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/*************************************************************************** |
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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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/** File */ |
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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_file.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_file_read 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 reads the specified number of bytes (or as many as */ |
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/* possible into the buffer supplied by the caller. The actual number */ |
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/* of bytes and the status of the read operation is returned to the */ |
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/* caller. In addition, various internal file pointers in the file */ |
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/* control block are also updated. */ |
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/* */ |
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/* INPUT */ |
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/* */ |
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/* file_ptr File control block pointer */ |
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/* buffer_ptr Buffer pointer */ |
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/* request_size Number of bytes requested */ |
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/* actual_size Pointer to variable for the */ |
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/* number of bytes read */ |
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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_FAT_entry_read Read a FAT entry */ |
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/* _fx_utility_logical_sector_read Read a logical sector */ |
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/* _fx_utility_memory_copy Fast memory copy routine */ |
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/* */ |
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/* CALLED BY */ |
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/* */ |
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/* Application Code */ |
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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), verified */ |
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/* memcpy usage, */ |
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/* resulting in version 6.1 */ |
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/* */ |
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/**************************************************************************/ |
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178683 |
UINT _fx_file_read(FX_FILE *file_ptr, VOID *buffer_ptr, ULONG request_size, ULONG *actual_size) |
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{ |
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UINT status; |
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ULONG bytes_remaining, i; |
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ULONG copy_bytes; |
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UCHAR *destination_ptr; |
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ULONG cluster, next_cluster; |
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UINT sectors; |
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FX_MEDIA *media_ptr; |
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#ifdef TX_ENABLE_EVENT_TRACE |
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TX_TRACE_BUFFER_ENTRY *trace_event; |
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ULONG trace_timestamp; |
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#endif |
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/* First, determine if the file is still open. */ |
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✓✓ |
178683 |
if (file_ptr -> fx_file_id != FX_FILE_ID) |
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{ |
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/* Return the file not open error status. */ |
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return(FX_NOT_OPEN); |
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} |
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#ifndef FX_MEDIA_STATISTICS_DISABLE |
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/* Setup pointer to media structure. */ |
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178682 |
media_ptr = file_ptr -> fx_file_media_ptr; |
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/* Increment the number of times this service has been called. */ |
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178682 |
media_ptr -> fx_media_file_reads++; |
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#endif |
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/* Setup pointer to associated media control block. */ |
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178682 |
media_ptr = file_ptr -> fx_file_media_ptr; |
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/* If trace is enabled, insert this event into the trace buffer. */ |
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FX_TRACE_IN_LINE_INSERT(FX_TRACE_FILE_READ, file_ptr, buffer_ptr, request_size, 0, FX_TRACE_FILE_EVENTS, &trace_event, &trace_timestamp) |
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/* Protect against other threads accessing the media. */ |
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178682 |
FX_PROTECT |
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/* Next, determine if there is any more bytes to read in the file. */ |
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178682 |
if (file_ptr -> fx_file_current_file_offset >= |
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✓✓ |
178682 |
file_ptr -> fx_file_current_file_size) |
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{ |
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/* Release media protection. */ |
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FX_UNPROTECT |
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/* The file is at the end, return the proper status and set the |
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actual size to 0. */ |
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*actual_size = 0; |
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return(FX_END_OF_FILE); |
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} |
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/* At this point there is something to read. */ |
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/* Setup local buffer pointer. */ |
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178669 |
destination_ptr = (UCHAR *)buffer_ptr; |
