/*      $NetBSD: citrus_iconv.c,v 1.11 2019/10/09 23:24:00 christos Exp $       */

/*-
 * Copyright (c)2003 Citrus Project,
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: citrus_iconv.c,v 1.11 2019/10/09 23:24:00 christos Exp $");
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"
#include "reentrant.h"

#include <sys/types.h>
#include <sys/queue.h>

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <limits.h>
#include <paths.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "citrus_namespace.h"
#include "citrus_bcs.h"
#include "citrus_region.h"
#include "citrus_memstream.h"
#include "citrus_mmap.h"
#include "citrus_module.h"
#include "citrus_lookup.h"
#include "citrus_hash.h"
#include "citrus_iconv.h"

#define _CITRUS_ICONV_DIR       "iconv.dir"
#define _CITRUS_ICONV_ALIAS     "iconv.alias"

#define CI_HASH_SIZE 101
#define CI_INITIAL_MAX_REUSE    5
#define CI_ENV_MAX_REUSE        "ICONV_MAX_REUSE"

#ifdef _REENTRANT
static rwlock_t lock = RWLOCK_INITIALIZER;
#endif

static bool isinit = false;
static _CITRUS_HASH_HEAD(, _citrus_iconv_shared, CI_HASH_SIZE) shared_pool;
static TAILQ_HEAD(, _citrus_iconv_shared) shared_unused;
static int shared_num_unused, shared_max_reuse;

static __inline void
init_cache(void)
{
        rwlock_wrlock(&lock);
        if (!isinit) {
                _CITRUS_HASH_INIT(&shared_pool, CI_HASH_SIZE);
                TAILQ_INIT(&shared_unused);
                shared_max_reuse = -1;
                if (!issetugid() && getenv(CI_ENV_MAX_REUSE))
                        shared_max_reuse = atoi(getenv(CI_ENV_MAX_REUSE));
                if (shared_max_reuse < 0)
                        shared_max_reuse = CI_INITIAL_MAX_REUSE;
                isinit = true;
        }
        rwlock_unlock(&lock);
}

/*
 * lookup_iconv_entry:
 *      lookup iconv.dir entry in the specified directory.
 *
 * line format of iconv.dir file:
 *      key  module  arg
 * key    : lookup key.
 * module : iconv module name.
 * arg    : argument for the module (generally, description file name)
 *
 */
static __inline int
lookup_iconv_entry(const char *curdir, const char *key,
                   char *linebuf, size_t linebufsize,
                   const char **module, const char **variable)
{
        const char *cp, *cq;
        char *p, path[PATH_MAX];

        /* iconv.dir path */
        snprintf(path, (size_t)PATH_MAX, ("%s/" _CITRUS_ICONV_DIR), curdir);

        /* lookup db */
        cp = p = _lookup_simple(path, key, linebuf, linebufsize,
                                _LOOKUP_CASE_IGNORE);
        if (p == NULL)
                return ENOENT;

        /* get module name */
        *module = p;
        cq = _bcs_skip_nonws(cp);
        p[cq-cp] = '\0';
        p += cq-cp+1;
        cq++;

        /* get variable */
        cp = _bcs_skip_ws(cq);
        *variable = p += cp - cq;
        cq = _bcs_skip_nonws(cp);
        p[cq-cp] = '\0';

        return 0;
}

static __inline void
close_shared(struct _citrus_iconv_shared *ci)
{
        if (ci) {
                if (ci->ci_module) {
                        if (ci->ci_ops) {
                                if (ci->ci_closure)
                                        (*ci->ci_ops->io_uninit_shared)(ci);
                                free(ci->ci_ops);
                        }
                        _citrus_unload_module(ci->ci_module);
                }
                free(ci);
        }
}

static __inline int
open_shared(struct _citrus_iconv_shared * __restrict * __restrict rci,
            const char * __restrict basedir, const char * __restrict convname,
            const char * __restrict src, const char * __restrict dst)
{
        int ret;
        struct _citrus_iconv_shared *ci;
        _citrus_iconv_getops_t getops;
        char linebuf[LINE_MAX];
        const char *module, *variable;
        size_t len_convname;

        /* search converter entry */
        ret = lookup_iconv_entry(basedir, convname, linebuf, sizeof(linebuf),
                                 &module, &variable);
        if (ret) {
                if (ret == ENOENT)
                        /* fallback */
                        ret = lookup_iconv_entry(basedir, "*",
                                                 linebuf, sizeof(linebuf),
                                                 &module, &variable);
                if (ret)
                        return ret;
        }

        /* initialize iconv handle */
        len_convname = strlen(convname);
        ci = malloc(sizeof(*ci)+len_convname+1);
        if (!ci) {
                ret = errno;
                goto err;
        }
        ci->ci_module = NULL;
        ci->ci_ops = NULL;
        ci->ci_closure = NULL;
        ci->ci_convname = (void *)&ci[1];
        memcpy(ci->ci_convname, convname, len_convname+1);

        /* load module */
        ret = _citrus_load_module(&ci->ci_module, module);
        if (ret)
                goto err;

        /* get operators */
        getops = (_citrus_iconv_getops_t)
            _citrus_find_getops(ci->ci_module, module, "iconv");
        if (!getops) {
                ret = EOPNOTSUPP;
                goto err;
        }
        ci->ci_ops = malloc(sizeof(*ci->ci_ops));
        if (!ci->ci_ops) {
                ret = errno;
                goto err;
        }
        ret = (*getops)(ci->ci_ops, sizeof(*ci->ci_ops),
                        _CITRUS_ICONV_ABI_VERSION);
        if (ret)
                goto err;

