lib/isc/symtab.c

	symtab.c revision 15a44745412679c30a6d022733925af70a38b715
/*
 * Copyright (C) 1996-2000  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: symtab.c,v 1.19 2000/07/27 09:51:16 tale Exp $ */

#include <config.h>

#include <ctype.h>

#include <isc/mem.h>
#include <isc/string.h>
#include <isc/symtab.h>
#include <isc/util.h>

typedef struct elt {
    char *              key;
    unsigned int            type;
    isc_symvalue_t          value;
    LINK(struct elt)        link;
} elt_t;

typedef LIST(elt_t)         eltlist_t;

#define SYMTAB_MAGIC            0x53796D54U /* SymT. */
#define VALID_SYMTAB(st)        ((st) != NULL && \
                     (st)->magic == SYMTAB_MAGIC)

struct isc_symtab {
    /* Unlocked. */
    unsigned int            magic;
    isc_mem_t *         mctx;
    unsigned int            size;
    eltlist_t *         table;
    isc_symtabaction_t      undefine_action;
    void *              undefine_arg;
    isc_boolean_t           case_sensitive;
};

isc_result_t
isc_symtab_create(isc_mem_t *mctx, unsigned int size,
          isc_symtabaction_t undefine_action,
          void *undefine_arg,
          isc_boolean_t case_sensitive,
          isc_symtab_t **symtabp)
{
    isc_symtab_t *symtab;
    unsigned int i;

    REQUIRE(mctx != NULL);
    REQUIRE(symtabp != NULL && *symtabp == NULL);
    REQUIRE(size > 0);  /* Should be prime. */

    symtab = (isc_symtab_t *)isc_mem_get(mctx, sizeof *symtab);
    if (symtab == NULL)
        return (ISC_R_NOMEMORY);
    symtab->table = (eltlist_t *)isc_mem_get(mctx,
                         size * sizeof (eltlist_t));
    if (symtab->table == NULL) {
        isc_mem_put(mctx, symtab, sizeof *symtab);
        return (ISC_R_NOMEMORY);
    }
    for (i = 0; i < size; i++)
        INIT_LIST(symtab->table[i]);
    symtab->mctx = mctx;
    symtab->size = size;
    symtab->undefine_action = undefine_action;
    symtab->undefine_arg = undefine_arg;
    symtab->case_sensitive = case_sensitive;
    symtab->magic = SYMTAB_MAGIC;

    *symtabp = symtab;

    return (ISC_R_SUCCESS);
}

void
isc_symtab_destroy(isc_symtab_t **symtabp) {
    isc_symtab_t *symtab;
    unsigned int i;
    elt_t *elt, *nelt;

    REQUIRE(symtabp != NULL);
    symtab = *symtabp;
    REQUIRE(VALID_SYMTAB(symtab));

    for (i = 0; i < symtab->size; i++) {
        for (elt = HEAD(symtab->table[i]); elt != NULL; elt = nelt) {
            nelt = NEXT(elt, link);
            if (symtab->undefine_action != NULL)
                   (symtab->undefine_action)(elt->key,
                             elt->type,
                             elt->value,
                             symtab->undefine_arg);
            isc_mem_put(symtab->mctx, elt, sizeof *elt);
        }
    }
    isc_mem_put(symtab->mctx, symtab->table,
            symtab->size * sizeof (eltlist_t));
    symtab->magic = 0;
    isc_mem_put(symtab->mctx, symtab, sizeof *symtab);

    *symtabp = NULL;
}

static inline unsigned int
hash(const char *key, isc_boolean_t case_sensitive) {
    const char *s;
    unsigned int h = 0;
    unsigned int g;
    int c;

