Function spectrusty_formats::snapshot::ensure_cpu_is_safe_for_snapshot

source · 
pub fn ensure_cpu_is_safe_for_snapshot<C: Cpu, M: ControlUnit + Video + MemoryAccess>(
    cpu: &mut C,
    chip: &mut M
)
Expand description

Makes sure CPU is in a state that is safe for a snapshot, otherwise executes instructions until it’s safe.

In some rare cases, a CPU will be in a state that most snapshot formats are unable to preserve it correctly.

That is while CPU is in a state after:

  • Executing one of the 0xFD or 0xDD prefixes before executing the prefixed instruction, in this instance the “after the prefix” state is being lost, which will end up executing the next instruction in the wrong way.
  • Executing the EI instruction which temporarily prevents interrupts until the next instruction is executed, in this instance the “after EI” state is lost and an interrupt may be accepted while it shouldn’t be just yet.