+/* Other parts of Emacs pass large int values to allocator functions
+ expecting ptrdiff_t. This is portable in practice, but check it to
+ be safe. */
+verify (INT_MAX <= PTRDIFF_MAX);
+
+
+/* Allocate an array of NITEMS items, each of size ITEM_SIZE.
+ Signal an error on memory exhaustion, and block interrupt input. */
+
+void *
+xnmalloc (ptrdiff_t nitems, ptrdiff_t item_size)
+{
+ xassert (0 <= nitems && 0 < item_size);
+ if (min (PTRDIFF_MAX, SIZE_MAX) / item_size < nitems)
+ memory_full (SIZE_MAX);
+ return xmalloc (nitems * item_size);
+}
+
+
+/* Reallocate an array PA to make it of NITEMS items, each of size ITEM_SIZE.
+ Signal an error on memory exhaustion, and block interrupt input. */
+
+void *
+xnrealloc (void *pa, ptrdiff_t nitems, ptrdiff_t item_size)
+{
+ xassert (0 <= nitems && 0 < item_size);
+ if (min (PTRDIFF_MAX, SIZE_MAX) / item_size < nitems)
+ memory_full (SIZE_MAX);
+ return xrealloc (pa, nitems * item_size);
+}
+
+
+/* Grow PA, which points to an array of *NITEMS items, and return the
+ location of the reallocated array, updating *NITEMS to reflect its
+ new size. The new array will contain at least NITEMS_INCR_MIN more
+ items, but will not contain more than NITEMS_MAX items total.
+ ITEM_SIZE is the size of each item, in bytes.
+
+ ITEM_SIZE and NITEMS_INCR_MIN must be positive. *NITEMS must be
+ nonnegative. If NITEMS_MAX is -1, it is treated as if it were
+ infinity.
+
+ If PA is null, then allocate a new array instead of reallocating
+ the old one. Thus, to grow an array A without saving its old
+ contents, invoke xfree (A) immediately followed by xgrowalloc (0,
+ &NITEMS, ...).
+
+ Block interrupt input as needed. If memory exhaustion occurs, set
+ *NITEMS to zero if PA is null, and signal an error (i.e., do not
+ return). */
+
+void *
+xpalloc (void *pa, ptrdiff_t *nitems, ptrdiff_t nitems_incr_min,
+ ptrdiff_t nitems_max, ptrdiff_t item_size)
+{
+ /* The approximate size to use for initial small allocation
+ requests. This is the largest "small" request for the GNU C
+ library malloc. */
+ enum { DEFAULT_MXFAST = 64 * sizeof (size_t) / 4 };
+
+ /* If the array is tiny, grow it to about (but no greater than)
+ DEFAULT_MXFAST bytes. Otherwise, grow it by about 50%. */
+ ptrdiff_t n = *nitems;
+ ptrdiff_t tiny_max = DEFAULT_MXFAST / item_size - n;
+ ptrdiff_t half_again = n >> 1;
+ ptrdiff_t incr_estimate = max (tiny_max, half_again);
+
+ /* Adjust the increment according to three constraints: NITEMS_INCR_MIN,
+ NITEMS_MAX, and what the C language can represent safely. */
+ ptrdiff_t C_language_max = min (PTRDIFF_MAX, SIZE_MAX) / item_size;
+ ptrdiff_t n_max = (0 <= nitems_max && nitems_max < C_language_max
+ ? nitems_max : C_language_max);
+ ptrdiff_t nitems_incr_max = n_max - n;
+ ptrdiff_t incr = max (nitems_incr_min, min (incr_estimate, nitems_incr_max));
+
+ xassert (0 < item_size && 0 < nitems_incr_min && 0 <= n && -1 <= nitems_max);
+ if (! pa)
+ *nitems = 0;
+ if (nitems_incr_max < incr)
+ memory_full (SIZE_MAX);
+ n += incr;
+ pa = xrealloc (pa, n * item_size);
+ *nitems = n;
+ return pa;
+}
+
+