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cosmopolitan/third_party/lex/tblcmp.c

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2020-06-15 14:18:57 +00:00
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
│vi: set et ft=c ts=8 sw=8 fenc=utf-8 :vi│
└─────────────────────────────────────────────────────────────────────────────*/
/* clang-format off */
/* $OpenBSD: tblcmp.c,v 1.10 2015/11/19 23:34:56 mmcc 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 "libc/str/str.h"
#include "third_party/lex/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);
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(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;
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()
{
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, onedef2)
int state, sym, onenxt, onedef2;
{
if (firstfree < sym)
firstfree = sym;
while (chk[firstfree] != 0)
if (++firstfree >= current_max_xpairs)
expand_nxt_chk();
base[state] = firstfree - sym;
def[state] = onedef2;
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];
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(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;
}