From ee350362d38922760d47516fab79797f425683e3 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 28 Jun 2022 03:01:41 +0200
Subject: [PATCH] Debug loop range squishing

When the loop-range is defined in BeatTime, the disk-reader encounters
rounding issues due to time-domain mismatches.

With a simple session fixed BPM at 120,  48kHz.
looping 1 bar exactly 2 sec at the start of the session:
```
 Range::squish start: b0 end: b7680 squish: a113554560
 Range::squish using modulo:       b45 = a661500
 Range::squish using modulo in TD: a5760
 Range::squish using earlier():    a658560
```
The correct answer is a113554560 - 2 * 56448000 [SC/sec] = a658560

Calculating the modulo iteratively is not great, however usually
only one iteration is required.
---
 libs/temporal/range.cc         | 42 ++++++++++++++++++++++++++++++++++
 libs/temporal/temporal/range.h |  7 +-----
 2 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/libs/temporal/range.cc b/libs/temporal/range.cc
index 3cd3948175..2eb42ba4b5 100644
--- a/libs/temporal/range.cc
+++ b/libs/temporal/range.cc
@@ -16,6 +16,10 @@
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
+#ifndef NDEBUG
+#include <sstream>
+#endif
+
 #include "temporal/range.h"
 
 using namespace Temporal;
@@ -96,6 +100,44 @@ Range::subtract (RangeList & sub) const
 	return result;
 }
 
+timepos_t
+Range::squish (timepos_t const & t) const
+{
+	if (t < _end) {
+		return t;
+	}
+#if 1
+#ifndef NDEBUG
+	std::stringstream dbg;
+	dbg << "Range::squish start: " << _start << " end: " << _end << " squish: " << t << "\n";
+#endif
+
+	timepos_t rv = t;
+	while (rv >= _end) {
+		rv = rv.earlier (length ());
+	}
+
+#ifndef NDEBUG
+	timepos_t sq = _start + (_start.distance (t) % length());
+	dbg << "Range::squish using modulo:       " << sq << " = ";
+	sq.set_time_domain (t.time_domain());
+	dbg << sq << "\n";
+
+	timepos_t start = _start;
+	start.set_time_domain (t.time_domain());
+	timepos_t sqt = start + (start.distance (t) % length());
+
+	dbg << "Range::squish using modulo in TD: " << sqt << "\n";
+	dbg << "Range::squish using earlier():    " << rv << "\n";
+	std::cout << dbg.str ();
+#endif
+
+	return rv;
+#else
+	return _start + (_start.distance (t) % length());
+#endif
+}
+
 template<> OverlapType Temporal::coverage_exclusive_ends<int64_t> (int64_t sa, int64_t eaE, int64_t sb, int64_t ebE)
 {
 	/* convert end positions to inclusive */
diff --git a/libs/temporal/temporal/range.h b/libs/temporal/temporal/range.h
index 7b7894abf6..cce5dd7b73 100644
--- a/libs/temporal/temporal/range.h
+++ b/libs/temporal/temporal/range.h
@@ -169,12 +169,7 @@ class LIBTEMPORAL_API Range {
 	 * looping). If the argument is earlier than or equal to the end of
 	 * this range, do nothing.
 	 */
-	timepos_t squish (timepos_t const & t) const {
-		if (t >= _end) {
-			return _start + (_start.distance (t) % length());
-		}
-		return t;
-	}
+	timepos_t squish (timepos_t const & t) const;
 
 	/* end is exclusive */
 	OverlapType coverage (timepos_t const & s, timepos_t const & e) const {