/**
 * slibc — Yet another C library
 * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <stdlib.h>
#include <slibc-alloc.h>
#include <strings.h>
#include <sys/mman.h>



/**
 * Create a new memory allocation on the heap.
 * The allocation will not be initialised.
 * 
 * @param   size  The size of the allocation.
 * @return        Pointer to the beginning of the new allocation.
 *                If `size` is zero, this function will either return
 *                `NULL` (that is what this implement does) or return
 *                a unique pointer that can later be freed with `free`.
 *                `NULL` is returned on error, and `errno` is set to
 *                indicate the error.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* malloc(size_t size)
{
  /* TODO implement implementation of malloc */
  char* ptr;
  if (size == 0)
    return NULL;
  ptr = mmap(NULL, sizeof(size_t) + size, (PROT_READ | PROT_WRITE),
	     (MAP_PRIVATE | MAP_ANONYMOUS), -1, 0);
  *(size_t*)ptr = size;
  return ptr + sizeof(size_t);
}


/**
 * Variant of `malloc` that clears the allocation with zeroes.
 * 
 * `p = calloc(n, m)` is equivalent to
 * `(p = malloc(n * m), p ? (explicit_bzero(p, n * m), p) : NULL)`
 * 
 * @param   elem_count  The number of elements to allocate.
 * @param   elem_size   The size of each element.
 * @return              Pointer to the beginning of the new allocation.
 *                      If `elem_count` or `elem_size` is zero, this function
 *                      will either return `NULL` (that is what this implement
 *                      does) or return a unique pointer that can later be
 *                      freed with `free`. `NULL` is returned on error, and
 *                      `errno` is set to indicate the error.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* calloc(size_t elem_count, size_t elem_size)
{
  void* ptr = malloc(elem_count * elem_size);
  if (ptr != NULL)
    explicit_bzero(ptr, elem_count * elem_size);
  return ptr;
}


/**
 * Variant of `malloc` that extends, or shrinks, an existing allocation,
 * if beneficial and possible, or creates a new allocation with the new
 * size, copies the data, and frees the old allocation.
 * 
 * On error, `ptr` is not freed.
 * 
 * @param   ptr   Pointer to the beginning of the old memory allocation.
 *                The process may crash if it does not point to the
 *                beginning of a memory allocation on the heap.
 *                However, if it is `NULL`, this function will behave
 *                like `malloc`.
 * @param   size  The new allocation size. If zero, this function will
 *                behave like `free`, and will return `NULL`.
 * @return        Pointer to the beginning of the new allocation.
 *                If `size` is zero, `NULL` is returned. On error `NULL`
 *                is returned and `errno` is set to indicate the error.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* realloc(void* ptr, size_t size)
{
  return fast_realloc(ptr, size);
}


/**
 * Free a memory allocation.
 * 
 * @param  ptr  Pointer to the beginning of the memory allocation.
 *              The process may crash if it does not point to the
 *              beginning of a memory allocation on the heap.
 *              However, if it is `NULL`, nothing will happen.
 */
void free(void* ptr)
{
  fast_free(ptr);
}


/**
 * This function is identical to `free`.
 * Any argument beyond the first argument, is ignored.
 * 
 * This function uses variadic arguments because there
 * there are multiple conflicting specifications for `cfree`.
 * 
 * @param  ptr  Pointer to the beginning of the memory allocation.
 *              The process may crash if it does not point to the
 *              beginning of a memory allocation on the heap.
 *              However, if it is `NULL`, nothing will happen.
 */
void cfree(void* ptr, ...)
{
  fast_free(ptr);
}