From d3c6d53819e9234e1929b230694d5fe814bafef7 Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Thu, 2 Mar 2023 01:11:02 -0500
Subject: [PATCH] SegaPCM: truly fix sample loop

issue #1005
---
 src/engine/platform/segapcm.cpp | 23 +++++++++++++----------
 src/engine/platform/segapcm.h   |  1 +
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/engine/platform/segapcm.cpp b/src/engine/platform/segapcm.cpp
index ee097abc6..b96e4452c 100644
--- a/src/engine/platform/segapcm.cpp
+++ b/src/engine/platform/segapcm.cpp
@@ -136,11 +136,12 @@ void DivPlatformSegaPCM::tick(bool sysTick) {
             rWrite(0x86+(i<<3),3+((sampleOffSegaPCM[chan[i].pcm.sample]>>16)<<3));
             rWrite(0x84+(i<<3),(sampleOffSegaPCM[chan[i].pcm.sample])&0xff);
             rWrite(0x85+(i<<3),(sampleOffSegaPCM[chan[i].pcm.sample]>>8)&0xff);
-            rWrite(6+(i<<3),MIN(255,((sampleOffSegaPCM[chan[i].pcm.sample]&0xffff)+actualLength-2)>>8));
+            rWrite(6+(i<<3),sampleEndSegaPCM[chan[i].pcm.sample]);
             if (loopStart<0 || loopStart>=actualLength) {
               rWrite(0x86+(i<<3),2+((sampleOffSegaPCM[chan[i].pcm.sample]>>16)<<3));
             } else {
               int loopPos=(sampleOffSegaPCM[chan[i].pcm.sample]&0xffff)+loopStart;
+              logV("sampleOff: %x loopPos: %x",sampleOffSegaPCM[chan[i].pcm.sample],loopPos);
               rWrite(4+(i<<3),loopPos&0xff);
               rWrite(5+(i<<3),(loopPos>>8)&0xff);
               rWrite(0x86+(i<<3),((sampleOffSegaPCM[chan[i].pcm.sample]>>16)<<3));
@@ -153,7 +154,7 @@ void DivPlatformSegaPCM::tick(bool sysTick) {
             rWrite(0x86+(i<<3),3+((sampleOffSegaPCM[chan[i].pcm.sample]>>16)<<3));
             rWrite(0x84+(i<<3),(sampleOffSegaPCM[chan[i].pcm.sample])&0xff);
             rWrite(0x85+(i<<3),(sampleOffSegaPCM[chan[i].pcm.sample]>>8)&0xff);
-            rWrite(6+(i<<3),MIN(255,((sampleOffSegaPCM[chan[i].pcm.sample]&0xffff)+actualLength-2)>>8));
+            rWrite(6+(i<<3),sampleEndSegaPCM[chan[i].pcm.sample]);
             if (loopStart<0 || loopStart>=actualLength) {
               rWrite(0x86+(i<<3),2+((sampleOffSegaPCM[chan[i].pcm.sample]>>16)<<3));
             } else {
@@ -450,16 +451,18 @@ void DivPlatformSegaPCM::reset() {
 
   memset(sampleMem,0,16777216);
   memset(sampleLoaded,0,256*sizeof(bool));
+  memset(sampleOffSegaPCM,0,256*sizeof(unsigned int));
+  memset(sampleEndSegaPCM,0,256);
   
   for (int i=0; i<parent->song.sampleLen; i++) {
     DivSample* sample=parent->getSample(i);
-    unsigned int alignedSize=(sample->getLoopEndPosition(DIV_SAMPLE_DEPTH_8BIT)+0xff)&(~0xff);
-    if (alignedSize>65536) alignedSize=65536;
-    if ((memPos&0xff0000)!=((memPos+alignedSize)&0xff0000)) {
-      memPos=(memPos+0xffff)&0xff0000;
+    unsigned int alignedSize=sample->getLoopEndPosition(DIV_SAMPLE_DEPTH_8BIT);
+    if (alignedSize>=65279) alignedSize=65279;
+    if ((memPos&(~0xffff))!=((memPos+alignedSize)&(~0xffff))) {
+      memPos=(memPos+0xffff)&(~0xffff);
     }
-    if (alignedSize&(~0xff)) {
-      memPos+=256-(alignedSize&0xff);
+    if (alignedSize&0xff) {
+      memPos=((memPos+255)&(~0xff))+256-(alignedSize&0xff);
     }
     logV("- sample %d will be at %x with length %x",i,memPos,alignedSize);
     sampleLoaded[i]=true;
@@ -467,11 +470,11 @@ void DivPlatformSegaPCM::reset() {
     sampleOffSegaPCM[i]=memPos;
     for (unsigned int j=0; j<alignedSize; j++) {
       sampleMem[memPos++]=((unsigned char)sample->data8[j]+0x80);
+      sampleEndSegaPCM[i]=((memPos+0xff)>>8)-1;
       if (memPos>=16777216) break;
     }
+    logV("  and it ends in %d",sampleEndSegaPCM[i]);
     if (memPos>=16777216) break;
-
-    memPos&=~0xff;
   }
   sampleMemLen=memPos;
 }
diff --git a/src/engine/platform/segapcm.h b/src/engine/platform/segapcm.h
index 4dd541e76..f99a24df3 100644
--- a/src/engine/platform/segapcm.h
+++ b/src/engine/platform/segapcm.h
@@ -76,6 +76,7 @@ class DivPlatformSegaPCM: public DivDispatch {
     short pendingWrites[256];
 
     unsigned int sampleOffSegaPCM[256];
+    unsigned char sampleEndSegaPCM[256];
     bool sampleLoaded[256];
   
     friend void putDispatchChip(void*,int);