fatnextcluster.c

来自「在51下的外挂硬盘和FLASH的MP3方案程序以及原理图」· C语言 代码 · 共 39 行

#ifndef _FAT_DEFINE
 #include "FAT.c"
#endif

void FATNextCluster(DWORD *CurrentCluster);

void FATNextCluster(DWORD *CurrentCluster)
{
	pdata BYTE Offset;
	pdata DWORD Sector;
	
	switch (sDPT[StorageMedia.CurrentPartition].FATType)
	{
		case FAT_TYPE_FAT32	:
			
			Sector=(*CurrentCluster)>>7;						//等价于CurrentCluster/128
			Offset=(BYTE)((*CurrentCluster)&0x0000007f);		//等价于CurrentCluster%128
			if (Sector!=FATTable.Sector)
			{
				FATTable.Sector=Sector;
				StorageMedia.ReadSector(FAT.FATSec + Sector,FATTable.FAT.F12);
			}
			*CurrentCluster=MEMSwap32(FATTable.FAT.F32[Offset]);
			return;
		case FAT_TYPE_FAT16	:
			Sector=(*CurrentCluster)>>8;						//等价于CurrentCluster/256
			Offset=(BYTE)((*CurrentCluster)&0x000000ff);		//等价于CurrentCluster%256
			if (Sector!=FATTable.Sector)
			{
				FATTable.Sector=Sector;
				StorageMedia.ReadSector(FAT.FATSec + Sector,FATTable.FAT.F12);
			}
			*CurrentCluster=(DWORD) MEMSwap16(FATTable.FAT.F16[Offset]);
			return;
		case FAT_TYPE_FAT12	:
		break;
	}
}