516 lines
13 KiB
C
516 lines
13 KiB
C
/*
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* array.c - routines for associative arrays.
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*/
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/*
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* Copyright (C) 1986, 1988, 1989, 1991, 1992, 1993 the Free Software Foundation, Inc.
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*
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* This file is part of GAWK, the GNU implementation of the
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* AWK Progamming Language.
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*
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* GAWK is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GAWK is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GAWK; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* Tree walks (``for (iggy in foo)'') and array deletions use expensive
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* linear searching. So what we do is start out with small arrays and
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* grow them as needed, so that our arrays are hopefully small enough,
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* most of the time, that they're pretty full and we're not looking at
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* wasted space.
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*
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* The decision is made to grow the array if the average chain length is
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* ``too big''. This is defined as the total number of entries in the table
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* divided by the size of the array being greater than some constant.
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*/
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#define AVG_CHAIN_MAX 10 /* don't want to linear search more than this */
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#include "awk.h"
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static NODE *assoc_find P((NODE *symbol, NODE *subs, int hash1));
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static void grow_table P((NODE *symbol));
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NODE *
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concat_exp(tree)
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register NODE *tree;
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{
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register NODE *r;
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char *str;
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char *s;
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size_t len;
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int offset;
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size_t subseplen;
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char *subsep;
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if (tree->type != Node_expression_list)
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return force_string(tree_eval(tree));
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r = force_string(tree_eval(tree->lnode));
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if (tree->rnode == NULL)
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return r;
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subseplen = SUBSEP_node->lnode->stlen;
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subsep = SUBSEP_node->lnode->stptr;
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len = r->stlen + subseplen + 2;
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emalloc(str, char *, len, "concat_exp");
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memcpy(str, r->stptr, r->stlen+1);
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s = str + r->stlen;
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free_temp(r);
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tree = tree->rnode;
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while (tree) {
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if (subseplen == 1)
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*s++ = *subsep;
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else {
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memcpy(s, subsep, subseplen+1);
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s += subseplen;
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}
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r = force_string(tree_eval(tree->lnode));
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len += r->stlen + subseplen;
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offset = s - str;
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erealloc(str, char *, len, "concat_exp");
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s = str + offset;
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memcpy(s, r->stptr, r->stlen+1);
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s += r->stlen;
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free_temp(r);
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tree = tree->rnode;
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}
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r = make_str_node(str, s - str, ALREADY_MALLOCED);
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r->flags |= TEMP;
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return r;
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}
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/* Flush all the values in symbol[] before doing a split() */
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void
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assoc_clear(symbol)
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NODE *symbol;
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{
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int i;
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NODE *bucket, *next;
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if (symbol->var_array == 0)
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return;
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for (i = 0; i < symbol->array_size; i++) {
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for (bucket = symbol->var_array[i]; bucket; bucket = next) {
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next = bucket->ahnext;
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unref(bucket->ahname);
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unref(bucket->ahvalue);
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freenode(bucket);
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}
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symbol->var_array[i] = 0;
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}
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free(symbol->var_array);
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symbol->var_array = NULL;
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symbol->array_size = symbol->table_size = 0;
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symbol->flags &= ~ARRAYMAXED;
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}
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/*
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* calculate the hash function of the string in subs
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*/
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unsigned int
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hash(s, len, hsize)
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register const char *s;
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register size_t len;
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unsigned long hsize;
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{
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register unsigned long h = 0;
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#ifdef this_is_really_slow
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register unsigned long g;
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while (len--) {
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h = (h << 4) + *s++;
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g = (h & 0xf0000000);
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if (g) {
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h = h ^ (g >> 24);
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h = h ^ g;
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}
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}
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#else /* this_is_really_slow */
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/*
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* This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
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* units. On the first time through the loop we get the "leftover bytes"
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* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
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* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
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* this routine is heavily used enough, it's worth the ugly coding.
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*
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* OZ's original sdbm hash, copied from Margo Seltzers db package.
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*
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*/
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/* Even more speed: */
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/* #define HASHC h = *s++ + 65599 * h */
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/* Because 65599 = pow(2,6) + pow(2,16) - 1 we multiply by shifts */
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#define HASHC htmp = (h << 6); \
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h = *s++ + htmp + (htmp << 10) - h
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unsigned long htmp;
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h = 0;
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#if defined(VAXC)
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/*
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* [This was an implementation of "Duff's Device", but it has been
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* redone, separating the switch for extra iterations from the loop.
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* This is necessary because the DEC VAX-C compiler is STOOPID.]
