From: Ilya Zakharevich Date: Thu, 9 Sep 1999 02:49:49 +0000 (-0400) Subject: Clear up PL_regcc issues. X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=2ab053812751d8a65a6b8eda6829e97c0876564b;p=p5sagit%2Fp5-mst-13.2.git Clear up PL_regcc issues. To: perl5-porters@perl.org (Mailing list Perl5) Subject: [PATCH 5.005_60] Another regexec.c unobfuscation Message-Id: <199909090649.CAA26119@monk.mps.ohio-state.edu> p4raw-id: //depot/cfgperl@4109 --- diff --git a/regexec.c b/regexec.c index 3fb1826..54f5e22 100644 --- a/regexec.c +++ b/regexec.c @@ -642,7 +642,6 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char * register I32 tmp; I32 minlen; /* must match at least this many chars */ I32 dontbother = 0; /* how many characters not to try at end */ - CURCUR cc; I32 start_shift = 0; /* Offset of the start to find constant substr. */ /* CC */ I32 end_shift = 0; /* Same for the end. */ /* CC */ @@ -650,9 +649,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char * char *scream_olds; SV* oreplsv = GvSV(PL_replgv); - cc.cur = 0; - cc.oldcc = 0; - PL_regcc = &cc; + PL_regcc = 0; cache_re(prog); #ifdef DEBUGGING @@ -2109,7 +2106,6 @@ S_regmatch(pTHX_ regnode *prog) regexp *re; MAGIC *mg = Null(MAGIC*); re_cc_state state; - CURCUR cctmp; CHECKPOINT cp, lastcp; if(SvROK(ret) || SvRMAGICAL(ret)) { @@ -2152,9 +2148,7 @@ S_regmatch(pTHX_ regnode *prog) state.cc = PL_regcc; state.re = PL_reg_re; - cctmp.cur = 0; - cctmp.oldcc = 0; - PL_regcc = &cctmp; + PL_regcc = 0; cp = regcppush(0); /* Save *all* the positions. */ REGCP_SET; @@ -2227,6 +2221,81 @@ S_regmatch(pTHX_ regnode *prog) case LOGICAL: logical = scan->flags; break; +/******************************************************************* + PL_regcc contains infoblock about the innermost (...)* loop, and + a pointer to the next outer infoblock. + + Here is how Y(A)*Z is processed (if it is compiled into CURLYX/WHILEM): + + 1) After matching X, regnode for CURLYX is processed; + + 2) This regnode creates infoblock on the stack, and calls + regmatch() recursively with the starting point at WHILEM node; + + 3) Each hit of WHILEM node tries to match A and Z (in the order + depending on the current iteration, min/max of {min,max} and + greediness). The information about where are nodes for "A" + and "Z" is read from the infoblock, as is info on how many times "A" + was already matched, and greediness. + + 4) After A matches, the same WHILEM node is hit again. + + 5) Each time WHILEM is hit, PL_regcc is the infoblock created by CURLYX + of the same pair. Thus when WHILEM tries to match Z, it temporarily + resets PL_regcc, since this Y(A)*Z can be a part of some other loop: + as in (Y(A)*Z)*. If Z matches, the automaton will hit the WHILEM node + of the external loop. + + Currently present infoblocks form a tree with a stem formed by PL_curcc + and whatever it mentions via ->next, and additional attached trees + corresponding to temporarily unset infoblocks as in "5" above. + + In the following picture infoblocks for outer loop of + (Y(A)*?Z)*?T are denoted O, for inner I. NULL starting block + is denoted by x. The matched string is YAAZYAZT. Temporarily postponed + infoblocks are drawn below the "reset" infoblock. + + In fact in the picture below we do not show failed matches for Z and T + by WHILEM blocks. [We illustrate minimal matches, since for them it is + more obvious *why* one needs to *temporary* unset infoblocks.] + + Matched REx position InfoBlocks Comment + (Y(A)*?Z)*?T x + Y(A)*?Z)*?T x <- O + Y (A)*?Z)*?T x <- O + Y A)*?Z)*?T x <- O <- I + YA )*?Z)*?T x <- O <- I + YA A)*?Z)*?T x <- O <- I + YAA )*?Z)*?T x <- O <- I + YAA Z)*?T x <- O # Temporary unset I + I + + YAAZ Y(A)*?Z)*?T x <- O + I + + YAAZY (A)*?Z)*?T x <- O + I + + YAAZY A)*?Z)*?T x <- O <- I + I + + YAAZYA )*?Z)*?T x <- O <- I + I + + YAAZYA Z)*?T x <- O # Temporary unset I + I,I + + YAAZYAZ )*?T x <- O + I,I + + YAAZYAZ T x # Temporary unset O + O + I,I + + YAAZYAZT x + O + I,I + *******************************************************************/ case CURLYX: { CURCUR cc; CHECKPOINT cp = PL_savestack_ix; @@ -2279,7 +2348,8 @@ S_regmatch(pTHX_ regnode *prog) if (locinput == cc->lastloc && n >= cc->min) { PL_regcc = cc->oldcc; - ln = PL_regcc->cur; + if (PL_regcc) + ln = PL_regcc->cur; DEBUG_r( PerlIO_printf(Perl_debug_log, "%*s empty match detected, try continuation...\n", @@ -2292,7 +2362,8 @@ S_regmatch(pTHX_ regnode *prog) "%*s failed...\n", REPORT_CODE_OFF+PL_regindent*2, "") ); - PL_regcc->cur = ln; + if (PL_regcc) + PL_regcc->cur = ln; PL_regcc = cc; sayNO; } @@ -2363,7 +2434,8 @@ S_regmatch(pTHX_ regnode *prog) if (cc->minmod) { PL_regcc = cc->oldcc; - ln = PL_regcc->cur; + if (PL_regcc) + ln = PL_regcc->cur; cp = regcppush(cc->parenfloor); REGCP_SET; if (regmatch(cc->next)) { @@ -2372,7 +2444,8 @@ S_regmatch(pTHX_ regnode *prog) } REGCP_UNWIND; regcppop(); - PL_regcc->cur = ln; + if (PL_regcc) + PL_regcc->cur = ln; PL_regcc = cc; if (n >= cc->max) { /* Maximum greed exceeded? */ @@ -2443,14 +2516,16 @@ S_regmatch(pTHX_ regnode *prog) /* Failed deeper matches of scan, so see if this one works. */ PL_regcc = cc->oldcc; - ln = PL_regcc->cur; + if (PL_regcc) + ln = PL_regcc->cur; if (regmatch(cc->next)) sayYES; DEBUG_r( PerlIO_printf(Perl_debug_log, "%*s failed...\n", REPORT_CODE_OFF+PL_regindent*2, "") ); - PL_regcc->cur = ln; + if (PL_regcc) + PL_regcc->cur = ln; PL_regcc = cc; cc->cur = n - 1; cc->lastloc = lastloc;