Add the runrom crate and the vnf library

The vnf library supports the runrom crate and they both combined enable
users to "run" a ROM file. This is basically an emulator, but with two
key differences:

1. It is to be run programatically. That is, you are not expected to
   play games with this, but to run code by steps, start at a given
   address, run a function, etc.
2. It is headless: there are no graphics displayed on screen, nor sound
   being delivered.

Thus, the target for both these things are developers, not players. This
way developers can validate code paths without needing a full blown
emulator. You can write tests with this and be able to run some checks
as part of your testing infrastructure.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/xixanta/src/opcodes.rs b/lib/xixanta/src/opcodes.rs
index d5bb97a..a296aa5 100644
--- a/lib/xixanta/src/opcodes.rs
+++ b/lib/xixanta/src/opcodes.rs
@@ -96,6 +96,10 @@ pub enum InstructionIdentifier {
     Txa,
     Txs,
     Tya,
+
+    // Pseudo-instructions used by 'vnf'.
+    Start,
+    Unknown,
 }
 
 /// An entry to the 'INSTRUCTIONS' map, which holds some values relevant for
@@ -215,6 +219,8 @@ impl Instruction {
             InstructionIdentifier::Txa => "txa",
             InstructionIdentifier::Txs => "txs",
             InstructionIdentifier::Tya => "tya",
+            InstructionIdentifier::Start => "<start>",
+            InstructionIdentifier::Unknown => "<unknown>",
         };
 
         // On most addressing modes, if the current value is actually found on