1 /*************************************************************************** 2 * Copyright (c) 2024 Microsoft Corporation 3 * 4 * This program and the accompanying materials are made available under the 5 * terms of the MIT License which is available at 6 * https://opensource.org/licenses/MIT. 7 * 8 * SPDX-License-Identifier: MIT 9 **************************************************************************/ 10 11 12 /**************************************************************************/ 13 /**************************************************************************/ 14 /** */ 15 /** FileX Component */ 16 /** */ 17 /** Utility */ 18 /** */ 19 /**************************************************************************/ 20 /**************************************************************************/ 21 22 #define FX_SOURCE_CODE 23 24 25 /* Include necessary system files. */ 26 27 #include "fx_api.h" 28 #include "fx_utility.h" 29 30 31 /**************************************************************************/ 32 /* */ 33 /* FUNCTION RELEASE */ 34 /* */ 35 /* _fx_utility_FAT_sector_get PORTABLE C */ 36 /* 6.1 */ 37 /* AUTHOR */ 38 /* */ 39 /* William E. Lamie, Microsoft Corporation */ 40 /* */ 41 /* DESCRIPTION */ 42 /* */ 43 /* This function gets the sector of supplied FAT entry. */ 44 /* */ 45 /* INPUT */ 46 /* */ 47 /* media_ptr Media control block pointer */ 48 /* cluster Cluster entry number */ 49 /* */ 50 /* OUTPUT */ 51 /* */ 52 /* return sector of FAT entry */ 53 /* */ 54 /* CALLS */ 55 /* */ 56 /* */ 57 /* CALLED BY */ 58 /* */ 59 /* FileX System Functions */ 60 /* */ 61 /* RELEASE HISTORY */ 62 /* */ 63 /* DATE NAME DESCRIPTION */ 64 /* */ 65 /* 05-19-2020 William E. Lamie Initial Version 6.0 */ 66 /* 09-30-2020 William E. Lamie Modified comment(s), */ 67 /* resulting in version 6.1 */ 68 /* */ 69 /**************************************************************************/ _fx_utility_FAT_sector_get(FX_MEDIA * media_ptr,ULONG cluster)70ULONG _fx_utility_FAT_sector_get(FX_MEDIA *media_ptr, ULONG cluster) 71 { 72 73 ULONG FAT_sector; 74 ULONG byte_offset; 75 76 /* Determine which type of FAT is present. */ 77 if (media_ptr -> fx_media_12_bit_FAT) 78 { 79 80 /* 12-bit FAT is present. */ 81 82 /* Calculate the byte offset to the cluster entry. */ 83 byte_offset = (((ULONG)cluster << 1) + cluster) >> 1; 84 85 } 86 else if (!media_ptr -> fx_media_32_bit_FAT) 87 { 88 89 /* 16-bit FAT is present. */ 90 91 /* Calculate the byte offset to the cluster entry. */ 92 byte_offset = (((ULONG)cluster) << 1); 93 } 94 else 95 { 96 97 /* 32-bit FAT is present. */ 98 99 /* Calculate the byte offset to the cluster entry. */ 100 byte_offset = (((ULONG)cluster) * 4); 101 } 102 103 /* Calculate the FAT sector the requested FAT entry resides in. */ 104 FAT_sector = (byte_offset / media_ptr -> fx_media_bytes_per_sector) + 105 (ULONG)media_ptr -> fx_media_reserved_sectors; 106 107 /* Return successful status. */ 108 return(FAT_sector); 109 } 110 111
