Implement realloc and add realloc rounds to random test

realloc returns the same pointer if the chunk is large enough,
otherwise malloc + memcpy + free. The random test now verifies
data integrity after resizing across all three categories.

1 files changed, 31 insertions, 5 deletions

diff --git a/src/realloc.c b/src/realloc.c
index c0bbfed..3cc92f1 100644
--- a/src/realloc.c
+++ b/src/realloc.c
@@ -1,16 +1,42 @@
 /**
  * @file   realloc.c
- * @brief  Stub implementation of realloc.
+ * @brief  realloc implementation.
  */
 
 #include "libft.h"
 #include "malloc.h"
+#include "malloc_internal.h"
+
+static t_chunk *
+_s_ptr_to_chunk (void *ptr)
+{
+  return ((t_chunk *)((char *)ptr - ALIGN (sizeof (t_chunk))));
+}
 
 void *
 realloc (void *ptr, size_t size)
 {
-  (void)ptr;
-  (void)size;
-  ft_putendl_fd ("REALLOC", 1);
-  return (NULL);
+  t_chunk *chunk;
+  void *new_ptr;
+  size_t copy_size;
+
+  if (!ptr)
+    return (malloc (size));
+  if (size == 0)
+    {
+      free (ptr);
+      return (NULL);
+    }
+  chunk = _s_ptr_to_chunk (ptr);
+  if (chunk->size >= ALIGN (size))
+    return (ptr);
+  new_ptr = malloc (size);
+  if (!new_ptr)
+    return (NULL);
+  copy_size = chunk->size;
+  if (copy_size > size)
+    copy_size = size;
+  ft_memcpy (new_ptr, ptr, copy_size);
+  free (ptr);
+  return (new_ptr);
 }