        /* version check */
        if (ci->ci_ops->io_abi_version == 1) {
                /* binary compatibility broken at ver.2 */
                ret = EINVAL;
                goto err;
        }

        if (ci->ci_ops->io_init_shared == NULL ||
            ci->ci_ops->io_uninit_shared == NULL ||
            ci->ci_ops->io_init_context == NULL ||
            ci->ci_ops->io_uninit_context == NULL ||
            ci->ci_ops->io_convert == NULL) {
                ret = EINVAL;
                goto err;
        }

        /* initialize the converter */
        ret = (*ci->ci_ops->io_init_shared)(ci, basedir, src, dst,
                                            (const void *)variable,
                                            strlen(variable)+1);
        if (ret)
                goto err;

        *rci = ci;

        return 0;
err:
        close_shared(ci);
        return ret;
}

static __inline int
hash_func(const char *key)
{
        return _string_hash_func(key, CI_HASH_SIZE);
}

static __inline int
match_func(struct _citrus_iconv_shared * __restrict ci,
           const char * __restrict key)
{
        return strcmp(ci->ci_convname, key);
}

static int
get_shared(struct _citrus_iconv_shared * __restrict * __restrict rci,
           const char *basedir, const char *src, const char *dst)
{
        int ret = 0;
        int hashval;
        struct _citrus_iconv_shared * ci;
        char convname[2 * PATH_MAX];

        snprintf(convname, sizeof(convname), "%s/%s", src, dst);

        rwlock_wrlock(&lock);

        /* lookup alread existing entry */
        hashval = hash_func(convname);
        _CITRUS_HASH_SEARCH(&shared_pool, ci, ci_hash_entry, match_func,
                            convname, hashval);
        if (ci != NULL) {
                /* found */
                if (ci->ci_used_count == 0) {
                        TAILQ_REMOVE(&shared_unused, ci, ci_tailq_entry);
                        shared_num_unused--;
                }
                ci->ci_used_count++;
                *rci = ci;
                goto quit;
        }

        /* create new entry */
        ret = open_shared(&ci, basedir, convname, src, dst);
        if (ret)
                goto quit;

        _CITRUS_HASH_INSERT(&shared_pool, ci, ci_hash_entry, hashval);
        ci->ci_used_count = 1;
        *rci = ci;

quit:
        rwlock_unlock(&lock);

        return ret;
}

static void
release_shared(struct _citrus_iconv_shared * __restrict ci)
{
        rwlock_wrlock(&lock);

        ci->ci_used_count--;
        if (ci->ci_used_count == 0) {
                /* put it into unused list */
                shared_num_unused++;
                TAILQ_INSERT_TAIL(&shared_unused, ci, ci_tailq_entry);
                /* flood out */
                while (shared_num_unused > shared_max_reuse) {
                        ci = TAILQ_FIRST(&shared_unused);
                        _DIAGASSERT(ci != NULL);
                        TAILQ_REMOVE(&shared_unused, ci, ci_tailq_entry);
                        _CITRUS_HASH_REMOVE(ci, ci_hash_entry);
                        shared_num_unused--;
                        close_shared(ci);
                }
        }

        rwlock_unlock(&lock);
}

/*
 * _citrus_iconv_open:
 *      open a converter for the specified in/out codes.
 */
int
_citrus_iconv_open(struct _citrus_iconv * __restrict * __restrict rcv,
                   const char * __restrict basedir,
                   const char * __restrict src, const char * __restrict dst)
{
        int ret;
        struct _citrus_iconv_shared *ci = NULL;
        struct _citrus_iconv *cv;
        char realsrc[PATH_MAX], realdst[PATH_MAX];
        char buf[PATH_MAX], path[PATH_MAX];

        init_cache();

        /* resolve codeset name aliases */
        snprintf(path, sizeof(path), "%s/%s", basedir, _CITRUS_ICONV_ALIAS);
        strlcpy(realsrc,
                _lookup_alias(path, src, buf, (size_t)PATH_MAX,
                _LOOKUP_CASE_IGNORE),
                (size_t)PATH_MAX);
        strlcpy(realdst,
                _lookup_alias(path, dst, buf, (size_t)PATH_MAX,
                _LOOKUP_CASE_IGNORE),
                (size_t)PATH_MAX);

        /* sanity check */
        if (strchr(realsrc, '/') != NULL || strchr(realdst, '/'))
                return EINVAL;

        /* get shared record */
        ret = get_shared(&ci, basedir, realsrc, realdst);
        if (ret)
                return ret;

        /* create/init context */
        cv = malloc(sizeof(*cv));
        if (cv == NULL) {
                ret = errno;
                release_shared(ci);
                return ret;
        }
        cv->cv_shared = ci;
        ret = (*ci->ci_ops->io_init_context)(cv);
        if (ret) {
                release_shared(ci);
                free(cv);
                return ret;
        }
        *rcv = cv;

        return 0;
}

/*
 * _citrus_iconv_close:
 *      close the specified converter.
 */
void
_citrus_iconv_close(struct _citrus_iconv *cv)
{
        if (cv) {
                (*cv->cv_shared->ci_ops->io_uninit_context)(cv);
                release_shared(cv->cv_shared);
                free(cv);
        }
}