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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 */
/** */
/** Utility */
/** */
/**************************************************************************/
/**************************************************************************/
#define FX_SOURCE_CODE
/* Include necessary system files. */
#include "fx_api.h"
#include "fx_system.h"
#include "fx_utility.h"
#ifdef FX_ENABLE_FAULT_TOLERANT
#include "fx_fault_tolerant.h"
#endif /* FX_ENABLE_FAULT_TOLERANT */
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _fx_utility_FAT_entry_read PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function reads the supplied FAT entry from the first FAT of */
/* the media. 12-bit, 16-bit, and 32-bit FAT reading is supported. */
/* */
/* INPUT */
/* */
/* media_ptr Media control block pointer */
/* cluster Cluster entry number */
/* entry_ptr Pointer to destination for */
/* the FAT entry */
/* */
/* OUTPUT */
/* */
/* return status */
/* */
/* CALLS */
/* */
/* _fx_utility_16_unsigned_read Read a UINT from FAT buffer */
/* _fx_utility_32_unsigned_read Read a ULONG form FAT buffer */
/* _fx_utility_FAT_flush Flush FAT entry cache */
/* _fx_utility_logical_sector_read Read FAT sector into memory */
/* _fx_fault_tolerant_read_FAT Read FAT entry from log file */
/* */
/* CALLED BY */
/* */
/* FileX System Functions */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 William E. Lamie Initial Version 6.0 */
/* 09-30-2020 William E. Lamie Modified comment(s), and */
/* added conditional to */
/* disable fat entry refresh, */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
UINT _fx_utility_FAT_entry_read(FX_MEDIA *media_ptr, ULONG cluster, ULONG *entry_ptr)
{
ULONG FAT_sector;
ULONG byte_offset, entry32;
UCHAR *FAT_ptr;
UINT entry, index;
UINT status;
FX_FAT_CACHE_ENTRY *cache_entry_ptr;
FX_FAT_CACHE_ENTRY temp_cache_entry;
#ifdef FX_ENABLE_FAULT_TOLERANT
if (media_ptr -> fx_media_fault_tolerant_enabled &&
(media_ptr -> fx_media_fault_tolerant_state & FX_FAULT_TOLERANT_STATE_STARTED))
{
/* Redirect this request to log file. */
status = _fx_fault_tolerant_read_FAT(media_ptr, cluster, entry_ptr, FX_FAULT_TOLERANT_FAT_LOG_TYPE);
/* Return on success. */
if (status != FX_READ_CONTINUE)
{
return(status);
}
}
#endif /* FX_ENABLE_FAULT_TOLERANT */
#ifndef FX_MEDIA_STATISTICS_DISABLE
/* Increment the number of FAT entry reads and cache hits. */
media_ptr -> fx_media_fat_entry_reads++;
media_ptr -> fx_media_fat_entry_cache_read_hits++;
#endif
/* Extended port-specific processing macro, which is by default defined to white space. */
FX_UTILITY_FAT_ENTRY_READ_EXTENSION
/* Calculate the area of the cache for this FAT entry. */
index = (cluster & FX_FAT_CACHE_HASH_MASK) * FX_FAT_CACHE_DEPTH;
/* Build a pointer to the cache entry. */
cache_entry_ptr = &media_ptr -> fx_media_fat_cache[index];
#ifndef FX_DISABLE_FAT_ENTRY_REFRESH
/* Determine if the FAT entry is in the cache - assuming the depth of the FAT cache is
4 entries. */
if ((cache_entry_ptr -> fx_fat_cache_entry_cluster) == cluster)
{
/* Yes, return the cached value. */
*entry_ptr = cache_entry_ptr -> fx_fat_cache_entry_value;
/* Don't move anything since we found the entry. */
/* Return a successful status. */
return(FX_SUCCESS);
}
else if (((cache_entry_ptr + 1) -> fx_fat_cache_entry_cluster) == cluster)
{
/* Yes, return the cached value. */
*entry_ptr = (cache_entry_ptr + 1) -> fx_fat_cache_entry_value;
/* Just swap the first and second entry. */
temp_cache_entry = *(cache_entry_ptr);
*(cache_entry_ptr) = *(cache_entry_ptr + 1);
*(cache_entry_ptr + 1) = temp_cache_entry;
/* Return a successful status. */
return(FX_SUCCESS);
}
else if (((cache_entry_ptr + 2) -> fx_fat_cache_entry_cluster) == cluster)
{
/* Yes, return the cached value. */
