and does not transliterate completely, then this method rolls back
// the changes made during the pass, extends the pass by one code point,
// and tries again.
//----------------------------------------------------------------------
// globalLimit is the limit value for the entire operation. We
// set index.limit to the end of each unfiltered run before
// calling handleTransliterate(), so we need to maintain the real
// value of index.limit here. After each transliteration, we
// update globalLimit for insertions or deletions that have
// happened.
int globalLimit = index.limit;
// If there is a non-null filter, then break the input text up. Say the
// input text has the form:
// xxxabcxxdefxx
// where 'x' represents a filtered character (filter.contains('x') ==
// false). Then we break this up into:
// xxxabc xxdef xx
// Each pass through the loop consumes a run of filtered
// characters (which are ignored) and a subsequent run of
// unfiltered characters (which are transliterated).
StringBuffer log = null;
if (DEBUG) {
log = new StringBuffer();
}
for (;;) {
if (filter != null) {
// Narrow the range to be transliterated to the first run
// of unfiltered characters at or after index.start.
// Advance past filtered chars
int c;
while (index.start < globalLimit &&
!filter.contains(c=text.char32At(index.start))) {
index.start += UTF16.getCharCount(c);
}
// Find the end of this run of unfiltered chars
index.limit = index.start;
while (index.limit < globalLimit &&
filter.contains(c=text.char32At(index.limit))) {
index.limit += UTF16.getCharCount(c);
}
}
// Check to see if the unfiltered run is empty. This only
// happens at the end of the string when all the remaining
// characters are filtered.
if (index.start == index.limit) {
break;
}
// Is this run incremental? If there is additional
// filtered text (if limit < globalLimit) then we pass in
// an incremental value of false to force the subclass to
// complete the transliteration for this run.
boolean isIncrementalRun =
(index.limit < globalLimit ? false : incremental);
int delta;
// Implement rollback. To understand the need for rollback,
// consider the following transliterator:
//
// "t" is "a > A;"
// "u" is "A > b;"
// "v" is a compound of "t; NFD; u" with a filter [:Ll:]
//
// Now apply "v" to the input text "a". The result is "b". But if
// the transliteration is done incrementally, then the NFD holds
// things up after "t" has already transformed "a" to "A". When
// finishTransliterate() is called, "A" is _not_ processed because
// it gets excluded by the [:Ll:] filter, and the end result is "A"
// -- incorrect. The problem is that the filter is applied to a
// partially-transliterated result, when we only want it to apply to
// input text. Although this example describes a compound
// transliterator containing NFD and a specific filter, it can
// happen with any transliterator which does a partial
// transformation in incremental mode into characters outside its
// filter.
//
// To handle this, when in incremental mode we supply characters to
// handleTransliterate() in several passes. Each pass adds one more
// input character to the input text. That is, for input "ABCD", we
// first try "A", then "AB", then "ABC", and finally "ABCD". If at
// any point we block (upon return, start < limit) then we roll
// back. If at any point we complete the run (upon return start ==
// limit) then we commit that run.
if (rollback && isIncrementalRun) {
if (DEBUG) {
log.setLength(0);
System.out.println("filteredTransliterate{"+getID()+"}i: IN=" +
UtilityExtensions.formatInput(text, index));
}
int runStart = index.start;
int runLimit = index.limit;
int runLength = runLimit - runStart;
// Make a rollback copy at the end of the string
int rollbackOrigin = text.length();
text.copy(runStart, runLimit, rollbackOrigin);
// Variables reflecting the commitment of completely
// transliterated text. passStart is the runStart, advanced
// past committed text. rollbackStart is the rollbackOrigin,
// advanced past rollback text that corresponds to committed
// text.
int passStart = runStart;
int rollbackStart = rollbackOrigin;
// The limit for each pass; we advance by one code point with
// each iteration.
int passLimit = index.start;
// Total length, in 16-bit code units, of uncommitted text.
