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(). (However, this does not
* mean that threads may share transliterators without synchronizing
* them. Transliterators are not immutable, so they must be
* synchronized when shared between threads.) 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);
*
* will transliterate it and return the result. Other methods allow
* the client to specify a substring to be transliterated and to use
* {@link Replaceable } objects instead of strings, in order to
* preserve out-of-band information (such as text styles).
*
*
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}
*
*
* When the user types 't', nothing will happen, since the
* transliterator is waiting to see if the next character is 'h'. To
* remedy this, we introduce the notion of a cursor, marked by a '|'
* in the output string:
*
* t>|{tau}
* {tau}h>{theta}
*
*
* Now when the user types 't', tau appears, and if the next character
* is 'h', the tau changes to a theta. This is accomplished by
* maintaining a cursor position (independent of the insertion point,
* and invisible in the GUI) across calls to
* 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. Since these indices are changed by the method, they are
* passed in an int[] array. 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 in a rule-based Transliterator.
* 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
*
* \htmlonly
\endhtmlonly"A" x AB -> "B"\endhtmlonly * * where 'x' represents transliteration. However, * * \htmlonly
* "B" x BA -> "A"\htmlonly
\endhtmlonly"ABCD" x AB -> "BBCD"\endhtmlonly * * 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"\htmlonly
.getInverse() could legitimately return
* BA.
*
* 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 }. * *
Factory methods and registration * *
In general, client code should use the factory method
* {@link #createInstance } to obtain an instance of a
* transliterator given its ID. Valid IDs may be enumerated using
* getAvailableIDs(). Since transliterators are mutable,
* multiple calls to {@link #createInstance } with the same ID will
* return distinct objects.
*
*
In addition to the system transliterators registered at startup,
* user transliterators may be registered by calling
* registerInstance() at run time. A registered instance
* acts a template; future calls to {@link #createInstance } with the ID
* of the registered object return clones of that object. Thus any
* object passed to registerInstance() must implement
* clone() properly. To register a transliterator subclass
* without instantiating it (until it is needed), users may call
* {@link #registerFactory }. In this case, the objects are
* instantiated by invoking the zero-argument public constructor of
* the class.
*
*
Subclassing
*
* Subclasses must implement the abstract method
* handleTransliterate().
Subclasses should override
* the transliterate() method taking a
* Replaceable and the transliterate()
* method taking a String and StringBuffer
* if the performance of these methods can be improved over the
* performance obtained by the default implementations in this class.
*
*
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<>$alefmadda;Translation rules consist of a match pattern and an output
* string. The match pattern consists of literal characters,
* optionally preceded by context, and optionally followed by
* context. Context characters, like literal pattern characters,
* must be matched in the text being transliterated. However, unlike
* literal pattern characters, they are not replaced by the output
* text. For example, the pattern "abc{def}"
* indicates the characters "def" must be
* preceded by "abc" for a successful match.
* If there is a successful match, "def" will
* be replaced, but not "abc". The final '}'
* is optional, so "abc{def" is equivalent to
* "abc{def}". Another example is "{123}456"
* (or "123}456") in which the literal
* pattern "123" must be followed by "456".
*
*
The output string of a forward or reverse rule consists of
* characters to replace the literal pattern characters. If the
* output string contains the character '|', this is
* taken to indicate the location of the cursor after
* replacement. The cursor is the point in the text at which the
* next replacement, if any, will be applied. The cursor is usually
* placed within the replacement text; however, it can actually be
* placed into the preceding or following context by using the
* special character '@'. Examples:
*
*
* a {foo} z > | @ bar; # foo -> bar, move cursor before a
* {foo} xyz > bar @@|; # foo -> bar, cursor between y and z
*
*
* UnicodeSet * *
UnicodeSet patterns may appear anywhere that
* makes sense. They may appear in variable definitions.
* Contrariwise, UnicodeSet patterns may themselves
* contain variable references, such as "$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
* @stable ICU 2.0
*/
class U_I18N_API Transliterator : public UObject {
private:
/**
* Programmatic name, e.g., "Latin-Arabic".
*/
UnicodeString 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.
*/
UnicodeFilter* filter;
int32_t maximumContextLength;
public:
/**
* A context integer or pointer for a factory function, passed by
* value.
* @stable ICU 2.4
*/
union Token {
/**
* This token, interpreted as a 32-bit integer.
