com.ibm.icu.text.TransliterationRule Maven / Gradle / Ivy
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/*
*******************************************************************************
* Copyright (C) 1996-2010, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*/
package com.ibm.icu.text;
import com.ibm.icu.impl.Utility;
/**
* A transliteration rule used by
* RuleBasedTransliterator.
* TransliterationRule is an immutable object.
*
* A rule consists of an input pattern and an output string. When
* the input pattern is matched, the output string is emitted. The
* input pattern consists of zero or more characters which are matched
* exactly (the key) and optional context. Context must match if it
* is specified. Context may be specified before the key, after the
* key, or both. The key, preceding context, and following context
* may contain variables. Variables represent a set of Unicode
* characters, such as the letters a through z.
* Variables are detected by looking up each character in a supplied
* variable list to see if it has been so defined.
*
*
A rule may contain segments in its input string and segment
* references in its output string. A segment is a substring of the
* input pattern, indicated by an offset and limit. The segment may
* be in the preceding or following context. It may not span a
* context boundary. A segment reference is a special character in
* the output string that causes a segment of the input string (not
* the input pattern) to be copied to the output string. The range of
* special characters that represent segment references is defined by
* RuleBasedTransliterator.Data.
*
*
Example: The rule "([a-z]) . ([0-9]) > $2 . $1" will change the input
* string "abc.123" to "ab1.c23".
*
*
Copyright © IBM Corporation 1999. All rights reserved.
*
* @author Alan Liu
*/
class TransliterationRule {
// TODO Eliminate the pattern and keyLength data members. They
// are used only by masks() and getIndexValue() which are called
// only during build time, not during run-time. Perhaps these
// methods and pattern/keyLength can be isolated into a separate
// object.
/**
* The match that must occur before the key, or null if there is no
* preceding context.
*/
private StringMatcher anteContext;
/**
* The matcher object for the key. If null, then the key is empty.
*/
private StringMatcher key;
/**
* The match that must occur after the key, or null if there is no
* following context.
*/
private StringMatcher postContext;
/**
* The object that performs the replacement if the key,
* anteContext, and postContext are matched. Never null.
*/
private UnicodeReplacer output;
/**
* The string that must be matched, consisting of the anteContext, key,
* and postContext, concatenated together, in that order. Some components
* may be empty (zero length).
* @see anteContextLength
* @see keyLength
*/
private String pattern;
/**
* An array of matcher objects corresponding to the input pattern
* segments. If there are no segments this is null. N.B. This is
* a UnicodeMatcher for generality, but in practice it is always a
* StringMatcher. In the future we may generalize this, but for
* now we sometimes cast down to StringMatcher.
*/
UnicodeMatcher[] segments;
/**
* The length of the string that must match before the key. If
* zero, then there is no matching requirement before the key.
* Substring [0,anteContextLength) of pattern is the anteContext.
*/
private int anteContextLength;
/**
* The length of the key. Substring [anteContextLength,
* anteContextLength + keyLength) is the key.
*/
private int keyLength;
/**
* Miscellaneous attributes.
*/
byte flags;
/**
* Flag attributes.
*/
static final int ANCHOR_START = 1;
static final int ANCHOR_END = 2;
/**
* An alias pointer to the data for this rule. The data provides
* lookup services for matchers and segments.
*/
private final RuleBasedTransliterator.Data data;
/**
* Construct a new rule with the given input, output text, and other
* attributes. A cursor position may be specified for the output text.
* @param input input string, including key and optional ante and
* post context
* @param anteContextPos offset into input to end of ante context, or -1 if
* none. Must be <= input.length() if not -1.
* @param postContextPos offset into input to start of post context, or -1
* if none. Must be <= input.length() if not -1, and must be >=
* anteContextPos.
* @param output output string
* @param cursorPos offset into output at which cursor is located, or -1 if
* none. If less than zero, then the cursor is placed after the
* output; that is, -1 is equivalent to
* output.length(). If greater than
* output.length() then an exception is thrown.
* @param cursorOffset an offset to be added to cursorPos to position the
* cursor either in the ante context, if < 0, or in the post context, if >
* 0. For example, the rule "abc{def} > | @@@ xyz;" changes "def" to
* "xyz" and moves the cursor to before "a". It would have a cursorOffset
* of -3.