    /*
     * P. J. Weinberger's hash function, adapted from p. 436 of
     * _Compilers: Principles, Techniques, and Tools_, Aho, Sethi
     * and Ullman, Addison-Wesley, 1986, ISBN 0-201-10088-6.
     */

    if (case_sensitive) {
        for (s = key; *s != '\0'; s++) {
            h = ( h << 4 ) + *s;
            if ((g = ( h & 0xf0000000 )) != 0) {
                h = h ^ (g >> 24);
                h = h ^ g;
            }
        }
    } else {
        for (s = key; *s != '\0'; s++) {
            c = *s;
            c = tolower((unsigned char)c);
            h = ( h << 4 ) + c;
            if ((g = ( h & 0xf0000000 )) != 0) {
                h = h ^ (g >> 24);
                h = h ^ g;
            }
        }
    }

    return (h);
}

#define FIND(s, k, t, b, e) \
    b = hash((k), (s)->case_sensitive) % (s)->size; \
    if ((s)->case_sensitive) { \
        for (e = HEAD((s)->table[b]); e != NULL; e = NEXT(e, link)) { \
            if (((t) == 0 || e->type == (t)) && \
                strcmp(e->key, (k)) == 0) \
                break; \
        } \
    } else { \
        for (e = HEAD((s)->table[b]); e != NULL; e = NEXT(e, link)) { \
            if (((t) == 0 || e->type == (t)) && \
                strcasecmp(e->key, (k)) == 0) \
                break; \
        } \
    }

isc_result_t
isc_symtab_lookup(isc_symtab_t *symtab, const char *key, unsigned int type,
          isc_symvalue_t *value)
{
    unsigned int bucket;
    elt_t *elt;

    REQUIRE(VALID_SYMTAB(symtab));
    REQUIRE(key != NULL);

    FIND(symtab, key, type, bucket, elt);

    if (elt == NULL)
        return (ISC_R_NOTFOUND);

    if (value != NULL)
        *value = elt->value;

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_symtab_define(isc_symtab_t *symtab, const char *key, unsigned int type,
          isc_symvalue_t value, isc_symexists_t exists_policy)
{
    unsigned int bucket;
    elt_t *elt;

    REQUIRE(VALID_SYMTAB(symtab));
    REQUIRE(key != NULL);
    REQUIRE(type != 0);

    FIND(symtab, key, type, bucket, elt);

    if (exists_policy != isc_symexists_add && elt != NULL) {
        if (exists_policy == isc_symexists_reject)
            return (ISC_R_EXISTS);
        INSIST(exists_policy == isc_symexists_replace);
        UNLINK(symtab->table[bucket], elt, link);
        if (symtab->undefine_action != NULL)
            (symtab->undefine_action)(elt->key, elt->type,
                          elt->value,
                          symtab->undefine_arg);
    } else {
        elt = (elt_t *)isc_mem_get(symtab->mctx, sizeof *elt);
        if (elt == NULL)
            return (ISC_R_NOMEMORY);
    }

    /*
     * Though the "key" can be const coming in, it is not stored as const
     * so that the calling program can easily have writable access to
     * it in its undefine_action function.  In the event that it *was*
     * truly const coming in and then the caller modified it anyway ...
     * well, don't do that!
     */
    DE_CONST(key, elt->key);
    elt->type = type;
    elt->value = value;

    /*
     * We prepend so that the most recent definition will be found.
     */
    PREPEND(symtab->table[bucket], elt, link);

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_symtab_undefine(isc_symtab_t *symtab, const char *key, unsigned int type) {
    unsigned int bucket;
    elt_t *elt;

    REQUIRE(VALID_SYMTAB(symtab));
    REQUIRE(key != NULL);

    FIND(symtab, key, type, bucket, elt);

    if (elt == NULL)
        return (ISC_R_NOTFOUND);

    if (symtab->undefine_action != NULL)
        (symtab->undefine_action)(elt->key, elt->type,
                      elt->value, symtab->undefine_arg);
    UNLINK(symtab->table[bucket], elt, link);
    isc_mem_put(symtab->mctx, elt, sizeof *elt);

    return (ISC_R_SUCCESS);
}