fix bugs in lingering rom reading cursor caching code that made the winport memview capable of ruining rom reads

desmume/src/NDSSystem.cpp

@@ -559,7 +559,6 @@ bool GameInfo::loadROM(std::string fname, u32 type)
 			}
 		}
 		reader->Seek(fROM, headerOffset, SEEK_SET);
-		lastReadPos = 0;
 		return true;
 	}
 
@@ -580,17 +579,16 @@ void GameInfo::closeROM()
 	reader = NULL;
 	romdataForReader = NULL;
 	romsize = 0;
-	lastReadPos = 0xFFFFFFFF;
 }
 
 u32 GameInfo::readROM(u32 pos)
 {
 	u32 num;
 	u32 data;
-	if (lastReadPos != pos)
-		reader->Seek(fROM, pos + headerOffset, SEEK_SET);
+
+	//reader must try to be efficient and not do unneeded seeks
+	reader->Seek(fROM, pos, SEEK_SET);
 	num = reader->Read(fROM, &data, 4);
-	lastReadPos = (pos + num);
 
 	//in case we didn't read enough data, pad the remainder with 0xFF
 	u32 pad = 0;

desmume/src/NDSSystem.h

@@ -323,7 +323,6 @@ struct GameInfo
 	u32 mask;
 	u32 crc;
 	u32 chipID;
-	u32 lastReadPos;
 	u32	romType;
 	u32 headerOffset;
 	char ROMserial[20];
@@ -342,7 +341,6 @@ struct GameInfo
 					romsize(0),
 					cardSize(0),
 					mask(0),
-					lastReadPos(0xFFFFFFFF),
 					romType(ROM_NDS),
 					headerOffset(0),
 					_isDSiEnhanced(false)

desmume/src/ROMReader.cpp

@@ -69,7 +69,13 @@ ROMReader_struct STDROMReader =
 	STDROMReaderWrite
 };
 
-void * STDROMReaderInit(const char * filename)
+struct STDROMReaderData
+{
+	FILE* file;
+	long pos;
+};
+
+void* STDROMReaderInit(const char* filename)
 {
 #ifndef _MSC_VER
 	struct stat sb;
@@ -80,13 +86,21 @@ void * STDROMReaderInit(const char * filename)
 		return 0;
 #endif
 
-	return (void *) fopen(filename, "rb");
+	FILE* inf = fopen(filename, "rb");
+	if(!inf) return NULL;
+
+	STDROMReaderData* ret = new STDROMReaderData();
+	ret->file = inf;
+	ret->pos = 0;
+	return (void*)ret;
 }
 
+
 void STDROMReaderDeInit(void * file)
 {
 	if (!file) return ;
-	fclose((FILE*)file);
+	fclose(((STDROMReaderData*)file)->file);
+	delete ((STDROMReaderData*)file);
 }
 
 u32 STDROMReaderSize(void * file)
@@ -95,23 +109,32 @@ u32 STDROMReaderSize(void * file)
 
 	if (!file) return 0;
 
-	fseek((FILE*)file, 0, SEEK_END);
-	size = ftell((FILE*)file);
-	fseek((FILE*)file, 0, SEEK_SET);
+	FILE* inf = ((STDROMReaderData*)file)->file;
+
+	fseek(inf, 0, SEEK_END);
+	size = ftell(inf);
+	fseek(inf, ((STDROMReaderData*)file)->pos, SEEK_SET);
 
 	return size;
 }
 
 int STDROMReaderSeek(void * file, int offset, int whence)
 {
+	//not normal fseek return value meanings. awesome.
 	if (!file) return 0;
-	return fseek((FILE*)file, offset, whence);
+	if(whence == SEEK_SET && offset == ((STDROMReaderData*)file)->pos)
+		return 1;
+	fseek(((STDROMReaderData*)file)->file, offset, whence);
+	((STDROMReaderData*)file)->pos = ftell(((STDROMReaderData*)file)->file);
+	return 1;
 }
 
 int STDROMReaderRead(void * file, void * buffer, u32 size)
 {
 	if (!file) return 0;
-	return fread(buffer, 1, size, (FILE*)file);
+	int read = fread(buffer, 1, size, ((STDROMReaderData*)file)->file);
+	((STDROMReaderData*)file)->pos += read;
+	return read;
 }
 
 int STDROMReaderWrite(void *, void *, u32)
@@ -300,7 +323,9 @@ int MemROMReaderRead(void * file, void * buffer, u32 size)
 	if(remain<todo)
 		todo = remain;
 
-	if(todo==1) *(u8*)buffer = ((u8*)mem.buf)[mem.pos];
+	if(todo<=0)
+		return 0;
+	else if(todo==1) *(u8*)buffer = ((u8*)mem.buf)[mem.pos];
 	else memcpy(buffer,(u8*)mem.buf + mem.pos, todo);
 	mem.pos += todo;
 	return todo;