From 2cafbb2aba3181be6ac43cab21fdabce2f6a8327 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Fri, 3 Dec 2021 23:43:13 +0100
Subject: [PATCH] player/CrossFade: move code to CanCrossFade()

---
 src/player/CrossFade.cxx | 27 ++++++++++++++++-----------
 src/player/CrossFade.hxx | 21 +++++++++++++++------
 src/player/Thread.cxx    | 17 +++++++++++------
 3 files changed, 42 insertions(+), 23 deletions(-)

diff --git a/src/player/CrossFade.cxx b/src/player/CrossFade.cxx
index d61c0d0a5..1df8e978e 100644
--- a/src/player/CrossFade.cxx
+++ b/src/player/CrossFade.cxx
@@ -94,23 +94,28 @@ mixramp_interpolate(const char *ramp_list, float required_db) noexcept
 	return FloatDuration(-1);
 }
 
+bool
+CrossFadeSettings::CanCrossFade(SignedSongTime current_total_time,
+				SignedSongTime next_total_time,
+				AudioFormat af,
+				AudioFormat old_format) const noexcept
+{
+	return IsEnabled() &&
+		CanCrossFadeSong(current_total_time) &&
+		CanCrossFadeSong(next_total_time) &&
+		/* we can't crossfade when the audio formats are different */
+		af == old_format;
+}
+
 unsigned
-CrossFadeSettings::Calculate(SignedSongTime current_total_time,
-			     SignedSongTime next_total_time,
-			     float replay_gain_db, float replay_gain_prev_db,
+CrossFadeSettings::Calculate(float replay_gain_db, float replay_gain_prev_db,
 			     const char *mixramp_start, const char *mixramp_prev_end,
 			     const AudioFormat af,
-			     const AudioFormat old_format,
 			     unsigned max_chunks) const noexcept
 {
-	unsigned int chunks = 0;
+	assert(IsEnabled());
 
-	if (!IsEnabled() ||
-	    !CanCrossFadeSong(current_total_time) ||
-	    !CanCrossFadeSong(next_total_time) ||
-	    /* we can't crossfade when the audio formats are different */
-	    af != old_format)
-		return 0;
+	unsigned int chunks = 0;
 
 	assert(duration > FloatDuration::zero());
 	assert(af.IsValid());
diff --git a/src/player/CrossFade.hxx b/src/player/CrossFade.hxx
index 38e919666..062c8cb49 100644
--- a/src/player/CrossFade.hxx
+++ b/src/player/CrossFade.hxx
@@ -53,27 +53,36 @@ struct CrossFadeSettings {
 	}
 
 	/**
-	 * Calculate how many music pipe chunks should be used for crossfading.
+	 * Determine whether cross-fading the two songs is possible.
 	 *
 	 * @param current_total_time the duration of the current song
 	 * @param next_total_time the duration of the new song
+	 * @param af the audio format of the new song
+	 * @param old_format the audio format of the current song
+	 * @return true if cross-fading is possible
+	 */
+	[[gnu::pure]]
+	bool CanCrossFade(SignedSongTime current_total_time,
+			  SignedSongTime next_total_time,
+			  AudioFormat af, AudioFormat old_format) const noexcept;
+
+	/**
+	 * Calculate how many music pipe chunks should be used for crossfading.
+	 *
 	 * @param replay_gain_db the ReplayGain adjustment used for this song
 	 * @param replay_gain_prev_db the ReplayGain adjustment used on the last song
 	 * @param mixramp_start the next songs mixramp_start tag
 	 * @param mixramp_prev_end the last songs mixramp_end setting
 	 * @param af the audio format of the new song
-	 * @param old_format the audio format of the current song
 	 * @param max_chunks the maximum number of chunks
 	 * @return the number of chunks for crossfading, or 0 if cross fading
 	 * should be disabled for this song change
 	 */
 	[[gnu::pure]]
-	unsigned Calculate(SignedSongTime current_total_time,
-			   SignedSongTime next_total_time,
-			   float replay_gain_db, float replay_gain_prev_db,
+	unsigned Calculate(float replay_gain_db, float replay_gain_prev_db,
 			   const char *mixramp_start,
 			   const char *mixramp_prev_end,
-			   AudioFormat af, AudioFormat old_format,
+			   AudioFormat af,
 			   unsigned max_chunks) const noexcept;
 
 private:
diff --git a/src/player/Thread.cxx b/src/player/Thread.cxx
index 56da75d62..18178bf63 100644
--- a/src/player/Thread.cxx
+++ b/src/player/Thread.cxx
@@ -804,24 +804,29 @@ Player::CheckCrossFade() noexcept
 		   can decide */
 		return;
 
+	if (!pc.cross_fade.CanCrossFade(pc.total_time, dc.total_time,
+					dc.out_audio_format,
+					play_audio_format)) {
+		/* cross fading is disabled or the next song is too
+		   short */
+		xfade_state = CrossFadeState::DISABLED;
+		return;
+	}
+
 	/* enable cross fading in this song?  if yes, calculate how
 	   many chunks will be required for it */
 	cross_fade_chunks =
-		pc.cross_fade.Calculate(pc.total_time,
-					dc.total_time,
-					dc.replay_gain_db,
+		pc.cross_fade.Calculate(dc.replay_gain_db,
 					dc.replay_gain_prev_db,
 					dc.GetMixRampStart(),
 					dc.GetMixRampPreviousEnd(),
-					dc.out_audio_format,
 					play_audio_format,
 					buffer.GetSize() -
 					buffer_before_play);
 	if (cross_fade_chunks > 0)
 		xfade_state = CrossFadeState::ENABLED;
 	else
-		/* cross fading is disabled or the
-		   next song is too short */
+		// TODO: eliminate this "else" branch
 		xfade_state = CrossFadeState::DISABLED;
 }