|
|
/* 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 are permitted provided * that: (1) source distributions retain this entire copyright notice and * comment, and (2) distributions including binaries display the following * acknowledgement: ``This product includes software developed by the * University of California, Berkeley and its contributors'' in the * documentation or other materials provided with the distribution and in * all advertising materials mentioning features or use of this software. * 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. */
#ifndef lint
static char rcsid[] = "@(#) $Header: /usr/fsys/odin/a/vern/flex/RCS/tblcmp.c,v 2.5 90/06/27 23:48:38 vern Exp $ (LBL)"; #endif
#include "flexdef.h"
/* declarations for functions that have forward references */
void mkentry PROTO((register 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; int checkcom;
/* 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 */
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
* * synopsis * cmptmps(); * * 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. until this point, the tables for templates have been stored * up at the top end of the nxt array; they will now be compressed and have * table entries made for them. */
void cmptmps()
{ int tmpstorage[CSIZE + 1]; register int *tmp = tmpstorage, i, j; int totaltrans, trans;
peakpairs = numtemps * numecs + tblend;
if ( usemecs ) { /* create equivalence classes base on data gathered on template
* transitions */
nummecs = cre8ecs( tecfwd, tecbck, numecs ); } else nummecs = numecs;
if ( lastdfa + numtemps + 1 >= current_max_dfas ) increase_max_dfas();
/* loop through each template */
for ( i = 1; i <= numtemps; ++i ) { totaltrans = 0; /* number of non-jam transitions out of this template */
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()
{ register 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 );
bzero( (char *) (chk + old_max), MAX_XPAIRS_INCREMENT * sizeof( int ) / sizeof( char ) ); }
/* 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 */ register int i; register int *state_ptr, *chk_ptr; register 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 );
i = tblend - numecs; /* start searching for table space near the
* end of chk/nxt arrays */ }
else i = firstfree; /* start searching for table space from the
* beginning (skipping only the elements * which will definitely not hold the new * state) */
while ( 1 ) /* loops until a space is found */ { if ( i + numecs > current_max_xpairs ) expand_nxt_chk();
/* loops until space for end-of-buffer and action number are found */ while ( 1 ) { if ( chk[i - 1] == 0 ) /* check for action number space */ { if ( chk[i] == 0 ) /* check for end-of-buffer space */ break;
else i += 2; /* 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 */ }
else ++i;
if ( 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
* * synopsis * inittbl(); * * Initializes "firstfree" to be one beyond the end of the table. Initializes * all "chk" entries to be zero. Note that templates are built in their * own tbase/tdef tables. They are shifted down to be contiguous * with the non-template entries during table generation. */ void inittbl()
{ register int i;
bzero( (char *) chk, current_max_xpairs * sizeof( int ) / sizeof( char ) );
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
* * synopsis * mkdeftbl(); */
void mkdeftbl()
{ int i;
jamstate = lastdfa + 1;
++tblend; /* room for transition on end-of-buffer character */
if ( 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 ) register int *state; int numchars, statenum, deflink, totaltrans;
{ register 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 not only are * negative base addresses dangerous at run-time (because indexing the * next array with one and a low-valued character might generate an * array-out-of-bounds error message), but at compile-time negative * base addresses denote TEMPLATES. */
/* 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 tabls */ 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 ( baseaddr + maxec - minec >= current_max_xpairs ) expand_nxt_chk();
for ( i = minec; i <= maxec; ++i ) if ( state[i] != SAME_TRANS ) if ( state[i] != 0 || deflink != JAMSTATE ) if ( chk[baseaddr + i - minec] != 0 ) { /* baseaddr unsuitable - find another */ for ( ++baseaddr; baseaddr < current_max_xpairs && chk[baseaddr] != 0; ++baseaddr ) ;
if ( baseaddr + maxec - minec >= 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;
if ( tbllast >= 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 * * synopsis * int state, sym, onenxt, onedef; * mk1tbl( state, sym, onenxt, onedef ); */
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
* * synopsis * int state[], statenum, comstate; * mkprot( state, statenum, comstate ); */
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 * * synopsis * int state[], statenum, comstate, totaltrans; * mktemplate( state, statenum, comstate, totaltrans ); */
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
* * synopsis * int qelm; * mv2front( qelm ); */
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
* * synopsis * int *state, statenum, transnum; * place_state( state, statenum, transnum ); * * 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;
{ register int i; register 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
* * synopsis * int statenum, sym, nextstate, deflink; * stack1( statenum, sym, nextstate, deflink ); * * if there's room for another state one 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
* * synopsis * int state[], pr, ext[]; * int tbldiff, numdifferences; * numdifferences = tbldiff( state, pr, ext ) * * "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[];
{ register int i, *sp = state, *ep = ext, *protp; register 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 ); }
|