From 76a181d97532f0ae916ffcf05852248c93e97620 Mon Sep 17 00:00:00 2001
From: Karl Williamson <public@khwilliamson.com>
Date: Mon, 9 Jul 2012 18:44:46 -0600
Subject: [PATCH] regcomp.c: Add func to test 2 inversion lists for equality

This adds _invlistEQ which for now is commented out
---
 embed.fnc |  1 +
 regcomp.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/embed.fnc b/embed.fnc
index 33f77c9..2e758aa 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1051,6 +1051,7 @@ Ap	|SV*	|regclass_swash	|NULLOK const regexp *prog \
 #ifdef PERL_IN_REGCOMP_C
 EMs	|void	|add_alternate	|NN AV** alternate_ptr|NN U8* string|STRLEN len
 EMsR	|SV*	|_new_invlist_C_array|NN UV* list
+: Not used currently: EXMs	|bool	|_invlistEQ	|NN SV* const a|NN SV* const b|bool complement_b
 #endif
 Ap	|I32	|pregexec	|NN REGEXP * const prog|NN char* stringarg \
 				|NN char* strend|NN char* strbeg|I32 minend \
diff --git a/regcomp.c b/regcomp.c
index 519186e..c237c64 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -8180,6 +8180,77 @@ S_invlist_dump(pTHX_ SV* const invlist, const char * const header)
 }
 #endif
 
+#if 0
+bool
+S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
+{
+    /* Return a boolean as to if the two passed in inversion lists are
+     * identical.  The final argument, if TRUE, says to take the complement of
+     * the second inversion list before doing the comparison */
+
+    UV* array_a = invlist_array(a);
+    UV* array_b = invlist_array(b);
+    UV len_a = invlist_len(a);
+    UV len_b = invlist_len(b);
+
+    UV i = 0;		    /* current index into the arrays */
+    bool retval = TRUE;     /* Assume are identical until proven otherwise */
+
+    PERL_ARGS_ASSERT__INVLISTEQ;
+
+    /* If are to compare 'a' with the complement of b, set it
+     * up so are looking at b's complement. */
+    if (complement_b) {
+
+        /* The complement of nothing is everything, so <a> would have to have
+         * just one element, starting at zero (ending at infinity) */
+        if (len_b == 0) {
+            return (len_a == 1 && array_a[0] == 0);
+        }
+        else if (array_b[0] == 0) {
+
+            /* Otherwise, to complement, we invert.  Here, the first element is
+             * 0, just remove it.  To do this, we just pretend the array starts
+             * one later, and clear the flag as we don't have to do anything
+             * else later */
+
+            array_b++;
+            len_b--;
+            complement_b = FALSE;
+        }
+        else {
+
+            /* But if the first element is not zero, we unshift a 0 before the
+             * array.  The data structure reserves a space for that 0 (which
+             * should be a '1' right now), so physical shifting is unneeded,
+             * but temporarily change that element to 0.  Before exiting the
+             * routine, we must restore the element to '1' */
+            array_b--;
+            len_b++;
+            array_b[0] = 0;
+        }
+    }
+
+    /* Make sure that the lengths are the same, as well as the final element
+     * before looping through the remainder.  (Thus we test the length, final,
+     * and first elements right off the bat) */
+    if (len_a != len_b || array_a[len_a-1] != array_b[len_a-1]) {
+        retval = FALSE;
+    }
+    else for (i = 0; i < len_a - 1; i++) {
+        if (array_a[i] != array_b[i]) {
+            retval = FALSE;
+            break;
+        }
+    }
+
+    if (complement_b) {
+        array_b[0] = 1;
+    }
+    return retval;
+}
+#endif
+
 #undef HEADER_LENGTH
 #undef INVLIST_INITIAL_LENGTH
 #undef TO_INTERNAL_SIZE
-- 
2.7.4