mirror of
https://github.com/eclipse-threadx/filex.git
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163 lines
7.6 KiB
C
163 lines
7.6 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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/** Media */
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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_media.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_media_check_FAT_chain_check 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 walks the supplied FAT chain looking for cross links */
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/* (FAT entries already used in another FAT chain) and abnormal FAT */
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/* entries and invalid chain termination. */
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/* */
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/* INPUT */
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/* */
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/* media_ptr Pointer to a previously */
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/* opened media */
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/* starting_cluster Starting cluster of FAT chain */
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/* last_valid_cluster Last valid cluster of chain */
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/* total_valid_clusters Total number of valid clusters*/
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/* logical_fat Pointer to the logical FAT */
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/* bit map */
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/* */
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/* OUTPUT */
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/* */
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/* error Error code */
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/* */
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/* CALLS */
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/* */
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/* _fx_utility_FAT_entry_read Read a FAT entry */
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/* */
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/* CALLED BY */
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/* */
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/* _fx_check_media Check media function */
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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_media_check_FAT_chain_check(FX_MEDIA *media_ptr, ULONG starting_cluster, ULONG *last_valid_cluster, ULONG *total_valid_clusters, UCHAR *logical_fat)
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{
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ULONG prev_cluster, cluster, next_clust = 0;
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ULONG cluster_number;
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ULONG count, error;
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UINT status;
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/* Initialize the error code. */
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error = 0;
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/* Setup at the first cluster. */
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cluster = starting_cluster;
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/* Initialize the previous cluster. */
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prev_cluster = 0;
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/* Initialize the count to 0. */
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count = 0;
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/* Loop to walk through the FAT chain. */
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while ((cluster >= (ULONG)FX_FAT_ENTRY_START) &&
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(cluster < (FX_FAT_ENTRY_START + media_ptr -> fx_media_total_clusters)))
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{
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cluster_number = cluster;
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/* Determine if this cluster is already in the logical FAT bit map. */
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if (logical_fat[cluster_number >> 3] & (1 << (cluster_number & 7)))
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{
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/* Yes, the cluster is already being used by another file or
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sub-directory. */
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error = FX_FAT_CHAIN_ERROR;
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break;
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}
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/* Now read the contents of the cluster. */
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status = _fx_utility_FAT_entry_read(media_ptr, cluster, &next_clust);
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/* Check the return status. */
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if (status != FX_SUCCESS)
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{
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/* Yes, the cluster is already being used by another file or
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sub-directory. */
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error = FX_IO_ERROR;
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break;
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}
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/* Determine if the link is circular or the count is greater than the
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total clusters. */
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if ((cluster == next_clust) ||
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(next_clust < (ULONG)FX_FAT_ENTRY_START) ||
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((next_clust >= (FX_FAT_ENTRY_START + media_ptr -> fx_media_total_clusters)) &&
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(next_clust != media_ptr -> fx_media_fat_last)))
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{
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error = FX_FAT_CHAIN_ERROR;
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break;
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}
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/* Everything is good with the chain at this point. Mark it as valid. */
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logical_fat[cluster_number >> 3] = (UCHAR)(logical_fat[cluster_number >> 3] | (1 << (cluster_number & 7)));
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/* Move the cluster variable forward. */
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prev_cluster = cluster;
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cluster = next_clust;
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/* Increment the number of valid clusters. */
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count++;
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}
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/* Return the last valid cluster and the total valid cluster count. */
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*last_valid_cluster = prev_cluster;
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*total_valid_clusters = count;
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/* Return error code. */
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return(error);
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}
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