+/* Changes the allocation size of the specified memory block P
+ managed by POOL to N * S bytes and returns a pointer to the
+ beginning of the block.
+ N must be nonnegative, S must be positive.
+ If POOL is a null pointer, then the block is reallocated in
+ the usual way with xrealloc().
+ Terminates the program if the memory cannot be obtained,
+ including the case where N * S overflows the range of size_t. */
+void *
+pool_nrealloc (struct pool *pool, void *p, size_t n, size_t s)
+{
+ if (xalloc_oversized (n, s))
+ xalloc_die ();
+ return pool_realloc (pool, p, n * s);
+}
+
+/* If P is null, allocate a block of at least *PN such objects;
+ otherwise, reallocate P so that it contains more than *PN
+ objects each of S bytes. *PN must be nonzero unless P is
+ null, and S must be nonzero. Set *PN to the new number of
+ objects, and return the pointer to the new block. *PN is
+ never set to zero, and the returned pointer is never null.
+
+ The block returned is managed by POOL. If POOL is a null
+ pointer, then the block is reallocated in the usual way with
+ x2nrealloc().
+
+ Terminates the program if the memory cannot be obtained,
+ including the case where the memory required overflows the
+ range of size_t.
+
+ Repeated reallocations are guaranteed to make progress, either by
+ allocating an initial block with a nonzero size, or by allocating a
+ larger block.
+
+ In the following implementation, nonzero sizes are doubled so that
+ repeated reallocations have O(N log N) overall cost rather than
+ O(N**2) cost, but the specification for this function does not
+ guarantee that sizes are doubled.
+
+ Here is an example of use:
+
+ int *p = NULL;
+ struct pool *pool;
+ size_t used = 0;
+ size_t allocated = 0;
+
+ void
+ append_int (int value)
+ {
+ if (used == allocated)
+ p = pool_2nrealloc (pool, p, &allocated, sizeof *p);
+ p[used++] = value;
+ }
+
+ This causes x2nrealloc to allocate a block of some nonzero size the
+ first time it is called.
+
+ To have finer-grained control over the initial size, set *PN to a
+ nonzero value before calling this function with P == NULL. For
+ example:
+
+ int *p = NULL;
+ struct pool *pool;
+ size_t used = 0;
+ size_t allocated = 0;
+ size_t allocated1 = 1000;
+
+ void
+ append_int (int value)
+ {
+ if (used == allocated)
+ {
+ p = pool_2nrealloc (pool, p, &allocated1, sizeof *p);
+ allocated = allocated1;
+ }
+ p[used++] = value;
+ }
+
+ This function implementation is from gnulib. */
+void *
+pool_2nrealloc (struct pool *pool, void *p, size_t *pn, size_t s)
+{
+ size_t n = *pn;
+
+ if (p == NULL)
+ {
+ if (n == 0)
+ {
+ /* The approximate size to use for initial small allocation
+ requests, when the invoking code specifies an old size of
+ zero. 64 bytes is the largest "small" request for the
+ GNU C library malloc. */
+ enum { DEFAULT_MXFAST = 64 };
+
+ n = DEFAULT_MXFAST / s;
+ n += !n;
+ }
+ }
+ else
+ {
+ if (SIZE_MAX / 2 / s < n)
+ xalloc_die ();
+ n *= 2;
+ }
+
+ *pn = n;
+ return pool_realloc (pool, p, n * s);
+}
+