From 255dadc152a967219b447f02bfe95dd9d6bce07c Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 4 Feb 2025 22:02:11 +0000
Subject: [PATCH] [set] Speed up may_intersect()

---
 src/hb-bit-page.hh           |  7 +++++++
 src/hb-bit-set-invertible.hh |  3 +++
 src/hb-bit-set.hh            | 20 ++++++++++++++++++++
 src/hb-set.hh                |  8 ++------
 4 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/hb-bit-page.hh b/src/hb-bit-page.hh
index 869c67895..df08c834e 100644
--- a/src/hb-bit-page.hh
+++ b/src/hb-bit-page.hh
@@ -227,6 +227,13 @@ struct hb_bit_page_t
 	return false;
     return true;
   }
+  bool may_intersect (const hb_bit_page_t &other) const
+  {
+    for (unsigned i = 0; i < len (); i++)
+      if (v[i] & other.v[i])
+	return true;
+    return false;
+  }
   bool operator <= (const hb_bit_page_t &larger_page) const { return is_subset (larger_page); }
   bool is_subset (const hb_bit_page_t &larger_page) const
   {
diff --git a/src/hb-bit-set-invertible.hh b/src/hb-bit-set-invertible.hh
index d5d1326d9..862b1a659 100644
--- a/src/hb-bit-set-invertible.hh
+++ b/src/hb-bit-set-invertible.hh
@@ -139,6 +139,9 @@ struct hb_bit_set_invertible_t
   hb_bit_set_invertible_t& operator << (const hb_codepoint_pair_t& range)
   { add_range (range.first, range.second); return *this; }
 
+  bool may_intersect (const hb_bit_set_invertible_t &other) const
+  { return inverted || other.inverted || s.may_intersect (other.s); }
+
   bool intersects (hb_codepoint_t first, hb_codepoint_t last) const
   {
     hb_codepoint_t c = first - 1;
diff --git a/src/hb-bit-set.hh b/src/hb-bit-set.hh
index 032c5b5c4..c303e2bef 100644
--- a/src/hb-bit-set.hh
+++ b/src/hb-bit-set.hh
@@ -358,6 +358,26 @@ struct hb_bit_set_t
   hb_bit_set_t& operator << (const hb_codepoint_pair_t& range)
   { add_range (range.first, range.second); return *this; }
 
+  bool may_intersect (const hb_bit_set_t &other) const
+  {
+    unsigned int na = pages.length;
+    unsigned int nb = other.pages.length;
+
+    unsigned int a = 0, b = 0;
+    for (; a < na && b < nb; )
+    {
+      if (page_map.arrayZ[a].major == other.page_map.arrayZ[b].major &&
+	  page_at (a).may_intersect (other.page_at (b)))
+	return true;
+
+      if (page_map.arrayZ[a].major < other.page_map.arrayZ[b].major)
+	a++;
+      else
+	b++;
+    }
+    return false;
+  }
+
   bool intersects (hb_codepoint_t first, hb_codepoint_t last) const
   {
     hb_codepoint_t c = first - 1;
diff --git a/src/hb-set.hh b/src/hb-set.hh
index 8d0d9692b..8ea20bb71 100644
--- a/src/hb-set.hh
+++ b/src/hb-set.hh
@@ -120,12 +120,8 @@ struct hb_sparseset_t
   hb_sparseset_t& operator << (const hb_codepoint_pair_t& range)
   { add_range (range.first, range.second); return *this; }
 
-  bool may_intersect (const hb_set_t &other) const
-  {
-    hb_sparseset_t tmp = *this;
-    tmp.intersect (other);
-    return !tmp.is_empty ();
-  }
+  bool may_intersect (const hb_sparseset_t &other) const
+  { return s.may_intersect (other.s); }
 
   bool intersects (hb_codepoint_t first, hb_codepoint_t last) const
   { return s.intersects (first, last); }