fat32_base.c

嵌入式系统中的完整FAT16和FAT32源码

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//					    FAT32 File IO Library for AVR 
//								  V0.1c
// 	  							Rob Riglar
//							Copyright 2003,2004 
//
//   					  Email: [e-mail]
//
//			    Compiled with Imagecraft C Compiler for the AVR series
//-----------------------------------------------------------------------------
//
// This file is part of FAT32 File IO Library.
//
// FAT32 File IO Library is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// FAT32 File IO Library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with FAT32 File IO Library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------



//-----------------------------------------------------------------------------
// FAT32_InitLBA: This function is used to find the LBA Address of the first
//				  volume on the disc. Also checks are performed on the signature
//				  and identity codes to make sure the partition is FAT32.
//-----------------------------------------------------------------------------
UI32 FAT32_FindLBABegin(void)
{
		byte tempdata;
		UI32 LBABEGIN;
		
		// Load MBR (LBA 0) into the 512 byte buffer
		IDE_BufferSector(0);	
		
		// Make Sure 0x55 and 0xAA are at end of sector
	    if (IDE_SectorWord(Signature_Position)!=Signature_Value) 
	   	  {
		  printf("\r\nInvalid MBR, Please Format Drive");
		  while(1);
		  }
		   
		// Verify Type Code as 0C or 0B for FAT32
		tempdata=IDE_SectorByte(PARTITION1_TYPECODE_LOCATION);
		
		if ((tempdata==FAT32_TYPECODE1)||(tempdata==FAT32_TYPECODE2))
		  	 printf("\r\nValid FAT32 Partition Found");
		else
		  {
		   	 printf("\r\nNon FAT32 Partition Found 0x%x",tempdata);
			 while (1);
		  }
		  
		// Read LBA Begin for FAT32 File system is located for partition
		LBABEGIN=IDE_SectorUI32(PARTITION1_LBA_BEGIN_LOCATION);
  
  		// Return the LBA address of FAT table
		return LBABEGIN;			
}

//-----------------------------------------------------------------------------
// LBAofCluster: This function converts a cluster number into a sector / LBA 
//				 number.
//-----------------------------------------------------------------------------
UI32 FAT32_LBAofCluster(UI32 Cluster_Number)
{
 return ((FAT32.cluster_begin_lba + ((Cluster_Number-2)*FAT32.SectorsPerCluster)));
}


//-----------------------------------------------------------------------------
// FindFATDetails: Uses FAT32_FindLBABegin to find the LBA for the volume, 
//				   and loads into memory some specific details of the partition
//				   which are used in further calculations.
//-----------------------------------------------------------------------------
void FAT32_FindFAT32Details(void)
{
	 byte Number_of_FATS;
	 UI32 Sectors_per_FAT;
	 word Reserved_Sectors;
	 UI32 LBA_BEGIN;
	 
	 LBA_BEGIN = FAT32_FindLBABegin();	// Check Volume 1 and find LBA address
	 IDE_BufferSector(LBA_BEGIN);	// Load Volume 1 table in 'clusterbuffer'
	 
	 // Make sure there are 512 bytes per cluster
	 if (IDE_SectorWord(0x0B)!=0x200) 
	 {
	  	 printf("\r\nError: Bytes per cluster is not 512");
		 while(1);
	 }

	 // Load Parameters of FAT32	 
 	 FAT32.SectorsPerCluster = IDE_SectorByte(0x0D);
	 Reserved_Sectors = IDE_SectorWord(0x0E);
	 Number_of_FATS = IDE_SectorByte(0x10);
	 Sectors_per_FAT = IDE_SectorUI32(0x24);
	 FAT32.RootDir_First_Cluster = IDE_SectorUI32(0x2C);
	 
	 FAT32.fat_begin_lba = LBA_BEGIN + Reserved_Sectors;	// First FAT LBA address
	 
	 // The address of the first data cluster on this volume
	 FAT32.cluster_begin_lba = FAT32.fat_begin_lba + (Number_of_FATS * Sectors_per_FAT);

	 if (IDE_SectorWord(0x1FE)!=0xAA55) // This signature should be AA55
	 {
	  	 printf("\r\nError: Incorrect Volume Signature");
		 while(1);
	 } 
}

//-----------------------------------------------------------------------------
// FindNextCluster: Return Cluster number of next cluster in chain by reading
//					FAT table and traversing it. Return 0xffffffff for end of 
//					chain.
//-----------------------------------------------------------------------------
UI32 FAT32_FindNextCluster(UI32 Current_Cluster)
{
	UI32 FAT_sector_offset, UI32position;
	UI32 nextcluster;
	
	// Why is '..' labelled with cluster 0 when it should be 2 ??
	if (Current_Cluster==0) Current_Cluster=2;
	
	// Find which sector of FAT table to read
	FAT_sector_offset = Current_Cluster / 128;
	 
	// Read FAT sector into buffer
	IDE_BufferSector(FAT32.fat_begin_lba+FAT_sector_offset);
	 
	// Find 32 bit entry of current sector relating to cluster number 
	UI32position = (Current_Cluster - (FAT_sector_offset * 128)) * 4; 

	// Read Next Clusters value from Sector Buffer
	nextcluster = IDE_SectorUI32(UI32position);	 

	// Mask out MS 4 bits (its 28bit addressing)
	nextcluster = nextcluster & 0x0FFFFFFF;		
				 
	// If 0x0FFFFFFF then end of chain found
	if (nextcluster==0x0FFFFFFF) 
	   return (0xFFFFFFFF); 
	else 
		 // Else return next cluster
		 return (nextcluster);						 
}