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TRegExpr

Implements regular expressions in pure Pascal. Compatible with Free Pascal, Delphi 2-7, C++Builder 3-6.

To use it, copy files "regexpr.pas", "regexpr_unicodedata.pas", "regexpr_compilers.inc", to your project folder.

The library is already included into Lazarus (Free Pascal) project so you do not need to copy anything if you use Lazarus.

TRegExpr class

VersionMajor, VersionMinor

Return major and minor version of the component.

VersionMajor = 1
VersionMinor = 101

Expression

Regular expression.

For optimization, regular expression is automatically compiled into P-code. Human-readable form of the P-code is returned by Dump.

In case of any errors in compilation, Error method is called (by default Error raises exception ERegExpr).

ModifierStr

Set or get values of regular expression modifiers.

Format of the string is similar to (?ismx-ismx). For example ModifierStr := ‘i-x’ will switch on the modifier /i, switch off /x and leave unchanged others.

If you try to set unsupported modifier, Error will be called.

ModifierI

Modifier /i, "case-insensitive", initialized with RegExprModifierI value.

ModifierR

Modifier /r, "Russian range extension", initialized with RegExprModifierR value.

ModifierS

Modifier /s, "single line strings", initialized with RegExprModifierS value.

ModifierG

Modifier /g, "greediness", initialized with RegExprModifierG value.

ModifierM

Modifier /m, "multi-line strings", initialized with RegExprModifierM value.

ModifierX

Modifier /x, "eXtended syntax", initialized with RegExprModifierX value.

Exec

Finds regular expression against AInputString, starting from the beginning.

The overloaded Exec version without AInputString exists, it uses AInputString from previous call.

See also global function ExecRegExpr that you can use without explicit TRegExpr object creation.

ExecNext

Finds next match. If parameter ABackward is True, it goes downto position 1, ie runs backward search.

Without parameter it works the same as:

if MatchLen [0] = 0
  then ExecPos (MatchPos [0] + 1)
  else ExecPos (MatchPos [0] + MatchLen [0]);

Raises exception if used without preceeding successful call to Exec, ExecPos or ExecNext.

So you always must use something like:

if Exec(InputString)
  then
    repeat
      { proceed results}
    until not ExecNext;

ExecPos

Finds match for AInputString starting from AOffset position (1-based).

Parameter ABackward means going from AOffset downto 1, ie backward search.

Parameter ATryOnce means that testing for regex will be only at the initial position, without going to next/previous positions.

InputString

Returns current input string (from last Exec call or last assign to this property).

Any assignment to this property clears Match, MatchPos and MatchLen.

Substitute

function Substitute (const ATemplate : RegExprString) : RegExprString;

Returns ATemplate, where $& or $0 are replaced with the found match, and $1 to $9 are replaced with found groups 1 to 9.

To use in template the characters $ or \, escape them with a backslash \, like \\ or \$.

Symbol Description
$& whole regular expression match
$0 whole regular expression match
$1 .. $9 contents of numbered group 1 .. 9
\n in Windows replaced with \r\n
\l lowercase one next char
\L lowercase all chars after that
\u uppercase one next char
\U uppercase all chars after that
'1\$ is $2\\rub\\' -> '1$ is <Match[2]>\rub\'
'\U$1\\r' transforms into '<Match[1] in uppercase>\r'

If you want to place raw digit after ‘$n’ you must delimit n with curly braces {}.

'a$12bc' -> 'a<Match[12]>bc'
'a${1}2bc' -> 'a<Match[1]>2bc'.

To use found named groups, use syntax ${name}, where "name" is valid identifier of previously found named group (starting with non-digit).

Split

Splits AInputStr into APieces by regex occurrences.

Internally calls Exec / ExecNext

See also global function SplitRegExpr that you can use without explicit TRegExpr object creation.

