fatreadfile.c

c51文件系统源码

#ifndef _FAT32_DEFINE
 #include "FAT32.c"
#endif

WORD FAT32ReadFile(BYTE fp);

WORD FAT32ReadFile(BYTE fp)
{
	register WORD tmp;

	if (FCB[fp].ByteCnt==FCB[fp].Size) return(0);
	else
	{
		FCB[fp].ByteCnt+=IDE.BytesPerSec;
		if (FCB[fp].ByteCnt<=FCB[fp].Size) tmp=IDE.BytesPerSec;
		else
		{
			FCB[fp].ByteCnt-=IDE.BytesPerSec;
			tmp=FCB[fp].Size-FCB[fp].ByteCnt;
			FCB[fp].ByteCnt=FCB[fp].Size;
		}

		if (FCB[fp].ClusSecCnt==FAT32.SecPerClus)			//读下一簇
		{
			FCB[fp].LastCluster=FAT32NextCluster(FCB[fp].LastCluster);
			if (FCB[fp].LastCluster==0x0fffffff) return(0);
			IDEReadSector(ClusterToSector(FCB[fp].LastCluster));
			FCB[fp].ClusSecCnt=1;
		}
		else if (FCB[fp].ClusSecCnt==0)					//读第一簇
		{
			IDEReadSector(ClusterToSector(FCB[fp].LastCluster));
			FCB[fp].ClusSecCnt++;
		}
		else										//读当前簇下一扇区
		{
			IDEReadSector(ClusterToSector(FCB[fp].LastCluster)+FCB[fp].ClusSecCnt);
			FCB[fp].ClusSecCnt++;
		}
	}
	return(tmp);
}