I have multiple threads reading data from a file, sometimes it is necessary to write data to this file. If I try to open this file for reading and writing, only one thread executes functions. I read something on the internet that you can do this by sending IRP WRITE. Is it possible?
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Open file once, use handle in all functions in your threads.
I tried to share, only the first thread could read and write.
Hello,
opening the file with FILE_SHARE_READ | FILE_SHARE_WRITE did not solve the problem? If it solved the problem, you need to synchronize the threads anyway since reading a block of data that is being modified at the same time is really not a good idea.
opening the file with FILE_SHARE_READ | FILE_SHARE_WRITE did not solve the problem? If it solved the problem, you need to synchronize the threads anyway since reading a block of data that is being modified at the same time is really not a good idea.
When I open the file for reading and writing since I can not even read with a second thread, even using file_share_read flag. so if I'm not mistaken, for this reason I have not tried putting the flag share_write.
but I'll try, thanks for the help ...
but I'll try, thanks for the help ...
Structured data within that file (reading in position 1 and writing data in 15), I need to insert and do not edit the data within that file.
What do you think? at first I did not see a problem ...
What do you think? at first I did not see a problem ...
Show your code that opens the file.
What error are you getting?
If you are absolutely sure you never read and write the same block at once, all should be fine (I hope the Cache Manager will ensure coherency accross multiple threads).
What error are you getting?
If you are absolutely sure you never read and write the same block at once, all should be fine (I hope the Cache Manager will ensure coherency accross multiple threads).
I tested in user mode with FILE_SHARE_WRITE and read flag and also did not work.
The doubt is because the function and ZwWriteFile Zwreadfile has the OFFSET option, then to my mind, if you do not read and write the same data block, I think has no biggie ...
The doubt is because the function and ZwWriteFile Zwreadfile has the OFFSET option, then to my mind, if you do not read and write the same data block, I think has no biggie ...
FileOpen with FILE_READ_DATA, FILE_WRITE_DATA "SYNCHRONIZE" and the flags FILE_SHARE READ AND WRITE ...
I open the file and try to read with the main thread of the program. The reading happens normally. I create a new thread, and pass the handle to try to run some read function is not working.
If I put just file_read_data file_share_read and then works ...
I open the file and try to read with the main thread of the program. The reading happens normally. I create a new thread, and pass the handle to try to run some read function is not working.
If I put just file_read_data file_share_read and then works ...
I open the file and try to read with the main thread of the program. The reading happens normally. I create a new thread, and pass the handle to try to run some read function is not working.Which error code are you getting?