Replace, ReplaceEx

function Replace (Const AInputStr : RegExprString;
  const AReplaceStr : RegExprString;
  AUseSubstitution : boolean= False)
 : RegExprString; overload;

function Replace (Const AInputStr : RegExprString;
  AReplaceFunc : TRegExprReplaceFunction)
 : RegExprString; overload;

function ReplaceEx (Const AInputStr : RegExprString;
  AReplaceFunc : TRegExprReplaceFunction):
  RegExprString;

Returns the string with regex occurencies replaced by the replace string.

If last argument (AUseSubstitution) is true, then AReplaceStr will be used as template for Substitution methods.

Expression := '((?i)block|var)\s*(\s*\([^ ]*\)\s*)\s*';
Replace ('BLOCK( test1)', 'def "$1" value "$2"', True);

Returns def "BLOCK" value "test1"

Replace ('BLOCK( test1)', 'def "$1" value "$2"', False)

Returns def "$1" value "$2"

Internally calls Exec / ExecNext

Overloaded version and ReplaceEx operate with callback function, so you can implement really complex functionality.

See also global function ReplaceRegExpr that you can use without explicit TRegExpr object creation.

SubExprMatchCount

Count of groups (subexpressions) found in last Exec / ExecNext call.

If there are no groups found, but some string was found (Exec* returned True), it returns 0. If no groups nor some string were found (Exec / ExecNext returned false), it returns -1.

Note, that some group may be not found, and for such group MathPos=MatchLen=-1 and Match=’’.

Expression := '(1)?2(3)?';
Exec ('123'): SubExprMatchCount=2, Match[0]='123', [1]='1', [2]='3'

Exec ('12'): SubExprMatchCount=1, Match[0]='12', [1]='1'

Exec ('23'): SubExprMatchCount=2, Match[0]='23', [1]='', [2]='3'

Exec ('2'): SubExprMatchCount=0, Match[0]='2'

Exec ('7') - return False: SubExprMatchCount=-1

MatchPos

Position (1-based) of group with specified index. Result is valid only after some match was found. First group has index 1, the entire match has index 0.

Returns -1 if no group with specified index was found.

MatchLen

Length of group with specified index. Result is valid only after some match was found. First group has index 1, the entire match has index 0.

Returns -1 if no group with specified index was found.

Match

String of group with specified index. First group has index 1, the entire match has index 0. Returns empty string, if no such group was found.

MatchIndexFromName

Returns group index (1-based) from group name, which is needed for "named groups". Returns -1 if no such named group was found.

LastError

Returns Id of last error, or 0 if no errors occured (unusable if Error method raises exception). It also clears internal status to 0 (no errors).

ErrorMsg

Returns Error message for error with ID = AErrorID.

CompilerErrorPos

Returns position in regex, where P-code compilation was stopped.

Useful for error diagnostics.

SpaceChars

Contains chars, treated as \s (initially filled with RegExprSpaceChars global constant).

WordChars

Contains chars, treated as \w (initially filled with RegExprWordChars global constant).

LineSeparators

Line separators (like \n in Unix), initially filled with RegExprLineSeparators global constant).

See also Line Boundaries

UseLinePairedBreak

Boolean property, enables to detect paired line separator CR LF.

See also Line Boundaries

For example, if you need only Unix-style separator LF, assign LineSeparators := #$a and UseLinePairedBreak := False.

If you want to accept as line separators only CR LF but not CR or LF alone, then assign LineSeparators := '' (empty string) and UseLinePairedBreak := True.

By default, "mixed" mode is used (defined in RegExprLineSeparators global constant):

LineSeparators := #$d#$a;
UseLinePairedBreak := True;

Behaviour of this mode is described in the Line Boundaries.

Compile

Compiles regular expression to internal P-code.

Useful for example for GUI regular expressions editors - to check regular expression without using it.

Dump

Shows P-code (compiled regular expression) as human-readable string.

Global constants

EscChar

Escape character, by default backslash '\'.

SubstituteGroupChar

Char used to prefix groups (numbered and named) in Substitute method, by default '$'.

RegExprModifierI

Modifier i default value.

RegExprModifierR

Modifier r default value.

RegExprModifierS

Modifier s default value.

