/*
   This file was retrieved from
       http://gitweb.dragonflybsd.org/dragonfly.git/blob_plain/HEAD:/lib/libc/stdio/fmemopen.c
    on 26/04/2013 by Abel Luck for inclusion in tlsdate for the Android port.
*/
/* $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"
//#include "priv_stdio.h"

int MIN(int a, int b) {
    return a < b ? a : b;
}

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;
}