+ return (width == -1 ? basis
+ : width == 0 ? hash_double (value->f, basis)
+ : hash_bytes (value->s, width, basis));
+}
+
+/* Tests whether VALUE may be resized from OLD_WIDTH to
+ NEW_WIDTH, using the following rules that match those for
+ resizing missing values and value labels. First, OLD_WIDTH
+ and NEW_WIDTH must be both numeric or both string. Second, if
+ NEW_WIDTH is less than OLD_WIDTH, then the bytes that would be
+ trimmed off the right end of VALUE must be all spaces. */
+bool
+value_is_resizable (const union value *value, int old_width, int new_width)
+{
+ if (old_width == new_width)
+ return true;
+ else if (val_type_from_width (old_width) != val_type_from_width (new_width))
+ return false;
+ else
+ {
+ const uint8_t *str = value->s;
+ int i;
+
+ for (i = new_width; i < old_width; i++)
+ if (str[i] != ' ')
+ return false;
+ return true;
+ }
+}
+
+/* Resizes VALUE from OLD_WIDTH to NEW_WIDTH. The arguments must
+ satisfy the rules specified above for value_is_resizable. */
+void
+value_resize (union value *value, int old_width, int new_width)
+{
+ assert (value_is_resizable (value, old_width, new_width));
+ if (new_width != old_width && new_width > 0)
+ {
+ union value tmp;
+ value_init (&tmp, new_width);
+ value_copy_rpad (&tmp, new_width, value, old_width, ' ');
+ value_destroy (value, old_width);
+ *value = tmp;
+ }
+}
+
+/* Returns true if VALUE, with the given WIDTH, is all spaces, false otherwise.
+ Returns false if VALUE is numeric. */
+bool
+value_is_spaces (const union value *value, int width)
+{
+ int i;
+
+ for (i = 0; i < width; i++)
+ if (value->s[i] != ' ')
+ return false;
+
+ return true;
+}
+
+/* Returns true if resizing a value from OLD_WIDTH to NEW_WIDTH
+ actually changes anything, false otherwise. If false is
+ returned, calls to value_resize() with the specified
+ parameters may be omitted without any ill effects.
+
+ This is generally useful only if many values can skip being
+ resized from OLD_WIDTH to NEW_WIDTH. Otherwise you might as
+ well just call value_resize directly. */
+bool
+value_needs_resize (int old_width, int new_width)
+{
+ assert (val_type_from_width (old_width) == val_type_from_width (new_width));
+
+ return old_width != new_width;
+}
+
+/* Same as value_init, except that memory for VALUE (if
+ necessary) is allocated from POOL and will be freed
+ automatically when POOL is destroyed.
+
+ VALUE must not be freed manually by calling value_destroy. If
+ it needs to be resized, it must be done using
+ value_resize_pool instead of value_resize. */
+void
+value_init_pool (struct pool *pool, union value *value, int width)
+{
+ if (width > 0)
+ value->s = pool_alloc_unaligned (pool, width);
+}
+
+/* Same as value_clone(), except that memory for VALUE (if necessary) is
+ allocated from POOL and will be freed automatically when POOL is destroyed.
+
+ VALUE must not be freed manually by calling value_destroy(). If it needs to
+ be resized, it must be done using value_resize_pool() instead of
+ value_resize(). */
+void
+value_clone_pool (struct pool *pool,
+ union value *value, const union value *src, int width)
+{
+ if (width > 0)
+ value->s = pool_clone_unaligned (pool, src->s, width);
+ else
+ value->f = src->f;
+}
+
+/* Same as value_resize, except that VALUE must have been
+ allocated from POOL using value_init_pool.
+
+ This function causes some memory in POOL to be wasted in some
+ cases (until the pool is freed), so it should only be done if
+ this is acceptable. */
+void
+value_resize_pool (struct pool *pool, union value *value,
+ int old_width, int new_width)
+{
+ assert (value_is_resizable (value, old_width, new_width));
+ if (new_width > old_width)
+ {
+ uint8_t *new_string = pool_alloc_unaligned (pool, new_width);
+ memcpy (new_string, value->s, old_width);
+ value->s = new_string;
+
+ memset (value->s + old_width, ' ', new_width - old_width);
+ }