*entry_ptr = (cache_entry_ptr + 2) -> fx_fat_cache_entry_value;
/* Move the third entry to the top and the first two entries down. */
temp_cache_entry = *(cache_entry_ptr);
*(cache_entry_ptr) = *(cache_entry_ptr + 2);
*(cache_entry_ptr + 2) = *(cache_entry_ptr + 1);
*(cache_entry_ptr + 1) = temp_cache_entry;
/* Return a successful status. */
return(FX_SUCCESS);
}
else if (((cache_entry_ptr + 3) -> fx_fat_cache_entry_cluster) == cluster)
{
/* Yes, return the cached value. */
*entry_ptr = (cache_entry_ptr + 3) -> fx_fat_cache_entry_value;
/* Move the last entry to the top and the first three entries down. */
temp_cache_entry = *(cache_entry_ptr);
*(cache_entry_ptr) = *(cache_entry_ptr + 3);
*(cache_entry_ptr + 3) = *(cache_entry_ptr + 2);
*(cache_entry_ptr + 2) = *(cache_entry_ptr + 1);
*(cache_entry_ptr + 1) = temp_cache_entry;
/* Return a successful status. */
return(FX_SUCCESS);
}
#else
for (UINT i = 0; i < 4; i++)
{
if (((cache_entry_ptr + i) -> fx_fat_cache_entry_cluster) == cluster)
{
*entry_ptr = (cache_entry_ptr + i) -> fx_fat_cache_entry_value;
/* Return a successful status. */
return(FX_SUCCESS);
}
}
#endif /* FX_DISABLE_FAT_ENTRY_REFRESH */
/* Determine if the oldest entry was modified, i.e. whether or not it is
dirty. */
if (media_ptr -> fx_media_fat_cache[index + 3].fx_fat_cache_entry_dirty)
{
/* Yes, the entry is dirty and needs to be flushed out. */
status = _fx_utility_FAT_flush(media_ptr);
/* Check for completion status. */
if (status != FX_SUCCESS)
{
/* Return error status. */
return(status);
}
}
/* If we get here, the entry was not found in the FAT entry cache. We need to
actually read the FAT entry. */
#ifndef FX_MEDIA_STATISTICS_DISABLE
/* Decrement the number of cache hits. */
media_ptr -> fx_media_fat_entry_cache_read_hits--;
/* Increment the number of cache misses. */
media_ptr -> fx_media_fat_entry_cache_read_misses++;
#endif
/* Determine which type of FAT is present. */
if (media_ptr -> fx_media_12_bit_FAT)
{
/* Calculate the byte offset to the cluster entry. */
byte_offset = (((ULONG)cluster << 1) + cluster) >> 1;
/* Calculate the FAT sector the requested FAT entry resides in. */
FAT_sector = (byte_offset / media_ptr -> fx_media_bytes_per_sector) +
(ULONG)media_ptr -> fx_media_reserved_sectors;
/* Read the sector in. */
status = _fx_utility_logical_sector_read(media_ptr, (ULONG64) FAT_sector,
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
/* Determine if an error occurred. */
if (status != FX_SUCCESS)
{
/* Return the error status. */
return(status);
}
/* Now calculate the byte offset into this FAT sector. */
byte_offset = byte_offset -
((FAT_sector - (ULONG)media_ptr -> fx_media_reserved_sectors) *
media_ptr -> fx_media_bytes_per_sector);
/* Setup a pointer into the buffer. */
FAT_ptr = (UCHAR *)media_ptr -> fx_media_memory_buffer + (UINT)byte_offset;
/* Determine if the cluster entry is odd or even. */
if (cluster & 1)
{
/* Odd cluster number. */
/* Pickup the lower nibble of the FAT entry. */
entry = (((UINT)*FAT_ptr) & 0xF0) >> 4;
/* Move to the next byte of the FAT entry. */
FAT_ptr++;
/* Determine if we are now past the end of the FAT buffer in memory. */
if (byte_offset == (ULONG)(media_ptr -> fx_media_bytes_per_sector - 1))
{
/* Yes, we need to read the next sector. */
FAT_sector++;
status = _fx_utility_logical_sector_read(media_ptr, (ULONG64) FAT_sector,
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
/* Determine if an error occurred. */
if (status != FX_SUCCESS)
{
/* Return the error status. */
return(status);
}
/* Setup a pointer into the buffer. */
FAT_ptr = (UCHAR *)media_ptr -> fx_media_memory_buffer;
}
/* Pickup the upper 8 bits of the FAT entry. */
entry = entry | (((UINT)*FAT_ptr) << 4);
}
else
{
/* Even cluster number. */
/* Pickup the lower byte of the FAT entry. */
entry = (UINT)(((UINT)*FAT_ptr) & 0xFF);