* @stable ICU 2.4
*/
int32_t integer;
/**
* This token, interpreted as a native pointer.
* @stable ICU 2.4
*/
void* pointer;
};
#ifndef U_HIDE_INTERNAL_API
/**
* Return a token containing an integer.
* @return a token containing an integer.
* @internal
*/
inline static Token integerToken(int32_t);
/**
* Return a token containing a pointer.
* @return a token containing a pointer.
* @internal
*/
inline static Token pointerToken(void*);
#endif /* U_HIDE_INTERNAL_API */
/**
* A function that creates and returns a Transliterator. When
* invoked, it will be passed the ID string that is being
* instantiated, together with the context pointer that was passed
* in when the factory function was first registered. Many
* factory functions will ignore both parameters, however,
* functions that are registered to more than one ID may use the
* ID or the context parameter to parameterize the transliterator
* they create.
* @param ID the string identifier for this transliterator
* @param context a context pointer that will be stored and
* later passed to the factory function when an ID matching
* the registration ID is being instantiated with this factory.
* @stable ICU 2.4
*/
typedef Transliterator* (U_EXPORT2 *Factory)(const UnicodeString& ID, Token context);
protected:
/**
* Default constructor.
* @param ID the string identifier for this transliterator
* @param adoptedFilter the 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.
* @stable ICU 2.4
*/
Transliterator(const UnicodeString& ID, UnicodeFilter* adoptedFilter);
/**
* Copy constructor.
* @stable ICU 2.4
*/
Transliterator(const Transliterator&);
/**
* Assignment operator.
* @stable ICU 2.4
*/
Transliterator& operator=(const Transliterator&);
/**
* Create a transliterator from a basic ID. This is an ID
* containing only the forward direction source, target, and
* variant.
* @param id a basic ID of the form S-T or S-T/V.
* @param canon canonical ID to assign to the object, or
* nullptr to leave the ID unchanged
* @return a newly created Transliterator or null if the ID is
* invalid.
* @stable ICU 2.4
*/
static Transliterator* createBasicInstance(const UnicodeString& id,
const UnicodeString* canon);
friend class TransliteratorParser; // for parseID()
friend class TransliteratorIDParser; // for createBasicInstance()
friend class TransliteratorAlias; // for setID()
public:
/**
* Destructor.
* @stable ICU 2.0
*/
virtual ~Transliterator();
/**
* Implements Cloneable.
* All subclasses are encouraged to implement this method if it is
* possible and reasonable to do so. Subclasses that are to be
* registered with the system using registerInstance()
* are required to implement this method. If a subclass does not
* implement clone() properly and is registered with the system
* using registerInstance(), then the default clone() implementation
* will return null, and calls to createInstance() will fail.
*
* @return a copy of the object.
* @see #registerInstance
* @stable ICU 2.0
*/
virtual Transliterator* clone() const;
/**
* Transliterates a segment of a string, with optional filtering.
*
* @param text the string to be transliterated
* @param start the beginning index, inclusive; 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.
* @stable ICU 2.0
*/
virtual int32_t transliterate(Replaceable& text,
int32_t start, int32_t limit) const;
/**
* Transliterates an entire string in place. Convenience method.
* @param text the string to be transliterated
* @stable ICU 2.0
*/
virtual void transliterate(Replaceable& text) const;
/**
* 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.limit, advancing
* index.limit by insertion.length().
* Then the transliterator will try to transliterate characters of
* text between index.cursor and
* index.limit. Characters before
* index.cursor will not be changed.
*
*
Upon return, values in index will be updated.
* index.start will be advanced to the first
* character that future calls to this method will read.
* index.cursor and index.limit will
* be adjusted to delimit the range of text that future calls to
* this method may change.
*
*
Typical usage of this method begins with an initial call
* with index.start and index.limit
* set to indicate the portion of text to be
* transliterated, and index.cursor == index.start.
* Thereafter, index can be used without
* modification in future calls, provided that all changes to
* text are made via this method.
*
*
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 an array of three integers. * *
index.start: the beginning index,
* inclusive; 0 <= index.start <= index.limit.
*
* index.limit: the ending index, exclusive;
* index.start <= index.limit <= text.length().
* insertion is inserted at
* index.limit.
*
* index.cursor: the next character to be
* considered for transliteration; index.start <=
* index.cursor <= index.limit. Characters before
* index.cursor will not be changed by future calls
* to this method.index.limit. If null then no text
* is inserted.
