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Contents of README:$XFree86: xc/programs/xedit/lisp/re/README,v 1.3 2002/09/23 01:25:41 paulo Exp $ LAST UPDATED: $Date: 2008/07/30 04:16:29 $ This is a small regex library for fast matching tokens in text. It was built to be used by xedit and it's syntax highlight code. It is not compliant with IEEE Std 1003.2, but is expected to be used where very fast matching is required, and exotic patterns will not be used. To understand what kind of patterns this library is expected to be used with, see the file <XRoot>xc/programs/xedit/lisp/modules/progmodes/c.lsp and some samples in the file tests.txt, with comments for patterns that will not work, or may give incorrect results. The library is not built upon the standard regex library by Henry Spencer, but is completely written from scratch, but it's syntax is heavily based on that library, and the only reason for it to exist is that unfortunately the standard version does not fit the requirements needed by xedit. Anyways, I would like to thanks Henry for his regex library, it is a really very useful tool. Small description of understood tokens: M A T C H I N G ------------------------------------------------------------------------ . Any character (won't match newline if compiled with RE_NEWLINE) \w Any word letter (shortcut to [a-zA-Z0-9_] \W Not a word letter (shortcut to [^a-zA-Z0-9_] \d Decimal number \D Not a decimal number \s A space \S Not a space \l A lower case letter \u An upper case letter \c A control character, currently the range 1-32 (minus tab) \C Not a control character \o Octal number \O Not an octal number \x Hexadecimal number \X Not an hexadecimal number \< Beginning of a word (matches an empty string) \> End of a word (matches an empty string) ^ Beginning of a line (matches an empty string) $ End of a line (matches an empty string) [...] Matches one of the characters inside the brackets ranges are specified separating two characters with "-". If the first character is "^", matches only if the character is not in this range. To add a "]" make it the first character, and to add a "-" make it the last. \1 to \9 Backreference, matches the text that was matched by a group, that is, text that was matched by the pattern inside "(" and ")". O P E R A T O R S ------------------------------------------------------------------------ () Any pattern inside works as a backreference, and is also used to group patterns. | Alternation, allows choosing different possibilities, like character ranges, but allows patterns of different lengths. R E P E T I T I O N ------------------------------------------------------------------------ <re>* <re> may occur any number of times, including zero <re>+ <re> must occur at least once <re>? <re> is optional <re>{<e>} <re> must occur exactly <e> times <re>{<n>,} <re> must occur at least <n> times <re>{,<m>} <re> must not occur more than <m> times <re>{<n>,<m>} <re> must occur at least <n> times, but no more than <m> Note that "." is a special character, and when used with a repetition operator it changes completely its meaning. For example, ".*" matches anything up to the end of the input string (unless the pattern was compiled with RE_NEWLINE, in that case it will match anything, but a newline). Limitations: o Only minimal matches supported. The engine has only one level "backtracking", so, it also only does minimal matches to allow backreferences working properly, and to avoid failing to match depending on the input. o Only one level "grouping", for example, with the pattern: (a(b)c) If "abc" is anywhere in the input, it will be in "\1", but there will not exist a "\2" for "b". o Some "special repetitions" were not implemented, these are: .{<e>} .{<n>,} .{,<m>} .{<n>,<m>} o Some patterns will never match, for example: \w*\d Since "\w*" already includes all possible matches of "\d", "\d" will only be tested when "\w*" failed. There are no plans to make such patterns work. Some of these limitations may be worked on future versions of the library, but this is not what the library is expected to do, and, adding support for correct handling of these would probably make the library slower, what is not the reason of it to exist in the first time. If you need "true" regex than this library is not for you, but if all you need is support for very quickly finding simple patterns, than this library can be a very powerful tool, on some patterns it can run more than 200 times faster than "true" regex implementations! And this is the reason it was written. Send comments and code to me (paulo@XFree86.Org) or to the XFree86 mailing/patch lists. -- Paulo |
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CVS/ 19-Mar-2020 23:40 -
README 30-Jul-2008 06:16 4.6K
re.c 19-Jul-2015 21:43 62K
re.h 30-Jul-2008 06:16 3.5K
rec.c 30-Jul-2008 06:16 23K
reo.c 30-Jul-2008 06:16 16K
rep.h 30-Jul-2008 06:16 11K
tests.c 10-Mar-2009 04:48 5.2K
tests.txt 10-Mar-2009 04:48 8.9K
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