// This is the length to be rolled back.
int uncommittedLength = 0;
// Total delta (change in length) for all passes
int totalDelta = 0;
// PASS MAIN LOOP -- Start with a single character, and extend
// the text by one character at a time. Roll back partial
// transliterations and commit complete transliterations.
for (;;) {
// Length of additional code point, either one or two
int charLength =
UTF16.getCharCount(text.char32At(passLimit));
passLimit += charLength;
if (passLimit > runLimit) {
break;
}
uncommittedLength += charLength;
index.limit = passLimit;
if (DEBUG) {
log.setLength(0);
log.append("filteredTransliterate{"+getID()+"}i: ");
UtilityExtensions.formatInput(log, text, index);
}
// Delegate to subclass for actual transliteration. Upon
// return, start will be updated to point after the
// transliterated text, and limit and contextLimit will be
// adjusted for length changes.
handleTransliterate(text, index, true);
if (DEBUG) {
log.append(" => ");
UtilityExtensions.formatInput(log, text, index);
}
delta = index.limit - passLimit; // change in length
// We failed to completely transliterate this pass.
// Roll back the text. Indices remain unchanged; reset
// them where necessary.
if (index.start != index.limit) {
// Find the rollbackStart, adjusted for length changes
// and the deletion of partially transliterated text.
int rs = rollbackStart + delta - (index.limit - passStart);
// Delete the partially transliterated text
text.replace(passStart, index.limit, "");
// Copy the rollback text back
text.copy(rs, rs + uncommittedLength, passStart);
// Restore indices to their original values
index.start = passStart;
index.limit = passLimit;
index.contextLimit -= delta;
if (DEBUG) {
log.append(" (ROLLBACK)");
}
}
// We did completely transliterate this pass. Update the
// commit indices to record how far we got. Adjust indices
// for length change.
else {
// Move the pass indices past the committed text.
passStart = passLimit = index.start;
// Adjust the rollbackStart for length changes and move
// it past the committed text. All characters we've
// processed to this point are committed now, so zero
// out the uncommittedLength.
rollbackStart += delta + uncommittedLength;
uncommittedLength = 0;
// Adjust indices for length changes.
runLimit += delta;
totalDelta += delta;
}
if (DEBUG) {
System.out.println(Utility.escape(log.toString()));
}
}
// Adjust overall limit and rollbackOrigin for insertions and
// deletions. Don't need to worry about contextLimit because
// handleTransliterate() maintains that.
rollbackOrigin += totalDelta;
globalLimit += totalDelta;
// Delete the rollback copy
text.replace(rollbackOrigin, rollbackOrigin + runLength, "");
// Move start past committed text
index.start = passStart;
}
else {
// Delegate to subclass for actual transliteration.
if (DEBUG) {
log.setLength(0);
log.append("filteredTransliterate{"+getID()+"}: ");
UtilityExtensions.formatInput(log, text, index);
}
int limit = index.limit;
handleTransliterate(text, index, isIncrementalRun);
delta = index.limit - limit; // change in length
if (DEBUG) {
log.append(" => ");
UtilityExtensions.formatInput(log, text, index);
}
// In a properly written transliterator, start == limit after
// handleTransliterate() returns when incremental is false.
// Catch cases where the subclass doesn't do this, and throw
// an exception. (Just pinning start to limit is a bad idea,
// because what's probably happening is that the subclass
// isn't transliterating all the way to the end, and it should
// in non-incremental mode.)
if (!isIncrementalRun && index.start != index.limit) {
throw new RuntimeException("ERROR: Incomplete non-incremental transliteration by " + getID());
}
// Adjust overall limit for insertions/deletions. Don't need
// to worry about contextLimit because handleTransliterate()
// maintains that.
globalLimit += delta;
if (DEBUG) {
System.out.println(Utility.escape(log.toString()));
}
}
if (filter == null || isIncrementalRun) {
break;
}
// If we did completely transliterate this
// run, then repeat with the next unfiltered run.
}
// Start is valid where it is. Limit needs to be put back where
// it was, modulo adjustments for deletions/insertions.
index.limit = globalLimit;
if (DEBUG) {
System.out.println("filteredTransliterate{"+getID()+"}: OUT=" +
UtilityExtensions.formatInput(text, index));
}
}
/**
* Transliterate a substring of text, as specified by index, taking filters
* into account. This method is for subclasses that need to delegate to
* another transliterator.
* @param text the text to be transliterated
* @param index the position indices
* @param incremental if true, then assume more characters may be inserted
* at index.limit, and postpone processing to accommodate future incoming
* characters
*/
public void filteredTransliterate(Replaceable text,
Position index,
boolean incremental) {
filteredTransliterate(text, index, incremental, false);
}
/**
* Returns the length of the longest context required by this transliterator.
