The filename of the file to read.
A GC allocated buffer that may be enlarged if it is too small.
The maxmimum amount of bytes to read from the file.
The contents of the file up to maxLen or EOF. The data is a slice of the buffer argument case to a char[].
Reads a file into a given buffer with a specified maximum length. If the file is bigger than the buffer, the buffer will be resized using the GC and updated through the ref argument.