gistfile1.c

// Functions for reading files from a disc formatted with the bfs512 file system.

#ifndef DCPUB_LIB_BFS512_FILES
#define DCPUB_LIB_BFS512_FILES

#include bfs512.dc
#include m35fd.dc

#define BFS512_MODE_READ 0
#define BFS512_MODE_WRITE 1

#define BFS512_ERR_NONE 0
//#define M35FD_ERROR_BUSY  	0x0001  //Avoid conflicting with m35fd error codes.
//#define M35FD_ERROR_NO_MEDIA 	0x0002
//#define M35FD_ERROR_PROTECTED	0x0003
//#define M35FD_ERROR_EJECT		0x0004
//#define M35FD_ERROR_BAD_SECTOR	0x0005
#define BFS512_ERR_WRONG_MODE 0x0006
#define BFS512_ERR_DISC_FULL 0x0007
#define BFS512_ERR_EOF 0x0008
#define BFS512_ERR_UNKNOWN 0x0009

struct bfs512_FILE
{
	device; //The m35fd device this file resides on
	file_system:bfs512_SYSTEM_HEADER; //The filesystem this file belongs to 
	sector; //The current sector being referenced
	offset; //
	mode; 
	buffer:sfs_FILE_HEADER[M35FD_SECTOR_SIZE]; //Contents of active sector
}

//Open a file for reading
function bfs512_open_read(file:bfs512_FILE, file_system:bfs512_SYSTEM_HEADER, device, sector)
{
	local err = m35fd_blocking_read(device, sector, file.buffer);
	if (err != M35FD_ERROR_NONE) return err;
	file.device = device;
	file.file_system = file_system;
	file.sector = sector;
	file.offset = 0;
	file.mode = BFS512_MODE_READ;
	return BFS512_ERR_NONE;
}

//Read size words from file into 'into'. 
function bfs512_read(file:bfs512_FILE, into, size)
{
	if (file.mode != BFS512_MODE_READ) return BFS512_ERR_WRONG_MODE;
	local i = 0;
	while (i < size)
	{
		//Expect file blocks to have a size of M35FD_SECTOR_SIZE unless they are the last block in the file.
		if (file.offset == M35FD_SECTOR_SIZE) //Advance file to next sector.
		{
			local next_sector = bfs512_next_sector(file.file_system, file.sector);
			if (next_sector == 0xFFFF) return BFS512_ERR_EOF;
			local err = bfs512_open_read(file, file.file_system, file.drive, next_sector);
			if (err != BFS512_ERR_NONE) return err;
		}
		
		into[i] = file.buffer[file.offset];
		i += 1;
		file.offset += 1;
	}
	return BFS512_ERR_NONE;
}

//Creates a new file to write to. Returns the first sector of the file.
function bfs512_open_write(file:bfs512_FILE, file_system:bfs512_SYSTEM_HEADER, device)
{
	local first_sector = bfs512_find_free_sector(file_system);
	if (first_sector == 0xFFFF) return 0xFFFF;
	bfs512_allocate_sector(file_system, first_sector);
	bfs512_link_sectors(file_system, first_sector, 0xFFFF); //Clean up any old file link that wasn't cleared.
	bfs512_save_header(device, file_system); //Save changed header to disc.
	file.device = device;
	file.file_system = file_system;
	file.sector = first_sector;
	file.offset = 0;
	file.mode = BFS512_MODE_WRITE;
	return first_sector;
}

//Write data to a file.
function bfs512_write(file:bfs512_FILE, what, size)
{
	if (file.mode != BFS512_MODE_WRITE) return BFS512_ERR_WRONG_MODE;
	local i = 0;
	while (i < size)
	{
		if (file.offset == M35FD_SECTOR_SIZE) //Buffer is full.
		{
			m35fd_blocking_write(file.device, file.sector, file.buffer);
			local next_sector = bfs512_find_free_sector(file.file_system);
			if (next_sector == 0xFFFF) return BFS512_ERR_DISC_FULL; //Out of space
			bfs512_allocate_sector(file.file_system, next_sector);
			bfs512_link_sectors(file.file_system, file.sector, next_sector);
			bfs512_save_header(file.device, file.file_system);
			file.sector = next_sector;
			file.offset =0;
		}

		file.buffer[file.offset] = what[i];
		i += 1;
		file.offset += 1;
	}
	return BFS512_ERR_NONE;
}

//Flush a write file
function bfs512_flush(file:bfs512_FILE)
{
	if (file.mode != BFS512_MODE_WRITE) return BFS512_ERR_WRONG_MODE;
	m35fd_blocking_write(file.device, file.sector, file.buffer);
	return BFS512_ERR_NONE;
}

#endif