* This is preceding context. The default value is zero, but
* subclasses can change this by calling If no localized names exist in the system resource bundles,
* a name is synthesized using a localized
* If no localized names exist in the system resource bundles,
* a name is synthesized using a localized
* Callers must take care if a transliterator is in use by
* multiple threads. The filter should not be changed by one
* thread while another thread may be transliterating.
*/
public void setFilter(UnicodeFilter filter) {
if (filter == null) {
this.filter = null;
} else {
try {
// fast high-runner case
this.filter = new UnicodeSet((UnicodeSet)filter).freeze();
} catch (Exception e) {
this.filter = new UnicodeSet();
filter.addMatchSetTo(this.filter);
this.filter.freeze();
}
}
}
/**
* Returns a SHOULD BE OVERRIDDEN BY SUBCLASSES.
* It is probably an error for any transliterator to NOT override this, but we can't force them to
* for backwards compatibility.
* Other methods vector through this.
* When gathering the information on source and target, the compound transliterator makes things complicated.
* For example, suppose we have:
* There is another complication:
* Subclasses with knowledge of their inverse may wish to
* override this method.
*
* @return a transliterator that is an inverse, not necessarily
* exact, of this transliterator, or Because ICU may choose to cache Transliterator objects internally, this must
* be called at application startup, prior to any calls to
* Transliterator.getInstance to avoid undefined behavior.
*
* @param ID the ID of this transliterator
* @param factory the factory object
* @hide unsupported on Android
*/
public static void registerFactory(String ID, Factory factory) {
registry.put(ID, factory, true);
}
/**
* Register a Transliterator object with the given ID.
*
* Because ICU may choose to cache Transliterator objects internally, this must
* be called at application startup, prior to any calls to
* Transliterator.getInstance to avoid undefined behavior.
*
* @param trans the Transliterator object
* @hide unsupported on Android
*/
public static void registerInstance(Transliterator trans) {
registry.put(trans.getID(), trans, true);
}
/**
* Register a Transliterator object.
*
* Because ICU may choose to cache Transliterator objects internally, this must
* be called at application startup, prior to any calls to
* Transliterator.getInstance to avoid undefined behavior.
*
* @param trans the Transliterator object
*/
static void registerInstance(Transliterator trans, boolean visible) {
registry.put(trans.getID(), trans, visible);
}
/**
* Register an ID as an alias of another ID. Instantiating
* alias ID produces the same result as instantiating the original ID.
* This is generally used to create short aliases of compound IDs.
*
* Because ICU may choose to cache Transliterator objects internally, this must
* be called at application startup, prior to any calls to
* Transliterator.getInstance to avoid undefined behavior.
*
* @param aliasID The new ID being registered.
* @param realID The existing ID that the new ID should be an alias of.
* @hide unsupported on Android
*/
public static void registerAlias(String aliasID, String realID) {
registry.put(aliasID, realID, true);
}
/**
* Register two targets as being inverses of one another. For
* example, calling registerSpecialInverse("NFC", "NFD", true) causes
* Transliterator to form the following inverse relationships:
*
* The relationship is symmetrical; registering (a, b) is
* equivalent to registering (b, a).
*
* The relevant IDs must still be registered separately as
* factories or classes.
*
* Only the targets are specified. Special inverses always
* have the form Any-Target1 <=> Any-Target2. The target should
* have canonical casing (the casing desired to be produced when
* an inverse is formed) and should contain no whitespace or other
* extraneous characters.
*
* @param target the target against which to register the inverse
* @param inverseTarget the inverse of target, that is
* Any-target.getInverse() => Any-inverseTarget
* @param bidirectional if true, register the reverse relation
* as well, that is, Any-inverseTarget.getInverse() => Any-target
*/
static void registerSpecialInverse(String target,
String inverseTarget,
boolean bidirectional) {
TransliteratorIDParser.registerSpecialInverse(target, inverseTarget, bidirectional);
}
/**
* Unregisters a transliterator or class. This may be either
* a system transliterator or a user transliterator or class.
*
* @param ID the ID of the transliterator or class
* @see #registerClass
* @hide unsupported on Android
*/
public static void unregister(String ID) {
displayNameCache.remove(new CaseInsensitiveString(ID));
registry.remove(ID);
}
/**
* Returns an enumeration over the programmatic names of registered
* 0 <= start
* <= limit.
* @param limit the ending index, exclusive; start <= limit
* <= text.length().
