The following listing contains the interface of the RegEx unit.
This unit provides routines to match strings against regular expressions and perform substitutions using matched subexpressions. Regular expressions are strings with some characters having special meanings. They describe (match) a class of strings. They are similar to wild cards used in file name matching, but much more powerful.
To use this unit, you will need the rx library which can be found in http://www.gnu-pascal.de/libs/.
{$nested-comments} { Regular expression matching and replacement The RegEx unit provides routines to match strings against regular expressions and perform substitutions using matched subexpressions. To use the RegEx unit, you will need the rx library which can be found in http://www.gnu-pascal.de/libs/ Regular expressions are strings with some characters having special meanings. They describe (match) a class of strings. They are similar to wild cards used in file name matching, but much more powerful. There are two kinds of regular expressions supported by this unit, basic and extended regular expressions. The difference between them is not functionality, but only syntax. The following is a short overview of regular expressions. For a more thorough explanation see the literature, or the documentation of the rx library, or man pages of programs like grep(1) and sed(1). Basic Extended Meaning . . matches any single character [aei-z] [aei-z] matches either a, e, or any character from i to z [^aei-z] [^aei-z] matches any character but a, e, or i .. z To include in such a list the the characters ], ^, or -, put them first, anywhere but first, or first or last, resp. [[:alnum:]] [[:alnum:]] matches any alphanumeric character [^[:digit:]] [^[:digit:]] matches anything but a digit [a[:space:]] [a[:space:]] matches the letter a or a space character (space, tab) ... (there are more classes available) \w \w = [[:alnum:]] \W \W = [^[:alnum:]] ^ ^ matches the empty string at the beginning of a line $ $ matches the empty string at the end of a line * * matches zero or more occurences of the preceding expression \+ + matches one or more occurences of the preceding expression \? ? matches zero or one occurence of the preceding expression \{N\} {N} matches exactly N occurences of the preceding expression (N is an integer number) \{M,N\} {M,N} matches M to N occurences of the preceding expression (M and N are integer numbers, M <= N) AB AB matches A followed by B (A and B are regular expressions) A\|B A|B matches A or B (A and B are regular expressions) \( \) ( ) forms a subexpression, to override precedence, and for subexpression references \7 \7 matches the 7'th parenthesized subexpression (counted by their start in the regex), where 7 is a number from 1 to 9 ;-). *Please note:* using this feature can be *very* slow or take very much memory (exponential time and space in the worst case, if you know what that means ...). \ \ quotes the following character if it's special (i.e. listed above) rest rest any other character matches itself Precedence, from highest to lowest: * parentheses (()) * repetition (*, +, ?, {}) * concatenation * alternation (|) When performing substitutions using matched subexpressions of a regular expression (see ReplaceSubExpressionReferences), the replacement string can reference the whole matched expression with & or \0, the 7th subexpression with \7 (just like in the regex itself, but using it in replacements is not slow), and the 7th subexpression converted to upper/lower case with \u7 or \l7, resp. (which also works for the whole matched expression with \u0 or \l0). A verbatim & or \ can be specified with \& or \\, resp. Copyright (C) 1998-2005 Free Software Foundation, Inc. Author: Frank Heckenbach <frank@pascal.gnu.de> This file is part of GNU Pascal. GNU Pascal is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Pascal is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Pascal; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. As a special exception, if you link this file with files compiled with a GNU compiler to produce an executable, this does not cause the resulting executable to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why the executable file might be covered by the GNU General Public License. Please also note the license of the rx library. } {$gnu-pascal,I-} {$if __GPC_RELEASE__ < 20030303} {$error This unit requires GPC release 20030303 or newer.