/* $NetBSD: fmemopen.c,v 1.4 2010/09/27 16:50:13 tnozaki Exp $ */

/*-
 * Copyright (c)2007, 2010 Takehiko NOZAKI,
 * Copyright (c) 2012, Venkatesh Srinivas <vsrinivas@dragonflybsd.org>
 * 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/param.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

#include "local.h"

struct fmemopen_cookie {
        char *head, *tail, *cur, *eob;
};

static int
fmemopen_read(void *cookie, char *buf, int nbytes)
{
        struct fmemopen_cookie *p;
        char *s;
        int len;

        assert(cookie != NULL);
        assert(buf != NULL && nbytes > 0);

        p = cookie;
        s = p->cur;
        len = MIN(p->tail - p->cur, nbytes);
        bcopy(p->cur, buf, len);
        p->cur += len;

        return (int)(p->cur - s);
}

static int
fmemopen_write(void *cookie, const char *buf, int nbytes)
{
        struct fmemopen_cookie *p;
        char *s;
        int len;

        assert(cookie != NULL);
        assert(buf != NULL && nbytes > 0);

        p = cookie;
        if (p->cur >= p->tail)
                return 0;
        s = p->cur;
        
        len = MIN(p->tail - p->cur, nbytes);

        bcopy(buf, p->cur, len);
        
        p->cur += len - 1;
        if (p->cur == p->tail - 1) {
                *p->cur = '\0';
                if (buf[len - 1] == '\0')
                        p->cur++;
        } else {
                *++p->cur = '\0';
        }
        
        if (p->cur > p->eob)
                p->eob = p->cur;

        return (int)(p->cur - s);
}

static fpos_t
fmemopen_seek(void *cookie, fpos_t offset, int whence)
{
        struct fmemopen_cookie *p;
 
        assert(cookie != NULL);

        p = (struct fmemopen_cookie *)cookie;
        switch (whence) {
        case SEEK_SET:
                break;
        case SEEK_CUR:
                offset += p->cur - p->head;
                break;
        case SEEK_END:
                offset += p->eob - p->head;
                break;
        default:
                errno = EINVAL;
                goto error;
        }
        if (offset >= (fpos_t)0 && offset <= p->tail - p->head) {
                p->cur = p->head + (ptrdiff_t)offset;
                return (fpos_t)(p->cur - p->head);
        }
error:
        return (fpos_t)-1;
}

static int
fmemopen_close0(void *cookie)
{
        assert(cookie != NULL);

        free(cookie);

        return 0;
}

static int
fmemopen_close1(void *cookie)
{
        struct fmemopen_cookie *p;

        assert(cookie != NULL);

        p = cookie;
        free(p->head);
        free(p);

        return 0;
}


FILE *
fmemopen(void * __restrict buf, size_t size, const char * __restrict mode)
{
        int flags, oflags;
        FILE *fp;
        struct fmemopen_cookie *cookie;

        if (size < (size_t)1)
                goto invalid;

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

        if ((oflags & O_RDWR) == 0 && buf == NULL)
                goto invalid;

        fp = __sfp();
        if (fp == NULL)
                return NULL;

        cookie = malloc(sizeof(*cookie));
        if (cookie == NULL)
                goto release;

        if (buf == NULL) {
                cookie->head = malloc(size);
                if (cookie->head == NULL) {
                        free(cookie);
                        goto release;
                }
                *cookie->head = '\0';
                fp->_close = &fmemopen_close1;
        } else {
                cookie->head = (char *)buf;
                if (oflags & O_TRUNC)
                        *cookie->head = '\0';
                fp->_close = &fmemopen_close0;
        }

        cookie->tail = cookie->head + size;
        cookie->eob  = cookie->head;
        do {
                if (*cookie->eob == '\0')
                        break;
                ++cookie->eob;
        } while (--size > 0);

        cookie->cur = (oflags & O_APPEND) ? cookie->eob : cookie->head;

        fp->pub._flags  = flags;
        fp->_write  = (flags & __SRD) ? NULL : &fmemopen_write;
        fp->_read   = (flags & __SWR) ? NULL : &fmemopen_read;
        fp->_seek   = &fmemopen_seek;
        fp->_cookie = (void *)cookie;

        return fp;

invalid:
        errno = EINVAL;
        return NULL;

release:
        fp->pub._flags = 0;
        return NULL;
}