[PATCH] added malloc usable size and test

[zack leung]

diff --git a/cpukit/include/rtems/libcsupport.h b/cpukit/include/rtems/libcsupport.h
index f4be4cfc9a..ec385bb71a 100644
--- a/cpukit/include/rtems/libcsupport.h
+++ b/cpukit/include/rtems/libcsupport.h
@@ -73,7 +73,10 @@ extern size_t malloc_free_space(void);
  * Find amount of free heap remaining.
  */
 extern int malloc_info(Heap_Information_block *the_info);
-
+/**
+ * @brief Find the usable size of the block of memory.
+ */
+extern size_t malloc_usable_size( void *ptr );
 /*
  *  Prototypes required to install newlib reentrancy user extension
  */
@@ -185,6 +188,7 @@ bool rtems_resource_snapshot_equal(
  */
 bool rtems_resource_snapshot_check(const rtems_resource_snapshot *snapshot);
 
+
 /** @} */
 
 #ifdef __cplusplus
diff --git a/cpukit/libcsupport/src/mallocusablesize.c b/cpukit/libcsupport/src/mallocusablesize.c
new file mode 100644
index 0000000000..d9211b1390
--- /dev/null
+++ b/cpukit/libcsupport/src/mallocusablesize.c
@@ -0,0 +1,51 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (C) 2022 Zacchaeus Leung
+ *
+ * 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
+ */
+ 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/libcsupport.h>
+#include <rtems/malloc.h>
+#include <rtems/score/heapimpl.h>
+
+size_t malloc_usable_size(void *ptr) {
+  Heap_Control *heap_ptr ;
+  size_t size;
+  if (ptr == NULL) {
+    return 0;
+  }
+
+  
+  heap_ptr = malloc_get_heap_pointer();
+  bool rv=_Heap_Size_of_alloc_area(heap_ptr, ptr, &size);
+  if( rv==false ){
+    return 0;
+  }
+
+  return size;
+}
\ No newline at end of file
diff --git a/spec/build/cpukit/librtemscpu.yml b/spec/build/cpukit/librtemscpu.yml
index 7d6dbae0db..5902008c94 100644
--- a/spec/build/cpukit/librtemscpu.yml
+++ b/spec/build/cpukit/librtemscpu.yml
@@ -670,6 +670,7 @@ source:
 - cpukit/libcsupport/src/lseek.c
 - cpukit/libcsupport/src/lstat.c
 - cpukit/libcsupport/src/malloc.c
+- cpukit/libcsupport/src/mallocusablesize.c 
 - cpukit/libcsupport/src/malloc_deferred.c
 - cpukit/libcsupport/src/malloc_dirtier.c
 - cpukit/libcsupport/src/malloc_walk.c
diff --git a/testsuites/libtests/malloctest/init.c b/testsuites/libtests/malloctest/init.c
index a33764177d..38f5554440 100644
--- a/testsuites/libtests/malloctest/init.c
+++ b/testsuites/libtests/malloctest/init.c
@@ -1362,6 +1362,18 @@ static void test_alloc_zero_size(void)
   rtems_test_assert( p == NULL );
   rtems_test_assert( errno == -1 );
 }
+static void test_usablesize(void)
+{
+  int * a = malloc(sizeof( int )*100);
+  int alloc_size=sizeof( int ) *100 ;
+  rtems_test_assert(  malloc_usable_size(a) <= alloc_size + CPU_HEAP_ALIGNMENT);
+  free(a);
+
+  char * b = malloc(sizeof( char )* 100);
+  int alloc_size2=sizeof( char ) * 100; 
+  rtems_test_assert( malloc_usable_size ( b ) <= alloc_size2 + CPU_HEAP_ALIGNMENT);
+  free(b);
+}
 
 rtems_task Init(
   rtems_task_argument argument
@@ -1405,6 +1417,7 @@ rtems_task Init(
   test_protected_heap_info();
   test_rtems_heap_allocate_aligned_with_boundary();
   test_rtems_malloc();
+  test_usablesize();
   test_rtems_calloc();
   test_greedy_allocate();
   test_alloc_zero_size();
-- 
2.35.1