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/**************************************************************************/ |
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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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/** 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_directory.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_extended_relative_seek 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 positions the internal file pointers to the specified */ |
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/* byte relative offset such that the next read or write operation is */ |
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/* performed there. */ |
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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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/* byte_offset Byte offset of the seek */ |
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/* seek_from Direction for relative seek, */ |
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/* legal values are: */ |
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/* */ |
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/* FX_SEEK_BEGIN */ |
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/* FX_SEEK_END */ |
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/* FX_SEEK_FORWARD */ |
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/* FX_SEEK_BACK */ |
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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_file_extended_seek Seek to specified position */ |
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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), */ |
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/* resulting in version 6.1 */ |
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/* */ |
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/**************************************************************************/ |
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UINT _fx_file_extended_relative_seek(FX_FILE *file_ptr, ULONG64 byte_offset, UINT seek_from) |
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{ |
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#ifndef FX_MEDIA_STATISTICS_DISABLE |
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FX_MEDIA *media_ptr; |
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/* First, determine if the file is still open. */ |
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✓✓ |
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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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/* Setup pointer to media structure. */ |
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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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media_ptr -> fx_media_file_relative_seeks++; |
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#endif |
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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_RELATIVE_SEEK, file_ptr, byte_offset, seek_from, file_ptr -> fx_file_current_file_offset, FX_TRACE_FILE_EVENTS, 0, 0) |
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/* Determine if seeking from the beginning is requested. */ |
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✓✓ |
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if (seek_from == FX_SEEK_BEGIN) |
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{ |
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/* Yes, use the base file seek routine to seek from the beginning of |
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the file. */ |
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return(_fx_file_extended_seek(file_ptr, byte_offset)); |
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} |
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/* Otherwise, determine if seeking from the end is requested. */ |
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✓✓ |
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else if (seek_from == FX_SEEK_END) |
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{ |
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/* Yes, seek from the end of the file. */ |
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/* Determine if the requested seek offset is greater than |
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the file size. */ |
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✓✓ |
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if (byte_offset >= file_ptr -> fx_file_current_file_size) |
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{ |
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/* Yes, just seek to the beginning of the file. */ |
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return(_fx_file_extended_seek(file_ptr, ((ULONG64) 0))); |
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} |
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else |
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{ |
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/* Logically seek from the end of the file. */ |
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return(_fx_file_extended_seek(file_ptr, file_ptr -> fx_file_current_file_size - byte_offset)); |
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} |
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} |
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/* Otherwise, determine if seeking from the current position is requested. */ |
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✓✓ |
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else if (seek_from == FX_SEEK_FORWARD) |
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{ |
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/* Yes, just seek ahead from the current file position. */ |
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return(_fx_file_extended_seek(file_ptr, file_ptr -> fx_file_current_file_offset + byte_offset)); |
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} |
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/* Otherwise, seeking backward from the current position is assumed. */ |
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else |
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{ |
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/* Determine if the backward offset is greater than the current file offset. */ |
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✓✓ |
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if (byte_offset >= file_ptr -> fx_file_current_file_offset) |
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{ |
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/* Yes, just position the file to the beginning. */ |
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return(_fx_file_extended_seek(file_ptr, ((ULONG64) 0))); |
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} |
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else |
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{ |
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/* Seek backward relative to the current position. */ |
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return(_fx_file_extended_seek(file_ptr, file_ptr -> fx_file_current_file_offset - byte_offset)); |
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} |
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} |
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} |
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