/* $OpenBSD: tblcmp.c,v 1.6 2003/06/04 17:34:44 millert Exp $ */ /* tblcmp - table compression routines */ /*- * Copyright (c) 1990 The Regents of the University of California. * All rights reserved. * * This code is derived from software contributed to Berkeley by * Vern Paxson. * * The United States Government has rights in this work pursuant * to contract no. DE-AC03-76SF00098 between the United States * Department of Energy and the University of California. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE. */ /* $Header: /cvs/OpenBSD/src/usr.bin/lex/tblcmp.c,v 1.6 2003/06/04 17:34:44 millert Exp $ */ #include "flexdef.h" /* declarations for functions that have forward references */ void mkentry PROTO((int*, int, int, int, int)); void mkprot PROTO((int[], int, int)); void mktemplate PROTO((int[], int, int)); void mv2front PROTO((int)); int tbldiff PROTO((int[], int, int[])); /* bldtbl - build table entries for dfa state * * synopsis * int state[numecs], statenum, totaltrans, comstate, comfreq; * bldtbl( state, statenum, totaltrans, comstate, comfreq ); * * State is the statenum'th dfa state. It is indexed by equivalence class and * gives the number of the state to enter for a given equivalence class. * totaltrans is the total number of transitions out of the state. Comstate * is that state which is the destination of the most transitions out of State. * Comfreq is how many transitions there are out of State to Comstate. * * A note on terminology: * "protos" are transition tables which have a high probability of * either being redundant (a state processed later will have an identical * transition table) or nearly redundant (a state processed later will have * many of the same out-transitions). A "most recently used" queue of * protos is kept around with the hope that most states will find a proto * which is similar enough to be usable, and therefore compacting the * output tables. * "templates" are a special type of proto. If a transition table is * homogeneous or nearly homogeneous (all transitions go to the same * destination) then the odds are good that future states will also go * to the same destination state on basically the same character set. * These homogeneous states are so common when dealing with large rule * sets that they merit special attention. If the transition table were * simply made into a proto, then (typically) each subsequent, similar * state will differ from the proto for two out-transitions. One of these * out-transitions will be that character on which the proto does not go * to the common destination, and one will be that character on which the * state does not go to the common destination. Templates, on the other * hand, go to the common state on EVERY transition character, and therefore * cost only one difference. */ void bldtbl( state, statenum, totaltrans, comstate, comfreq ) int state[], statenum, totaltrans, comstate, comfreq; { int extptr, extrct[2][CSIZE + 1]; int mindiff, minprot, i, d; /* If extptr is 0 then the first array of extrct holds the result * of the "best difference" to date, which is those transitions * which occur in "state" but not in the proto which, to date, * has the fewest differences between itself and "state". If * extptr is 1 then the second array of extrct hold the best * difference. The two arrays are toggled between so that the * best difference to date can be kept around and also a difference * just created by checking against a candidate "best" proto. */ extptr = 0; /* If the state has too few out-transitions, don't bother trying to * compact its tables. */ if ( (totaltrans * 100) < (numecs * PROTO_SIZE_PERCENTAGE) ) mkentry( state, numecs, statenum, JAMSTATE, totaltrans ); else { /* "checkcom" is true if we should only check "state" against * protos which have the same "comstate" value. */ int checkcom = comfreq * 100 > totaltrans * CHECK_COM_PERCENTAGE; minprot = firstprot; mindiff = totaltrans; if ( checkcom ) { /* Find first proto which has the same "comstate". */ for ( i = firstprot; i != NIL; i = protnext[i] ) if ( protcomst[i] == comstate ) { minprot = i; mindiff = tbldiff( state, minprot, extrct[extptr] ); break; } } else { /* Since