/* 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 (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 (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;
/* 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.
*/
/* 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;
/* 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.
*/
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 ();
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) ;
}
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;
}
/* 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;
/* 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.
*/
/* 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;
}
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