Allow a header in inversion lists.

An inversion list is an array of UVs.  This allows for other UVs
to be added at the beginning for ancillary purposes.  This patch
does not allocate any space for these, however.

diff --git a/regcomp.c b/regcomp.c
index fd1a978..02062a6 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -5825,7 +5825,8 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
 /* This section of code defines the inversion list object and its methods.  The
  * interfaces are highly subject to change, so as much as possible is static to
  * this file.  An inversion list is here implemented as a malloc'd C array with
- * some added info.  More will be coming when functionality is added later.
+ * some added info that is placed as UVs at the beginning in a header portion.
+ * More will be coming when functionality is added later.
  *
  * It is currently implemented as an SV pointing to an array of UVs that the SV
  * thinks are bytes.  This allows us to have an array of UV whose memory
@@ -5834,8 +5835,12 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
  * Some of the methods should always be private to the implementation, and some
  * should eventually be made public */
 
-#define TO_INTERNAL_SIZE(x) (x * sizeof(UV))   /* Internally things are UVs */
-#define FROM_INTERNAL_SIZE(x) (x / sizeof(UV))
+#define HEADER_LENGTH 0
+
+/* Internally things are UVs */
+#define TO_INTERNAL_SIZE(x) ((x + HEADER_LENGTH) * sizeof(UV))
+#define FROM_INTERNAL_SIZE(x) ((x / sizeof(UV)) - HEADER_LENGTH)
+
 #define INVLIST_INITIAL_LEN 10
 
 PERL_STATIC_INLINE UV*
@@ -5847,7 +5852,7 @@ S_invlist_array(pTHX_ SV* const invlist)
 
     PERL_ARGS_ASSERT_INVLIST_ARRAY;
 
-    return (UV *) SvPVX(invlist);
+    return (UV *) (SvPVX(invlist) + TO_INTERNAL_SIZE(0));
 }
 
 PERL_STATIC_INLINE UV
@@ -5890,12 +5895,17 @@ Perl__new_invlist(pTHX_ IV initial_size)
      * space to store 'initial_size' elements.  If that number is negative, a
      * system default is used instead */
 
+    SV* new_list;
+
     if (initial_size < 0) {
        initial_size = INVLIST_INITIAL_LEN;
     }
 
     /* Allocate the initial space */
-    return newSV(TO_INTERNAL_SIZE(initial_size));
+    new_list = newSV(TO_INTERNAL_SIZE(initial_size));
+    invlist_set_len(new_list, 0);
+
+    return new_list;
 }
 #endif
 
@@ -6352,6 +6362,7 @@ S_add_cp_to_invlist(pTHX_ SV* invlist, const UV cp) {
     return add_range_to_invlist(invlist, cp, cp);
 }
 
+#undef HEADER_LENGTH
 #undef INVLIST_INITIAL_LENGTH
 #undef TO_INTERNAL_SIZE
 #undef FROM_INTERNAL_SIZE