we've decided that the most common destination * out of "state" does not occur with a high enough * frequency, we set the "comstate" to zero, assuring * that if this state is entered into the proto list, * it will not be considered a template. */ comstate = 0; if ( firstprot != NIL ) { minprot = firstprot; mindiff = tbldiff( state, minprot, extrct[extptr] ); } } /* We now have the first interesting proto in "minprot". If * it matches within the tolerances set for the first proto, * we don't want to bother scanning the rest of the proto list * to see if we have any other reasonable matches. */ if ( mindiff * 100 > totaltrans * FIRST_MATCH_DIFF_PERCENTAGE ) { /* Not a good enough match. Scan the rest of the * protos. */ for ( i = minprot; i != NIL; i = protnext[i] ) { d = tbldiff( state, i, extrct[1 - extptr] ); if ( d < mindiff ) { extptr = 1 - extptr; mindiff = d; minprot = i; } } } /* Check if the proto we've decided on as our best bet is close * enough to the state we want to match to be usable. */ if ( mindiff * 100 > totaltrans * ACCEPTABLE_DIFF_PERCENTAGE ) { /* No good. If the state is homogeneous enough, * we make a template out of it. Otherwise, we * make a proto. */ if ( comfreq * 100 >= totaltrans * TEMPLATE_SAME_PERCENTAGE ) mktemplate( state, statenum, comstate ); else { mkprot( state, statenum, comstate ); mkentry( state, numecs, statenum, JAMSTATE, totaltrans ); } } else { /* use the proto */ mkentry( extrct[extptr], numecs, statenum, prottbl[minprot], mindiff ); /* If this state was sufficiently different from the * proto we built it from, make it, too, a proto. */ if ( mindiff * 100 >= totaltrans * NEW_PROTO_DIFF_PERCENTAGE ) mkprot( state, statenum, comstate ); /* Since mkprot added a new proto to the proto queue, * it's possible that "minprot" is no longer on the * proto queue (if it happened to have been the last * entry, it would have been bumped off). If it's * not there, then the new proto took its physical * place (though logically the new proto is at the * beginning of the queue), so in that case the * following call will do nothing. */ mv2front( minprot ); } } } /* cmptmps - compress template table entries * * Template tables are compressed by using the 'template equivalence * classes', which are collections of transition character equivalence * classes which always appear together in templates - really meta-equivalence * classes. */ void cmptmps() { int tmpstorage[CSIZE + 1]; int *tmp = tmpstorage, i, j; int totaltrans, trans; peakpairs = numtemps * numecs + tblend; if ( usemecs ) { /* Create equivalence classes based on data gathered on * template transitions. */ nummecs = cre8ecs( tecfwd, tecbck, numecs ); } else nummecs = numecs; while ( lastdfa + numtemps + 1 >= current_max_dfas ) increase_max_dfas(); /* Loop through each template. */ for ( i = 1; i <= numtemps; ++i ) { /* Number of non-jam transitions out of this template. */ totaltrans = 0; for ( j = 1; j <= numecs; ++j ) { trans = tnxt[numecs * i + j]; if ( usemecs ) { /* The absolute value of tecbck is the * meta-equivalence class of a given * equivalence class, as set up by cre8ecs(). */ if ( tecbck[j] > 0 ) { tmp[tecbck[j]] = trans; if ( trans > 0 ) ++totaltrans; } } else { tmp[j] = trans; if ( trans > 0 ) ++totaltrans; } } /* It is assumed (in a rather subtle way) in the skeleton * that if we're using meta-equivalence classes, the def[] * entry for all templates is the jam template, i.e., * templates never default to other non-jam table entries * (e.g., another template) */ /* Leave room for the jam-state after the last real state. */ mkentry( tmp, nummecs, lastdfa + i + 1, JAMSTATE, totaltrans ); } } /* expand_nxt_chk - expand the next check arrays */ void expand_nxt_chk() { int old_max = current_max_xpairs; current_max_xpairs += MAX_XPAIRS_INCREMENT; ++num_reallocs; nxt = reallocate_integer_array( nxt, current_max_xpairs ); chk = reallocate_integer_array( chk, current_max_xpairs ); zero_out( (char *) (chk + old_max), (size_t) (MAX_XPAIRS_INCREMENT * sizeof( int )) ); } /* find_table_space - finds a space in the table for a state to be placed * * synopsis * int *state, numtrans, block_start; * int find_table_space(); * * block_start = find_table_space( state, numtrans ); * * State is the state to be added to the full speed transition table. * Numtrans is the number of out-transitions for the state. * * find_table_space() returns the position of the start of the first block (in * chk) able to accommodate the state * * In determining if a state will or will not fit, find_table_space() must take * into account the fact that an end-of-buffer state will be added at [0], * and an action number will be added in [-1]. */ int find_table_space( state, numtrans ) int *state, numtrans; { /* Firstfree is the position of the first possible occurrence of two * consecutive unused records in the chk and nxt arrays. */ int i; int *state_ptr, *chk_ptr; int *ptr_to_last_entry_in_state; /* If there are too many out-transitions, put the state at the end of * nxt and chk. */ if ( numtrans > MAX_XTIONS_FULL_INTERIOR_FIT ) { /* If table is empty, return the first available spot in * chk/nxt, which should be 1. */ if ( tblend < 2 ) return 1; /* Start searching for table space near the end of * chk/nxt arrays. */ i = tblend - numecs; } else /* Start searching for table space from the beginning * (skipping only the elements which will definitely not * hold the new state). */ i = firstfree; while ( 1 ) /* loops until a space is found */ { while ( i + numecs >= current_max_xpairs ) expand_nxt_chk(); /* Loops until space for end-of-buffer and action number * are found. */ while ( 1 ) { /* Check for action number space. */ if ( chk[i - 1] == 0 ) { /* Check for end-of-buffer space. */ if ( chk[i] == 0 ) break; else /* Since i != 0, there is no use * checking to see if (++i) - 1 == 0, * because that's the same as i == 0, * so we skip a space. */ i += 2; } else ++i; while ( i + numecs >= current_max_xpairs ) expand_nxt_chk(); } /* If we started search from the beginning, store the new * firstfree for the next call of find_table_space(). */ if ( numtrans <= MAX_XTIONS_FULL_INTERIOR_FIT ) firstfree = i + 1; /* Check to see if all elements in chk (and therefore nxt) * that are needed for the new state have not yet been taken. */ state_ptr = &state[1]; ptr_to_last_entry_in_state = &chk[i + numecs + 1]; for ( chk_ptr = &chk[i + 1]; chk_ptr != ptr_to_last_entry_in_state; ++chk_ptr ) if ( *(state_ptr++) != 0 && *chk_ptr != 0 ) break; if ( chk_ptr == ptr_to_last_entry_in_state ) return i; else ++i; } } /* inittbl - initialize transition tables * * Initializes "firstfree" to be one beyond the end of the table. Initializes * all "chk" entries to be zero. */ void inittbl() { int i; zero_out( (char *) chk, (size_t) (current_max_xpairs * sizeof( int )) ); tblend = 0; firstfree = tblend + 1; numtemps = 0; if ( usemecs ) { /* Set up doubly-linked meta-equivalence classes; these * are sets of equivalence classes which all have identical * transitions out of TEMPLATES. */ tecbck[1] = NIL; for ( i = 2; i <= numecs; ++i ) { tecbck[i] = i - 1; tecfwd[i - 1] = i; } tecfwd[numecs] = NIL; } } /* mkdeftbl - make the default, "jam" table entries */ void mkdeftbl() { int i; jamstate = lastdfa + 1; ++tblend; /* room for transition on end-of-buffer character */ while ( tblend + numecs >= current_max_xpairs ) expand_nxt_chk(); /* Add in default end-of-buffer transition. */ nxt[tblend] = end_of_buffer_state; chk[tblend] = jamstate; for ( i = 1; i <= numecs; ++i ) { nxt[tblend + i] = 0; chk[tblend + i] = jamstate; } jambase = tblend; base[jamstate] = jambase; def[jamstate] = 0; tblend += numecs; ++numtemps; } /* mkentry - create base/def and nxt/chk entries for transition array * * synopsis * int state[numchars + 1], numchars, statenum, deflink, totaltrans; * mkentry( state, numchars, statenum, deflink, totaltrans ); * * "state" is a transition array "numchars" characters in size, "statenum" * is the offset to be used into the base/def tables, and "deflink" is the * entry to put in the "def" table entry. If "deflink" is equal to * "JAMSTATE", then no attempt will be made to fit zero entries of "state" * (i.e., jam entries) into the table. It is assumed that by linking to * "JAMSTATE" they will be taken care of. In any case, entries in "state" * marking transitions to "SAME_TRANS" are treated as