add malloc_usable_size

Signed-off-by: Mattias Andrée <maandree@operamail.com>

2 files changed, 30 insertions, 0 deletions

diff --git a/include/malloc.h b/include/malloc.h
index 0e17817..956a5e5 100644
--- a/include/malloc.h
+++ b/include/malloc.h
@@ -241,6 +241,21 @@ void* aligned_alloc(size_t, size_t)
 #endif
 
 
+#if defined(_GNU_SOURCE) && !defined(_PORTABLE_SOURCE)
+/**
+ * This function returns the allocation size of
+ * a memory segment.
+ * 
+ * `p = malloc(n), malloc_usable_size(p)` will return `n`.
+ * 
+ * @param   segment  The memory segment.
+ * @return           The size of the memory segment, 0 if `segment` is `NULL`.
+ */
+size_t malloc_usable_size(void*)
+  __GCC_ONLY(__attribute__((warn_unused_result)));
+#endif
+
+
 
 #endif
 
diff --git a/src/malloc.c b/src/malloc.c
index f7a2e95..e09cc85 100644
--- a/src/malloc.c
+++ b/src/malloc.c
@@ -307,3 +307,18 @@ void* aligned_alloc(size_t boundary, size_t size)
   return memalign(boundary, size);
 }
 
+
+/**
+ * This function returns the allocation size of
+ * a memory segment.
+ * 
+ * `p = malloc(n), malloc_usable_size(p)` will return `n`.
+ * 
+ * @param   segment  The memory segment.
+ * @return           The size of the memory segment, 0 if `segment` is `NULL`.
+ */
+size_t malloc_usable_size(void* segment)
+{
+  return allocsize(segment);  
+}
+