* @return The new limit index. The text previously occupying [start,
* limit) has been transliterated, possibly to a string of a different
* length, at [start, new-limit), where
* new-limit is the return value. If the input offsets are out of bounds,
* the returned value is -1 and the input string remains unchanged.
*/
public final int transliterate(Replaceable text, int start, int limit) {
if (start < 0 ||
limit < start ||
text.length() < limit) {
return -1;
}
Position pos = new Position(start, limit, start);
filteredTransliterate(text, pos, false, true);
return pos.limit;
}
/**
* Transliterates an entire string in place. Convenience method.
* @param text the string to be transliterated
*/
public final void transliterate(Replaceable text) {
transliterate(text, 0, text.length());
}
/**
* Transliterate an entire string and returns the result. Convenience method.
*
* @param text the string to be transliterated
* @return The transliterated text
*/
public final String transliterate(String text) {
ReplaceableString result = new ReplaceableString(text);
transliterate(result);
return result.toString();
}
/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly after new text has been inserted,
* typically as a result of a keyboard event. The new text in
* insertion will be inserted into text
* at index.contextLimit, advancing
* index.contextLimit by insertion.length().
* Then the transliterator will try to transliterate characters of
* text between index.start and
* index.contextLimit. Characters before
* index.start will not be changed.
*
* index will be updated.
* index.contextStart will be advanced to the first
* character that future calls to this method will read.
* index.start and index.contextLimit will
* be adjusted to delimit the range of text that future calls to
* this method may change.
*
* index.contextStart and index.contextLimit
* set to indicate the portion of text to be
* transliterated, and index.start == index.contextStart.
* Thereafter, index can be used without
* modification in future calls, provided that all changes to
* text are made via this method.
*
* index.contextLimit. If null then no text
* is inserted.
* @exception IllegalArgumentException if index
* is invalid
*/
public final void transliterate(Replaceable text, Position index,
String insertion) {
index.validate(text.length());
// int originalStart = index.contextStart;
if (insertion != null) {
text.replace(index.limit, index.limit, insertion);
index.limit += insertion.length();
index.contextLimit += insertion.length();
}
if (index.limit > 0 &&
UTF16.isLeadSurrogate(text.charAt(index.limit - 1))) {
// Oops, there is a dangling lead surrogate in the buffer.
// This will break most transliterators, since they will
// assume it is part of a pair. Don't transliterate until
// more text comes in.
return;
}
filteredTransliterate(text, index, true, true);
// TODO
// This doesn't work once we add quantifier support. Need to rewrite
// this code to support quantifiers and 'use maximum backup index.contextLimit.
* @see #transliterate(Replaceable, Transliterator.Position, String)
*/
public final void transliterate(Replaceable text, Position index,
int insertion) {
transliterate(text, index, UTF16.valueOf(insertion));
}
/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly. This is a convenience method; see
* {@link #transliterate(Replaceable, Transliterator.Position,
* String)} for details.
* @param text the buffer holding transliterated and
* untransliterated text
* @param index the start and limit of the text, the position
* of the cursor, and the start and limit of transliteration.
* @see #transliterate(Replaceable, Transliterator.Position, String)
*/
public final void transliterate(Replaceable text, Position index) {
transliterate(text, index, null);
}
/**
* Finishes any pending transliterations that were waiting for
* more characters. Clients should call this method as the last
* call after a sequence of one or more calls to
* transliterate().
* @param text the buffer holding transliterated and
* untransliterated text.
* @param index the array of indices previously passed to {@link
* #transliterate}
*/
public final void finishTransliteration(Replaceable text,
Position index) {
index.validate(text.length());
filteredTransliterate(text, index, false, true);
}
/**
* Abstract method that concrete subclasses define to implement
* their transliteration algorithm. This method handles both
* incremental and non-incremental transliteration. Let
* originalStart refer to the value of
* pos.start upon entry.
*
*
*
*
* incremental is false, then this method
* should transliterate all characters between
* pos.start and pos.limit. Upon return
* pos.start must == pos.limit.incremental is true, then this method
* should transliterate all characters between
* pos.start and pos.limit that can be
* unambiguously transliterated, regardless of future insertions
* of text at pos.limit. Upon return,
* pos.start should be in the range
* [originalStart, pos.limit).
* pos.start should be positioned such that
* characters [originalStart,
* pos.start) will not be changed in the future by this
* transliterator and characters [pos.start,
* pos.limit) are unchanged.
