/* $OpenBSD: tblcmp.c,v 1.12 2024/11/09 18:03:44 op 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. */ /* This file is part of flex. */ /* 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. */ #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(int state[], int statenum, int totaltrans, int comstate, int 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(void) { 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(void) { 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); memset((chk + old_max), 0, 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(int *state, int 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(void) { int i; memset(chk, 0, 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(void) { 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 wherever "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(int *state, int numchars, int statenum, int deflink, int 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(int state, int sym, int onenxt, int 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(int state[], int statenum, int 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(int state[], int statenum, int comstate) { int i, numdiff, tmpbase, tmp[CSIZE + 1]; u_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(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(int *state, int statenum, int 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(int statenum, int sym, int nextstate, int 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(int state[], int pr, int 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; }
