From df7a0d0fec98d56cd88e4c28ceffa4ed18881477 Mon Sep 17 00:00:00 2001
From: He Junyan <junyan.he@intel.com>
Date: Wed, 20 Nov 2024 15:02:19 +0800
Subject: [PATCH] utils: Add gst_util_floor_log2 helper function

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5003>
---
 subprojects/gstreamer/gst/gstutils.c | 45 ++++++++++++++++++++++++++++
 subprojects/gstreamer/gst/gstutils.h |  3 ++
 2 files changed, 48 insertions(+)

diff --git a/subprojects/gstreamer/gst/gstutils.c b/subprojects/gstreamer/gst/gstutils.c
index 3893aad552..d026db70c7 100644
--- a/subprojects/gstreamer/gst/gstutils.c
+++ b/subprojects/gstreamer/gst/gstutils.c
@@ -4518,6 +4518,51 @@ gst_util_ceil_log2 (guint32 v)
   return y;
 }
 
+/**
+ * gst_util_floor_log2:
+ * @v: a #guint32 value.
+ *
+ * Returns smallest integral value not bigger than log2(v).
+ *
+ * Returns: a computed #guint val.
+ *
+ * Since: 1.26
+ */
+guint
+gst_util_floor_log2 (guint32 v)
+{
+  guint32 result = 0;
+
+  g_return_val_if_fail (v != 0, -1);
+
+  if (v & 0xffff0000) {
+    v >>= 16;
+    result += 16;
+  }
+
+  if (v & 0xff00) {
+    v >>= 8;
+    result += 8;
+  }
+
+  if (v & 0xf0) {
+    v >>= 4;
+    result += 4;
+  }
+
+  if (v & 0xc) {
+    v >>= 2;
+    result += 2;
+  }
+
+  if (v & 0x2) {
+    v >>= 1;
+    result += 1;
+  }
+
+  return result;
+}
+
 /**
  * gst_calculate_linear_regression: (skip)
  * @xy: Pairs of (x,y) values
diff --git a/subprojects/gstreamer/gst/gstutils.h b/subprojects/gstreamer/gst/gstutils.h
index f42dab843a..9400507f71 100644
--- a/subprojects/gstreamer/gst/gstutils.h
+++ b/subprojects/gstreamer/gst/gstutils.h
@@ -1243,6 +1243,9 @@ gboolean      gst_type_is_plugin_api            (GType type, GstPluginAPIFlags *
 GST_API
 guint         gst_util_ceil_log2                (guint32 v);
 
+GST_API
+guint         gst_util_floor_log2               (guint32 x);
+
 GST_API
 gint          gst_util_filename_compare        (const gchar *a, const gchar *b);