Merge branch 'optimize_g_double_hash' into 'main'

Optimize the implementation of `g_double_hash`

See merge request GNOME/glib!2924

2 files changed, 38 insertions, 2 deletions

diff --git a/glib/ghash.c b/glib/ghash.c
index 5fb722c04..6c9514207 100644
--- a/glib/ghash.c
+++ b/glib/ghash.c
@@ -2490,7 +2490,7 @@ g_int64_equal (gconstpointer v1,
 guint
 g_int64_hash (gconstpointer v)
 {
-  return (guint) *(const gint64*) v;
+  return (guint) ((const guint) (*(guint64 *) v >> 32)) ^ (*(const guint *) v);
 }
 
 /**
@@ -2531,5 +2531,5 @@ g_double_equal (gconstpointer v1,
 guint
 g_double_hash (gconstpointer v)
 {
-  return (guint) *(const gdouble*) v;
+  return (guint) ((const guint) (*(guint64 *) v >> 32)) ^ (*(const guint *) v);
 }
diff --git a/glib/tests/hash.c b/glib/tests/hash.c
index 32d357979..604dcc049 100644
--- a/glib/tests/hash.c
+++ b/glib/tests/hash.c
@@ -460,6 +460,19 @@ int64_hash_test (void)
 }
 
 static void
+int64_hash_collision_test (void)
+{
+  gint64 m;
+  gint64 n;
+
+  g_test_summary ("Check int64 Hash collisions caused by ignoring high word");
+
+  m = 722;
+  n = ((gint64) 2003 << 32) + 722;
+  g_assert_cmpuint (g_int64_hash (&m), !=, g_int64_hash (&n));
+}
+
+static void
 double_hash_test (void)
 {
   gint       i, rc;
@@ -489,6 +502,27 @@ double_hash_test (void)
 }
 
 static void
+double_hash_collision_test (void)
+{
+  gdouble m;
+  gdouble n;
+
+  g_test_summary ("Check double Hash collisions caused by int conversion " \
+                  "and by numbers larger than 2^64-1 (G_MAXUINT64)");
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2771");
+
+  /* Equal when directly converted to integers */
+  m = 0.1;
+  n = 0.2;
+  g_assert_cmpuint (g_double_hash (&m), !=, g_double_hash (&n));
+
+  /* Numbers larger than 2^64-1 (G_MAXUINT64) */
+  m = 1e100;
+  n = 1e200;
+  g_assert_cmpuint (g_double_hash (&m), !=, g_double_hash (&n));
+}
+
+static void
 string_free (gpointer data)
 {
   GString *s = data;
@@ -1715,7 +1749,9 @@ main (int argc, char *argv[])
   g_test_add_func ("/hash/direct2", direct_hash_test2);
   g_test_add_func ("/hash/int", int_hash_test);
   g_test_add_func ("/hash/int64", int64_hash_test);
+  g_test_add_func ("/hash/int64/collisions", int64_hash_collision_test);
   g_test_add_func ("/hash/double", double_hash_test);
+  g_test_add_func ("/hash/double/collisions", double_hash_collision_test);
   g_test_add_func ("/hash/string", string_hash_test);
   g_test_add_func ("/hash/set", set_hash_test);
   g_test_add_func ("/hash/set-ref", set_ref_hash_test);