/*
 * Copyright (c) 2016, EMC / Isilon Storage Division
 * 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDERS 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>
__FBSDID("$FreeBSD$");

#include <sys/fcntl.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

#include "local.h"

struct fopencookie_thunk {
        void                    *foc_cookie;
        cookie_io_functions_t   foc_io;
};

static int _fopencookie_read(void *, char *, int);
static int _fopencookie_write(void *, const char *, int);
static fpos_t _fopencookie_seek(void *, fpos_t, int);
static int _fopencookie_close(void *);

FILE *
fopencookie(void *cookie, const char *mode, cookie_io_functions_t io_funcs)
{
        int (*readfn)(void *, char *, int);
        int (*writefn)(void *, const char *, int);
        struct fopencookie_thunk *thunk;
        FILE *fp;
        int flags, oflags;

        if ((flags = __sflags(mode, &oflags)) == 0)
                return (NULL);

        thunk = malloc(sizeof(*thunk));
        if (thunk == NULL)
                return (NULL);

        thunk->foc_cookie = cookie;
        thunk->foc_io = io_funcs;

        readfn = _fopencookie_read;
        writefn = _fopencookie_write;
        if (flags == __SWR)
                readfn = NULL;
        else if (flags == __SRD)
                writefn = NULL;

        fp = funopen(thunk, readfn, writefn, _fopencookie_seek,
            _fopencookie_close);
        if (fp == NULL) {
                free(thunk);
                return (NULL);
        }

        if ((oflags & O_APPEND) != 0)
                fp->pub._flags |= __SAPP;

        return (fp);
}

static int
_fopencookie_read(void *cookie, char *buf, int size)
{
        struct fopencookie_thunk *thunk;

        thunk = cookie;

        /* Reads from a stream with NULL read return EOF. */
        if (thunk->foc_io.read == NULL)
                return (0);

        return ((int)thunk->foc_io.read(thunk->foc_cookie, buf, (size_t)size));
}

static int
_fopencookie_write(void *cookie, const char *buf, int size)
{
        struct fopencookie_thunk *thunk;

        thunk = cookie;

        /* Writes to a stream with NULL write discard data. */
        if (thunk->foc_io.write == NULL)
                return (size);

        return ((int)thunk->foc_io.write(thunk->foc_cookie, buf,
                (size_t)size));
}

static fpos_t
_fopencookie_seek(void *cookie, fpos_t offset, int whence)
{
        struct fopencookie_thunk *thunk;
        off_t off64;
        int res;

        switch (whence) {
        case SEEK_SET:
        case SEEK_CUR:
        case SEEK_END:
                break;
        default:
                /* fopencookie(3) only allows these three seek modes. */
                errno = EINVAL;
                return (-1);
        }

        thunk = cookie;

        /*
         * If seek is NULL, it is not possible to perform seek operations on
         * the stream.
         */
        if (thunk->foc_io.seek == NULL) {
                errno = ENOTSUP;
                return (-1);
        }

        off64 = (off_t)offset;
        res = thunk->foc_io.seek(thunk->foc_cookie, &off64, whence);
        if (res < 0)
                return (res);

        return ((fpos_t)off64);
}

static int
_fopencookie_close(void *cookie)
{
        struct fopencookie_thunk *thunk;
        int ret, serrno;

        ret = 0;
        thunk = cookie;
        if (thunk->foc_io.close != NULL)
                ret = thunk->foc_io.close(thunk->foc_cookie);

        serrno = errno;
        free(thunk);
        errno = serrno;
        return (ret);
}