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https://github.com/eclipse-threadx/filex.git
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112 lines
5.5 KiB
C
112 lines
5.5 KiB
C
/**************************************************************************/
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/* */
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/* Copyright (c) Microsoft Corporation. All rights reserved. */
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/* */
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/* This software is licensed under the Microsoft Software License */
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/* Terms for Microsoft Azure RTOS. Full text of the license can be */
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/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
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/* and in the root directory of this software. */
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/* */
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/**************************************************************************/
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/**************************************************************************/
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/**************************************************************************/
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/** */
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/** FileX Component */
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/** */
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/** Utility */
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/** */
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/**************************************************************************/
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/**************************************************************************/
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#define FX_SOURCE_CODE
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/* Include necessary system files. */
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#include "fx_api.h"
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#include "fx_utility.h"
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/**************************************************************************/
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/* */
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/* FUNCTION RELEASE */
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/* */
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/* _fx_utility_FAT_sector_get PORTABLE C */
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/* 6.1 */
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/* AUTHOR */
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/* */
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/* William E. Lamie, Microsoft Corporation */
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/* */
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/* DESCRIPTION */
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/* */
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/* This function gets the sector of supplied FAT entry. */
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/* */
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/* INPUT */
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/* */
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/* media_ptr Media control block pointer */
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/* cluster Cluster entry number */
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/* */
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/* OUTPUT */
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/* */
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/* return sector of FAT entry */
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/* */
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/* CALLS */
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/* */
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/* */
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/* CALLED BY */
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/* */
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/* FileX System Functions */
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/* */
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/* RELEASE HISTORY */
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/* */
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/* DATE NAME DESCRIPTION */
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/* */
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/* 05-19-2020 William E. Lamie Initial Version 6.0 */
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/* 09-30-2020 William E. Lamie Modified comment(s), */
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/* resulting in version 6.1 */
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/* */
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/**************************************************************************/
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ULONG _fx_utility_FAT_sector_get(FX_MEDIA *media_ptr, ULONG cluster)
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{
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ULONG FAT_sector;
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ULONG byte_offset;
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/* Determine which type of FAT is present. */
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if (media_ptr -> fx_media_12_bit_FAT)
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{
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/* 12-bit FAT is present. */
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/* Calculate the byte offset to the cluster entry. */
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byte_offset = (((ULONG)cluster << 1) + cluster) >> 1;
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}
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else if (!media_ptr -> fx_media_32_bit_FAT)
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{
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/* 16-bit FAT is present. */
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/* Calculate the byte offset to the cluster entry. */
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byte_offset = (((ULONG)cluster) << 1);
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}
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else
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{
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/* 32-bit FAT is present. */
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/* Calculate the byte offset to the cluster entry. */
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byte_offset = (((ULONG)cluster) * 4);
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}
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/* Calculate the FAT sector the requested FAT entry resides in. */
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FAT_sector = (byte_offset / media_ptr -> fx_media_bytes_per_sector) +
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(ULONG)media_ptr -> fx_media_reserved_sectors;
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/* Return successful status. */
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return(FAT_sector);
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}
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