/* Move to the next nibble of the FAT entry. */
FAT_ptr++;
/* Determine if we are now past the end of the FAT buffer in memory. */
if (byte_offset == (ULONG)(media_ptr -> fx_media_bytes_per_sector - 1))
{
/* Yes, we need to read the next sector. */
FAT_sector++;
status = _fx_utility_logical_sector_read(media_ptr, (ULONG64) FAT_sector,
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
/* Determine if an error occurred. */
if (status != FX_SUCCESS)
{
return(status);
}
/* Setup a pointer into the buffer. */
FAT_ptr = (UCHAR *)media_ptr -> fx_media_memory_buffer;
}
/* Pickup the upper 4 bits of the FAT entry. */
entry = entry | ((((UINT)*FAT_ptr) & 0x0F) << 8);
}
/* Determine if we need to do sign extension on the 12-bit eof value. */
if (entry >= FX_MAX_12BIT_CLUST)
{
/* Yes, we need to sign extend. */
entry = entry | FX_SIGN_EXTEND;
}
*entry_ptr = entry;
}
/* Check for a 16-bit FAT. */
#ifdef FX_ENABLE_EXFAT
else if (FX_FAT16 == media_ptr -> fx_media_FAT_type)
#else
else if (!media_ptr -> fx_media_32_bit_FAT)
#endif /* FX_ENABLE_EXFAT */
{
/* 16-bit FAT is present. */
/* Calculate the byte offset to the cluster entry. */
byte_offset = (((ULONG)cluster) * 2);
/* Calculate the FAT sector the requested FAT entry resides in. */
FAT_sector = (byte_offset / media_ptr -> fx_media_bytes_per_sector) +
(ULONG)media_ptr -> fx_media_reserved_sectors;
/* Read the FAT sector. */
status = _fx_utility_logical_sector_read(media_ptr, (ULONG64) FAT_sector,
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
/* Determine if an error occurred. */
if (status != FX_SUCCESS)
{
/* Return the error code. */
return(status);
}
/* Now calculate the byte offset into this FAT sector. */
byte_offset = byte_offset -
((FAT_sector - (ULONG)media_ptr -> fx_media_reserved_sectors) *
media_ptr -> fx_media_bytes_per_sector);
/* Setup a pointer into the buffer. */
FAT_ptr = (UCHAR *)media_ptr -> fx_media_memory_buffer + (UINT)byte_offset;
/* Pickup the FAT entry. */
entry = _fx_utility_16_unsigned_read(FAT_ptr);
*entry_ptr = entry;
}
#ifdef FX_ENABLE_EXFAT
else if ((media_ptr -> fx_media_FAT_type == FX_FAT32) ||
(media_ptr -> fx_media_FAT_type == FX_exFAT))
#else
else
#endif /* FX_ENABLE_EXFAT */
{
/* Otherwise, a 32 bit FAT present. */
byte_offset = (((ULONG)cluster) * 4);
/* Calculate the FAT sector the requested FAT entry resides in. */
FAT_sector = (byte_offset / media_ptr -> fx_media_bytes_per_sector) +
(ULONG)media_ptr -> fx_media_reserved_sectors;
/* Calculate the byte offset to the FAT entry. */
byte_offset = (byte_offset % media_ptr -> fx_media_bytes_per_sector);
/* Read the appropriate FAT sector. */
status = _fx_utility_logical_sector_read(media_ptr, (ULONG64) FAT_sector,
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_FAT_SECTOR);
/* Determine if an error occurred. */
if (status != FX_SUCCESS)
{
/* Return the error code. */
return(status);
}
/* Setup a pointer into the buffer. */
FAT_ptr = (UCHAR *)media_ptr -> fx_media_memory_buffer + (ULONG)byte_offset;
/* Pickup the FAT entry. */
entry32 = _fx_utility_32_unsigned_read(FAT_ptr);
#ifdef FX_ENABLE_EXFAT
/* FAT32 uses 28 bit cluster addressing but exFAT uses 32 bit. */
if (media_ptr -> fx_media_FAT_type == FX_FAT32)
{
#endif /* FX_ENABLE_EXFAT */
/* Clear upper nibble. */
entry32 = entry32 & 0x0FFFFFFF;
#ifdef FX_ENABLE_EXFAT
}
#endif /* FX_ENABLE_EXFAT */
*entry_ptr = entry32;
}
/* Move all the cache entries down so the oldest is at the bottom. */
*(cache_entry_ptr + 3) = *(cache_entry_ptr + 2);
*(cache_entry_ptr + 2) = *(cache_entry_ptr + 1);
*(cache_entry_ptr + 1) = *(cache_entry_ptr);
/* Setup the new FAT entry in the cache. */
cache_entry_ptr -> fx_fat_cache_entry_cluster = cluster;
cache_entry_ptr -> fx_fat_cache_entry_value = *entry_ptr;
/* Return success to the caller. */
return(FX_SUCCESS);
}