* @param status Output param to filled in with a success or an error.
* @see #handleTransliterate
* @exception IllegalArgumentException if index
* is invalid
* @see UTransPosition
* @stable ICU 2.0
*/
virtual void transliterate(Replaceable& text, UTransPosition& index,
const UnicodeString& insertion,
UErrorCode& status) const;
/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly after a new character has been
* inserted, typically as a result of a keyboard event. This is a
* convenience method.
* @param text the buffer holding transliterated and
* untransliterated text
* @param index an array of three integers.
* @param insertion text to be inserted and possibly
* transliterated into the translation buffer at
* index.limit.
* @param status Output param to filled in with a success or an error.
* @see #transliterate(Replaceable&, UTransPosition&, const UnicodeString&, UErrorCode&) const
* @stable ICU 2.0
*/
virtual void transliterate(Replaceable& text, UTransPosition& index,
UChar32 insertion,
UErrorCode& status) const;
/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly. This is a convenience method; see
* {@link #transliterate(Replaceable&, UTransPosition&, const UnicodeString&, UErrorCode&) const }
* for details.
* @param text the buffer holding transliterated and
* untransliterated text
* @param index an array of three integers.
* @param status Output param to filled in with a success or an error.
* @see #transliterate(Replaceable&, UTransPosition&, const UnicodeString&, UErrorCode &) const
* @stable ICU 2.0
*/
virtual void transliterate(Replaceable& text, UTransPosition& index,
UErrorCode& status) const;
/**
* 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 }
* @stable ICU 2.0
*/
virtual void finishTransliteration(Replaceable& text,
UTransPosition& index) const;
private:
/**
* This internal method does incremental transliteration. If the
* 'insertion' is non-null then we append it to 'text' before
* proceeding. This method calls through to the pure virtual
* framework method handleTransliterate() to do the actual
* work.
* @param text the buffer holding transliterated and
* untransliterated text
* @param index an array of three integers. See {@link
* #transliterate(Replaceable, int[], String)}.
* @param insertion text to be inserted and possibly
* transliterated into the translation buffer at
* index.limit.
* @param status Output param to filled in with a success or an error.
*/
void _transliterate(Replaceable& text,
UTransPosition& index,
const UnicodeString* insertion,
UErrorCode &status) const;
protected:
/**
* 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.Implementations of this method should also obey the * following invariants:
* *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.Subclasses may safely assume that all characters in
* [pos.start, pos.limit) are filtered.
* In other words, the filter has already been applied by the time
* this method is called. See
* filteredTransliterate().
*
*
This method is not for public consumption. Calling
* this method directly will transliterate
* [pos.start, pos.limit) without
* applying the filter. End user code should call
* transliterate() instead of this method. Subclass code
* and wrapping transliterators should call
* filteredTransliterate() instead of this method.
*
* @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
* 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
* @stable ICU 2.4
*/
virtual void handleTransliterate(Replaceable& text,
UTransPosition& pos,
UBool incremental) const = 0;
public:
/**
* 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
* @stable ICU 2.4
*/
virtual void filteredTransliterate(Replaceable& text,
UTransPosition& index,
UBool incremental) const;
private:
/**
* 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.
*
*
If this transliterator has a filter, break up the input text into runs * of unfiltered characters. Pass each run to * subclass.handleTransliterate(). * *
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.
*/
virtual void filteredTransliterate(Replaceable& text,
UTransPosition& index,
UBool incremental,
UBool rollback) const;
public:
/**
* Returns the length of the longest context required by this transliterator.
* This is preceding context. The default implementation supplied
* by Transliterator returns zero; subclasses
* that use preceding context should override this method to return the
* correct value. 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
* @stable ICU 2.0
*/
int32_t getMaximumContextLength(void) const;
protected:
/**
* Method for subclasses to use to set the maximum context length.
* @param maxContextLength the new value to be set.
* @see #getMaximumContextLength
* @stable ICU 2.4
*/
void setMaximumContextLength(int32_t maxContextLength);
public:
/**
* Returns a programmatic identifier for this transliterator.
* If this identifier is passed to createInstance(), it
* will return this object, if it has been registered.
* @return a programmatic identifier for this transliterator.
