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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 */
/** */
/** File */
/** */
/**************************************************************************/
/**************************************************************************/
#define FX_SOURCE_CODE
/* Include necessary system files. */
#include "fx_api.h"
#include "fx_system.h"
#include "fx_directory.h"
#include "fx_file.h"
#include "fx_utility.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _fx_file_extended_relative_seek PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function positions the internal file pointers to the specified */
/* byte relative offset such that the next read or write operation is */
/* performed there. */
/* */
/* INPUT */
/* */
/* file_ptr File control block pointer */
/* byte_offset Byte offset of the seek */
/* seek_from Direction for relative seek, */
/* legal values are: */
/* */
/* FX_SEEK_BEGIN */
/* FX_SEEK_END */
/* FX_SEEK_FORWARD */
/* FX_SEEK_BACK */
/* */
/* OUTPUT */
/* */
/* return status */
/* */
/* CALLS */
/* */
/* _fx_file_extended_seek Seek to specified position */
/* */
/* CALLED BY */
/* */
/* Application Code */
/* */
/* 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 */
/* */
/**************************************************************************/
UINT _fx_file_extended_relative_seek(FX_FILE *file_ptr, ULONG64 byte_offset, UINT seek_from)
{
#ifndef FX_MEDIA_STATISTICS_DISABLE
FX_MEDIA *media_ptr;
/* First, determine if the file is still open. */
if (file_ptr -> fx_file_id != FX_FILE_ID)
{
/* Return the file not open error status. */
return(FX_NOT_OPEN);
}
/* Setup pointer to media structure. */
media_ptr = file_ptr -> fx_file_media_ptr;
/* Increment the number of times this service has been called. */
media_ptr -> fx_media_file_relative_seeks++;
#endif
/* If trace is enabled, insert this event into the trace buffer. */
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)
/* Determine if seeking from the beginning is requested. */
if (seek_from == FX_SEEK_BEGIN)
{
/* Yes, use the base file seek routine to seek from the beginning of
the file. */
return(_fx_file_extended_seek(file_ptr, byte_offset));
}
/* Otherwise, determine if seeking from the end is requested. */
else if (seek_from == FX_SEEK_END)
{
/* Yes, seek from the end of the file. */
/* Determine if the requested seek offset is greater than
the file size. */
if (byte_offset >= file_ptr -> fx_file_current_file_size)
{
/* Yes, just seek to the beginning of the file. */
return(_fx_file_extended_seek(file_ptr, ((ULONG64) 0)));
}
else
{
/* Logically seek from the end of the file. */
return(_fx_file_extended_seek(file_ptr, file_ptr -> fx_file_current_file_size - byte_offset));
}
}
/* Otherwise, determine if seeking from the current position is requested. */
else if (seek_from == FX_SEEK_FORWARD)
{
/* Yes, just seek ahead from the current file position. */
return(_fx_file_extended_seek(file_ptr, file_ptr -> fx_file_current_file_offset + byte_offset));
}
/* Otherwise, seeking backward from the current position is assumed. */
else
{
/* Determine if the backward offset is greater than the current file offset. */
if (byte_offset >= file_ptr -> fx_file_current_file_offset)
{
/* Yes, just position the file to the beginning. */
return(_fx_file_extended_seek(file_ptr, ((ULONG64) 0)));
}
else
{
/* Seek backward relative to the current position. */
return(_fx_file_extended_seek(file_ptr, file_ptr -> fx_file_current_file_offset - byte_offset));
}
}
}