/*
 * Copyright (c) 1997 - 2000, 2002 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * 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.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE 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 INSTITUTE 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 "krb5_locl.h"
#include "store-int.h"

typedef struct mem_storage{
    unsigned char *base;
    size_t size;
    unsigned char *ptr;
}mem_storage;

static ssize_t
mem_fetch(krb5_storage *sp, void *data, size_t size)
{
    mem_storage *s = (mem_storage*)sp->data;
    if(size > s->base + s->size - s->ptr)
	size = s->base + s->size - s->ptr;
    memmove(data, s->ptr, size);
    sp->seek(sp, size, SEEK_CUR);
    return size;
}

static ssize_t
mem_store(krb5_storage *sp, const void *data, size_t size)
{
    mem_storage *s = (mem_storage*)sp->data;
    if(size > s->base + s->size - s->ptr)
	size = s->base + s->size - s->ptr;
    memmove(s->ptr, data, size);
    sp->seek(sp, size, SEEK_CUR);
    return size;
}

static ssize_t
mem_no_store(krb5_storage *sp, const void *data, size_t size)
{
    return -1;
}

static off_t
mem_seek(krb5_storage *sp, off_t offset, int whence)
{
    mem_storage *s = (mem_storage*)sp->data;
    switch(whence){
    case SEEK_SET:
	if(offset > s->size)
	    offset = s->size;
	if(offset < 0)
	    offset = 0;
	s->ptr = s->base + offset;
	break;
    case SEEK_CUR:
	return sp->seek(sp, s->ptr - s->base + offset, SEEK_SET);
    case SEEK_END:
	return sp->seek(sp, s->size + offset, SEEK_SET);
    default:
	errno = EINVAL;
	return -1;
    }
    return s->ptr - s->base;
}

static int
mem_trunc(krb5_storage *sp, off_t offset)
{
    mem_storage *s = (mem_storage*)sp->data;
    if(offset > s->size)
	return ERANGE;
    s->size = offset;
    if ((s->ptr - s->base) > offset)
	s->ptr = s->base + offset;
    return 0;
}

static int
mem_no_trunc(krb5_storage *sp, off_t offset)
{
    return EINVAL;
}

/**
 * Create a fixed size memory storage block
 *
 * @return A krb5_storage on success, or NULL on out of memory error.
 *
 * @ingroup krb5_storage
 *
 * @sa krb5_storage_mem()
 * @sa krb5_storage_from_readonly_mem()
 * @sa krb5_storage_from_data()
 * @sa krb5_storage_from_fd()
 */

KRB5_LIB_FUNCTION krb5_storage * KRB5_LIB_CALL
krb5_storage_from_mem(void *buf, size_t len)
{
    krb5_storage *sp = malloc(sizeof(krb5_storage));
    mem_storage *s;
    if(sp == NULL)
	return NULL;
    s = malloc(sizeof(*s));
    if(s == NULL) {
	free(sp);
	return NULL;
    }
    sp->data = s;
    sp->flags = 0;
    sp->eof_code = HEIM_ERR_EOF;
    s->base = buf;
    s->size = len;
    s->ptr = buf;
    sp->fetch = mem_fetch;
    sp->store = mem_store;
    sp->seek = mem_seek;
    sp->trunc = mem_trunc;
    sp->free = NULL;
    return sp;
}

/**
 * Create a fixed size memory storage block
 *
 * @return A krb5_storage on success, or NULL on out of memory error.
 *
 * @ingroup krb5_storage
 *
 * @sa krb5_storage_mem()
 * @sa krb5_storage_from_mem()
 * @sa krb5_storage_from_readonly_mem()
 * @sa krb5_storage_from_fd()
 */

KRB5_LIB_FUNCTION krb5_storage * KRB5_LIB_CALL
krb5_storage_from_data(krb5_data *data)
{
    return krb5_storage_from_mem(data->data, data->length);
}

/**
 * Create a fixed size memory storage block that is read only
 *
 * @return A krb5_storage on success, or NULL on out of memory error.
 *
 * @ingroup krb5_storage
 *
 * @sa krb5_storage_mem()
 * @sa krb5_storage_from_mem()
 * @sa krb5_storage_from_data()
 * @sa krb5_storage_from_fd()
 */

KRB5_LIB_FUNCTION krb5_storage * KRB5_LIB_CALL
krb5_storage_from_readonly_mem(const void *buf, size_t len)
{
    krb5_storage *sp = malloc(sizeof(krb5_storage));
    mem_storage *s;
    if(sp == NULL)
	return NULL;
    s = malloc(sizeof(*s));
    if(s == NULL) {
	free(sp);
	return NULL;
    }
    sp->data = s;
    sp->flags = 0;
    sp->eof_code = HEIM_ERR_EOF;
    s->base = rk_UNCONST(buf);
    s->size = len;
    s->ptr = rk_UNCONST(buf);
    sp->fetch = mem_fetch;
    sp->store = mem_no_store;
    sp->seek = mem_seek;
    sp->trunc = mem_no_trunc;
    sp->free = NULL;
    return sp;
}
