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30fdf114 LG |
1 | /** @file\r |
2 | \r | |
3 | Get Drv Num offset from Fat file system.\r | |
4 | \r | |
5 | Copyright 2006 - 2008, Intel Corporation \r | |
6 | All rights reserved. This program and the accompanying materials \r | |
7 | are licensed and made available under the terms and conditions of the BSD License \r | |
8 | which accompanies this distribution. The full text of the license may be found at \r | |
9 | http://opensource.org/licenses/bsd-license.php \r | |
10 | \r | |
11 | THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, \r | |
12 | WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. \r | |
13 | \r | |
14 | **/\r | |
15 | \r | |
16 | #include <stdio.h>\r | |
17 | #include "FatFormat.h"\r | |
18 | \r | |
19 | INTN\r | |
20 | GetDrvNumOffset (\r | |
21 | IN VOID *BootSector\r | |
22 | )\r | |
23 | {\r | |
24 | FAT_BPB_STRUCT *FatBpb;\r | |
25 | UINTN RootDirSectors;\r | |
26 | UINTN FATSz;\r | |
27 | UINTN TotSec;\r | |
28 | UINTN DataSec;\r | |
29 | UINTN CountOfClusters;\r | |
30 | \r | |
31 | FatBpb = (FAT_BPB_STRUCT *) BootSector;\r | |
32 | \r | |
33 | //\r | |
34 | // Check FAT type algorithm from FAT spec\r | |
35 | //\r | |
36 | RootDirSectors = ((FatBpb->Fat12_16.BPB_RootEntCnt * sizeof(FAT_DIRECTORY_ENTRY)) +\r | |
37 | (FatBpb->Fat12_16.BPB_BytsPerSec - 1)) / FatBpb->Fat12_16.BPB_BytsPerSec;\r | |
38 | \r | |
39 | if (FatBpb->Fat12_16.BPB_FATSz16 != 0) {\r | |
40 | FATSz = FatBpb->Fat12_16.BPB_FATSz16;\r | |
41 | } else {\r | |
42 | FATSz = FatBpb->Fat32.BPB_FATSz32;\r | |
43 | }\r | |
44 | if (FATSz == 0) {\r | |
45 | fprintf (stderr, "error E3003: FAT - BPB_FATSz16, BPB_FATSz32 - 0, expected: Non-Zero number\n");\r | |
46 | return -1;\r | |
47 | }\r | |
48 | \r | |
49 | if (FatBpb->Fat12_16.BPB_TotSec16 != 0) {\r | |
50 | TotSec = FatBpb->Fat12_16.BPB_TotSec16;\r | |
51 | } else {\r | |
52 | TotSec = FatBpb->Fat12_16.BPB_TotSec32;\r | |
53 | }\r | |
54 | if (TotSec == 0) {\r | |
55 | fprintf (stderr, "error E3003: FAT - BPB_TotSec16, BPB_TotSec32 - 0, expected: Non-Zero number\n");\r | |
56 | return -1;\r | |
57 | }\r | |
58 | \r | |
59 | DataSec = TotSec - (\r | |
60 | FatBpb->Fat12_16.BPB_RsvdSecCnt +\r | |
61 | FatBpb->Fat12_16.BPB_NumFATs * FATSz +\r | |
62 | RootDirSectors\r | |
63 | );\r | |
64 | \r | |
65 | CountOfClusters = DataSec / FatBpb->Fat12_16.BPB_SecPerClus;\r | |
66 | \r | |
67 | if (CountOfClusters < FAT_MAX_FAT16_CLUSTER) {\r | |
68 | return (INTN) ((UINTN) &FatBpb->Fat12_16.BS_DrvNum - (UINTN) FatBpb);\r | |
69 | } else {\r | |
70 | return (INTN) ((UINTN) &FatBpb->Fat32.BS_DrvNum - (UINTN) FatBpb);\r | |
71 | }\r | |
72 | }\r | |
73 | \r |