linux文件系统实现源码 VC源码 FAT文件系统

#ifndef _FAT_DEFINE #include "FAT.c" #endif BYTE FATMountVolumeID(BYTE Partition); BYTE FATMountVolumeID(BYTE Partition) { pdata DWORD TotSec,DataSec,CountofCluster; if (Partition>=StorageMedia.TotalPartitions) return(FAT_ERR_PARTITION_NOT_FOUND); //没找到指定扇区 StorageMedia.ReadSector(sDPT[Partition].LBABegin,DiskBuffer); //读FAT VolumeID扇区 //检查VolumeID扇区标记 if (DiskBuffer[510] != 0x55||DiskBuffer[511] != 0xaa) return(FAT_ERR_MBR_FLAG); //不正常的引导扇区标志 //检查分区类型 StorageMedia.CurrentPartition = Partition; //当前分区号 BOOTSEC->BPB_RsvdSecCnt=MEMSwap16(BOOTSEC->BPB_RsvdSecCnt); BOOTSEC->BPB_RootEntCnt=MEMSwap16(BOOTSEC->BPB_RootEntCnt); BOOTSEC->FAT.F32.BPB_RootClus=MEMSwap32(BOOTSEC->FAT.F32.BPB_RootClus); BOOTSEC->FAT.F32.BPB_FSInfo=MEMSwap16(BOOTSEC->FAT.F32.BPB_FSInfo); BOOTSEC->BPB_TotSec16=MEMSwap16(BOOTSEC->BPB_TotSec16); BOOTSEC->BPB_FATSz16=MEMSwap16(BOOTSEC->BPB_FATSz16); BOOTSEC->BPB_TotSec32=MEMSwap32(BOOTSEC->BPB_TotSec32); BOOTSEC->FAT.F32.BPB_FATSz32=MEMSwap32(BOOTSEC->FAT.F32.BPB_FATSz32); FAT.RootSectors = (BOOTSEC->BPB_RootEntCnt * 32) / 512; if (BOOTSEC->BPB_FATSz16!=0) FAT.FATSz = BOOTSEC->BPB_FATSz16; else FAT.FATSz = BOOTSEC->FAT.F32.BPB_FATSz32; if (BOOTSEC->BPB_TotSec16!=0) TotSec = BOOTSEC->BPB_TotSec16; else TotSec = BOOTSEC->BPB_TotSec32; DataSec = TotSec - (BOOTSEC->BPB_RsvdSecCnt + (BOOTSEC->BPB_NumFATs * FAT.FATSz) + FAT.RootSectors); CountofCluster = DataSec / (DWORD)(BOOTSEC->BPB_SecPerClus); if (CountofCluster<4085) { sDPT[Partition].FATType=FAT_TYPE_FAT12; FAT.RootClus = BOOTSEC->BPB_RsvdSecCnt + (BOOTSEC->BPB_NumFATs * BOOTSEC->BPB_FATSz16); } else if (CountofCluster<65525) { sDPT[Partition].FATType=FAT_TYPE_FAT16; FAT.RootClus = sDPT[StorageMedia.CurrentPartition].LBABegin + BOOTSEC->BPB_RsvdSecCnt + (BOOTSEC->BPB_NumFATs * BOOTSEC->BPB_FATSz16); } else { sDPT[Partition].FATType=FAT_TYPE_FAT32; FAT.RootClus = BOOTSEC->FAT.F32.BPB_RootClus; //根目录簇号 } FAT.SecPerClus = BOOTSEC->BPB_SecPerClus; //每簇扇区数 FAT.CurrentDirectory = FAT.RootClus; //当前目录入口（簇号） FAT.FATSec = sDPT[StorageMedia.CurrentPartition].LBABegin + BOOTSEC->BPB_RsvdSecCnt; //FAT表开始的扇区号 FAT.ClusSec = sDPT[StorageMedia.CurrentPartition].LBABegin + BOOTSEC->BPB_RsvdSecCnt + (BOOTSEC->BPB_NumFATs * FAT.FATSz) + FAT.RootSectors; //簇开始的扇区 FAT.FSISec = BOOTSEC->FAT.F32.BPB_FSInfo + sDPT[Partition].LBABegin; //FAT32扩展信息扇区号 //加载第一个FAT表 StorageMedia.ReadSector(FAT.FATSec,FATTable.FAT.F12); FATTable.Sector=0; return(0); }