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/* Determine if there are less bytes left in the file than that specified |
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by the request. If so, adjust the requested size. */ |
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178669 |
if ((ULONG64)request_size > |
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✓✓ |
178669 |
(file_ptr -> fx_file_current_file_size - file_ptr -> fx_file_current_file_offset)) |
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{ |
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/* Adjust the bytes remaining to what's available. */ |
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request_size = (ULONG)(file_ptr -> fx_file_current_file_size - file_ptr -> fx_file_current_file_offset); |
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} |
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/* Setup the remaining number of bytes to read. */ |
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178669 |
bytes_remaining = request_size; |
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/* Loop to read all of the bytes. */ |
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✓✓ |
310134 |
while (bytes_remaining) |
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{ |
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/* Determine if a beginning or ending partial read is required. */ |
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✓✓ |
201774 |
if ((file_ptr -> fx_file_current_logical_offset) || |
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✓✓ |
35408 |
(bytes_remaining < media_ptr -> fx_media_bytes_per_sector)) |
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{ |
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/* A partial sector read is required. */ |
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/* Read the current logical sector. */ |
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171332 |
status = _fx_utility_logical_sector_read(media_ptr, |
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file_ptr -> fx_file_current_logical_sector, |
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171332 |
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_DATA_SECTOR); |
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/* Check for good completion status. */ |
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✓✓ |
171332 |
if (status != FX_SUCCESS) |
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{ |
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/* Release media protection. */ |
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23211 |
FX_UNPROTECT |
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/* Return the error status. */ |
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23211 |
return(status); |
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} |
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/* Copy the appropriate number of bytes into the destination buffer. */ |
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148121 |
copy_bytes = media_ptr -> fx_media_bytes_per_sector - |
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148121 |
file_ptr -> fx_file_current_logical_offset; |
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/* Check to see if only a portion of the read sector needs to be |
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copied. */ |
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✓✓ |
148121 |
if (copy_bytes > bytes_remaining) |
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{ |
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/* Adjust the number of bytes to copy. */ |
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97440 |
copy_bytes = bytes_remaining; |
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} |
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/* Actually perform the memory copy. */ |
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148121 |
_fx_utility_memory_copy(((UCHAR *)media_ptr -> fx_media_memory_buffer) + /* Use case of memcpy is verified. */ |
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148121 |
file_ptr -> fx_file_current_logical_offset, |
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destination_ptr, copy_bytes); |
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/* Increment the logical sector byte offset. */ |
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148121 |
file_ptr -> fx_file_current_logical_offset = |
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148121 |
file_ptr -> fx_file_current_logical_offset + copy_bytes; |
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/* Adjust the remaining bytes to read. */ |
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148121 |
bytes_remaining = bytes_remaining - copy_bytes; |
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/* Adjust the pointer to the destination buffer. */ |
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148121 |
destination_ptr = destination_ptr + copy_bytes; |
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} |
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else |
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{ |
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/* Attempt to read multiple sectors directly into the destination |
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buffer. */ |
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/* Calculate the number of whole sectors to read directly into |
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the destination buffer. */ |
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30442 |
sectors = (UINT)(bytes_remaining / media_ptr -> fx_media_bytes_per_sector); |
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30442 |
next_cluster = cluster = file_ptr -> fx_file_current_physical_cluster; |
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for (i = (media_ptr -> fx_media_sectors_per_cluster - |
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✓✓ |
31210 |
file_ptr -> fx_file_current_relative_sector); i < sectors; i += media_ptr -> fx_media_sectors_per_cluster) |
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{ |
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status = _fx_utility_FAT_entry_read(media_ptr, cluster, &next_cluster); |
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/* Determine if an error is present. */ |
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✓✓✓✓
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1515 |
if ((status != FX_SUCCESS) || (next_cluster < FX_FAT_ENTRY_START) || |
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✓✓ |
1513 |
(next_cluster > media_ptr -> fx_media_fat_reserved)) |
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{ |
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/* Release media protection. */ |
