main.c

extern void AtaLbaRead(uint32_t lba, void* dest, uint8_t sectorsToRead);
extern void AtaLbaWrite(uint32_t lba, void* dest, uint8_t sectorsToRead);

/*
  NanoShell File System
*/
#define NSFSBootSector struct nsfs_boot_sector
NSFSBootSector
{
	uint8_t 	jmpInstruction;     
	uint16_t 	jmpAddress;         
	char 		OemName[8];         
	uint16_t 	BytesPerSector;     
	uint8_t 	SectorsPerCluster;  
	uint16_t 	ReservedSectorCount;
	uint8_t		Reserved_00;			
	uint16_t 	RootEntryCount;		
	uint16_t 	TotalSectors16;		
	uint8_t		Media;
	uint16_t 	Reserved_01;
	uint16_t 	SectorsPerTrack;
	uint16_t 	HeadCount;
	uint32_t	HiddenSectors;
	uint32_t 	TotalSectors32;
	// At offset 36, the BPB/boot sector for FAT12 and FAT16 differs from the 
	// BPB/Boot Sector for FAT32. Thus, we needed separate structs.
	uint8_t		DriveNumber;			// Unused since BIOS interrupts are not available
	uint8_t 	Reserved_02; 			// Used by Windows NT, ALWAYS set to 0
	uint8_t 	ExtBootSig;
	uint32_t	VolumeID;				// Volume Serial Number
	char 		VolumeLabel[11];		// Volume label
	char		FileSystemType[8];		// File system type string (unsure)
	uint8_t		RootDirFileCount;
}__attribute__((packed));

#define NSFSRootEntry struct nsfs_root_entry
NSFSRootEntry
{
	char		FileName[8];
	char		Extension[3];
	#define ATTRIB_READONLY 	0x01
	#define ATTRIB_HIDDEN		0x02
	#define ATTRIB_SYSTEM		0x04
	#define ATTRIB_SUBDIR		0x10
	#define ATTRIB_ARCHIVE 		0x20
	#define ATTRIB_DEVICE		0x40
	uint8_t		Attributes;
    uint8_t 	Reserved[10];
    uint16_t 	ModifyTime;
    uint16_t 	ModifyDate;
    uint16_t 	StartingSector;
    uint32_t 	FileSize;
}__attribute__((packed));

NSFSBootSector nsfsBootSector;
NSFSRootEntry nsfsRootEntries[256];

#define NSFSFile struct nsfs_file
NSFSFile
{
	uint32_t length;
	uint8_t* contents;
	
};



void InitFilesystem()
{
	AtaLbaRead(0, &nsfsBootSector, 1);
	AtaLbaRead(1, &nsfsRootEntries, 16);
}

char* GetExtension(char* filename)
{
	for(int i = 0; i < 12; i++)
	{
		if(filename[i] == '.')
		{
			filename[i] = 0;
			return filename + i + 1;
			break;
		}
	}
	return filename;
}

char* FileNameOpen = "        ";
char* ExtensionOpen = "   ";
#define DiskbufferSize 262144
uint8_t DiskBuffer[DiskbufferSize] = {0x0, };

void FileOpen(char* filename, uint8_t* dest)
{
	char* extension = GetExtension(filename);
	for(int i = 0; i < 12; i++)
	{
		if(filename[i] == '.')
		{
			filename[i] = 0;
			break;
		}
	}
	memset(FileNameOpen, 0x20, 8);
	memset(ExtensionOpen, 0x20, 3);
	memcpy(FileNameOpen, filename, strlen(filename));
	memcpy(ExtensionOpen, extension, strlen(extension));
	int index = -1;
	for(int i = 0; i < 256; i++)
	{
		if (memcmp(FileNameOpen, nsfsRootEntries[i].FileName, 8) == 0 &&
			memcmp(ExtensionOpen, nsfsRootEntries[i].Extension, 3) == 0)
		{
			// found the file
			index = i;
			break;
		}
	}
	printf("Found file at: %x\r\n", index);
	if(index == -1) return;
	NSFSRootEntry* entry = &nsfsRootEntries[index];
	int sectorSize = entry->FileSize / 512 + 1;
	if(sectorSize < 512)
	{
		AtaLbaRead(entry->StartingSector, &DiskBuffer, sectorSize);
		fast_memcpy(dest, &DiskBuffer, entry->FileSize);
	}
}

void DumpFs()
{
	for(int i = 0; i < 16; i++)
	{
		printf("File ");
		TerminalWrite(nsfsRootEntries[i].FileName, 8);
		putch('.');
		TerminalWrite(nsfsRootEntries[i].Extension, 3);
		printf(", size %d\n", nsfsRootEntries[i].FileSize);
	}
}

void printf(const char* format, ...);
void TerminalWrite(char* data, size_t count);
void putch(char c);

int main()
{
  InitFilesystem();
  DumpFs();
  char* t = malloc(512);
  FileOpen("file1.txt", t);
  printf(t);
  while(true){}
}