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172 lines
8.0 KiB
C
172 lines
8.0 KiB
C
/***************************************************************************
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* Copyright (c) 2024 Microsoft Corporation
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*
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* This program and the accompanying materials are made available under the
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* terms of the MIT License which is available at
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* https://opensource.org/licenses/MIT.
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*
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* SPDX-License-Identifier: MIT
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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_system.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_map_flush 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 updates mirrors changes in the primary FAT to each of */
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/* secondary FATs in the media. */
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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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/* */
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/* OUTPUT */
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/* */
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/* return status */
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/* */
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/* CALLS */
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/* */
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/* _fx_utility_logical_sector_read Read FAT sector into memory */
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/* _fx_utility_logical_sector_write Write FAT sector back to disk */
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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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UINT _fx_utility_FAT_map_flush(FX_MEDIA *media_ptr)
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{
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ULONG FAT_sector, last_sector;
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UINT i, status, FATs;
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UCHAR sectors_per_bit;
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/* Determine how many FAT sectors each bit in the bit map represents. Depending on
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the number of sectors in the primary FAT, each bit in this map may represent one
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or more primary FAT sectors. Because of this, it is possible some FAT sectors that
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were not changed may get flushed out to the secondary FAT. However, this method
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provides very nice performance benefits during normal operation and is much more
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reasonable than performing a total copy of the primary FAT to each secondary FAT
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on media flush and media close. */
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if (media_ptr -> fx_media_sectors_per_FAT % (FX_FAT_MAP_SIZE << 3) == 0)
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{
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sectors_per_bit = (UCHAR)(media_ptr -> fx_media_sectors_per_FAT / (FX_FAT_MAP_SIZE << 3));
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}
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else
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{
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sectors_per_bit = (UCHAR)(media_ptr -> fx_media_sectors_per_FAT / (FX_FAT_MAP_SIZE << 3) + 1);
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}
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/* Loop through the FAT update map to mirror primary FAT sectors to secondary FAT(s). */
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for (i = 0; i < FX_FAT_MAP_SIZE << 3; i++)
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{
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/* Determine if there are FAT changes specified by this entry. */
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if ((media_ptr -> fx_media_fat_secondary_update_map[i >> 3] & (1 << (i & 7))) == 0)
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{
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/* No, look at the next bit map entry. */
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continue;
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}
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/* Setup the parameters for performing the update. */
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FAT_sector = i * sectors_per_bit + media_ptr -> fx_media_reserved_sectors;
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last_sector = FAT_sector + sectors_per_bit;
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/* Make sure the last update sector is within range. */
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if (last_sector > (media_ptr -> fx_media_sectors_per_FAT + media_ptr -> fx_media_reserved_sectors))
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{
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last_sector = media_ptr -> fx_media_sectors_per_FAT + media_ptr -> fx_media_reserved_sectors;
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}
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/* Loop to mirror primary FAT sectors to secondary FAT(s). */
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for (; FAT_sector < last_sector; FAT_sector++)
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{
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/* Read the FAT sector. */
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status = _fx_utility_logical_sector_read(media_ptr, (ULONG64) FAT_sector,
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media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
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/* Determine if an error occurred. */
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if (status != FX_SUCCESS)
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{
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/* Return the error status. */
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return(status);
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}
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/* Pickup how many secondary FATs there are. */
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FATs = media_ptr -> fx_media_number_of_FATs - 1;
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/* Loop to update additional FAT entries. */
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while (FATs)
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{
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/* Mirror main FAT sector write into the additional FATs. */
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status = _fx_utility_logical_sector_write(media_ptr,
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((ULONG64) FAT_sector) + ((ULONG64)FATs * (ULONG64)(media_ptr -> fx_media_sectors_per_FAT)),
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media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
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/* Determine if an error occurred. */
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if (status != FX_SUCCESS)
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{
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/* Return the error status. */
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return(status);
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}
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/* Decrement the number of FATs. */
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FATs--;
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}
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}
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}
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/* Clear the bit map that indicates primary FAT updates. */
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for (i = 0; i < FX_FAT_MAP_SIZE; i++)
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{
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/* Clear each entry in the bit map. */
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media_ptr -> fx_media_fat_secondary_update_map[i] = 0;
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}
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/* Return a successful completion. */
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return(FX_SUCCESS);
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}
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