mawk/hash.c

/********************************************
hash.c
copyright 2008-2012,2021, Thomas E. Dickey
copyright 1991-1993,1994, Michael D. Brennan

This is a source file for mawk, an implementation of
the AWK programming language.

Mawk is distributed without warranty under the terms of
the GNU General Public License, version 2, 1991.
********************************************/

/*
 * $MawkId: hash.c,v 1.20 2021/05/28 23:59:20 tom Exp $
 */

/* hash.c */

#include "mawk.h"
#include "memory.h"
#include "symtype.h"

#ifdef NO_LEAKS
#include "bi_vars.h"
#endif

/*
 * FNV-1 hash function
 * http://www.isthe.com/chongo/tech/comp/fnv/index.html
 */
unsigned
hash(const char *s)
{
    /* FNV-1 */
    register unsigned h = 2166136261U;

    while (*s) {
	h ^= (UChar) (*s++);
	h *= 16777619U;
    }
    return h;
}

unsigned
hash2(const char *s, size_t len)
{
    /* FNV-1 */
    register unsigned h = 2166136261U;

    while (len-- != 0) {
	h ^= (UChar) (*s++);
	h *= 16777619U;
    }
    return h;
}

typedef struct hash {
    struct hash *link;
    SYMTAB symtab;
} HASHNODE;

static HASHNODE *hash_table[HASH_PRIME];

#ifdef NO_LEAKS
static void free_hashnode(HASHNODE *);
#else
#define free_hashnode(p) zfree(delete(p->symtab.name), sizeof(HASHNODE))
#endif

/*
insert a string in the symbol table.
Caller knows the symbol is not there
-- used for initialization
*/

SYMTAB *
insert(const char *s)
{
    register HASHNODE *p = ZMALLOC(HASHNODE);
    register unsigned h;

    p->link = hash_table[h = hash(s) % HASH_PRIME];
    p->symtab.name = s;
#ifdef NO_LEAKS
    p->symtab.free_name = 0;
#endif
    hash_table[h] = p;
    return &p->symtab;
}

/* Find s in the symbol table,
   if not there insert it,  s must be dup'ed  */

SYMTAB *
find(const char *s)
{
    register HASHNODE *p;
    HASHNODE *q;
    unsigned h;

    p = hash_table[h = hash(s) % HASH_PRIME];
    q = (HASHNODE *) 0;
    while (1) {
	if (!p) {
	    p = ZMALLOC(HASHNODE);
	    p->symtab.type = ST_NONE;
	    p->symtab.name = strcpy(zmalloc(strlen(s) + 1), s);
#ifdef NO_LEAKS
	    p->symtab.free_name = 1;
#endif
	    break;
	}

	if (strcmp(p->symtab.name, s) == 0)	/* found */
	{
	    if (!q)		/* already at the front */
		return &p->symtab;
	    else {		/* delete from the list */
		q->link = p->link;
		break;
	    }
	}

	q = p;
	p = p->link;
    }
    /* put p on front of the list */
    p->link = hash_table[h];
    hash_table[h] = p;
    return &p->symtab;
}

/* remove a node from the hash table
   return a ptr to the node */

static unsigned last_hash;

static HASHNODE *
delete(const char *s)
{
    register HASHNODE *p;
    HASHNODE *q = (HASHNODE *) 0;
    unsigned h;

    p = hash_table[last_hash = h = hash(s) % HASH_PRIME];
    while (p) {
	if (strcmp(p->symtab.name, s) == 0)	/* found */
	{
	    if (q)
		q->link = p->link;
	    else
		hash_table[h] = p->link;
	    return p;
	} else {
	    q = p;
	    p = p->link;
	}
    }

#ifdef	DEBUG			/* we should not ever get here */
    bozo("delete");
#endif
    return (HASHNODE *) 0;
}

/* when processing user functions,  global ids which are
   replaced by local ids are saved on this list */

static HASHNODE *save_list;

/* store a global id on the save list,
   return a ptr to the local symtab  */
SYMTAB *
save_id(const char *s)
{
    HASHNODE *p, *q;
    unsigned h;

    p = delete(s);
    q = ZMALLOC(HASHNODE);
    q->symtab.type = ST_LOCAL_NONE;
    q->symtab.name = p->symtab.name;
    /* put q in the hash table */
    q->link = hash_table[h = last_hash];
    hash_table[h] = q;

    /* save p */
    p->link = save_list;
    save_list = p;

    return &q->symtab;
}

/* restore all global identifiers */
void
restore_ids(void)
{
    register HASHNODE *p, *q;

    q = save_list;
    save_list = (HASHNODE *) 0;
    while (q) {
	register unsigned h;
	p = q;
	q = q->link;
	free_hashnode(p);
	p->link = hash_table[h = last_hash];
	hash_table[h] = p;
    }
}

/* search the symbol table backwards for the
   disassembler.  This is slow -- so what
*/

const char *
reverse_find(int type, PTR ptr)
{
    CELL *cp = 0;
    ARRAY array = 0;
    static char uk[] = "unknown";

    int i;
    HASHNODE *p;

    switch (type) {
    case ST_VAR:
    case ST_FIELD:
	cp = *(CELL **) ptr;
	break;

    case ST_ARRAY:
	array = *(ARRAY *) ptr;
	break;

    default:
	return uk;
    }

    for (i = 0; i < HASH_PRIME; i++) {
	p = hash_table[i];
	while (p) {
	    if (p->symtab.type == type) {
		switch (type) {
		case ST_VAR:
		case ST_FIELD:
		    if (cp == p->symtab.stval.cp)
			return p->symtab.name;
		    break;

		case ST_ARRAY:
		    if (array == p->symtab.stval.array)
			return p->symtab.name;
		    break;
		}
	    }

	    p = p->link;
	}
    }
    return uk;
}

#ifdef NO_LEAKS
static void
free_symtab_name(HASHNODE * p)
{
    if (p->symtab.free_name) {
	zfree((PTR) (p->symtab.name), strlen(p->symtab.name) + 1);
    }
}

static void
free_hashnode(HASHNODE * p)
{
    CELL *cp;

    TRACE(("...deleting hash %p (%p) %s %d\n",
	   (void *) p,
	   (void *) &(p->symtab),
	   p->symtab.name, p->symtab.type));
    p = delete(p->symtab.name);
    switch (p->symtab.type) {
    case ST_FUNCT:
	free_codes(p->symtab.name,
		   p->symtab.stval.fbp->code,
		   p->symtab.stval.fbp->size);
	if (p->symtab.stval.fbp->nargs)
	    zfree(p->symtab.stval.fbp->typev, p->symtab.stval.fbp->nargs);
	zfree(p->symtab.stval.fbp, sizeof(FBLOCK));
	break;
    case ST_NONE:
	break;
    case ST_VAR:
	cp = p->symtab.stval.cp;
	if (cp != 0
	    && (cp < bi_vars || cp > bi_vars + NUM_BI_VAR)) {
	    switch (cp->type) {
	    case C_STRING:
	    case C_STRNUM:
	    case C_MBSTRN:
		free_STRING(string(cp));
		break;
	    }
	    zfree(cp, sizeof(CELL));
	}
	break;
    default:
	break;
    }
    free_symtab_name(p);
    zfree(p, sizeof(HASHNODE));
}

void
hash_leaks(void)
{
    int i;
    HASHNODE *p;

    TRACE(("hash_leaks\n"));
    for (i = 0; i < HASH_PRIME; i++) {
	while ((p = hash_table[i]) != 0) {
	    free_hashnode(p);
	}
    }
}
#endif