* @see #registerInstance
* @see #registerFactory
* @see #getAvailableIDs
* @stable ICU 2.0
*/
virtual const UnicodeString& getID(void) const;
/**
* Returns a name for this transliterator that is appropriate for
* display to the user in the default locale. See {@link #getDisplayName }
* for details.
* @param ID the string identifier for this transliterator
* @param result Output param to receive the display name
* @return A reference to 'result'.
* @stable ICU 2.0
*/
static UnicodeString& U_EXPORT2 getDisplayName(const UnicodeString& ID,
UnicodeString& result);
/**
* 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.
*
*
If no localized names exist in the system resource bundles,
* a name is synthesized using a localized
* 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 ID the string identifier for this transliterator
* @param inLocale the Locale in which the display name should be
* localized.
* @param result Output param to receive the display name
* @return A reference to 'result'.
* @stable ICU 2.0
*/
static UnicodeString& U_EXPORT2 getDisplayName(const UnicodeString& ID,
const Locale& inLocale,
UnicodeString& result);
/**
* Returns the filter used by this transliterator, or nullptr
* if this transliterator uses no filter.
* @return the filter used by this transliterator, or nullptr
* if this transliterator uses no filter.
* @stable ICU 2.0
*/
const UnicodeFilter* getFilter(void) const;
/**
* Returns the filter used by this transliterator, or nullptr if this
* transliterator uses no filter. The caller must eventually delete the
* result. After this call, this transliterator's filter is set to
* nullptr.
* @return the filter used by this transliterator, or nullptr if this
* transliterator uses no filter.
* @stable ICU 2.4
*/
UnicodeFilter* orphanFilter(void);
/**
* Changes the filter used by this transliterator. If the filter
* is set to null then no filtering will occur.
*
*
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.
* @param adoptedFilter the new filter to be adopted.
* @stable ICU 2.0
*/
void adoptFilter(UnicodeFilter* adoptedFilter);
/**
* 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
* createInstance("B-A"), or null if that
* call fails.
*
*
Subclasses with knowledge of their inverse may wish to
* override this method.
*
* @param status Output param to filled in with a success or an error.
* @return a transliterator that is an inverse, not necessarily
* exact, of this transliterator, or null if no such
* transliterator is registered.
* @see #registerInstance
* @stable ICU 2.0
*/
Transliterator* createInverse(UErrorCode& status) const;
/**
* Returns a Transliterator object given its ID.
* The ID must be either a system transliterator ID or a ID registered
* using registerInstance().
*
* @param ID a valid ID, as enumerated by getAvailableIDs()
* @param dir either FORWARD or REVERSE.
* @param parseError Struct to receive information on position
* of error if an error is encountered
* @param status Output param to filled in with a success or an error.
* @return A Transliterator object with the given ID
* @see #registerInstance
* @see #getAvailableIDs
* @see #getID
* @stable ICU 2.0
*/
static Transliterator* U_EXPORT2 createInstance(const UnicodeString& ID,
UTransDirection dir,
UParseError& parseError,
UErrorCode& status);
/**
* Returns a Transliterator object given its ID.
* The ID must be either a system transliterator ID or a ID registered
* using registerInstance().
* @param ID a valid ID, as enumerated by getAvailableIDs()
* @param dir either FORWARD or REVERSE.
* @param status Output param to filled in with a success or an error.
* @return A Transliterator object with the given ID
* @stable ICU 2.0
*/
static Transliterator* U_EXPORT2 createInstance(const UnicodeString& ID,
UTransDirection dir,
UErrorCode& status);
/**
* Returns a Transliterator 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.
* @param parseError Struct to receive information on position
* of error if an error is encountered
* @param status Output param set to success/failure code.
* @return a newly created Transliterator
* @stable ICU 2.0
*/
static Transliterator* U_EXPORT2 createFromRules(const UnicodeString& ID,
const UnicodeString& rules,
UTransDirection dir,
UParseError& parseError,
UErrorCode& status);
/**
* Create a rule string that can be passed to createFromRules()
* to recreate this transliterator.
* @param result the string to receive the rules. Previous
* contents will be deleted.
* @param escapeUnprintable if true then convert unprintable
* character to their hex escape representations, \\uxxxx or
* \\Uxxxxxxxx. Unprintable characters are those other than
* U+000A, U+0020..U+007E.