} {$endif} unit RegEx; interface uses GPC; const { BasicRegExSpecialChars contains all characters that have special meanings in basic regular expressions. ExtRegExSpecialChars contains those that have special meanings in extended regular expressions. } BasicRegExSpecialChars = ['.', '[', ']', '^', '$', '*', '\']; ExtRegExSpecialChars = ['.', '[', ']', '^', '$', '*', '+', '?', '{', '}', '|', '(', ')', '\']; type { The type used by the routines of the RegEx unit to store regular expressions in an internal format. The fields RegEx, RegMatch, ErrorInternal, From and Length are only used internally. SubExpressions can be read after NewRegEx and will contain the number of parenthesized subexpressions. Error should be checked after NewRegEx. It will be nil when it succeeded, and contain an error message otherwise. } RegExType = record RegEx, RegMatch: Pointer; { Internal } ErrorInternal: CString; { Internal } From, Length: CInteger; { Internal } SubExpressions: CInteger; Error: PString end; { Simple interface to regular expression matching. Matches a regular expression against a string starting from a specified position. Returns the position of the first match, or 0 if it does not match, or the regular expression is invalid. } function RegExPosFrom (const Expression: String; ExtendedRegEx, CaseInsensitive: Boolean; const s: String; From: Integer) = MatchPosition: Integer; { Creates the internal format of a regular expression. If ExtendedRegEx is True, Expression is assumed to denote an extended regular expression, otherwise a basic regular expression. CaseInsensitive determines if the case of letters will be ignored when matching the expression. If NewLines is True, NewLine characters in a string matched against the expression will be treated as dividing the string in multiple lines, so that $ can match before the NewLine and ^ can match after. Also, . and [^...] will not match a NewLine then. } procedure NewRegEx (var RegEx: RegExType; const Expression: String; ExtendedRegEx, CaseInsensitive, NewLines: Boolean); { Disposes of a regular expression created with NewRegEx. *Must* be used after NewRegEx before the RegEx variable becomes invalid (i.e., goes out of scope or a pointer pointing to it is Dispose'd of). } procedure DisposeRegEx (var RegEx: RegExType); external name '_p_DisposeRegEx'; { Matches a regular expression created with NewRegEx against a string. } function MatchRegEx (var RegEx: RegExType; const s: String; NotBeginningOfLine, NotEndOfLine: Boolean): Boolean; { Matches a regular expression created with NewRegEx against a string, starting from a specified position. } function MatchRegExFrom (var RegEx: RegExType; const s: String; NotBeginningOfLine, NotEndOfLine: Boolean; From: Integer): Boolean; { Finds out where the regular expression matched, if MatchRegEx or MatchRegExFrom were successful. If n = 0, it returns the position of the whole match, otherwise the position of the n'th parenthesized subexpression. MatchPosition and MatchLength will contain the position (counted from 1) and length of the match, or 0 if it didn't match. (Note: MatchLength can also be 0 for a successful empty match, so check whether MatchPosition is 0 to find out if it matched at all.) MatchPosition or MatchLength may be Null and is ignored then. } procedure GetMatchRegEx (var RegEx: RegExType; n: Integer; var MatchPosition, MatchLength: Integer); { Checks if the string s contains any quoted characters or (sub)expression references to the regular expression RegEx created with NewRegEx. These are & or \0 for the whole matched expression (if OnlySub is not set) and \1 .. \9 for the n'th parenthesized subexpression. Returns 0 if it does not contain any, and the number of references and quoted characters if it does. If an invalid reference (i.e. a number bigger than the number of subexpressions in RegEx) is found, it returns the negative value of the (first) invalid reference. } function FindSubExpressionReferences (var RegEx: RegExType; const s: String; OnlySub: Boolean): Integer; { Replaces (sub)expression references in ReplaceStr by the actual (sub)expressions and unquotes quoted characters. To be used after the regular expression RegEx created with NewRegEx was matched against s successfully with MatchRegEx or MatchRegExFrom. } function ReplaceSubExpressionReferences (var RegEx: RegExType; const s, ReplaceStr: String) = Res: TString; { Returns the string for a regular expression that matches exactly one character out of the given set. It can be combined with the usual operators to form more complex expressions. } function CharSet2RegEx (const Characters: CharSet) = s: TString;