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373 lines
10 KiB
373 lines
10 KiB
/*
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* Simple symbol table manager using coalesced chaining to resolve collisions
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*
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* Doubly-linked lists are used for fast removal of entries.
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*
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* 'sym.h' must have a definition for typedef "Sym". Sym must include at
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* minimum the following fields:
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*
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* ...
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* char *symbol;
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* struct ... *next, *prev, **head, *scope;
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* unsigned int hash;
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* ...
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*
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* 'template.h' can be used as a template to create a 'sym.h'.
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*
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* 'head' is &(table[hash(itself)]).
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* The hash table is not resizable at run-time.
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* The scope field is used to link all symbols of a current scope together.
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* Scope() sets the current scope (linked list) to add symbols to.
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* Any number of scopes can be handled. The user passes the address of
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* a pointer to a symbol table
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* entry (INITIALIZED TO NULL first time).
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*
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* Available Functions:
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*
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* zzs_init(s1,s2) -- Create hash table with size s1, string table size s2.
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* zzs_done() -- Free hash and string table created with zzs_init().
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* zzs_add(key,rec)-- Add 'rec' with key 'key' to the symbol table.
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* zzs_newadd(key) -- create entry; add using 'key' to the symbol table.
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* zzs_get(key) -- Return pointer to last record entered under 'key'
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* Else return NULL
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* zzs_del(p) -- Unlink the entry associated with p. This does
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* NOT free 'p' and DOES NOT remove it from a scope
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* list. If it was a part of your intermediate code
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* tree or another structure. It will still be there.
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* It is only removed from further consideration
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* by the symbol table.
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* zzs_keydel(s) -- Unlink the entry associated with key s.
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* Calls zzs_del(p) to unlink.
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* zzs_scope(sc) -- Specifies that everything added to the symbol
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* table with zzs_add() is added to the list (scope)
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* 'sc'. 'sc' is of 'Sym **sc' type and must be
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* initialized to NULL before trying to add anything
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* to it (passing it to zzs_scope()). Scopes can be
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* switched at any time and merely links a set of
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* symbol table entries. If a NULL pointer is
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* passed, the current scope is returned.
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* zzs_rmscope(sc) -- Remove (zzs_del()) all elements of scope 'sc'
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* from the symbol table. The entries are NOT
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* free()'d. A pointer to the first
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* element in the "scope" is returned. The user
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* can then manipulate the list as he/she chooses
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* (such as freeing them all). NOTE that this
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* function sets your scope pointer to NULL,
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* but returns a pointer to the list for you to use.
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* zzs_stat() -- Print out the symbol table and some relevant stats.
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* zzs_new(key) -- Create a new record with calloc() of type Sym.
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* Add 'key' to the string table and make the new
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* records 'symbol' pointer point to it.
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* zzs_strdup(s) -- Add s to the string table and return a pointer
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* to it. Very fast allocation routine
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* and does not require strlen() nor calloc().
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*
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* Example:
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*
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* #include <stdio.h>
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* #include "sym.h"
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*
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* main()
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* {
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* Sym *scope1=NULL, *scope2=NULL, *a, *p;
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*
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* zzs_init(101, 100);
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*
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* a = zzs_new("Apple"); zzs_add(a->symbol, a); -- No scope
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* zzs_scope( &scope1 ); -- enter scope 1
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* a = zzs_new("Plum"); zzs_add(a->symbol, a);
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* zzs_scope( &scope2 ); -- enter scope 2
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* a = zzs_new("Truck"); zzs_add(a->symbol, a);
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*
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* p = zzs_get("Plum");
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* if ( p == NULL ) fprintf(stderr, "Hmmm...Can't find 'Plum'\n");
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*
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* p = zzs_rmscope(&scope1)
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* for (; p!=NULL; p=p->scope) {printf("Scope1: %s\n", p->symbol);}
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* p = zzs_rmscope(&scope2)
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* for (; p!=NULL; p=p->scope) {printf("Scope2: %s\n", p->symbol);}
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* }
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*
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* Terence Parr
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* Purdue University
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* February 1990
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*
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* CHANGES
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*
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* Terence Parr
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* May 1991
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* Renamed functions to be consistent with ANTLR
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* Made HASH macro
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* Added zzs_keydel()
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* Added zzs_newadd()
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* Fixed up zzs_stat()
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*
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* July 1991
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* Made symbol table entry save its hash code for fast comparison
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* during searching etc...
