[389-devel] Please review: Use thread aware library for complex regex searches

[Noriko Hosoi <nhosoi@xxxxxxxxxx>]

Subject: Use thread aware library for complex regex searches

Link: 
http://nhosoi.fedorapeople.org/0001-Use-thread-aware-library-for-complex-regex-searches.patch

Unfortunately, the fedoraproject.org is closed now.  I'm going to create 
the page http://directory.fedoraproject.org/wiki/Thread_Aware_Regex 
which contains the following notes as soon as the wiki is reopened.
------------------------------------------------------------------------
Directory Server used to use the regular expression pattern matching and 
replacing library which was not thread safe.  Thus, the operation should 
have been protected by the mutex lock.  Regular expression could be used 
by the search filters (syntax plugin), acl, schema file load, and SASL 
Mapping.  If one of them took a long time, the rest should have been 
blocked.  Replacing the library with the thread aware library solves the 
problem and improves the throughput.

[http://www.pcre.org/ PCRE - Perl Compatible Regular Expressions] 
library is installed on RHELs/Fedoras, by default.  We need just a 
subset of the APIs, thus we provide simplified slapi APIs wrapping the 
PCRE APIs.

NAME
slapi_re_comp -- compiles a regular expression pattern. A thin wrapper 
of pcre_compile.
SYNOPSIS
Slapi_Regex *slapi_re_comp( char *pat, char **error );
PARAMS
pat: Pattern to be compiled.
error: The error string is set if the compile fails.
RETURN VALUE
a pointer to the regex handler which stores the compiled pattern.
NULL if the compile fails.
WARNING
The regex handler should be released by slapi_re_free().

NAME
slapi_re_exec -- matches a compiled regular expression pattern against 
a given string. A thin wrapper of pcre_exec.
SYNOPSIS
int slapi_re_exec( Slapi_Regex *re_handle, char *subject, time_t 
time_up );
PARAMS
re_handle: The regex handler returned from slapi_re_comp.
subject: A string to be checked against the compiled pattern.
time_up: If the current time is larger than the value, this function 
returns immediately.  (-1) means no time limit.
RETURN VALUE
0 if the string did not match.
1 if the string matched.
other values if any error occurred.

NAME
slapi_re_subs -- substitutes '&' or '\#' in the param src with the 
matched string.
SYNOPSIS
int slapi_re_subs( Slapi_Regex *re_handle, char *subject, char *src, 
char **dst, unsigned long dstlen );
PARAMS
re_handle: The regex handler returned from slapi_re_comp.
subject: A string checked against the compiled pattern.
src: A given string which could contain the substitution symbols.
dst: A pointer pointing to the memory which stores the output string.
dstlen: Size of the memory dst.
RETURN VALUE
1 if the substitution was successful.
0 if the substitution failed.

NAME
slapi_re_free -- releases the regex handler which was returned from 
slapi_re_comp.
SYNOPSIS
void slapi_re_free(Slapi_Regex *re_handle);
PARAMS
re_handle: The regex handler to be released.
RETURN VALUE
none
------------------------------------------------------------------------

Thanks,
--noriko

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