*
*
* pos.limit and pos.contextLimit
* should be updated to reflect changes in length of the text
* between pos.start and pos.limit. The
* difference pos.contextLimit - pos.limit should
* not change.pos.contextStart should not change.pos.start nor
* pos.limit should be less than
* originalStart.originalStart and text after
* pos.limit should not change.pos.contextStart and text after
* pos.contextLimit should be ignored.pos.start, pos.limit) are filtered.
* In other words, the filter has already been applied by the time
* this method is called. See
* filteredTransliterate().
*
* pos.start, pos.limit) without
* applying the filter. End user code should call
* transliterate() instead of this method. Subclass code
* should call filteredTransliterate() instead of
* this method.pos.limit and act accordingly. Otherwise,
* transliterate all text between pos.start and
* pos.limit and move pos.start up to
* pos.limit.
*
* @see #transliterate
* @hide unsupported on Android
*/
protected abstract void handleTransliterate(Replaceable text,
Position pos, boolean incremental);
/**
* Top-level transliteration method, handling filtering, incremental and
* non-incremental transliteration, and rollback. All transliteration
* public API methods eventually call this method with a rollback argument
* of true. Other entities may call this method but rollback should be
* false.
*
* setMaximumContextLength().
* For example, if a transliterator translates "ddd" (where
* d is any digit) to "555" when preceded by "(ddd)", then the preceding
* context length is 5, the length of "(ddd)".
*
* @return The maximum number of preceding context characters this
* transliterator needs to examine
*/
public final int getMaximumContextLength() {
return maximumContextLength;
}
/**
* Method for subclasses to use to set the maximum context length.
* @see #getMaximumContextLength
* @hide unsupported on Android
*/
protected void setMaximumContextLength(int a) {
if (a < 0) {
throw new IllegalArgumentException("Invalid context length " + a);
}
maximumContextLength = a;
}
/**
* Returns a programmatic identifier for this transliterator.
* If this identifier is passed to getInstance(), it
* will return this object, if it has been registered.
* @see #getAvailableIDs
*/
public final String getID() {
return ID;
}
/**
* Set the programmatic identifier for this transliterator. Only
* for use by subclasses.
* @hide unsupported on Android
*/
protected final void setID(String id) {
ID = id;
}
/**
* Returns a name for this transliterator that is appropriate for
* display to the user in the default DISPLAY locale. See {@link
* #getDisplayName(String,Locale)} for details.
* @see android.icu.util.ULocale.Category#DISPLAY
*/
public final static String getDisplayName(String ID) {
return getDisplayName(ID, ULocale.getDefault(Category.DISPLAY));
}
/**
* Returns a name for this transliterator that is appropriate for
* display to the user in the given locale. This name is taken
* from the locale resource data in the standard manner of the
* java.text package.
*
* MessageFormat pattern from the resource data. The
* arguments to this pattern are an integer followed by one or two
* strings. The integer is the number of strings, either 1 or 2.
* The strings are formed by splitting the ID for this
* transliterator at the first '-'. If there is no '-', then the
* entire ID forms the only string.
* @param inLocale the Locale in which the display name should be
* localized.
* @see java.text.MessageFormat
*/
public static String getDisplayName(String id, Locale inLocale) {
return getDisplayName(id, ULocale.forLocale(inLocale));
}
/**
* Returns a name for this transliterator that is appropriate for
* display to the user in the given locale. This name is taken
* from the locale resource data in the standard manner of the
* java.text package.
*
* MessageFormat pattern from the resource data. The
* arguments to this pattern are an integer followed by one or two
* strings. The integer is the number of strings, either 1 or 2.
* The strings are formed by splitting the ID for this
* transliterator at the first '-'. If there is no '-', then the
* entire ID forms the only string.
* @param inLocale the ULocale in which the display name should be
* localized.
* @see java.text.MessageFormat
*/
public static String getDisplayName(String id, ULocale inLocale) {
// Resource bundle containing display name keys and the
// RB_RULE_BASED_IDS array.