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*/
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/*#include "bt_config.h"*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#ifdef MEMCHK
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#include "trax.h"
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#endif
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#include "sym.h"
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/*#include "my_dmalloc.h"*/
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#define StrSame 0
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static Sym **CurScope = NULL;
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static unsigned size = 0;
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static Sym **table=NULL;
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static char *strings;
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static char *strp;
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static int strsize = 0;
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void
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zzs_init(int sz, int strs)
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{
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if ( sz <= 0 || strs <= 0 ) return;
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table = (Sym **) calloc(sz, sizeof(Sym *));
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if ( table == NULL )
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{
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fprintf(stderr, "Cannot allocate table of size %d\n", sz);
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exit(1);
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}
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strings = (char *) calloc(strs, sizeof(char));
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if ( strings == NULL )
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{
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fprintf(stderr, "Cannot allocate string table of size %d\n", strs);
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exit(1);
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}
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size = sz;
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strsize = strs;
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strp = strings;
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}
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void
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zzs_free(void)
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{
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unsigned i;
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Sym *cur, *next;
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for (i = 0; i < size; i++)
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{
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cur = table[i];
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while (cur != NULL)
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{
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next = cur->next;
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free (cur);
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cur = next;
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}
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}
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}
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void
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zzs_done(void)
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{
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if ( table != NULL ) free( table );
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if ( strings != NULL ) free( strings );
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}
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void
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zzs_add(char *key, Sym *rec)
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{
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unsigned int h=0;
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char *p=key;
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HASH_FUN(p, h);
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rec->hash = h; /* save hash code for fast comp later */
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h %= size;
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if ( CurScope != NULL ) {rec->scope = *CurScope; *CurScope = rec;}
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rec->next = table[h]; /* Add to doubly-linked list */
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rec->prev = NULL;
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if ( rec->next != NULL ) (rec->next)->prev = rec;
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table[h] = rec;
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rec->head = &(table[h]);
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}
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Sym *
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zzs_get(char *key)
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{
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unsigned int h=0;
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char *p=key;
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Sym *q;
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HASH_FUN(p, h);
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for (q = table[h%size]; q != NULL; q = q->next)
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{
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if ( q->hash == h ) /* do we even have a chance of matching? */
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if ( strcasecmp(key, q->symbol) == StrSame ) return( q );
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}
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return( NULL );
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}
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/*
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* Unlink p from the symbol table. Hopefully, it's actually in the
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* symbol table.
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*
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* If p is not part of a bucket chain of the symbol table, bad things
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* will happen.
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*
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* Will do nothing if all list pointers are NULL
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*/
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void
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zzs_del(Sym *p)
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{
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if ( p == NULL ) {fprintf(stderr, "zzs_del(NULL)\n"); exit(1);}
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if ( p->prev == NULL ) /* Head of list */
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{
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Sym **t = p->head;
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if ( t == NULL ) return; /* not part of symbol table */
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(*t) = p->next;
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if ( (*t) != NULL ) (*t)->prev = NULL;
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}
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else
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{
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(p->prev)->next = p->next;
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if ( p->next != NULL ) (p->next)->prev = p->prev;
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}
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p->next = p->prev = NULL; /* not part of symbol table anymore */
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p->head = NULL;
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}
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void
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zzs_keydel(char *key)
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{
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Sym *p = zzs_get(key);
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if ( p != NULL ) zzs_del( p );
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}
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/* S c o p e S t u f f */
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/* Set current scope to 'scope'; return current scope if 'scope' == NULL */
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Sym **
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zzs_scope(Sym **scope)
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{
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if ( scope == NULL ) return( CurScope );
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CurScope = scope;
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return( scope );
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}
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/* Remove a scope described by 'scope'. Return pointer to 1st element in scope */
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Sym *
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zzs_rmscope(Sym **scope)
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{
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Sym *p;
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Sym *start;
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if ( scope == NULL ) return(NULL);
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start = p = *scope;
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for (; p != NULL; p=p->scope) { zzs_del( p ); }
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*scope = NULL;
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return( start );
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}
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void
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zzs_stat(void)
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{
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static unsigned short count[20];
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unsigned int i,n=0,low=0, hi=0;
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Sym **p;
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float avg=0.0;
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for (i=0; i<20; i++) count[i] = 0;
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for (p=table; p<&(table[size]); p++)
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{
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Sym *q = *p;
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unsigned int len;
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if ( q != NULL && low==0 ) low = p-table;
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len = 0;
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if ( q != NULL ) printf("[%d]", p-table);
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while ( q != NULL )
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{
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len++;
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n++;
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printf(" %s", q->symbol);
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q = q->next;
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if ( q == NULL ) printf("\n");
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}
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if ( len>=20 ) printf("zzs_stat: count table too small\n");
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else count[len]++;
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if ( *p != NULL ) hi = p-table;
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}
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printf("Storing %d recs used %d hash positions out of %d\n",
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n, size-count[0], size);
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printf("%f %% utilization\n",
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((float)(size-count[0]))/((float)size));
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for (i=0; i<20; i++)
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{
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if ( count[i] != 0 )
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{
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avg += (((float)(i*count[i]))/((float)n)) * i;
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printf("Buckets of len %d == %d (%f %% of recs)\n",
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i, count[i], 100.0*((float)(i*count[i]))/((float)n));
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}
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}
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printf("Avg bucket length %f\n", avg);
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printf("Range of hash function: %d..%d\n", low, hi);
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}
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/*
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* Given a string, this function allocates and returns a pointer to a
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* symbol table record whose "symbol" pointer is reset to a position
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* in the string table.
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*/
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Sym *
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zzs_new(char *text)
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{
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Sym *p;
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char *zzs_strdup(char *s);
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if ( (p = (Sym *) calloc(1,sizeof(Sym))) == 0 )
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{
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fprintf(stderr,"Out of memory\n");
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exit(1);
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}
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p->symbol = zzs_strdup(text);
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return p;
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}
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/* create a new symbol table entry and add it to the symbol table */
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Sym *
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zzs_newadd(char *text)
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{
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Sym *p = zzs_new(text);
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if ( p != NULL ) zzs_add(text, p);
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return p;
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}
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/* Add a string to the string table and return a pointer to it.
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* Bump the pointer into the string table to next avail position.
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*/
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char *
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zzs_strdup(char *s)
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{
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char *start=strp;
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while ( *s != '\0' )
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{
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if ( strp >= &(strings[strsize-2]) )
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{
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fprintf(stderr, "sym: string table overflow (%d chars)\n", strsize);
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exit(-1);
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}
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*strp++ = *s++;
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}
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*strp++ = '\0';
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return( start );
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}
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