RegExprModifierG

Modifier g default value.

RegExprModifierM

Modifier m default value.

RegExprModifierX

Modifier x default value.

RegExprSpaceChars

Default for SpaceChars property.

RegExprWordChars

Default value for WordChars property.

RegExprLineSeparators

Default value for LineSeparators property.

Global functions

All this functionality is available as methods of TRegExpr, but with global functions you do not need to create TReExpr instance so your code would be more simple if you just need one function.

ExecRegExpr

Returns True if the string matches the regular expression. Just like Exec in TRegExpr.

SplitRegExpr

Splits the string by regular expression occurences. See also Split if you prefer to create TRegExpr instance explicitly.

ReplaceRegExpr

function ReplaceRegExpr (
    const ARegExpr, AInputStr, AReplaceStr : RegExprString;
    AUseSubstitution : boolean= False
) : RegExprString; overload;

Type
  TRegexReplaceOption = (rroModifierI,
                         rroModifierR,
                         rroModifierS,
                         rroModifierG,
                         rroModifierM,
                         rroModifierX,
                         rroUseSubstitution,
                         rroUseOsLineEnd);
  TRegexReplaceOptions = Set of TRegexReplaceOption;

function ReplaceRegExpr (
    const ARegExpr, AInputStr, AReplaceStr : RegExprString;
    Options :TRegexReplaceOptions
) : RegExprString; overload;

Returns the string with regular expressions replaced by the AReplaceStr. See also Replace if you prefer to create TRegExpr instance explicitly.

If last argument (AUseSubstitution) is True, then AReplaceStr will be used as template for Substitution methods:

ReplaceRegExpr (
  '((?i)block|var)\s*(\s*\([^ ]*\)\s*)\s*',
  'BLOCK(test1)',
  'def "$1" value "$2"',
  True
)

Returns def 'BLOCK' value 'test1'

But this one (note there is no last argument):

ReplaceRegExpr (
  '((?i)block|var)\s*(\s*\([^ ]*\)\s*)\s*',
  'BLOCK(test1)',
  'def "$1" value "$2"'
)

Returns def "$1" value "$2"

Version with options

With Options you control \n behaviour (if rroUseOsLineEnd then \n is replaced with \n\r in Windows and \n in Linux). And so on.

Type
  TRegexReplaceOption = (rroModifierI,
                         rroModifierR,
                         rroModifierS,
                         rroModifierG,
                         rroModifierM,
                         rroModifierX,
                         rroUseSubstitution,
                         rroUseOsLineEnd);

QuoteRegExprMetaChars

Replace all metachars with its safe representation, for example abc'cd.( is converted to abc\'cd\.\(

This function is useful for regex auto-generation from user input.

RegExprSubExpressions

Makes list of subexpressions found in ARegExpr.

In ASubExps every item represents subexpression, from first to last, in format:

 String - subexpression text (without ‘()’)

 Low word of Object - starting position in ARegExpr, including ‘(’ if exists! (first position is 1)

 High word of Object - length, including starting ‘(’ and ending ‘)’ if exist!

AExtendedSyntax - must be True if modifier /x os on, while using the regex.

Usefull for GUI editors of regex (you can find example of usage in REStudioMain.pas)

Result code Meaning
0 Success. No unbalanced brackets were found.
-1 Not enough closing brackets ).
-(n+1) At position n it was found opening [ without corresponding closing ].
n At position n it was found closing bracket ) without corresponding opening (.

If Result <> 0, then ASubExprs can contain empty items or illegal ones.

ERegExpr

ERegExpr = class (Exception)
  public
   ErrorCode : integer; // error code. Compilation error codes are before 1000
   CompilerErrorPos : integer; // Position in r.e. where compilation error occured
 end;

Unicode

In Unicode mode, all strings (InputString, Expression, internal strings) are of type UnicodeString/WideString, instead of simple "string". Unicode slows down performance, so use it only if you really need Unicode support.

To use Unicode, uncomment {$DEFINE UniCode} in regexpr.pas (remove off).