Reading and Writing

Before we can draw anything, we must be able to open a file, read all of its lines and store them in our Buffer.

In main(), the first command line argument is passed to the Editor.startUp() function. If it is non-null, the file will be opened if existing.

To handle read/write operations, we'll use the Io.Reader and Io.Writer interfaces. They have methods to process incoming/outcoming data and can do buffered reading and writing. They are interfaces, meaning that independently from what they are attached to, they have the same way of operating. So if you read from stdin or from a file, you'll have access to the same ways of processing data.

They have been only recently added to the Zig standard library and are a vast subject, so I will only mention that they exist, and that we'll be using them for some tasks.

For now we can only read a file, because we don't have the means to fill our Buffer rows yet.