40d841f6a8
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10502 6f19259b-4bc3-4df7-8a09-765794883524
74 lines
2.4 KiB
C
74 lines
2.4 KiB
C
/** @file
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Get Drv Num offset from Fat file system.
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Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
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This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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**/
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#include <stdio.h>
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#include "FatFormat.h"
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INTN
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GetDrvNumOffset (
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IN VOID *BootSector
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)
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{
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FAT_BPB_STRUCT *FatBpb;
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UINTN RootDirSectors;
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UINTN FATSz;
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UINTN TotSec;
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UINTN DataSec;
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UINTN CountOfClusters;
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FatBpb = (FAT_BPB_STRUCT *) BootSector;
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//
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// Check FAT type algorithm from FAT spec
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//
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RootDirSectors = ((FatBpb->Fat12_16.BPB_RootEntCnt * sizeof(FAT_DIRECTORY_ENTRY)) +
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(FatBpb->Fat12_16.BPB_BytsPerSec - 1)) / FatBpb->Fat12_16.BPB_BytsPerSec;
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if (FatBpb->Fat12_16.BPB_FATSz16 != 0) {
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FATSz = FatBpb->Fat12_16.BPB_FATSz16;
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} else {
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FATSz = FatBpb->Fat32.BPB_FATSz32;
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}
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if (FATSz == 0) {
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fprintf (stderr, "error E3003: FAT - BPB_FATSz16, BPB_FATSz32 - 0, expected: Non-Zero number\n");
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return -1;
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}
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if (FatBpb->Fat12_16.BPB_TotSec16 != 0) {
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TotSec = FatBpb->Fat12_16.BPB_TotSec16;
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} else {
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TotSec = FatBpb->Fat12_16.BPB_TotSec32;
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}
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if (TotSec == 0) {
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fprintf (stderr, "error E3003: FAT - BPB_TotSec16, BPB_TotSec32 - 0, expected: Non-Zero number\n");
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return -1;
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}
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DataSec = TotSec - (
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FatBpb->Fat12_16.BPB_RsvdSecCnt +
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FatBpb->Fat12_16.BPB_NumFATs * FATSz +
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RootDirSectors
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);
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CountOfClusters = DataSec / FatBpb->Fat12_16.BPB_SecPerClus;
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if (CountOfClusters < FAT_MAX_FAT16_CLUSTER) {
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return (INTN) ((UINTN) &FatBpb->Fat12_16.BS_DrvNum - (UINTN) FatBpb);
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} else {
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return (INTN) ((UINTN) &FatBpb->Fat32.BS_DrvNum - (UINTN) FatBpb);
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}
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}
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