* @stable ICU 2.0
*/
virtual UnicodeString& toRules(UnicodeString& result,
UBool escapeUnprintable) const;
/**
* Return the number of elements that make up this transliterator.
* For example, if the transliterator "NFD;Jamo-Latin;Latin-Greek"
* were created, the return value of this method would be 3.
*
*
If this transliterator is not composed of other * transliterators, then this method returns 1. * @return the number of transliterators that compose this * transliterator, or 1 if this transliterator is not composed of * multiple transliterators * @stable ICU 3.0 */ int32_t countElements() const; /** * Return an element that makes up this transliterator. For * example, if the transliterator "NFD;Jamo-Latin;Latin-Greek" * were created, the return value of this method would be one * of the three transliterator objects that make up that * transliterator: [NFD, Jamo-Latin, Latin-Greek]. * *
If this transliterator is not composed of other
* transliterators, then this method will return a reference to
* this transliterator when given the index 0.
* @param index a value from 0..countElements()-1 indicating the
* transliterator to return
* @param ec input-output error code
* @return one of the transliterators that makes up this
* transliterator, if this transliterator is made up of multiple
* transliterators, otherwise a reference to this object if given
* an index of 0
* @stable ICU 3.0
*/
const Transliterator& getElement(int32_t index, UErrorCode& ec) const;
/**
* Returns the set of all characters that may be modified in the
* input text by this Transliterator. This incorporates this
* object's current filter; if the filter is changed, the return
* value of this function will change. The default implementation
* returns an empty set. Some subclasses may override
* {@link #handleGetSourceSet } to return a more precise result. The
* return result is approximate in any case and is intended for
* use by tests, tools, or utilities.
* @param result receives result set; previous contents lost
* @return a reference to result
* @see #getTargetSet
* @see #handleGetSourceSet
* @stable ICU 2.4
*/
UnicodeSet& getSourceSet(UnicodeSet& result) const;
/**
* Framework method that returns the set of all characters that
* may be modified in the input text by this Transliterator,
* ignoring the effect of this object's filter. The base class
* implementation returns the empty set. Subclasses that wish to
* implement this should override this method.
* @return the set of characters that this transliterator may
* modify. The set may be modified, so subclasses should return a
* newly-created object.
* @param result receives result set; previous contents lost
* @see #getSourceSet
* @see #getTargetSet
* @stable ICU 2.4
*/
virtual void handleGetSourceSet(UnicodeSet& result) const;
/**
* Returns the set of all characters that may be generated as
* replacement text by this transliterator. The default
* implementation returns the empty set. Some subclasses may
* override this method to return a more precise result. The
* return result is approximate in any case and is intended for
* use by tests, tools, or utilities requiring such
* meta-information.
* @param result receives result set; previous contents lost
* @return a reference to result
* @see #getTargetSet
* @stable ICU 2.4
*/
virtual UnicodeSet& getTargetSet(UnicodeSet& result) const;
public:
/**
* Registers a factory function that creates transliterators of
* a given ID.
*
* Because ICU may choose to cache Transliterators internally, this must
* be called at application startup, prior to any calls to
* Transliterator::createXXX to avoid undefined behavior.
*
* @param id the ID being registered
* @param factory a function pointer that will be copied and
* called later when the given ID is passed to createInstance()
* @param context a context pointer that will be stored and
* later passed to the factory function when an ID matching
* the registration ID is being instantiated with this factory.
* @stable ICU 2.0
*/
static void U_EXPORT2 registerFactory(const UnicodeString& id,
Factory factory,
Token context);
/**
* Registers an instance obj of a subclass of
* Transliterator with the system. When
* createInstance() is called with an ID string that is
* equal to obj->getID(), then obj->clone() is
* returned.
*
* After this call the Transliterator class owns the adoptedObj
* and will delete it.
*
* Because ICU may choose to cache Transliterators internally, this must
* be called at application startup, prior to any calls to
* Transliterator::createXXX to avoid undefined behavior.
*
* @param adoptedObj an instance of subclass of
* Transliterator that defines clone()
* @see #createInstance
* @see #registerFactory
* @see #unregister
* @stable ICU 2.0
*/
static void U_EXPORT2 registerInstance(Transliterator* adoptedObj);
/**
* Registers an ID string as an alias of another ID string.
* That is, after calling this function, createInstance(aliasID)
* will return the same thing as createInstance(realID).
* This is generally used to create shorter, more mnemonic aliases
* for long compound IDs.
