How to allow multiple files to be open at the same time using FileX

Joe Noonan 0

Hi,

I am trying to find a way to allow multiple files to be open at the same time using FileX.

If I try to open a seconda file without closing the first then I get FX_NOT_FOUND.

Is there any way to allow multiple files to be open at the same time?

Thanks.

LeelaRajeshSayana-MSFT 13,871 Reputation points

2023-10-25T20:07:02.29+00:00
Hi @Joe Noonan Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here.

May I know how you are trying to open the file using FileX? As per the documentation on FileX fx_file_open, a file may be opened for reading multiple times, while a file can only be opened for writing once until the writer closes the file. It implies that multiple files can be opened for reading. However, a single file can be opened at a given time for write access. Please refer the below code sample to see how to open the file with read access.

FX_MEDIA my_media; FX_FILE my_file; UINT status; /* Open the file "myfile.txt" for reading. */ status = fx_file_open(&my_media, &my_file, "myfile.txt", FX_OPEN_FOR_READ); /* If status equals FX_SUCCESS, file "myfile.txt" is now open and may be accessed now with the my_file pointer. */

Kindly note that care must be taken if a file is concurrently open for reading and writing. File writing performed when a file is simultaneously opened for reading may not be seen by the reader, unless the reader closes and reopens the file for reading. Similarly, the file writer should be careful when using file truncate services. If a file is truncated by the writer, readers of the same file could return invalid data.

Hope this helps. Please let us know if you have any additional questions or need further assistance on this.

Joe Noonan 0

This doesn't really help no. I don't need to read and write at the same time I only need to open multiple files at the same time but FileX does not allow me to.

Below is a rough code snippet - when I open the second file it does not open and gives me FX_NOT_FOUND.

Thanks.

static uint8_t media_memory[SECTOR_SIZE / sizeof(uint8_t)];
  
fx_media_open(&fxmSDCard, "/", fx_stm32_sd_driver, (VOID *)FX_NULL, (VOID *) media_memory, sizeof(media_memory));

FX_FILE fx_file1;
uint32_t result = fx_file_open(&fxmSDCard, fx_file1, "test1.txt", FX_OPEN_FOR_READ);

ULONG bytesRead = 0u;
uint8_t* data = {0}
fx_file_read(fx_file1, data, 512, &bytesRead))
	  
FX_FILE fx_file2;
result = fx_file_open(&fxmSDCard, fx_file2, "test2.txt", FX_OPEN_FOR_READ);

Joe Noonan 0 Reputation points

2023-10-26T08:32:49.2866667+00:00

Also, I cannot seem to find anything in the sparse documentation about opening multiple files at the same time only the same file for writing and reading.

Also I am using FileX in standalone mode.
LeelaRajeshSayana-MSFT 13,871 Reputation points

2023-10-26T14:29:45.0666667+00:00

Hi @Joe Noonan Thank you for your feedback and sharing additional details. I will check this issue with the product team internally and get back to you with more details on this. Please stay tuned to this thread for updates.
Joe Noonan 0 Reputation points

2023-11-02T09:20:14.6733333+00:00

Hi @LeelaRajeshSayana-MSFT , I have found the problem. My default directory was not what I expected. I had another function that was searching the SD card, when I also wanted to open a file in root, that's why it was NOT_FOUND. I added a "/" to the file name as its in root.

Still a question remains on how many files can be opened at the same time? Others online have mentioned FX_MAX_FILE_OPENINGS in filex.cfg but neither exists in my project (STM32 based). So how do I know how many files I can open? I am running in standalone mode. Is it dynamic memory allocation when opening files, and once I run out of memory that's it?

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How to allow multiple files to be open at the same time using FileX