Add internal facility for dynamic array handling

This is intended as a type-safe alternative to obstacks and
hand-written realloc constructs.  The implementation avoids
writing function pointers to the heap.

1 files changed, 69 insertions, 0 deletions

diff --git a/malloc/dynarray_emplace_enlarge.c b/malloc/dynarray_emplace_enlarge.c
new file mode 100644
index 0000000000..dfc70017ce
--- /dev/null
+++ b/malloc/dynarray_emplace_enlarge.c
@@ -0,0 +1,69 @@
+/* Increase the size of a dynamic array in preparation of an emplace operation.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <dynarray.h>
+#include <malloc-internal.h>
+#include <stdlib.h>
+#include <string.h>
+
+bool
+__libc_dynarray_emplace_enlarge (struct dynarray_header *list,
+                                 void *scratch, size_t element_size)
+{
+  size_t new_allocated;
+  if (list->allocated == 0)
+    {
+      /* No scratch buffer provided.  Choose a reasonable default
+         size.  */
+      if (element_size < 4)
+        new_allocated = 16;
+      if (element_size < 8)
+        new_allocated = 8;
+      else
+        new_allocated = 4;
+    }
+  else
+    /* Increase the allocated size, using an exponential growth
+       policy.  */
+    {
+      new_allocated = list->allocated + list->allocated / 2 + 1;
+      if (new_allocated <= list->allocated)
+        /* Overflow.  */
+        return false;
+    }
+
+  size_t new_size;
+  if (check_mul_overflow_size_t (new_allocated, element_size, &new_size))
+    return false;
+  void *new_array;
+  if (list->array == scratch)
+    {
+      /* The previous array was not heap-allocated.  */
+      new_array = malloc (new_size);
+      if (new_array != NULL && list->array != NULL)
+        memcpy (new_array, list->array, list->used * element_size);
+    }
+  else
+    new_array = realloc (list->array, new_size);
+  if (new_array == NULL)
+    return false;
+  list->array = new_array;
+  list->allocated = new_allocated;
+  return true;
+}
+libc_hidden_def (__libc_dynarray_emplace_enlarge)