Function snippetForFileRead

Tests/Libraries/Async/AsyncTest.cpp:603–669

}

SC::Result snippetForFileRead(AsyncEventLoop& eventLoop, Console& console)
{
ThreadPool threadPool;
SC_TRY(threadPool.create(4));
//! [AsyncFileReadSnippet]
// Assuming an already created (and running) AsyncEventLoop named `eventLoop`
// ...

// Assuming an already created threadPool named `threadPool`
// ...

// Open the file
FileDescriptor fd;
FileOpen openMode;
openMode.mode = FileOpen::Read;
openMode.blocking = true; // AsyncFileRead::Task enables using regular blocking file descriptors
SC_TRY(fd.open("MyFile.txt", openMode));

// Create the async file read request and async task
AsyncFileRead asyncReadFile;
asyncReadFile.callback = [&](AsyncFileRead::Result& res)
{
    Span<char> readData;
    if(res.get(readData))
    {
        if(res.completionData.endOfFile)
        {
            // Last callback invocation done when end of file has been reached
            // - completionData.endOfFile is == true
            // - readData.sizeInBytes() is == 0
            console.print("End of file reached");
        }
        else
        {
            // readData is a slice of receivedData with the received bytes
            console.print("Read {} bytes from file", readData.sizeInBytes());
            
            // OPTIONAL: Update file offset to receive a different range of bytes
            res.getAsync().setOffset(res.getAsync().getOffset()  + readData.sizeInBytes());
            
            // IMPORTANT: Reactivate the request to receive more data
            res.reactivateRequest(true);
        }
    }
    else
    {
        // Some error occurred, check res.returnCode
    }
};
char buffer[100] = {0};
asyncReadFile.buffer = {buffer, sizeof(buffer)};
// Obtain file descriptor handle and associate it with event loop
SC_TRY(fd.get(asyncReadFile.handle, Result::Error("Invalid handle")));

// Start the operation on a thread pool
AsyncTaskSequence asyncFileTask;
SC_TRY(asyncReadFile.executeOn(asyncFileTask, threadPool));
SC_TRY(asyncReadFile.start(eventLoop));