//
//If we ever integrate this with the Sun JDK, the resource bundle
// root will change to sun.text.resources.LocaleElements
ICUResourceBundle bundle = (ICUResourceBundle)UResourceBundle.
getBundleInstance(ICUData.ICU_TRANSLIT_BASE_NAME, inLocale);
// Normalize the ID
String stv[] = TransliteratorIDParser.IDtoSTV(id);
if (stv == null) {
// No target; malformed id
return "";
}
String ID = stv[0] + '-' + stv[1];
if (stv[2] != null && stv[2].length() > 0) {
ID = ID + '/' + stv[2];
}
// Use the registered display name, if any
String n = displayNameCache.get(new CaseInsensitiveString(ID));
if (n != null) {
return n;
}
// Use display name for the entire transliterator, if it
// exists.
try {
return bundle.getString(RB_DISPLAY_NAME_PREFIX + ID);
} catch (MissingResourceException e) {}
try {
// Construct the formatter first; if getString() fails
// we'll exit the try block
MessageFormat format = new MessageFormat(
bundle.getString(RB_DISPLAY_NAME_PATTERN));
// Construct the argument array
Object[] args = new Object[] { 2, stv[0], stv[1] };
// Use display names for the scripts, if they exist
for (int j=1; j<=2; ++j) {
try {
args[j] = bundle.getString(RB_SCRIPT_DISPLAY_NAME_PREFIX +
(String) args[j]);
} catch (MissingResourceException e) {}
}
// Format it using the pattern in the resource
return (stv[2].length() > 0) ?
(format.format(args) + '/' + stv[2]) :
format.format(args);
} catch (MissingResourceException e2) {}
// We should not reach this point unless there is something
// wrong with the build or the RB_DISPLAY_NAME_PATTERN has
// been deleted from the root RB_LOCALE_ELEMENTS resource.
throw new RuntimeException();
}
/**
* Returns the filter used by this transliterator, or null
* if this transliterator uses no filter.
*/
public final UnicodeFilter getFilter() {
return filter;
}
/**
* Changes the filter used by this transliterator. If the filter
* is set to null then no filtering will occur.
*
* Transliterator object given its ID.
* The ID must be a system transliterator ID.
*
* @param ID a valid ID, as enumerated by getAvailableIDs()
* @return A Transliterator object with the given ID
* @exception IllegalArgumentException if the given ID is invalid.
*/
public static final Transliterator getInstance(String ID) {
return getInstance(ID, FORWARD);
}
/**
* Returns a Transliterator object given its ID.
* The ID must be a system transliterator ID.
*
* @param ID a valid ID, as enumerated by getAvailableIDs()
* @param dir either FORWARD or REVERSE. If REVERSE then the
* inverse of the given ID is instantiated.
* @return A Transliterator object with the given ID
* @exception IllegalArgumentException if the given ID is invalid.
* @see #getAvailableIDs
* @see #getID
*/
public static Transliterator getInstance(String ID,
int dir) {
StringBuffer canonID = new StringBuffer();
ListTransliterator object constructed from
* the given rule string. This will be a rule-based Transliterator,
* if the rule string contains only rules, or a
* compound Transliterator, if it contains ID blocks, or a
* null Transliterator, if it contains ID blocks which parse as
* empty for the given direction.
*
* @param ID the id for the transliterator.
* @param rules rules, separated by ';'
* @param dir either FORWARD or REVERSE.
* @return a newly created Transliterator
* @throws IllegalArgumentException if there is a problem with the ID or the rules
*/
public static final Transliterator createFromRules(String ID, String rules, int dir) {
Transliterator t = null;
TransliteratorParser parser = new TransliteratorParser();
parser.parse(rules, dir);
// NOTE: The logic here matches that in TransliteratorRegistry.
if (parser.idBlockVector.size() == 0 && parser.dataVector.size() == 0) {
t = new NullTransliterator();
}
else if (parser.idBlockVector.size() == 0 && parser.dataVector.size() == 1) {
t = new RuleBasedTransliterator(ID, parser.dataVector.get(0), parser.compoundFilter);
}
else if (parser.idBlockVector.size() == 1 && parser.dataVector.size() == 0) {
// idBlock, no data -- this is an alias. The ID has
// been munged from reverse into forward mode, if
// necessary, so instantiate the ID in the forward
// direction.
if (parser.compoundFilter != null) {
t = getInstance(parser.compoundFilter.toPattern(false) + ";"
+ parser.idBlockVector.get(0));
} else {
t = getInstance(parser.idBlockVector.get(0));
}
if (t != null) {
t.setID(ID);
}
}
else {
List
* [Pp]{}[\u03A3\u03C2\u03C3\u03F7\u03F8\u03FA\u03FB] > \';
*
* With a filter of [], you still get some elements in the target set, because this rule will still match. It could
* be recast to the following if it were important.