* @param segs array of UnicodeMatcher corresponding to input pattern
* segments, or null if there are none
* @param anchorStart true if the the rule is anchored on the left to
* the context start
* @param anchorEnd true if the rule is anchored on the right to the
* context limit
*/
public TransliterationRule(String input,
int anteContextPos, int postContextPos,
String output,
int cursorPos, int cursorOffset,
UnicodeMatcher[] segs,
boolean anchorStart, boolean anchorEnd,
RuleBasedTransliterator.Data theData) {
data = theData;
// Do range checks only when warranted to save time
if (anteContextPos < 0) {
anteContextLength = 0;
} else {
if (anteContextPos > input.length()) {
throw new IllegalArgumentException("Invalid ante context");
}
anteContextLength = anteContextPos;
}
if (postContextPos < 0) {
keyLength = input.length() - anteContextLength;
} else {
if (postContextPos < anteContextLength ||
postContextPos > input.length()) {
throw new IllegalArgumentException("Invalid post context");
}
keyLength = postContextPos - anteContextLength;
}
if (cursorPos < 0) {
cursorPos = output.length();
} else if (cursorPos > output.length()) {
throw new IllegalArgumentException("Invalid cursor position");
}
// We don't validate the segments array. The caller must
// guarantee that the segments are well-formed (that is, that
// all $n references in the output refer to indices of this
// array, and that no array elements are null).
this.segments = segs;
pattern = input;
flags = 0;
if (anchorStart) {
flags |= ANCHOR_START;
}
if (anchorEnd) {
flags |= ANCHOR_END;
}
anteContext = null;
if (anteContextLength > 0) {
anteContext = new StringMatcher(pattern.substring(0, anteContextLength),
0, data);
}
key = null;
if (keyLength > 0) {
key = new StringMatcher(pattern.substring(anteContextLength, anteContextLength + keyLength),
0, data);
}
int postContextLength = pattern.length() - keyLength - anteContextLength;
postContext = null;
if (postContextLength > 0) {
postContext = new StringMatcher(pattern.substring(anteContextLength + keyLength),
0, data);
}
this.output = new StringReplacer(output, cursorPos + cursorOffset, data);
}
/**
* Return the preceding context length. This method is needed to
* support the Transliterator method
* getMaximumContextLength().
*/
public int getAnteContextLength() {
return anteContextLength + (((flags & ANCHOR_START) != 0) ? 1 : 0);
}
/**
* Internal method. Returns 8-bit index value for this rule.
* This is the low byte of the first character of the key,
* unless the first character of the key is a set. If it's a
* set, or otherwise can match multiple keys, the index value is -1.
*/
final int getIndexValue() {
if (anteContextLength == pattern.length()) {
// A pattern with just ante context {such as foo)>bar} can
// match any key.
return -1;
}
int c = UTF16.charAt(pattern, anteContextLength);
return data.lookupMatcher(c) == null ? (c & 0xFF) : -1;
}
/**
* Internal method. Returns true if this rule matches the given
* index value. The index value is an 8-bit integer, 0..255,
* representing the low byte of the first character of the key.
* It matches this rule if it matches the first character of the
* key, or if the first character of the key is a set, and the set
* contains any character with a low byte equal to the index
* value. If the rule contains only ante context, as in foo)>bar,
* then it will match any key.
*/
final boolean matchesIndexValue(int v) {
// Delegate to the key, or if there is none, to the postContext.
// If there is neither then we match any key; return true.
UnicodeMatcher m = (key != null) ? key : postContext;
return (m != null) ? m.matchesIndexValue(v) : true;
}
/**
* Return true if this rule masks another rule. If r1 masks r2 then
* r1 matches any input string that r2 matches. If r1 masks r2 and r2 masks
* r1 then r1 == r2. Examples: "a>x" masks "ab>y". "a>x" masks "a[b]>y".
* "[c]a>x" masks "[dc]a>y".
*/
public boolean masks(TransliterationRule r2) {
/* Rule r1 masks rule r2 if the string formed of the
* antecontext, key, and postcontext overlaps in the following
* way:
*
* r1: aakkkpppp
* r2: aaakkkkkpppp
* ^
*
* The strings must be aligned at the first character of the
* key. The length of r1 to the left of the alignment point
* must be <= the length of r2 to the left; ditto for the
* right. The characters of r1 must equal (or be a superset
* of) the corresponding characters of r2. The superset
* operation should be performed to check for UnicodeSet
* masking.