*
* @param aliasID The new ID being registered.
* @param realID The ID that the new ID is to be an alias for.
* This can be a compound ID and can include filters and should
* refer to transliterators that have already been registered with
* the framework, although this isn't checked.
* @stable ICU 3.6
*/
static void U_EXPORT2 registerAlias(const UnicodeString& aliasID,
const UnicodeString& realID);
protected:
#ifndef U_HIDE_INTERNAL_API
/**
* @param id the ID being registered
* @param factory a function pointer that will be copied and
* called later when the given ID is passed to createInstance()
* @param context a context pointer that will be stored and
* later passed to the factory function when an ID matching
* the registration ID is being instantiated with this factory.
* @internal
*/
static void _registerFactory(const UnicodeString& id,
Factory factory,
Token context);
/**
* @internal
*/
static void _registerInstance(Transliterator* adoptedObj);
/**
* @internal
*/
static void _registerAlias(const UnicodeString& aliasID, const UnicodeString& realID);
/**
* Register two targets as being inverses of one another. For
* example, calling registerSpecialInverse("NFC", "NFD", true) causes
* Transliterator to form the following inverse relationships:
*
*
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.
*
* 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
* @internal
*/
static void _registerSpecialInverse(const UnicodeString& target,
const UnicodeString& inverseTarget,
UBool bidirectional);
#endif /* U_HIDE_INTERNAL_API */
public:
/**
* Unregisters a transliterator or class. This may be either
* a system transliterator or a user transliterator or class.
* Any attempt to construct an unregistered transliterator based
* on its ID will fail.
*
* Because ICU may choose to cache Transliterators internally, this should
* be called during application shutdown, after all calls to
* Transliterator::createXXX to avoid undefined behavior.
*
* @param ID the ID of the transliterator or class
* @return the Object that was registered with
* ID, or null if none was
* @see #registerInstance
* @see #registerFactory
* @stable ICU 2.0
*/
static void U_EXPORT2 unregister(const UnicodeString& ID);
public:
/**
* Return a StringEnumeration over the IDs available at the time of the
* call, including user-registered IDs.
* @param ec input-output error code
* @return a newly-created StringEnumeration over the transliterators
* available at the time of the call. The caller should delete this object
* when done using it.
* @stable ICU 3.0
*/
static StringEnumeration* U_EXPORT2 getAvailableIDs(UErrorCode& ec);
/**
* Return the number of registered source specifiers.
* @return the number of registered source specifiers.
* @stable ICU 2.0
*/
static int32_t U_EXPORT2 countAvailableSources(void);
/**
* Return a registered source specifier.
* @param index which specifier to return, from 0 to n-1, where
* n = countAvailableSources()
* @param result fill-in parameter to receive the source specifier.
* If index is out of range, result will be empty.
* @return reference to result
* @stable ICU 2.0
*/
static UnicodeString& U_EXPORT2 getAvailableSource(int32_t index,
UnicodeString& result);
/**
* Return the number of registered target specifiers for a given
* source specifier.
* @param source the given source specifier.
* @return the number of registered target specifiers for a given
* source specifier.
* @stable ICU 2.0
*/
static int32_t U_EXPORT2 countAvailableTargets(const UnicodeString& source);
/**
* Return a registered target specifier for a given source.
* @param index which specifier to return, from 0 to n-1, where
* n = countAvailableTargets(source)
* @param source the source specifier
* @param result fill-in parameter to receive the target specifier.
* If source is invalid or if index is out of range, result will
* be empty.
* @return reference to result
* @stable ICU 2.0
*/
static UnicodeString& U_EXPORT2 getAvailableTarget(int32_t index,
const UnicodeString& source,
UnicodeString& result);
/**
* Return the number of registered variant specifiers for a given
* source-target pair.
* @param source the source specifiers.
* @param target the target specifiers.
* @stable ICU 2.0
*/
static int32_t U_EXPORT2 countAvailableVariants(const UnicodeString& source,
const UnicodeString& target);
/**
* Return a registered variant specifier for a given source-target
* pair.
* @param index which specifier to return, from 0 to n-1, where
* n = countAvailableVariants(source, target)
* @param source the source specifier
* @param target the target specifier
* @param result fill-in parameter to receive the variant
* specifier. If source is invalid or if target is invalid or if
* index is out of range, result will be empty.
