Allocate enough memory to store the System File Table (SFT)

Imported from dosbox-staging/dosbox-staging#3680

include/dos_inc.h

@@ -26,6 +26,48 @@
 
 #include <list>
 #include <stddef.h> //for offsetof
+
+ /* Macros SSET_* and SGET_* are used to safely access fields in memory-mapped
+  * DOS structures represented via classes inheriting from MemStruct class.
+  *
+  * All of these macros depend on 'pt' base pointer from MemStruct base class;
+  * all DOS-specific fields are accessed by reading memory relative to that
+  * pointer.
+  *
+  * Example usage:
+  *
+  *   SSET_WORD(dos-structure-name, field-name, value);
+  *   uint16_t x = SGET_WORD(dos-structure-name, field-name);
+  */
+template <size_t N, typename S, typename T1, typename T2 = T1>
+constexpr PhysPt assert_macro_args_ok()
+{
+    static_assert(sizeof(T1) == N, "Requested struct field has unexpected size");
+    static_assert(sizeof(T2) == N, "Type used to save value has unexpected size");
+    static_assert(std::is_standard_layout<S>::value,
+        "Struct needs to have standard layout for offsetof calculation");
+    // returning 0, so compiler can optimize-out no-op "0 +" expression
+    return 0;
+}
+
+#define VERIFY_SSET_ARGS(n, s, f, v)                                           \
+	assert_macro_args_ok<n, s, decltype(s::f), decltype(v)>()
+#define VERIFY_SGET_ARGS(n, s, f)                                              \
+	assert_macro_args_ok<n, s, decltype(s::f)>()
+
+#define SSET_BYTE(s, f, v)                                                     \
+	mem_writeb(VERIFY_SSET_ARGS(1, s, f, v) + pt + offsetof(s, f), v)
+#define SSET_WORD(s, f, v)                                                     \
+	mem_writew(VERIFY_SSET_ARGS(2, s, f, v) + pt + offsetof(s, f), v)
+#define SSET_DWORD(s, f, v)                                                    \
+	mem_writed(VERIFY_SSET_ARGS(4, s, f, v) + pt + offsetof(s, f), v)
+
+#define SGET_BYTE(s, f)                                                        \
+	mem_readb(VERIFY_SGET_ARGS(1, s, f) + pt + offsetof(s, f))
+#define SGET_WORD(s, f)                                                        \
+	mem_readw(VERIFY_SGET_ARGS(2, s, f) + pt + offsetof(s, f))
+#define SGET_DWORD(s, f)                                                       \
+	mem_readd(VERIFY_SGET_ARGS(4, s, f) + pt + offsetof(s, f))
 
 #ifdef _MSC_VER
 #pragma pack (1)
@@ -153,6 +195,10 @@ extern uint16_t DOS_MEM_START;// 0x158	 // regression to r3437 fixes nascar 2 co
 
 extern uint16_t DOS_PRIVATE_SEGMENT;// 0xc800
 extern uint16_t DOS_PRIVATE_SEGMENT_END;// 0xd000
+
+constexpr int SftHeaderSize = 6;
+constexpr int SftEntrySize = 59;
+constexpr int SftNumEntries = 16;
 
 /* internal Dos Tables */
 
@@ -276,7 +322,8 @@ bool DOS_AllocateMemory(uint16_t * segment,uint16_t * blocks);
 bool DOS_ResizeMemory(uint16_t segment,uint16_t * blocks);
 bool DOS_FreeMemory(uint16_t segment);
 void DOS_FreeProcessMemory(uint16_t pspseg);
-uint16_t DOS_GetMemory(uint16_t pages,const char *who=NULL);
+uint16_t DOS_GetMemory(uint16_t pages,const char *who=NULL);
+void DOS_FreeTableMemory();
 bool DOS_SetMemAllocStrategy(uint16_t strat);
 uint16_t DOS_GetMemAllocStrategy(void);
 void DOS_BuildUMBChain(bool umb_active,bool ems_active);

src/dos/dos.cpp

@@ -4715,6 +4715,7 @@ class DOS:public Module_base{
 		DOS_ShutdownFiles();
 		void DOS_ShutdownDevices(void);
 		DOS_ShutdownDevices();
+        DOS_FreeTableMemory();
 		RealSetVec(0x30,int30);
 		RealSetVec(0x31,int31);
 	}

src/dos/dos_classes.cpp

@@ -126,13 +126,42 @@ void DOS_InfoBlock::SetLocation(uint16_t segment) {
 	sSave(sDIB,nulString[6],(uint8_t)0x20);
 	sSave(sDIB,nulString[7],(uint8_t)0x20);
 
-	/* Create a fake SFT, so programs think there are 100 file handles */
+#if 0
+    /* Create a fake SFT, so programs think there are 100 file handles */
 	uint16_t sftOffset=offsetof(sDIB,firstFileTable)+0xa2;
 	sSave(sDIB,firstFileTable,RealMake(segment,sftOffset));
 	real_writed(segment,sftOffset+0x00,RealMake(segment+0x26,0));	//Next File Table
 	real_writew(segment,sftOffset+0x04,DOS_FILES/2);	//File Table supports DOS_FILES/2 files
 	real_writed(segment+0x26,0x00,0xffffffff);		//Last File Table
 	real_writew(segment+0x26,0x04,DOS_FILES-DOS_FILES/2);	//File Table supports DOS_FILES/2 files
+#endif
+    /* Imported from dosbox-staging/dosbox-staging#3680 */
+    constexpr int FakeHandles = 100;
+
+    constexpr uint32_t EndPointer = 0xffffffff;
+    constexpr uint16_t NextTableOffset = 0x0;
+    constexpr uint16_t NumberOfFilesOffset = 0x04;
+
+    // We only need to actually allocate enough space for 16 handles
+    // This is the maximum that will get written to by DOS_MultiplexFunctions() in dos_misc.cpp
+    constexpr int BytesPerPage = 16;
+    constexpr int TotalBytes = SftHeaderSize + (SftEntrySize * SftNumEntries);
+    constexpr int NumPages = (TotalBytes / BytesPerPage) + (TotalBytes % BytesPerPage > 0 ? 1 : 0);
+
+    const uint16_t first_sft_segment = DOS_GetMemory(NumPages);
+    const RealPt first_sft_addr = RealMake(first_sft_segment, 0);
+    SSET_DWORD(sDIB, firstFileTable, first_sft_addr);
+
+    // Windows for Workgroups requires a 2nd linked SFT table
+    // This one only needs to allocate the header
+    const uint16_t second_sft_segment = DOS_GetMemory(1);
+    const RealPt second_sft_addr = RealMake(second_sft_segment, 0);
+
+    real_writed(first_sft_segment, NextTableOffset, second_sft_addr);
+    real_writew(first_sft_segment, NumberOfFilesOffset, FakeHandles);
+
+    real_writed(second_sft_segment, NextTableOffset, EndPointer);
+    real_writew(second_sft_segment, NumberOfFilesOffset, FakeHandles);
 }
 
 void DOS_InfoBlock::SetFirstMCB(uint16_t _firstmcb) {

src/dos/dos_tables.cpp

@@ -74,6 +74,11 @@ void DOS_GetMemory_reset() {
 	dos_memseg = 0;
 }
 
+void DOS_FreeTableMemory()
+{
+    dos_memseg = DOS_PRIVATE_SEGMENT;
+}
+
 void DOS_GetMemory_reinit() {
     DOS_GetMemory_unmapped = false;
     DOS_GetMemory_reset();