Method ReadFromFile

src/GCodes/GCodeInput.cpp:341–386

Read another chunk of G-codes from the file and return true if more data is available

// Read another chunk of G-codes from the file and return true if more data is available
GCodeInputReadResult FileGCodeInput::ReadFromFile(FileData &file) noexcept
{
	size_t bytesCached = RegularGCodeInput::BytesCached();

	// Keep track of the last file we read from
	if (lastFileRead != file)
	{
		if (lastFileRead.IsLive() && bytesCached > 0)
		{
			// Rewind back to the right position so we can resume at the right position later.
			// This may be necessary when nested macros are executed.
			lastFileRead.Seek(lastFileRead.GetPosition() - bytesCached);
		}

		RegularGCodeInput::Reset();
		bytesCached = 0;

		lastFileRead.CopyFrom(file);
	}

	// Read more from the file
	if (bytesCached < GCodeInputFileReadThreshold)
	{
		// Reset the read+write pointers for better performance if possible
		if (readingPointer == writingPointer)
		{
			readingPointer = writingPointer = 0;
		}

		// The code here used to read into a local buffer in blocks that are multiples of 4 bytes.
		// However, unless we can use a buffer of at least 512 bytes then that is redundant,
		// because the data will be copied via the sector buffer in FatFS anyway. So we don't do that any more.
		const int bytesRead = file.Read(buffer + writingPointer, min<size_t>(BufferSpaceLeft(), GCodeInputBufferSize - writingPointer));
		if (bytesRead < 0)
		{
			return GCodeInputReadResult::error;
		}
		if (bytesRead > 0)
		{
			writingPointer = (writingPointer + (size_t)bytesRead) % GCodeInputBufferSize;
			return GCodeInputReadResult::haveData;
		}
	}

	return (bytesCached > 0) ? GCodeInputReadResult::haveData : GCodeInputReadResult::noData;
}

#endif