* @return reference to result
* @stable ICU 2.0
*/
static UnicodeString& U_EXPORT2 getAvailableVariant(int32_t index,
const UnicodeString& source,
const UnicodeString& target,
UnicodeString& result);
protected:
#ifndef U_HIDE_INTERNAL_API
/**
* Non-mutexed internal method
* @internal
*/
static int32_t _countAvailableSources(void);
/**
* Non-mutexed internal method
* @internal
*/
static UnicodeString& _getAvailableSource(int32_t index,
UnicodeString& result);
/**
* Non-mutexed internal method
* @internal
*/
static int32_t _countAvailableTargets(const UnicodeString& source);
/**
* Non-mutexed internal method
* @internal
*/
static UnicodeString& _getAvailableTarget(int32_t index,
const UnicodeString& source,
UnicodeString& result);
/**
* Non-mutexed internal method
* @internal
*/
static int32_t _countAvailableVariants(const UnicodeString& source,
const UnicodeString& target);
/**
* Non-mutexed internal method
* @internal
*/
static UnicodeString& _getAvailableVariant(int32_t index,
const UnicodeString& source,
const UnicodeString& target,
UnicodeString& result);
#endif /* U_HIDE_INTERNAL_API */
protected:
/**
* Set the ID of this transliterators. Subclasses shouldn't do
* this, unless the underlying script behavior has changed.
* @param id the new id t to be set.
* @stable ICU 2.4
*/
void setID(const UnicodeString& id);
public:
/**
* Return the class ID for this class. This is useful only for
* comparing to a return value from getDynamicClassID().
* Note that Transliterator is an abstract base class, and therefor
* no fully constructed object will have a dynamic
* UCLassID that equals the UClassID returned from
* TRansliterator::getStaticClassID().
* @return The class ID for class Transliterator.
* @stable ICU 2.0
*/
static UClassID U_EXPORT2 getStaticClassID(void);
/**
* Returns a unique class ID polymorphically. This method
* is to implement a simple version of RTTI, since not all C++
* compilers support genuine RTTI. Polymorphic operator==() and
* clone() methods call this method.
*
*
Concrete subclasses of Transliterator must use the * UOBJECT_DEFINE_RTTI_IMPLEMENTATION macro from * uobject.h to provide the RTTI functions. * * @return The class ID for this object. All objects of a given * class have the same class ID. Objects of other classes have * different class IDs. * @stable ICU 2.0 */ virtual UClassID getDynamicClassID(void) const override = 0; private: static UBool initializeRegistry(UErrorCode &status); public: #ifndef U_HIDE_OBSOLETE_API /** * Return the number of IDs currently registered with the system. * To retrieve the actual IDs, call getAvailableID(i) with * i from 0 to countAvailableIDs() - 1. * @return the number of IDs currently registered with the system. * @obsolete ICU 3.4 use getAvailableIDs() instead */ static int32_t U_EXPORT2 countAvailableIDs(void); /** * Return the index-th available ID. index must be between 0 * and countAvailableIDs() - 1, inclusive. If index is out of * range, the result of getAvailableID(0) is returned. * @param index the given ID index. * @return the index-th available ID. index must be between 0 * and countAvailableIDs() - 1, inclusive. If index is out of * range, the result of getAvailableID(0) is returned. * @obsolete ICU 3.4 use getAvailableIDs() instead; this function * is not thread safe, since it returns a reference to storage that * may become invalid if another thread calls unregister */ static const UnicodeString& U_EXPORT2 getAvailableID(int32_t index); #endif /* U_HIDE_OBSOLETE_API */ }; inline int32_t Transliterator::getMaximumContextLength(void) const { return maximumContextLength; } inline void Transliterator::setID(const UnicodeString& id) { ID = id; // NUL-terminate the ID string, which is a non-aliased copy. ID.append((char16_t)0); ID.truncate(ID.length()-1); } #ifndef U_HIDE_INTERNAL_API inline Transliterator::Token Transliterator::integerToken(int32_t i) { Token t; t.integer = i; return t; } inline Transliterator::Token Transliterator::pointerToken(void* p) { Token t; t.pointer = p; return t; } #endif /* U_HIDE_INTERNAL_API */ U_NAMESPACE_END #endif /* #if !UCONFIG_NO_TRANSLITERATION */ #endif /* U_SHOW_CPLUSPLUS_API */ #endif