From 738fa25344a607e5bb6894fc2293e2d688847fd5 Mon Sep 17 00:00:00 2001
From: cebix <>
Date: Fri, 29 Jun 2001 12:51:21 +0000
Subject: [PATCH] slot ROM checksum is recalculated after patching during
 resolution switch

---
 BasiliskII/src/include/slot_rom.h |  1 +
 BasiliskII/src/slot_rom.cpp       | 45 ++++++++++++++++++++++---------
 BasiliskII/src/video.cpp          |  6 ++++-
 3 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/BasiliskII/src/include/slot_rom.h b/BasiliskII/src/include/slot_rom.h
index ed9c5669..c7f65859 100644
--- a/BasiliskII/src/include/slot_rom.h
+++ b/BasiliskII/src/include/slot_rom.h
@@ -22,5 +22,6 @@
 #define SLOT_ROM_H
 
 extern bool InstallSlotROM(void);
+extern void ChecksumSlotROM(void);
 
 #endif
diff --git a/BasiliskII/src/slot_rom.cpp b/BasiliskII/src/slot_rom.cpp
index 5419d134..15625a66 100644
--- a/BasiliskII/src/slot_rom.cpp
+++ b/BasiliskII/src/slot_rom.cpp
@@ -42,6 +42,9 @@ static uint8 srom[4096];
 // Index in srom
 static uint32 p;
 
+// Length of slot ROM
+static int slot_rom_size = 0;
+
 
 // Check whether a mode with the specified depth exists
 static bool has_depth(video_depth depth)
@@ -433,23 +436,39 @@ bool InstallSlotROM(void)
 	// Format/header block
 	Offs(0, sRsrcDir);					// sResource directory
 	Long(p + 16);						// Length of declaration data
-	Long(0);							// CRC (calculated below)
+	Long(0);							// CRC (calculated later)
 	Word(0x0101);						// Rev. level, format
 	Long(0x5a932bc7);					// Test pattern
 	Word(0x000f);						// Byte lanes
 
-	// Calculate CRC
-	uint32 crc = 0;
-	for (uint32 i=0; i<p; i++) {
-		crc = (crc << 1) | (crc >> 31);
-		crc += srom[i];
-	}
-	srom[p - 12] = crc >> 24;
-	srom[p - 11] = crc >> 16;
-	srom[p - 10] = crc >> 8;
-	srom[p - 9] = crc;
-
 	// Copy slot ROM to Mac ROM
-	memcpy(ROMBaseHost + ROMSize - p, srom, p);
+	slot_rom_size = p;
+	memcpy(ROMBaseHost + ROMSize - slot_rom_size, srom, slot_rom_size);
+
+	// Calculate checksum
+	ChecksumSlotROM();
 	return true;
 }
+
+/*
+ *  Calculate slot ROM checksum (in-place)
+ */
+
+void ChecksumSlotROM(void)
+{
+	// Calculate CRC
+	uint8 *p = ROMBaseHost + ROMSize - slot_rom_size;
+	p[slot_rom_size - 12] = 0;
+	p[slot_rom_size - 11] = 0;
+	p[slot_rom_size - 10] = 0;
+	p[slot_rom_size - 9] = 0;
+	uint32 crc = 0;
+	for (uint32 i=0; i<slot_rom_size; i++) {
+		crc = (crc << 1) | (crc >> 31);
+		crc += p[i];
+	}
+	p[slot_rom_size - 12] = crc >> 24;
+	p[slot_rom_size - 11] = crc >> 16;
+	p[slot_rom_size - 10] = crc >> 8;
+	p[slot_rom_size - 9] = crc;
+}
diff --git a/BasiliskII/src/video.cpp b/BasiliskII/src/video.cpp
index c45a4b1c..f906bfde 100644
--- a/BasiliskII/src/video.cpp
+++ b/BasiliskII/src/video.cpp
@@ -31,6 +31,7 @@
 #include "cpu_emulation.h"
 #include "main.h"
 #include "macos_util.h"
+#include "slot_rom.h"
 #include "video.h"
 #include "video_defs.h"
 
@@ -349,7 +350,7 @@ int16 VideoDriverControl(uint32 pb, uint32 dce)
 				Execute68kTrap(0xa06e, &r);	// SRsrcInfo()
 				uint32 rsrc = ReadMacInt32(sp + spPointer);
 
-				// Patch minorBase
+				// Patch minorBase (otherwise rebooting won't work)
 				WriteMacInt8(sp + spID, 0x0a); // minorBase
 				r.d[0] = 0x0006;
 				Execute68kTrap(0xa06e, &r); // SFindStruct()
@@ -375,6 +376,9 @@ int16 VideoDriverControl(uint32 pb, uint32 dce)
 				ROMBaseHost[p + 16] = i->x >> 8;
 				ROMBaseHost[p + 17] = i->x;
 
+				// Recalculate slot ROM checksum
+				ChecksumSlotROM();
+
 				// Update sResource
 				WriteMacInt8(sp + spID, ReadMacInt8(dce + dCtlSlotId));
 				r.d[0] = 0x002b;