Safely ignoring unknown ANSI, ESC/P, ESC/POS sequences, know the length

Question

Some context first:
I'm making a device which transforms an electronic typewriter into a serial printer/terminal. (don't ask why; I know that this does not make much sense practically)
Device inserted between the typewriter's controller and its keyboard.
It can:

• let the keyboard through, transparently,
• obtain keys presses, with or without blocking the typewriter from seeing them,
• insert additional key presses.

With this I can make the typewriter work in different modes:

• normal typewriter,
• typewriter with each typed character logged through the serial port,
• serial printer,
• serial terminal.

For the serial printer/terminal modes I want to accept and understand some of the ANSI (for terminal), ESC/P, ESC/POS (for printer) escape sequences, depending on the mode.

And here comes the problem. Because the device is limited, it is possible to accept a very small subset of the escape sequences, which are possible to perform on the typewriter. I want to simply ignore any unsupported sequences.
The problem is that the sequences have different lengths.
When an unrecognised (by the device) sequence arrives, is there a general way to determine how many bytes long the sequence will be so that I know how many characters to ignore? (some simple rules based on first character(s) for example?)
Or am I forced to prepare a long lookup table (which takes precious flash space) for all possible sequences to always know how many bytes to ignore?

I want to avoid:

• ignoring actual valid data which comes after the sequence and not printing it
• printing parts of the escape sequences on paper
• interpreting parts of unknown sequences as start of a new sequence

Of course, I could define my own sequences but then I would need a custom driver for my device. I prefer to use existing standard.

Edited to Add: as @Raymond Chen shows in the comment below, for ANSI sequences it can be detected where they are terminated. So no problem there. However for the ESC/P sequences (when in printer mode) I haven't noticed a similar way to know it.