From c792d318e6a0ed54cdbcc3f6ecf9e0343a5c024e Mon Sep 17 00:00:00 2001
From: David Chocholaty <david.chocholaty@seznam.cz>
Date: Sun, 24 Jul 2022 18:24:14 +0200
Subject: [PATCH] EngineFilterDelay: clamp wrong delay values

This commit moves the correctness evaluation of the delay value
into a setter and the set value is directly checked
instead of calculated index values.
---
 src/engine/filters/enginefilterdelay.h | 33 ++++++--------------------
 1 file changed, 7 insertions(+), 26 deletions(-)

diff --git a/src/engine/filters/enginefilterdelay.h b/src/engine/filters/enginefilterdelay.h
index f52ff275dd4f..4b9832209ebd 100644
--- a/src/engine/filters/enginefilterdelay.h
+++ b/src/engine/filters/enginefilterdelay.h
@@ -29,6 +29,13 @@ class EngineFilterDelay : public EngineObjectConstIn {
 
     void setDelay(unsigned int delaySamples) {
         m_delaySamples = delaySamples;
+
+        // When mixxx will support other channel count variants than stereo,
+        // the kMaxDelay has to be divisible by the number of channels.
+        // Otherwise, channels may be swapped.
+        VERIFY_OR_DEBUG_ASSERT(m_delaySamples <= SIZE - mixxx::kEngineChannelCount) {
+            m_delaySamples = SIZE - mixxx::kEngineChannelCount;
+        }
     }
 
     virtual void process(const CSAMPLE* pIn, CSAMPLE* pOutput,
@@ -41,15 +48,6 @@ class EngineFilterDelay : public EngineObjectConstIn {
             // (but in math the result value is positive).
             int delaySourcePos = (m_delayPos + SIZE - m_delaySamples) % SIZE;
 
-            VERIFY_OR_DEBUG_ASSERT(delaySourcePos >= 0) {
-                SampleUtil::copy(pOutput, pIn, iBufferSize);
-                return;
-            }
-            VERIFY_OR_DEBUG_ASSERT(delaySourcePos <= static_cast<int>(SIZE)) {
-                SampleUtil::copy(pOutput, pIn, iBufferSize);
-                return;
-            }
-
             for (int i = 0; i < iBufferSize; ++i) {
                 // put sample into delay buffer:
                 m_buf[m_delayPos] = pIn[i];
@@ -68,23 +66,6 @@ class EngineFilterDelay : public EngineObjectConstIn {
             int delaySourcePos = (m_delayPos + SIZE - m_delaySamples + iBufferSize / 2) % SIZE;
             int oldDelaySourcePos = (m_delayPos + SIZE - m_oldDelaySamples) % SIZE;
 
-            VERIFY_OR_DEBUG_ASSERT(delaySourcePos >= 0) {
-                SampleUtil::copy(pOutput, pIn, iBufferSize);
-                return;
-            }
-            VERIFY_OR_DEBUG_ASSERT(delaySourcePos <= static_cast<int>(SIZE)) {
-                SampleUtil::copy(pOutput, pIn, iBufferSize);
-                return;
-            }
-            VERIFY_OR_DEBUG_ASSERT(oldDelaySourcePos >= 0) {
-                SampleUtil::copy(pOutput, pIn, iBufferSize);
-                return;
-            }
-            VERIFY_OR_DEBUG_ASSERT(oldDelaySourcePos <= static_cast<int>(SIZE)) {
-                SampleUtil::copy(pOutput, pIn, iBufferSize);
-                return;
-            }
-
             double cross_mix = 0.0;
             double cross_inc = 2 / static_cast<double>(iBufferSize);