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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) 1998-2003 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: Integer; { Internal }
SubExpressions: Integer;
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):
Integer; attribute (name = '_p_RegExPosFrom');
{ 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); attribute
(name = '_p_NewRegEx');
{ 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; attribute
(name = '_p_MatchRegEx');
{ 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; attribute (name = '_p_MatchRegExFrom');
{ 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); external
name '_p_GetMatchRegEx';
{ 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; attribute (name
= '_p_FindSubExpressionReferences');
{ 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): TString; attribute (name
= '_p_ReplaceSubExpressionReferences');
{ 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): TString;
attribute (name = '_p_CharSet2RegEx');