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*/
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switch (len & (8 - 1)) {
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case 7: HASHC;
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case 6: HASHC;
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case 5: HASHC;
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case 4: HASHC;
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case 3: HASHC;
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case 2: HASHC;
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case 1: HASHC;
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default: break;
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}
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if (len > (8 - 1)) {
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register size_t loop = len >> 3;
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do {
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HASHC;
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HASHC;
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HASHC;
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HASHC;
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HASHC;
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HASHC;
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HASHC;
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HASHC;
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} while (--loop);
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}
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#else /* !VAXC */
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/* "Duff's Device" for those who can handle it */
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if (len > 0) {
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register size_t loop = (len + 8 - 1) >> 3;
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switch (len & (8 - 1)) {
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case 0:
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do { /* All fall throughs */
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HASHC;
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case 7: HASHC;
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case 6: HASHC;
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case 5: HASHC;
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case 4: HASHC;
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case 3: HASHC;
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case 2: HASHC;
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case 1: HASHC;
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} while (--loop);
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}
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}
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#endif /* !VAXC */
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#endif /* this_is_really_slow - not */
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if (h >= hsize)
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h %= hsize;
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return h;
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}
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/*
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* locate symbol[subs]
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*/
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static NODE * /* NULL if not found */
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assoc_find(symbol, subs, hash1)
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NODE *symbol;
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register NODE *subs;
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int hash1;
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{
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register NODE *bucket, *prev = 0;
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for (bucket = symbol->var_array[hash1]; bucket; bucket = bucket->ahnext) {
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if (cmp_nodes(bucket->ahname, subs) == 0) {
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#if 0
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/*
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* Disable this code for now. It screws things up if we have
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* a ``for (iggy in foo)'' in progress. Interestingly enough,
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* this was not a problem in 2.15.3, only in 2.15.4. I'm not
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* sure why it works in 2.15.3.
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*/
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if (prev) { /* move found to front of chain */
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prev->ahnext = bucket->ahnext;
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bucket->ahnext = symbol->var_array[hash1];
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symbol->var_array[hash1] = bucket;
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}
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#endif
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return bucket;
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} else
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prev = bucket; /* save previous list entry */
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}
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return NULL;
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}
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/*
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* test whether the array element symbol[subs] exists or not
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*/
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int
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in_array(symbol, subs)
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NODE *symbol, *subs;
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{
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register int hash1;
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if (symbol->type == Node_param_list)
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symbol = stack_ptr[symbol->param_cnt];
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if (symbol->var_array == 0)
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return 0;
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subs = concat_exp(subs); /* concat_exp returns a string node */
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hash1 = hash(subs->stptr, subs->stlen, (unsigned long) symbol->array_size);
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if (assoc_find(symbol, subs, hash1) == NULL) {
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free_temp(subs);
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return 0;
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} else {
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free_temp(subs);
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return 1;
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}
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}
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/*
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* SYMBOL is the address of the node (or other pointer) being dereferenced.
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* SUBS is a number or string used as the subscript.
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*
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* Find SYMBOL[SUBS] in the assoc array. Install it with value "" if it
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* isn't there. Returns a pointer ala get_lhs to where its value is stored
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*/
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NODE **
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assoc_lookup(symbol, subs)
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NODE *symbol, *subs;
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{
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register int hash1;
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register NODE *bucket;
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(void) force_string(subs);
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if (symbol->var_array == 0) {
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symbol->type = Node_var_array;
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symbol->array_size = symbol->table_size = 0; /* sanity */
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symbol->flags &= ~ARRAYMAXED;
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grow_table(symbol);
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hash1 = hash(subs->stptr, subs->stlen,
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(unsigned long) symbol->array_size);
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} else {
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hash1 = hash(subs->stptr, subs->stlen,
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(unsigned long) symbol->array_size);
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bucket = assoc_find(symbol, subs, hash1);
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if (bucket != NULL) {
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free_temp(subs);
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return &(bucket->ahvalue);
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}
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}
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/* It's not there, install it. */
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if (do_lint && subs->stlen == 0)
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warning("subscript of array `%s' is null string",
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symbol->vname);
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/* first see if we would need to grow the array, before installing */
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symbol->table_size++;
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if ((symbol->flags & ARRAYMAXED) == 0
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&& symbol->table_size/symbol->array_size > AVG_CHAIN_MAX) {
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grow_table(symbol);
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/* have to recompute hash value for new size */
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hash1 = hash(subs->stptr, subs->stlen,
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(unsigned long) symbol->array_size);
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}
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getnode(bucket);
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bucket->type = Node_ahash;
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if (subs->flags & TEMP)
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bucket->ahname = dupnode(subs);
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else {
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unsigned int saveflags = subs->flags;
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subs->flags &= ~MALLOC;
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bucket->ahname = dupnode(subs);
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subs->flags = saveflags;
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}
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free_temp(subs);
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/* array subscripts are strings */
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bucket->ahname->flags &= ~NUMBER;
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bucket->ahname->flags |= STRING;
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bucket->ahvalue = Nnull_string;
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bucket->ahnext = symbol->var_array[hash1];
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symbol->var_array[hash1] = bucket;
