Brainfuck, on chain, a slice at a time

Demo of p/moul/x/vm/bf (the machine) and p/moul/x/vm/vmkit (the host ABI, the fuel meter, the instance store). This realm holds no logic of its own.

A program here does not run to completion. It runs until its fuel slice is spent, then pauses: the realm keeps the snapshot and the next caller pays for the next slice. Realm code cannot pause itself, and a guest can.

Samples

Hello World: 385 guest ops, five tape cells. Finishes in one slice.

++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.

Upload Hello World

Echo the input: Reads through Host.Input, which is what the naive interpreter could not do at all: it panicked on ,.

,[.,]

Upload Echo the input

Heavy loop: About 111k guest ops. Give it 20000 fuel and it takes six slices, which is the point.

++++++++++[->++++++++++[->++++++++++[-]<]<]

Upload Heavy loop

Instances

id	status	fuel used	slices	output
0000001	halted	32	1	Hello World

Limits

limit	value
instances	64
source bytes	65536
input bytes	1024
output bytes	4096
fuel per slice	5000000
tape cells	30000