Package net.sf.saxon.regex

Class REMatcher

java.lang.Object
net.sf.saxon.regex.REMatcher
public class REMatcher extends Object
Evaluator for regular expressions. A regular expression is represented as an REProgram, which is constructed using the RECompiler.

Although the regular expression engine was originally based on Apache Jakarta, the run-time evaluator has been completely re-written for Saxon.

The design is essentially following the interpreter pattern. The compiled regular expression is represented as a tree of Operation objects, each of which has an evaluation method Operation.iterateMatches(REMatcher, int). This takes as input the current position in the input string, and returns an iterator over the possible positions at which a match using this operation can end.

The REMatcher is stateful

  • Constructor Details

    • REMatcher

      public REMatcher(REProgram program)
      Construct a matcher for a pre-compiled regular expression from program (bytecode) data.
      Parameters:
      program - Compiled regular expression program
      See Also:

  • Method Details

    • getProgram

      public REProgram getProgram()
      Returns the current regular expression program in use by this matcher object.
      Returns:
      Regular expression program

    • getParenCount

      public int getParenCount()
      Returns the number of parenthesized subexpressions available after a successful match.
      Returns:
      Number of available parenthesized subexpressions

    • getParen

      public UnicodeString getParen(int which)
      Gets the contents of a parenthesized subexpression after a successful match.
      Parameters:
      which - Nesting level of subexpression
      Returns:
      String

    • getParenStart

      public final int getParenStart(int which)
      Returns the start index of a given paren level.
      Parameters:
      which - Nesting level of subexpression
      Returns:
      String index

    • getParenEnd

      public final int getParenEnd(int which)
      Returns the end index of a given paren level.
      Parameters:
      which - Nesting level of subexpression
      Returns:
      String index

    • capture

      protected final void capture(int which, int start, int end, boolean inLookahead)
      Sets a captured group
      Parameters:
      which - Which paren level
      start - start index in input string
      end - end index in input string
      inLookahead - true if the match is within a lookahead assertion

    • clearCapturedGroupsBeyond

      protected void clearCapturedGroupsBeyond(int pos)
      Clear any captured groups whose start position is at or beyond some specified position
      Parameters:
      pos - the specified position

    • matchAt

      protected boolean matchAt(int i, boolean anchored)
      Match the current regular expression program against the current input string, starting at index i of the input string. This method is only meant for internal use.
      Parameters:
      i - The input string index to start matching at
      anchored - true if the regex must match all characters up to the end of the string
      Returns:
      True if the input matched the expression

    • isAnchoredMatch

      public boolean isAnchoredMatch(UnicodeString search)
      Tests whether the regex matches a string in its entirety, anchored at both ends
      Parameters:
      search - the string to be matched
      Returns:
      true if the regex matches the whole string

    • match

      public boolean match(UnicodeString search, int i)
      Matches the current regular expression program against a character array, starting at a given index.
      Parameters:
      search - String to match against
      i - Index to start searching at
      Returns:
      True if string matched

    • match

      public boolean match(String search)
      Matches the current regular expression program against a String.
      Parameters:
      search - String to match against
      Returns:
      True if string matched

    • split

      public List<UnicodeString> split(UnicodeString s)
      Splits a string into an array of strings on regular expression boundaries. This function works the same way as the Perl function of the same name. Given a regular expression of "[ab]+" and a string to split of "xyzzyababbayyzabbbab123", the result would be the array of Strings "[xyzzy, yyz, 123]".

      Please note that the first string in the resulting array may be an empty string. This happens when the very first character of input string is matched by the pattern.

      Parameters:
      s - String to split on this regular exression
      Returns:
      A list of strings

    • replace

      public UnicodeString replace(UnicodeString in, UnicodeString replacement)
      Substitutes a string for this regular expression in another string. This method works like the Perl function of the same name. Given a regular expression of "a*b", a String to substituteIn of "aaaabfooaaabgarplyaaabwackyb" and the substitution String "-", the resulting String returned by subst would be "-foo-garply-wacky-".

      It is also possible to reference the contents of a parenthesized expression with $0, $1, ... $9. A regular expression of "http://[\\.\\w\\-\\?/~_@&=%]+", a String to substituteIn of "visit us: http://www.apache.org!" and the substitution String "<a href=\"$0\">$0</a>", the resulting String returned by subst would be "visit us: <a href=\"http://www.apache.org\">http://www.apache.org</a>!".

      Note: $0 represents the whole match.

      Parameters:
      in - String to substitute within
      replacement - String to substitute for matches of this regular expression
      Returns:
      The string substituteIn with zero or more occurrences of the current regular expression replaced with the substitution String (if this regular expression object doesn't match at any position, the original String is returned unchanged).

    • replaceWith

      public UnicodeString replaceWith(UnicodeString in, BiFunction<UnicodeString,UnicodeString[],UnicodeString> replacer)
      Substitutes a string for this regular expression in another string. This method works like the Perl function of the same name. Given a regular expression of "a*b", a String to substituteIn of "aaaabfooaaabgarplyaaabwackyb" and the substitution String "-", the resulting String returned by subst would be "-foo-garply-wacky-".

      It is also possible to reference the contents of a parenthesized expression with $0, $1, ... $9. A regular expression of "http://[\\.\\w\\-\\?/~_@&=%]+", a String to substituteIn of "visit us: http://www.apache.org!" and the substitution String "<a href=\"$0\">$0</a>", the resulting String returned by subst would be "visit us: <a href=\"http://www.apache.org\">http://www.apache.org</a>!".

      Note: $0 represents the whole match.

      Parameters:
      in - String to substitute within
      replacer - Function to process each matching substring and return a replacement
      Returns:
      The string substituteIn with zero or more occurrences of the current regular expression replaced with the substitution String (if this regular expression object doesn't match at any position, the original String is returned unchanged).

    • captureState

      public REMatcher.CapturedGroupState captureState()

    • resetState

      public void resetState(REMatcher.CapturedGroupState state)