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return &(bucket->ahvalue);
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}
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void
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do_delete(symbol, tree)
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NODE *symbol, *tree;
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{
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register int hash1;
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register NODE *bucket, *last;
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NODE *subs;
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if (symbol->type == Node_param_list)
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symbol = stack_ptr[symbol->param_cnt];
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if (symbol->var_array == 0)
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return;
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subs = concat_exp(tree); /* concat_exp returns string node */
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hash1 = hash(subs->stptr, subs->stlen, (unsigned long) symbol->array_size);
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last = NULL;
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for (bucket = symbol->var_array[hash1]; bucket; last = bucket, bucket = bucket->ahnext)
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if (cmp_nodes(bucket->ahname, subs) == 0)
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break;
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free_temp(subs);
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if (bucket == NULL)
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return;
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if (last)
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last->ahnext = bucket->ahnext;
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else
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symbol->var_array[hash1] = bucket->ahnext;
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unref(bucket->ahname);
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unref(bucket->ahvalue);
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freenode(bucket);
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symbol->table_size--;
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if (symbol->table_size <= 0) {
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memset(symbol->var_array, '\0',
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sizeof(NODE *) * symbol->array_size);
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symbol->table_size = symbol->array_size = 0;
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symbol->flags &= ~ARRAYMAXED;
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free((char *) symbol->var_array);
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symbol->var_array = NULL;
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}
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}
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void
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assoc_scan(symbol, lookat)
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NODE *symbol;
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struct search *lookat;
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{
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lookat->sym = symbol;
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lookat->idx = 0;
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lookat->bucket = NULL;
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lookat->retval = NULL;
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if (symbol->var_array != NULL)
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assoc_next(lookat);
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}
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void
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assoc_next(lookat)
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struct search *lookat;
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{
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register NODE *symbol = lookat->sym;
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if (symbol == NULL)
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fatal("null symbol in assoc_next");
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if (symbol->var_array == NULL || lookat->idx > symbol->array_size) {
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lookat->retval = NULL;
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return;
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}
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/*
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* This is theoretically unsafe. The element bucket might have
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* been freed if the body of the scan did a delete on the next
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* element of the bucket. The only way to do that is by array
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* reference, which is unlikely. Basically, if the user is doing
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* anything other than an operation on the current element of an
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* assoc array while walking through it sequentially, all bets are
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* off. (The safe way is to register all search structs on an
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* array with the array, and update all of them on a delete or
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* insert)
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*/
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if (lookat->bucket != NULL) {
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lookat->retval = lookat->bucket->ahname;
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lookat->bucket = lookat->bucket->ahnext;
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return;
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}
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for (; lookat->idx < symbol->array_size; lookat->idx++) {
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NODE *bucket;
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if ((bucket = symbol->var_array[lookat->idx]) != NULL) {
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lookat->retval = bucket->ahname;
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lookat->bucket = bucket->ahnext;
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lookat->idx++;
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return;
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}
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}
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lookat->retval = NULL;
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lookat->bucket = NULL;
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return;
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}
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/* grow_table --- grow a hash table */
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static void
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grow_table(symbol)
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NODE *symbol;
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{
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NODE **old, **new, *chain, *next;
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int i, j;
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unsigned long hash1;
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unsigned long oldsize, newsize;
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/*
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* This is an array of primes. We grow the table by an order of
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* magnitude each time (not just doubling) so that growing is a
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* rare operation. We expect, on average, that it won't happen
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* more than twice. The final size is also chosen to be small
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* enough so that MS-DOG mallocs can handle it. When things are
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* very large (> 8K), we just double more or less, instead of
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* just jumping from 8K to 64K.
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*/
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static long sizes[] = { 13, 127, 1021, 8191, 16381, 32749, 65497 };
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/* find next biggest hash size */
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oldsize = symbol->array_size;
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newsize = 0;
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for (i = 0, j = sizeof(sizes)/sizeof(sizes[0]); i < j; i++) {
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if (oldsize < sizes[i]) {
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newsize = sizes[i];
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break;
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}
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}
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if (newsize == oldsize) { /* table already at max (!) */
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symbol->flags |= ARRAYMAXED;
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return;
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}
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/* allocate new table */
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emalloc(new, NODE **, newsize * sizeof(NODE *), "grow_table");
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memset(new, '\0', newsize * sizeof(NODE *));
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/* brand new hash table, set things up and return */
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if (symbol->var_array == NULL) {
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symbol->table_size = 0;
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goto done;
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}
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/* old hash table there, move stuff to new, free old */
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old = symbol->var_array;
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for (i = 0; i < oldsize; i++) {
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if (old[i] == NULL)
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continue;
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for (chain = old[i]; chain != NULL; chain = next) {
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next = chain->ahnext;
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hash1 = hash(chain->ahname->stptr,
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chain->ahname->stlen, newsize);
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/* remove from old list, add to new */
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chain->ahnext = new[hash1];
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new[hash1] = chain;
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}
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}
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free(old);
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done:
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/*
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* note that symbol->table_size does not change if an old array,
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* and is explicitly set to 0 if a new one.
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*/
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symbol->var_array = new;
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symbol->array_size = newsize;
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}
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