*
* [Pp]{([\u03A3\u03C2\u03C3\u03F7\u03F8\u03FA\u03FB])} > \' | $1;
*
* @see #getTargetSet
*/
public UnicodeSet getTargetSet() {
UnicodeSet result = new UnicodeSet();
addSourceTargetSet(getFilterAsUnicodeSet(UnicodeSet.ALL_CODE_POINTS), new UnicodeSet(), result);
return result;
}
/**
* Returns the set of all characters that may be generated as
* replacement text by this transliterator, filtered by BOTH the input filter, and the current getFilter().
*
* Global FILTER = [ax]
* a > b;
* :: NULL;
* b > c;
* x > d;
*
* While the filter just allows a and x, b is an intermediate result, which could produce c. So the source and target sets
* cannot be gathered independently. What we have to do is filter the sources for the first transliterator according to
* the global filter, intersect that transliterator's filter. Based on that we get the target.
* The next transliterator gets as a global filter (global + last target). And so on.
*
* Global FILTER = [ax]
* a >|b;
* b >c;
*
* Even though b would be filtered from the input, whenever we have a backup, it could be part of the input. So ideally we will
* change the global filter as we go.
* @param targetSet TODO
* @see #getTargetSet
* @deprecated This API is ICU internal only.
* @hide original deprecated declaration
* @hide draft / provisional / internal are hidden on Android
*/
@Deprecated
public void addSourceTargetSet(UnicodeSet inputFilter, UnicodeSet sourceSet, UnicodeSet targetSet) {
UnicodeSet myFilter = getFilterAsUnicodeSet(inputFilter);
UnicodeSet temp = new UnicodeSet(handleGetSourceSet()).retainAll(myFilter);
// use old method, if we don't have anything better
sourceSet.addAll(temp);
// clumsy guess with target
for (String s : temp) {
String t = transliterate(s);
if (!s.equals(t)) {
targetSet.addAll(t);
}
}
}
/**
* Returns the intersectionof this instance's filter intersected with an external filter.
* The externalFilter must be frozen (it is frozen if not).
* The result may be frozen, so don't attempt to modify.
* @deprecated This API is ICU internal only.
* @hide original deprecated declaration
* @hide draft / provisional / internal are hidden on Android
*/
@Deprecated
// TODO change to getMergedFilter
public UnicodeSet getFilterAsUnicodeSet(UnicodeSet externalFilter) {
if (filter == null) {
return externalFilter;
}
UnicodeSet filterSet = new UnicodeSet(externalFilter);
// Most, but not all filters will be UnicodeSets. Optimize for
// the high-runner case.
UnicodeSet temp;
try {
temp = filter;
} catch (ClassCastException e) {
filter.addMatchSetTo(temp = new UnicodeSet());
}
return filterSet.retainAll(temp).freeze();
}
/**
* Returns this transliterator's inverse. See the class
* documentation for details. This implementation simply inverts
* the two entities in the ID and attempts to retrieve the
* resulting transliterator. That is, if getID()
* returns "A-B", then this method will return the result of
* getInstance("B-A"), or null if that
* call fails.
*
* null if no such
* transliterator is registered.
*/
public final Transliterator getInverse() {
return getInstance(ID, REVERSE);
}
/**
* Registers a subclass of Transliterator with the
* system. This subclass must have a public constructor taking no
* arguments. When that constructor is called, the resulting
* object must return the ID passed to this method if
* its getID() method is called.
*
* @param ID the result of getID() for this
* transliterator
* @param transClass a subclass of Transliterator
* @see #unregister
* @hide unsupported on Android
*/
public static void registerClass(String ID, Class transClass, String displayName) {
registry.put(ID, transClass, true);
if (displayName != null) {
displayNameCache.put(new CaseInsensitiveString(ID), displayName);
}
}
/**
* Register a factory object with the given ID. The factory
* method should return a new instance of the given transliterator.
*
* NFC => NFD
* Any-NFC => Any-NFD
* NFD => NFC
* Any-NFD => Any-NFC
*
* (Without the special inverse registration, the inverse of NFC
* would be NFC-Any.) Note that NFD is shorthand for Any-NFD, but
* that the presence or absence of "Any-" is preserved.
*
* Transliterator objects. This includes both system
* transliterators and user transliterators registered using
* registerClass(). The enumerated names may be
* passed to getInstance().
*
* @return An Enumeration over String objects
* @see #getInstance
*/
public static final Enumeration