qmckl/src/qmckl_memory.org

#+TITLE: Memory management
#+SETUPFILE: ../docs/theme.setup

We override the allocation functions to enable the possibility of
optimized libraries to fine-tune the memory allocation.


* Headers                                                          :noexport:

  #+NAME: filename
  #+begin_src elisp tangle: no 
(file-name-nondirectory (substring buffer-file-name 0 -4))
  #+end_src

  #+begin_src c :tangle (eval c)
#include <stdint.h>
#include <stdlib.h>
#include <assert.h>

#include "qmckl_error.h"
#include "qmckl_context.h"
#include "qmckl_context_private.h"
#include "qmckl_memory.h"
  #+end_src

  #+begin_src c :tangle (eval c_test) :noweb yes
#include "qmckl.h"
#include "munit.h"
MunitResult test_<<filename()>>() {
  #+end_src

* 
:PROPERTIES:
:UNNUMBERED: t
:END:

  Memory allocation inside the library should be done with
 ~qmckl_malloc~. It lets the library choose how the memory will be
  allocated, and a pointer is returned to the user.  The context is
  passed to let the library store data related to the allocation
  inside the context. In this particular implementation of the library,
  we store a list of allocated pointers so that all the memory can be
  properly freed when the library is de-initialized.
  If the allocation failed, the ~NULL~ pointer is returned.

  # Header
  #+begin_src c :tangle (eval h) :noexport
void* qmckl_malloc(qmckl_context context,
                   const size_t size);
  #+end_src
  
  In this implementation, we use ~calloc~ because it initializes the
  memory block to zero, so structs will have ~NULL~-initialized pointers.

  # Source
  #+begin_src c :tangle (eval c)
void* qmckl_malloc(qmckl_context context, const size_t size) {

  void * pointer = calloc(size, (size_t) 1);

  if (qmckl_context_check(context) != QMCKL_NULL_CONTEXT) {
    qmckl_exit_code rc;
    rc = qmckl_context_append_memory(context, pointer, size);
    assert (rc == QMCKL_SUCCESS);
  }

  return pointer;
}
  #+end_src

  # Fortran interface
  #+begin_src f90 :tangle (eval fh) :noexport
  interface
     type (c_ptr) function qmckl_malloc (context, size) bind(C)
       use, intrinsic :: iso_c_binding
       integer (c_int64_t), intent(in), value :: context
       integer (c_int64_t), intent(in), value :: size
     end function qmckl_malloc
  end interface
  #+end_src

   # Test                                                            :noexport:
   #+begin_src c :tangle (eval c_test)
qmckl_context context = qmckl_context_create();    

int *a = (int*) qmckl_malloc(context, 3*sizeof(int));
munit_assert(a != NULL);

a[0] = 1;  munit_assert_int(a[0], ==, 1);
a[1] = 2;  munit_assert_int(a[1], ==, 2);
a[2] = 3;  munit_assert_int(a[2], ==, 3);
   #+end_src

  When freeing the memory with ~qmckl_free~, the context is passed, in
  case some important information has been stored related to memory
  allocation and needs to be updated.

  #+begin_src c :tangle (eval h)
qmckl_exit_code qmckl_free(qmckl_context context,
                           void *ptr);
  #+end_src

  #+begin_src f90 :tangle (eval fh)
  interface
     integer (c_int32_t) function qmckl_free (context, ptr) bind(C)
       use, intrinsic :: iso_c_binding
       integer (c_int64_t), intent(in), value :: context
       type (c_ptr), intent(in), value :: ptr
     end function qmckl_free
  end interface
  #+end_src

   # Source
   #+begin_src c :tangle (eval c)
qmckl_exit_code qmckl_free(qmckl_context context, void *ptr) {
  if (qmckl_context_check(context) != QMCKL_NULL_CONTEXT) {

    if (ptr == NULL) {
      return qmckl_failwith(context,
                            QMCKL_INVALID_ARG_2,
                            "qmckl_free",
                            "NULL pointer");
    }
    
    qmckl_exit_code rc;
    rc = qmckl_context_remove_memory(context, ptr);

    assert (rc == QMCKL_SUCCESS);
  }
  free(ptr);
  return QMCKL_SUCCESS;
}
   #+end_src

   # Test
   #+begin_src c :tangle (eval c_test) :exports none
qmckl_exit_code rc;

munit_assert(a != NULL);
rc = qmckl_free(context, a);
munit_assert(rc == QMCKL_SUCCESS);

rc = qmckl_context_destroy(context);
munit_assert(rc == QMCKL_SUCCESS);

   #+end_src

* End of files                                                     :noexport:

** Test
  #+begin_src c :comments org :tangle (eval c_test)
  return MUNIT_OK;
}

  #+end_src
 

# -*- mode: org -*-
# vim: syntax=c