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3 |
FX_UNPROTECT |
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/* Send error message back to caller. */ |
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✓✓ |
3 |
if (status != FX_SUCCESS) |
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{ |
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1 |
return(status); |
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} |
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else |
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{ |
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return(FX_FILE_CORRUPT); |
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} |
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} |
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✓✓ |
1512 |
if (next_cluster != cluster + 1) |
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{ |
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744 |
break; |
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} |
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else |
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{ |
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768 |
cluster = next_cluster; |
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} |
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} |
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✓✓ |
30439 |
if (i < sectors) |
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{ |
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744 |
sectors = i; |
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} |
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/* Determine if this is a single sector read request. If so, read the sector so it will |
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come from the internal cache. */ |
265 |
✓✓ |
30439 |
if (sectors == 1) |
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{ |
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/* Read the current logical sector. */ |
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29188 |
status = _fx_utility_logical_sector_read(media_ptr, |
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file_ptr -> fx_file_current_logical_sector, |
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29188 |
media_ptr -> fx_media_memory_buffer, ((ULONG) 1), FX_DATA_SECTOR); |
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/* Check for good completion status. */ |
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✓✓ |
29188 |
if (status != FX_SUCCESS) |
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{ |
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/* Release media protection. */ |
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1054 |
FX_UNPROTECT |
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280 |
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/* Return the error status. */ |
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1054 |
return(status); |
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} |
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284 |
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/* Actually perform the memory copy. */ |
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28134 |
_fx_utility_memory_copy((UCHAR *)media_ptr -> fx_media_memory_buffer, destination_ptr, media_ptr -> fx_media_bytes_per_sector); /* Use case of memcpy is verified. */ |
286 |
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} |
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else |
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{ |
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/* Multiple sector read request. Read all the sectors at once. */ |
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292 |
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/* Perform the data read directly into the user's buffer of |
293 |
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the appropriate number of sectors. */ |
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1251 |
media_ptr -> fx_media_disable_burst_cache = file_ptr -> fx_file_disable_burst_cache; |
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1251 |
status = _fx_utility_logical_sector_read(media_ptr, file_ptr -> fx_file_current_logical_sector, |
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destination_ptr, (ULONG) sectors, FX_DATA_SECTOR); |
297 |
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1251 |
media_ptr -> fx_media_disable_burst_cache = FX_FALSE; |
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299 |
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/* Check for good completion status. */ |
300 |
✓✓ |
1251 |
if (status != FX_SUCCESS) |
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{ |
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/* Release media protection. */ |
304 |
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1 |
FX_UNPROTECT |
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306 |
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/* Return the error status. */ |
307 |
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1 |
return(status); |
308 |
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} |
309 |
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} |
310 |
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311 |
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/* Now adjust the various file pointers. */ |
312 |
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313 |
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/* Increment the current logical sector. Subtract one from |
314 |
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the sector count because we are going to use the logical |
315 |
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offset to do additional sector/cluster arithmetic below. */ |
316 |
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29384 |
file_ptr -> fx_file_current_logical_sector = |
317 |
|
29384 |
file_ptr -> fx_file_current_logical_sector + |
318 |
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29384 |
(sectors - 1); |
319 |
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320 |
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/* Move the relative sector and cluster as well. */ |
321 |
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29384 |
file_ptr -> fx_file_current_relative_cluster = file_ptr -> fx_file_current_relative_cluster + |
322 |
|
29384 |
(file_ptr -> fx_file_current_relative_sector + (sectors - 1)) / |
323 |
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29384 |
media_ptr -> fx_media_sectors_per_cluster; |
324 |
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325 |
|
29384 |
file_ptr -> fx_file_current_relative_sector = |
326 |
|
29384 |
(file_ptr -> fx_file_current_relative_sector + |
327 |
|
29384 |