though they will be * taken care of by whereever "deflink" points. "totaltrans" is the total * number of transitions out of the state. If it is below a certain threshold, * the tables are searched for an interior spot that will accommodate the * state array. */ void mkentry( state, numchars, statenum, deflink, totaltrans ) int *state; int numchars, statenum, deflink, totaltrans; { int minec, maxec, i, baseaddr; int tblbase, tbllast; if ( totaltrans == 0 ) { /* there are no out-transitions */ if ( deflink == JAMSTATE ) base[statenum] = JAMSTATE; else base[statenum] = 0; def[statenum] = deflink; return; } for ( minec = 1; minec <= numchars; ++minec ) { if ( state[minec] != SAME_TRANS ) if ( state[minec] != 0 || deflink != JAMSTATE ) break; } if ( totaltrans == 1 ) { /* There's only one out-transition. Save it for later to fill * in holes in the tables. */ stack1( statenum, minec, state[minec], deflink ); return; } for ( maxec = numchars; maxec > 0; --maxec ) { if ( state[maxec] != SAME_TRANS ) if ( state[maxec] != 0 || deflink != JAMSTATE ) break; } /* Whether we try to fit the state table in the middle of the table * entries we have already generated, or if we just take the state * table at the end of the nxt/chk tables, we must make sure that we * have a valid base address (i.e., non-negative). Note that * negative base addresses dangerous at run-time (because indexing * the nxt array with one and a low-valued character will access * memory before the start of the array. */ /* Find the first transition of state that we need to worry about. */ if ( totaltrans * 100 <= numchars * INTERIOR_FIT_PERCENTAGE ) { /* Attempt to squeeze it into the middle of the tables. */ baseaddr = firstfree; while ( baseaddr < minec ) { /* Using baseaddr would result in a negative base * address below; find the next free slot. */ for ( ++baseaddr; chk[baseaddr] != 0; ++baseaddr ) ; } while ( baseaddr + maxec - minec + 1 >= current_max_xpairs ) expand_nxt_chk(); for ( i = minec; i <= maxec; ++i ) if ( state[i] != SAME_TRANS && (state[i] != 0 || deflink != JAMSTATE) && chk[baseaddr + i - minec] != 0 ) { /* baseaddr unsuitable - find another */ for ( ++baseaddr; baseaddr < current_max_xpairs && chk[baseaddr] != 0; ++baseaddr ) ; while ( baseaddr + maxec - minec + 1 >= current_max_xpairs ) expand_nxt_chk(); /* Reset the loop counter so we'll start all * over again next time it's incremented. */ i = minec - 1; } } else { /* Ensure that the base address we eventually generate is * non-negative. */ baseaddr = MAX( tblend + 1, minec ); } tblbase = baseaddr - minec; tbllast = tblbase + maxec; while ( tbllast + 1 >= current_max_xpairs ) expand_nxt_chk(); base[statenum] = tblbase; def[statenum] = deflink; for ( i = minec; i <= maxec; ++i ) if ( state[i] != SAME_TRANS ) if ( state[i] != 0 || deflink != JAMSTATE ) { nxt[tblbase + i] = state[i]; chk[tblbase + i] = statenum; } if ( baseaddr == firstfree ) /* Find next free slot in tables. */ for ( ++firstfree; chk[firstfree] != 0; ++firstfree ) ; tblend = MAX( tblend, tbllast ); } /* mk1tbl - create table entries for a state (or state fragment) which * has only one out-transition */ void mk1tbl( state, sym, onenxt, onedef ) int state, sym, onenxt, onedef; { if ( firstfree < sym ) firstfree = sym; while ( chk[firstfree] != 0 ) if ( ++firstfree >= current_max_xpairs ) expand_nxt_chk(); base[state] = firstfree - sym; def[state] = onedef; chk[firstfree] = state; nxt[firstfree] = onenxt; if ( firstfree > tblend ) { tblend = firstfree++; if ( firstfree >= current_max_xpairs ) expand_nxt_chk(); } } /* mkprot - create new proto entry */ void mkprot( state, statenum, comstate ) int state[], statenum, comstate; { int i, slot, tblbase; if ( ++numprots >= MSP || numecs * numprots >= PROT_SAVE_SIZE ) { /* Gotta make room for the new proto by dropping last entry in * the queue. */ slot = lastprot; lastprot = protprev[lastprot]; protnext[lastprot] = NIL; } else slot = numprots; protnext[slot] = firstprot; if ( firstprot != NIL ) protprev[firstprot] = slot; firstprot = slot; prottbl[slot] = statenum; protcomst[slot] = comstate; /* Copy state into save area so it can be compared with rapidly. */ tblbase = numecs * (slot - 1); for ( i = 1; i <= numecs; ++i ) protsave[tblbase + i] = state[i]; } /* mktemplate - create a template entry based on a state, and connect the state * to it */ void mktemplate( state, statenum, comstate ) int state[], statenum, comstate; { int i, numdiff, tmpbase, tmp[CSIZE + 1]; Char transset[CSIZE + 1]; int tsptr; ++numtemps; tsptr = 0; /* Calculate where we will temporarily store the transition table * of the template in the tnxt[] array. The final transition table * gets created by cmptmps(). */ tmpbase = numtemps * numecs; if ( tmpbase + numecs >= current_max_template_xpairs ) { current_max_template_xpairs += MAX_TEMPLATE_XPAIRS_INCREMENT; ++num_reallocs; tnxt = reallocate_integer_array( tnxt, current_max_template_xpairs ); } for ( i = 1; i <= numecs; ++i ) if ( state[i] == 0 ) tnxt[tmpbase + i] = 0; else { transset[tsptr++] = i; tnxt[tmpbase + i] = comstate; } if ( usemecs ) mkeccl( transset, tsptr, tecfwd, tecbck, numecs, 0 ); mkprot( tnxt + tmpbase, -numtemps, comstate ); /* We rely on the fact that mkprot adds things to the beginning * of the proto queue. */ numdiff = tbldiff( state, firstprot, tmp ); mkentry( tmp, numecs, statenum, -numtemps, numdiff ); } /* mv2front - move proto queue element to front of queue */ void mv2front( qelm ) int qelm; { if ( firstprot != qelm ) { if ( qelm == lastprot ) lastprot = protprev[lastprot]; protnext[protprev[qelm]] = protnext[qelm]; if ( protnext[qelm] != NIL ) protprev[protnext[qelm]] = protprev[qelm]; protprev[qelm] = NIL; protnext[qelm] = firstprot; protprev[firstprot] = qelm; firstprot = qelm; } } /* place_state - place a state into full speed transition table * * State is the statenum'th state. It is indexed by equivalence class and * gives the number of the state to enter for a given equivalence class. * Transnum is the number of out-transitions for the state. */ void place_state( state, statenum, transnum ) int *state, statenum, transnum; { int i; int *state_ptr; int position = find_table_space( state, transnum ); /* "base" is the table of start positions. */ base[statenum] = position; /* Put in action number marker; this non-zero number makes sure that * find_table_space() knows that this position in chk/nxt is taken * and should not be used for another accepting number in another * state. */ chk[position - 1] = 1; /* Put in end-of-buffer marker; this is for the same purposes as * above. */ chk[position] = 1; /* Place the state into chk and nxt. */ state_ptr = &state[1]; for ( i = 1; i <= numecs; ++i, ++state_ptr ) if ( *state_ptr != 0 ) { chk[position + i] = i; nxt[position + i] = *state_ptr; } if ( position + numecs > tblend ) tblend = position + numecs; } /* stack1 - save states with only one out-transition to be processed later * * If there's room for another state on the "one-transition" stack, the * state is pushed onto it, to be processed later by mk1tbl. If there's * no room, we process the sucker right now. */ void stack1( statenum, sym, nextstate, deflink ) int statenum, sym, nextstate, deflink; { if ( onesp >= ONE_STACK_SIZE - 1 ) mk1tbl( statenum, sym, nextstate, deflink ); else { ++onesp; onestate[onesp] = statenum; onesym[onesp] = sym; onenext[onesp] = nextstate; onedef[onesp] = deflink; } } /* tbldiff - compute differences between two state tables * * "state" is the state array which is to be extracted from the pr'th * proto. "pr" is both the number of the proto we are extracting from * and an index into the save area where we can find the proto's complete * state table. Each entry in "state" which differs from the corresponding * entry of "pr" will appear in "ext". * * Entries which are the same in both "state" and "pr" will be marked * as transitions to "SAME_TRANS" in "ext". The total number of differences * between "state" and "pr" is returned as function value. Note that this * number is "numecs" minus the number of "SAME_TRANS" entries in "ext". */ int tbldiff( state, pr, ext ) int state[], pr, ext[]; { int i, *sp = state, *ep = ext, *protp; int numdiff = 0; protp = &protsave[numecs * (pr - 1)]; for ( i = numecs; i > 0; --i ) { if ( *++protp == *++sp ) *++ep = SAME_TRANS; else { *++ep = *sp; ++numdiff; } } return numdiff; }