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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** FileX Component */
/** */
/** Media */
/** */
/**************************************************************************/
/**************************************************************************/
#define FX_SOURCE_CODE
/* Include necessary system files. */
#include "fx_api.h"
#include "fx_media.h"
#include "fx_utility.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _fx_media_check_FAT_chain_check PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function walks the supplied FAT chain looking for cross links */
/* (FAT entries already used in another FAT chain) and abnormal FAT */
/* entries and invalid chain termination. */
/* */
/* INPUT */
/* */
/* media_ptr Pointer to a previously */
/* opened media */
/* starting_cluster Starting cluster of FAT chain */
/* last_valid_cluster Last valid cluster of chain */
/* total_valid_clusters Total number of valid clusters*/
/* logical_fat Pointer to the logical FAT */
/* bit map */
/* */
/* OUTPUT */
/* */
/* error Error code */
/* */
/* CALLS */
/* */
/* _fx_utility_FAT_entry_read Read a FAT entry */
/* */
/* CALLED BY */
/* */
/* _fx_check_media Check media function */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 William E. Lamie Initial Version 6.0 */
/* 09-30-2020 William E. Lamie Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
ULONG _fx_media_check_FAT_chain_check(FX_MEDIA *media_ptr, ULONG starting_cluster, ULONG *last_valid_cluster, ULONG *total_valid_clusters, UCHAR *logical_fat)
{
ULONG prev_cluster, cluster, next_clust = 0;
ULONG cluster_number;
ULONG count, error;
UINT status;
/* Initialize the error code. */
error = 0;
/* Setup at the first cluster. */
cluster = starting_cluster;
/* Initialize the previous cluster. */
prev_cluster = 0;
/* Initialize the count to 0. */
count = 0;
/* Loop to walk through the FAT chain. */
while ((cluster >= (ULONG)FX_FAT_ENTRY_START) &&
(cluster < (FX_FAT_ENTRY_START + media_ptr -> fx_media_total_clusters)))
{
cluster_number = cluster;
#ifdef FX_ENABLE_EXFAT
/* For the index of the first cluster in exFAT is 2, adjust the number of clusters to fit Allocation Bitmap Table. */
/* We will compare logical_fat with Aollcation Bitmap table later to find out lost clusters. */
if (media_ptr -> fx_media_FAT_type == FX_exFAT)
{
cluster_number = cluster - FX_FAT_ENTRY_START;
}
#endif /* FX_ENABLE_EXFAT */
/* Determine if this cluster is already in the logical FAT bit map. */
if (logical_fat[cluster_number >> 3] & (1 << (cluster_number & 7)))
{
/* Yes, the cluster is already being used by another file or
sub-directory. */
error = FX_FAT_CHAIN_ERROR;
break;
}
/* Now read the contents of the cluster. */
status = _fx_utility_FAT_entry_read(media_ptr, cluster, &next_clust);
/* Check the return status. */
if (status != FX_SUCCESS)
{
/* Yes, the cluster is already being used by another file or
sub-directory. */
error = FX_IO_ERROR;
break;
}
/* Determine if the link is circular or the count is greater than the
total clusters. */
if ((cluster == next_clust) ||
(next_clust < (ULONG)FX_FAT_ENTRY_START) ||
((next_clust >= (FX_FAT_ENTRY_START + media_ptr -> fx_media_total_clusters)) &&
(next_clust != media_ptr -> fx_media_fat_last)))
{
error = FX_FAT_CHAIN_ERROR;
break;
}
/* Everything is good with the chain at this point. Mark it as valid. */
logical_fat[cluster_number >> 3] = (UCHAR)(logical_fat[cluster_number >> 3] | (1 << (cluster_number & 7)));
/* Move the cluster variable forward. */
prev_cluster = cluster;
cluster = next_clust;
/* Increment the number of valid clusters. */
count++;
}
/* Return the last valid cluster and the total valid cluster count. */
*last_valid_cluster = prev_cluster;
*total_valid_clusters = count;
/* Return error code. */
return(error);
}
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