*
* Anchors: Two patterns that differ only in anchors only
* mask one another if they are exactly equal, and r2 has
* all the anchors r1 has (optionally, plus some). Here Y
* means the row masks the column, N means it doesn't.
*
* ab ^ab ab$ ^ab$
* ab Y Y Y Y
* ^ab N Y N Y
* ab$ N N Y Y
* ^ab$ N N N Y
*
* Post context: {a}b masks ab, but not vice versa, since {a}b
* matches everything ab matches, and {a}b matches {|a|}b but ab
* does not. Pre context is different (a{b} does not align with
* ab).
*/
/* LIMITATION of the current mask algorithm: Some rule
* maskings are currently not detected. For example,
* "{Lu}]a>x" masks "A]a>y". This can be added later. TODO
*/
int len = pattern.length();
int left = anteContextLength;
int left2 = r2.anteContextLength;
int right = pattern.length() - left;
int right2 = r2.pattern.length() - left2;
// TODO Clean this up -- some logic might be combinable with the
// next statement.
// Test for anchor masking
if (left == left2 && right == right2 &&
keyLength <= r2.keyLength &&
r2.pattern.regionMatches(0, pattern, 0, len)) {
// The following boolean logic implements the table above
return (flags == r2.flags) ||
(!((flags & ANCHOR_START) != 0) && !((flags & ANCHOR_END) != 0)) ||
(((r2.flags & ANCHOR_START) != 0) && ((r2.flags & ANCHOR_END) != 0));
}
return left <= left2 &&
(right < right2 ||
(right == right2 && keyLength <= r2.keyLength)) &&
r2.pattern.regionMatches(left2 - left, pattern, 0, len);
}
static final int posBefore(Replaceable str, int pos) {
return (pos > 0) ?
pos - UTF16.getCharCount(str.char32At(pos-1)) :
pos - 1;
}
static final int posAfter(Replaceable str, int pos) {
return (pos >= 0 && pos < str.length()) ?
pos + UTF16.getCharCount(str.char32At(pos)) :
pos + 1;
}
/**
* Attempt a match and replacement at the given position. Return
* the degree of match between this rule and the given text. The
* degree of match may be mismatch, a partial match, or a full
* match. A mismatch means at least one character of the text
* does not match the context or key. A partial match means some
* context and key characters match, but the text is not long
* enough to match all of them. A full match means all context
* and key characters match.
*
* If a full match is obtained, perform a replacement, update pos,
* and return U_MATCH. Otherwise both text and pos are unchanged.
*
* @param text the text
* @param pos the position indices
* @param incremental if TRUE, test for partial matches that may
* be completed by additional text inserted at pos.limit.
* @return one of U_MISMATCH,
* U_PARTIAL_MATCH, or U_MATCH. If
* incremental is FALSE then U_PARTIAL_MATCH will not be returned.
*/
public int matchAndReplace(Replaceable text,
Transliterator.Position pos,
boolean incremental) {
// Matching and replacing are done in one method because the
// replacement operation needs information obtained during the
// match. Another way to do this is to have the match method
// create a match result struct with relevant offsets, and to pass
// this into the replace method.
// ============================ MATCH ===========================
// Reset segment match data
if (segments != null) {
for (int i=0; i ", true, escapeUnprintable, quoteBuf);
// Emit the output pattern
Utility.appendToRule(rule, output.toReplacerPattern(escapeUnprintable),
true, escapeUnprintable, quoteBuf);
Utility.appendToRule(rule, ';', true, escapeUnprintable, quoteBuf);
return rule.toString();
}
/**
* Return a string representation of this object.
* @return string representation of this object
*/
public String toString() {
return '{' + toRule(true) + '}';
}
/**
* Find the source and target sets, subject to the input filter.
* There is a known issue with filters containing multiple characters.
*/
// TODO: Problem: the rule is [{ab}]c > x
// The filter is [a{bc}].
// If the input is abc, then the rule will work.
// However, following code applying the filter won't catch that case.
void addSourceTargetSet(UnicodeSet filter, UnicodeSet sourceSet, UnicodeSet targetSet, UnicodeSet revisiting) {
int limit = anteContextLength + keyLength;
UnicodeSet tempSource = new UnicodeSet();
UnicodeSet temp = new UnicodeSet();
// We need to walk through the pattern.
// Iff some of the characters at ALL of the the positions are matched by the filter, then we add temp to toUnionTo
for (int i=anteContextLength; i