/**
 * 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/>.
 */
#ifndef _SLIBC_ALLOC_H
#define _SLIBC_ALLOC_H
#include <slibc/version.h>
#include <slibc/features.h>
#ifndef __PORTABLE



#define __NEED_size_t
#include <bits/types.h>


/**
 * Configurations for `extalloc`.
 * There are independent of each other, and
 * multiple can be selected by using bitwise or
 * between them.
 */
enum extalloc_mode
  {
    /**
     * Clear disowned memory.
     */
    EXTALLOC_CLEAR = 1,
    
    /**
     * Create new allocation with `malloc` if necessary.
     */
    EXTALLOC_MALLOC = 2,
  };


/**
 * This function is identical to `free`, except it is guaranteed not to
 * override the memory segment with zeroes before freeing the allocation.
 * 
 * @param  segment  The memory segment to free.
 */
void fast_free(void*);

/**
 * This function is identical to `free`, except it is guaranteed to
 * override the memory segment with zeroes before freeing the allocation.
 * 
 * @param  segment  The memory segment to free.
 */
void secure_free(void*);

/**
 * This function returns the allocation size of
 * a memory segment.
 * 
 * Note, this only works for the malloc-family of functions.
 * It does not work on `alloca`, `strdupa` (or similar
 * functions), memory maps (that are not created by `malloc`,)
 * or arrays.
 * 
 * `p = malloc(n), allocsize(p)` will return `n`.
 * 
 * @param   segment  The memory segment.
 * @return           The size of the memory segment, 0 on error.
 * 
 * @throws  EINVAL  If `segment` is `NULL`.
 * @throws  EFAULT  If `segment` is not a pointer to an allocation
 *                  on the heap, or was not allocated with a function
 *                  implemented in slibc. It is however not guaranteed
 *                  that this will happen, undefined behaviour may be
 *                  invoked instead.
 */
size_t allocsize(void*)
  __GCC_ONLY(__attribute__((warn_unused_result)));

/**
 * Variant of `realloc` that overrides newly allocated space
 * with zeroes. Additionally, it will override any freed space
 * with zeroes, including the old allocation if it creates a
 * new allocation.
 * 
 * @param   ptr   The old allocation, see `realloc` for more details.
 * @param   size  The new allocation size, see `realloc` for more details.
 * @return        The new allocation, see `realloc` for more details.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* crealloc(void*, size_t)
  __GCC_ONLY(__attribute__((warn_unused_result)));

/**
 * This function behaves exactly like `realloc`, except it is
 * guaranteed to never initialise or errors data.
 * 
 * @param   ptr   The old allocation, see `realloc` for more details.
 * @param   size  The new allocation size, see `realloc` for more details.
 * @return        The new allocation, see `realloc` for more details.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* fast_realloc(void*, size_t)
  __GCC_ONLY(__attribute__((warn_unused_result)));

/**
 * This function behaves exactly like `crealloc`, except it
 * does not initialise newly allocated size.
 * 
 * @param   ptr   The old allocation, see `realloc` for more details.
 * @param   size  The new allocation size, see `realloc` for more details.
 * @return        The new allocation, see `realloc` for more details.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* secure_realloc(void*, size_t)
  __GCC_ONLY(__attribute__((warn_unused_result)));

/**
 * This function behaves exactly like `realloc`,
 * except you can freely select what memory it clears.
 * 
 * `crealloc(p, n)` is equivalent to (but slightly fast than)
 * `custom_realloc(p, n, 1, 1, 1)`.
 * 
 * `fast_realloc(p, n)` is equivalent to (but slightly fast than)
 * `custom_realloc(p, n, 0, 0, 0)`.
 * 
 * `secure_realloc(p, n)` is equivalent to (but slightly fast than)
 * `custom_realloc(p, n, 1, 0, 1)`.
 * 
 * @param   ptr         The old allocation, see `realloc` for more details.
 * @param   size        The new allocation size, see `realloc` for more details.
 * @param   clear_old   Whether the disowned area is cleared, even if `ptr` is returned.
 * @param   clear_new   Whether the newly claimed area is cleared.
 * @param   clear_free  Whether the old allocation is cleared if a new pointer is returned.
 * @return              The new allocation, see `realloc` for more details.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* custom_realloc(void*, size_t, int, int, int)
  __GCC_ONLY(__attribute__((warn_unused_result)));

/**
 * This function is similar to `realloc`, however it
 * does not copy the data in the memory segment when
 * a new pointer is created. Additionally, the
 * behaviour is undefined if `ptr` is `NULL`, `size`
 * is zero, or `size` equals the old allocation size.
 * These additional quirks were added to improve
 * performance; after all, this function was added
 * to improve performance.
 * 
 * The behaviour is undefined if `mode` does not
 * contain a valid flag-combination.
 * 
 * @param   ptr   The old allocation, see `realloc` for more details.
 * @param   size  The new allocation size, see `realloc` for more details.
 * @param   mode  `EXTALLOC_CLEAR` or `EXTALLOC_MALLOC`, or both or neither.
 * @return        The new allocation, see `realloc` for more details.
 *                If `EXTALLOC_MALLOC` is not used, `NULL` is returned
 *                and `errno` set to zero, if a new allocation is required.
 * 
 * @throws  0       `errno` is set to zero success if `NULL` is returned.
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* extalloc(void*, size_t, enum extalloc_mode)
  __GCC_ONLY(__attribute__((nonnull, warn_unused_result)));

/**
 * This function behaves exactly like `fast_realloc`, except:
 * - Its behaviour is undefined if `ptr` is `NULL`.
 * - Its behaviour is undefined if `size` equals the old allocation size.
 * - Its behaviour is undefined if `size` is zero.
 * - It will never free `ptr`.
 * 
 * @param   ptr   The old allocation, see `realloc` for more details.
 * @param   size  The new allocation size, see `realloc` for more details.
 * @return        The new allocation, see `realloc` for more details.
 * 
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* naive_realloc(void*, size_t) /* sic! we limit ourself to ASCII */
  __GCC_ONLY(__attribute__((nonnull, warn_unused_result)));

/**
 * This function behaves exactly like `__attribute__`, except
 * it will return `NULL` with `errno` set to zero, if it is
 * not possible to perform the shrink or growth without creating
 * new pointer.
 * 
 * @param   ptr   The old allocation, see `realloc` for more details.
 * @param   size  The new allocation size, see `realloc` for more details.
 * @return        `ptr` on success or `NULL` on error or if `malloc` is needed.
 * 
 * @throws  0       `malloc` is require to perform the action.
 * @throws  ENOMEM  The process cannot allocate more memory.
 */
void* naive_extalloc(void*, size_t) /* sic! we limit ourself to ASCII */
  __GCC_ONLY(__attribute__((nonnull, warn_unused_result)));


/**
 * This macro calls `fast_free` and then sets the pointer to `NULL`,
 * so that another attempt to free the segment will not crash the process.
 */
#define  FAST_FREE(segment)  (fast_free(segment), (segment) = NULL);

/**
 * This macro calls `secure_free` and then sets the pointer to `NULL`,
 * so that another attempt to free the segment will not crash the process.
 */
#define  SECURE_FREE(segment)  (secure_free(segment), (segment) = NULL);



#endif
#endif