Class representing a regular expression. More...

#include <src/regex.h>

Classes
class	Private
	Private members of a regular expression. More...

Public Types
enum class	Mode { RegEx , Wildcard }
	Matching algorithm. More...

Public Member Functions
	Ex (std::string_view pattern, Mode mode=Mode::RegEx)
	Creates a regular expression object given the pattern as a string.
	~Ex ()
	Destroys the regular expression object.
bool	match (std::string_view str, Match &match, size_t pos=0) const
	Check if a given string matches this regular expression.
bool	isValid () const

Private Attributes
std::unique_ptr< Private >	p

Detailed Description

Class representing a regular expression.

It has a similar API as std::regex, but is much faster (and also somewhat more limited).

Definition at line 38 of file regex.h.

Member Enumeration Documentation

◆ Mode

enum class reg::Ex::Mode

strong

Matching algorithm.

Enumerator
RegEx	full regular expression.
Wildcard	simple globbing pattern.

Definition at line 42 of file regex.h.

    {
      RegEx,    /**< full regular expression. */
      Wildcard  /**< simple globbing pattern. */
    };

Constructor & Destructor Documentation

◆ Ex()

reg::Ex::Ex	(	std::string_view	pattern,
		Mode	mode = Mode::RegEx )

Creates a regular expression object given the pattern as a string.

Two modes of matching are supported: RegEx and Wildcard

The following special characters are supported in Mode::RegEx mode.

c matches character c
. matches any character
^ matches the start of the input
$ matches the end of the input
\< matches the start of a word
\> matches the end of a word
[] matches a set of characters
x* matches a sequence of zero or more x's
x+ matches a sequence of one or more x's
x? matches an optional x
( matches the start of a capture range
) matches the ends a capture range
\c to escape a special character, such as +, [, *, (, etc.
\t matches a tab character
\n matches a newline character
\r matches a return character
\s matches any whitespace as defined by std::isspace()
\d matches any digit as defined by std::digit()
\a matches any alphabetical characters, same as [a-z_A-Z\x80-\xFF]
\w matches any alpha numerical character, same as [a-z_A-Z0-9\x80-\xFF]
\xHH matches a hexadecimal character, e.g. \xA0 matches character code 160.

A character range can be used to match a character that falls inside a range (or set of ranges). Within the opening [ and closing ] brackets of a character ranges the following is supported:

^ if at the start of the range, a character matches if it is not in the range, e.g. [^\d] matches any character not a digit
- when placed between 2 characters it defines a range from the first character to the second. any character that falls in the range will match, e.g. [0-9] matches the digit from 0 to 9.
\s, \d, \a, and \w as explained above.

Note: that special characters ., *, ?, $, +, [ do not have a special meaning in a character range. ^ only has a special meaning as the first character.; that capture ranges cannot be nested, and *, +, and ? do not work on capture ranges. e.g. (abd)? is not valid. If multiple capture ranges are specified then some character has to be in between them, e.g. this does not work (.*)(a.*), but this does (.*)a(.*).

In Wildcard mode * is used to match any sequence of zero or more characters. The character ? can be used to match an optional character. Character ranges are also supported, but other characters like $ and + are just treated as literal characters.

Definition at line 694 of file regex.cpp.

  : p(std::make_unique<Private>(mode==Mode::RegEx ? pattern : wildcard2regex(pattern)))
{
  p->compile();
#if ENABLE_DEBUG
  p->dump();
  assert(!p->error);
#endif
}

References p, RegEx, and reg::wildcard2regex().

Referenced by ~Ex().

◆ ~Ex()

reg::Ex::~Ex ( )

default

Destroys the regular expression object.

Frees resources.

References Ex(), and match().

Member Function Documentation

◆ isValid()

bool reg::Ex::isValid ( ) const

Definition at line 741 of file regex.cpp.

{
  return !p->pattern.empty() && !p->error;
}

References p.

Referenced by genericPatternMatch(), and getFilterFromList().

◆ match()

bool reg::Ex::match	(	std::string_view	str,
		Match &	match,
		size_t	pos = 0 ) const

Check if a given string matches this regular expression.

Parameters

str	The input string to match against.
match	The match object to hold the matching results.
pos	The position in the string at which to start the match.

Returns: true iff a match is found. Details are stored in the match object.

Definition at line 706 of file regex.cpp.

{
  bool found=false;
  if (p->data.size()==0 || p->error) return found;
  match.init(str);
 
  PToken tok = p->data[0];
  if (tok.kind()==PToken::Kind::BeginOfLine) // only test match at the given position
  {
    found = p->matchAt(0,p->data.size(),str,match,pos,0);
  }
  else
  {
    if (tok.kind()==PToken::Kind::Character) // search for the start character
    {
      size_t index = str.find(tok.asciiValue(),pos);
      if (index==std::string::npos)
      {
        DBG("Ex::match(str='%s',pos=%zu)=false (no start char '%c')\n",str.c_str(),pos,tok.asciiValue());
        return false;
      }
      DBG("pos=%zu str='%s' char='%c' index=%zu\n",index,str.c_str(),tok.asciiValue(),index);
      pos=index;
    }
    while (pos<str.length()) // search for a match starting at pos
    {
      found = p->matchAt(0,p->data.size(),str,match,pos,0);
      if (found) break;
      pos++;
    }
  }
  DBG("Ex::match(str='%s',pos=%zu)=%d\n",str.c_str(),pos,found);
  return found;
}