Check In tool source code based on Build tool project revision r1655.

[mirror_edk2.git] / BaseTools / Source / C / GenBootSector / GetDrvNumOffset.c

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