(sectors - 1)) % media_ptr -> fx_media_sectors_per_cluster; |
328 |
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329 |
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/* Increment the logical sector byte offset. */ |
330 |
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29384 |
file_ptr -> fx_file_current_logical_offset = |
331 |
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29384 |
media_ptr -> fx_media_bytes_per_sector; |
332 |
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333 |
|
29384 |
file_ptr -> fx_file_current_physical_cluster = cluster; |
334 |
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335 |
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/* Adjust the remaining bytes. */ |
336 |
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29384 |
bytes_remaining = bytes_remaining - |
337 |
|
29384 |
(((ULONG)media_ptr -> fx_media_bytes_per_sector) * sectors); |
338 |
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339 |
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/* Adjust the pointer to the destination buffer. */ |
340 |
|
29384 |
destination_ptr = destination_ptr + |
341 |
|
29384 |
(((ULONG)media_ptr -> fx_media_bytes_per_sector) * sectors); |
342 |
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} |
343 |
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344 |
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/* At this point, we have either read a partial sector or have successfully |
345 |
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read one or more whole sectors. Determine if we are at the end of |
346 |
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the current logical sector. */ |
347 |
|
177505 |
if (file_ptr -> fx_file_current_logical_offset >= |
348 |
✓✓ |
177505 |
media_ptr -> fx_media_bytes_per_sector) |
349 |
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{ |
350 |
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|
351 |
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/* Determine if we are at the exact physical end of the file at the end of reading. */ |
352 |
✓✓ |
80065 |
if ((bytes_remaining == 0) && ((file_ptr -> fx_file_current_file_offset + (ULONG64)request_size) >= |
353 |
✓✓ |
32390 |
file_ptr -> fx_file_current_available_size)) |
354 |
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{ |
355 |
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356 |
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/* Skip the following file parameter adjustments. The next write will |
357 |
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detect the logical offset out of the range of the sector and reset |
358 |
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all of the pertinent information. */ |
359 |
|
17802 |
break; |
360 |
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} |
361 |
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|
362 |
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/* We need to move to the next logical sector, but first |
363 |
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determine if the next logical sector is within the same |
364 |
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cluster. */ |
365 |
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|
366 |
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/* Increment the current relative sector in the cluster. */ |
367 |
|
62263 |
file_ptr -> fx_file_current_relative_sector++; |
368 |
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|
369 |
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/* Determine if this is in a new cluster. */ |
370 |
|
62263 |
if (file_ptr -> fx_file_current_relative_sector >= |
371 |
✓✓ |
62263 |
media_ptr -> fx_media_sectors_per_cluster) |
372 |
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{ |
373 |
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374 |
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/* Read the FAT entry of the current cluster to find |
375 |
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the next cluster. */ |
376 |
|
55719 |
status = _fx_utility_FAT_entry_read(media_ptr, |
377 |
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file_ptr -> fx_file_current_physical_cluster, &next_cluster); |
378 |
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|
379 |
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/* Determine if an error is present. */ |
380 |
✓✓✓✓
|
55719 |
if ((status != FX_SUCCESS) || (next_cluster < FX_FAT_ENTRY_START) || |
381 |
✓✓ |
51754 |
(next_cluster > media_ptr -> fx_media_fat_reserved)) |
382 |
|
|
{ |
383 |
|
|
|
384 |
|
|
/* Release media protection. */ |
385 |
|
28238 |
FX_UNPROTECT |
386 |
|
|
|
387 |
|
|
/* Send error message back to caller. */ |
388 |
✓✓ |
28238 |
if (status != FX_SUCCESS) |
389 |
|
|
{ |
390 |
|
3964 |
return(status); |
391 |
|
|
} |
392 |
|
|
else |
393 |
|
|
{ |
394 |
|
24274 |
return(FX_FILE_CORRUPT); |
395 |
|
|
} |
396 |
|
|
} |
397 |
|
|
|
398 |
|
|
/* Otherwise, we have a new cluster. Save it in the file |
399 |
|
|
control block and calculate a new logical sector value. */ |
400 |
|
27481 |
file_ptr -> fx_file_current_physical_cluster = next_cluster; |
401 |
|
27481 |
file_ptr -> fx_file_current_relative_cluster++; |
402 |
|
27481 |
file_ptr -> fx_file_current_logical_sector = ((ULONG)media_ptr -> fx_media_data_sector_start) + |
403 |
|
27481 |
((((ULONG64)next_cluster) - FX_FAT_ENTRY_START) * |
404 |
|
27481 |
((ULONG)media_ptr -> fx_media_sectors_per_cluster)); |
405 |
|
27481 |
file_ptr -> fx_file_current_relative_sector = 0; |
406 |
|
|
} |
407 |
|
|
else |
408 |
|
|
{ |
409 |
|
|
|
410 |
|
|
/* Still within the same cluster so just increment the |
411 |
|
|
logical sector. */ |
412 |
|
6544 |
file_ptr -> fx_file_current_logical_sector++; |
413 |
|
|
} |
414 |
|
|
|
415 |
|
|
/* In either case, we are now positioned at a new sector so |
416 |
|
|
clear the logical sector offset. */ |
417 |
|
34025 |
file_ptr -> fx_file_current_logical_offset = 0; |
418 |
|
|
} |
419 |
|
|
} |
420 |
|
|
|
421 |
|
|
/* Adjust the current file offset accordingly. */ |
422 |
|
126162 |
file_ptr -> fx_file_current_file_offset = |
423 |
|
126162 |
file_ptr -> fx_file_current_file_offset + (ULONG64)request_size; |
424 |
|
|
|
425 |
|
|
/* Store the number of bytes actually read. */ |
426 |
|
126162 |
*actual_size = request_size; |
427 |
|
|
|
428 |
|
|
/* Update the trace event with the bytes read. */ |
429 |
|
|
FX_TRACE_EVENT_UPDATE(trace_event, trace_timestamp, FX_TRACE_FILE_READ, 0, 0, 0, request_size) |
430 |
|
|
|
431 |
|
|
/* Update the last accessed date. */ |
432 |
|
126162 |
file_ptr -> fx_file_dir_entry.fx_dir_entry_last_accessed_date = _fx_system_date; |
433 |
|
|
|
434 |
|
|
/* Release media protection. */ |
435 |
|
126162 |
FX_UNPROTECT |
436 |
|
|
|
437 |
|
|
/* Return a successful status to the caller. */ |
438 |
|
126162 |
return(FX_SUCCESS); |
439 |
|
|
} |
440 |
|
|
|