/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or 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 ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC 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 1.6 2020/09/14 08:40:44 florian Exp $ */

/*! \file */

#include <ctype.h>
#include <stdlib.h>
#include <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;

struct isc_symtab {
        /* Unlocked. */
        unsigned int                    size;
        unsigned int                    count;
        unsigned int                    maxload;
        eltlist_t *                     table;
        isc_symtabaction_t              undefine_action;
        void *                          undefine_arg;
        int                     case_sensitive;
};

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

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

        symtab = (isc_symtab_t *)malloc(sizeof(*symtab));
        if (symtab == NULL)
                return (ISC_R_NOMEMORY);

        symtab->table = (eltlist_t *)reallocarray(NULL, size, sizeof(eltlist_t));
        if (symtab->table == NULL) {
                free(symtab);
                return (ISC_R_NOMEMORY);
        }
        for (i = 0; i < size; i++)
                INIT_LIST(symtab->table[i]);
        symtab->size = size;
        symtab->count = 0;
        symtab->maxload = size * 3 / 4;
        symtab->undefine_action = undefine_action;
        symtab->undefine_arg = undefine_arg;
        symtab->case_sensitive = case_sensitive;
        *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;

        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);
                        free(elt);
                }
        }
        free(symtab->table);
        free(symtab);
        *symtabp = NULL;
}

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

        /*
         * This hash function is similar to the one Ousterhout
         * uses in Tcl.
         */

        if (case_sensitive) {
                for (s = key; *s != '\0'; s++) {
                        h += (h << 3) + *s;
                }
        } else {
                for (s = key; *s != '\0'; s++) {
                        c = *s;
                        c = tolower((unsigned char)c);
                        h += (h << 3) + c;
                }
        }

        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(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);
}

static void
grow_table(isc_symtab_t *symtab) {
        eltlist_t *newtable;
        unsigned int i, newsize, newmax;

        REQUIRE(symtab != NULL);

        newsize = symtab->size * 2;
        newmax = newsize * 3 / 4;
        INSIST(newsize > 0U && newmax > 0U);

        newtable = reallocarray(NULL, newsize, sizeof(eltlist_t));
        if (newtable == NULL)
                return;

        for (i = 0; i < newsize; i++)
                INIT_LIST(newtable[i]);

        for (i = 0; i < symtab->size; i++) {
                elt_t *elt, *nelt;

                for (elt = HEAD(symtab->table[i]); elt != NULL; elt = nelt) {
                        unsigned int hv;

                        nelt = NEXT(elt, link);

                        UNLINK(symtab->table[i], elt, link);
                        hv = hash(elt->key, symtab->case_sensitive);
                        APPEND(newtable[hv % newsize], elt, link);
                }
        }

        free(symtab->table);

        symtab->table = newtable;
        symtab->size = newsize;
        symtab->maxload = newmax;
}

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(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 *)malloc(sizeof(*elt));
                if (elt == NULL)
                        return (ISC_R_NOMEMORY);
                ISC_LINK_INIT(elt, link);
                symtab->count++;
        }

        /*
         * 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);

        if (symtab->count > symtab->maxload)
                grow_table(symtab);

        return (ISC_R_SUCCESS);
}