#include "vmc.h"


// Fat table functions

unsigned int getFatEntry ( int fd, unsigned int cluster, unsigned int* indir_fat_clusters, GetFat_Mode Mode ) 
{

	int unit = ( fd == g_Vmc_Image[ 0 ].fd ) ? 0 : 1;

	// The fat index, aka which cluster we want to know about
	unsigned int fat_index = cluster;

	// The offset in the fat cluster where we can find information about the sector
	unsigned int fat_offset = fat_index % ( g_Vmc_Image[ unit ].cluster_size / 4 );

	// Which fat cluster that the information would be in
	unsigned int indirect_index = fat_index / ( g_Vmc_Image[ unit ].cluster_size / 4 );

	// The offset in the indirect fat cluster that points to the fat table we are interested in
	unsigned int indirect_offset = indirect_index % ( g_Vmc_Image[ unit ].cluster_size / 4 );

	// This gives the location of the fat_offset inside of the indirect fat cluster list.  Each indirect fat cluster can point to
	// 256 regular fat clusters, and each fat cluster holds information on 256 sectors.
	unsigned int dbl_indirect_index = fat_index / (  ( g_Vmc_Image[ unit ].cluster_size / 4 ) * ( g_Vmc_Image[ unit ].cluster_size / 4 )  );

	// Cache indirect file table? ( Generally we will be accessing the first part of it for most virtual memory cards ) 
	// Get the data for the indirect fat cluster ( as indicated by dbl_indirect_index ) 
	unsigned int indirect_cluster_num	 = indir_fat_clusters[ dbl_indirect_index ];

	if ( g_Vmc_Image[ unit ].last_idc != indirect_cluster_num ) 
		readCluster ( fd, ( unsigned char* ) g_Vmc_Image[ unit ].indirect_cluster, indirect_cluster_num );

	g_Vmc_Image[ unit ].last_idc = indirect_cluster_num;

	// Get the data from the fat cluster ( pointed to by the indirect fat cluster ) 
	unsigned int fat_cluster_num = g_Vmc_Image[ unit ].indirect_cluster[ indirect_offset ];

	if ( g_Vmc_Image[ unit ].last_cluster != fat_cluster_num ) 
		readCluster ( fd, ( unsigned char* ) g_Vmc_Image[ unit ].fat_cluster, fat_cluster_num );

	g_Vmc_Image[ unit ].last_cluster = fat_cluster_num;

	// Check if the entry in the fat table corresponds to a free cluster or a eof cluster
	if ( g_Vmc_Image[ unit ].fat_cluster[ fat_offset ] == FREE_CLUSTER || g_Vmc_Image[ unit ].fat_cluster[ fat_offset ] == EOF_CLUSTER ) 
		return g_Vmc_Image[ unit ].fat_cluster[ fat_offset ];

	if ( Mode == FAT_MASK )
	{

		if ( g_Vmc_Image[ unit ].fat_cluster[ fat_offset ] & MASK_CLUSTER )
		{

			return MASK_CLUSTER;

		}
		else
		{

			return 0;

		}
		
	}

	// Return the fat entry, but remove the most significant bit.
	return g_Vmc_Image[ unit ].fat_cluster[ fat_offset ] & FREE_CLUSTER;

}

unsigned int setFatEntry ( int fd, unsigned int cluster, unsigned int value, unsigned int* indir_fat_clusters, SetFat_Mode Mode ) 
{

	int unit = ( fd == g_Vmc_Image[ 0 ].fd ) ? 0 : 1;

	// The fat index, aka which cluster we want to know about
	unsigned int fat_index = cluster;

	// The offset in the fat cluster where we can find information about the sector
	unsigned int fat_offset = fat_index % ( g_Vmc_Image[ unit ].cluster_size / 4 );

	// Which fat cluster that the information would be in
	unsigned int indirect_index = fat_index / ( g_Vmc_Image[ unit ].cluster_size / 4 );

	// The offset in the indirect fat cluster that points to the fat table we are interested in
	unsigned int indirect_offset = indirect_index % ( g_Vmc_Image[ unit ].cluster_size / 4 );

	// This gives the location of the fat_offset inside of the indirect fat cluster list.  Each indirect fat cluster can point to
	// 256 regular fat clusters, and each fat cluster holds information on 256 sectors.
	unsigned int dbl_indirect_index = fat_index / (  ( g_Vmc_Image[ unit ].cluster_size / 4 ) * ( g_Vmc_Image[ unit ].cluster_size / 4 )  );

	// Cache indirect file table? ( Generally we will be accessing the first part of it for most virtual memory cards

	// Get the data for the indirect fat cluster ( as indicated by dbl_indirect_index ) 
	unsigned int indirect_cluster_num	 = indir_fat_clusters[ dbl_indirect_index ];

	if ( g_Vmc_Image[ unit ].last_idc != indirect_cluster_num ) 
		readCluster ( fd, ( unsigned char* ) g_Vmc_Image[ unit ].indirect_cluster, indirect_cluster_num );

	g_Vmc_Image[ unit ].last_idc = indirect_cluster_num;

	// Get the data from the fat cluster ( pointed to by the indirect fat cluster ) 
	unsigned int fat_cluster_num = g_Vmc_Image[ unit ].indirect_cluster[ indirect_offset ];

	if ( g_Vmc_Image[ unit ].last_cluster != fat_cluster_num ) 
		readCluster ( fd, ( unsigned char* ) g_Vmc_Image[ unit ].fat_cluster, fat_cluster_num );

	g_Vmc_Image[ unit ].last_cluster = fat_cluster_num;

	if ( value == FREE_CLUSTER || value == EOF_CLUSTER || Mode == FAT_RESET )
	{

		g_Vmc_Image[ unit ].fat_cluster[ fat_offset ] = value;

	}
	else
	{

		g_Vmc_Image[ unit ].fat_cluster[ fat_offset ] = value | MASK_CLUSTER;

	}

	writeCluster ( fd, ( unsigned char* ) g_Vmc_Image[ unit ].fat_cluster, fat_cluster_num );
	
	// Update last free cluster
	if ( ( value == FREE_CLUSTER && Mode == FAT_SET ) || ( Mode == FAT_RESET ) )
	{

		if ( cluster < g_Vmc_Image[ unit ].last_free_cluster )
		{

			g_Vmc_Image[ unit ].last_free_cluster = cluster;

		}

	}

	return 0;

}