Sets and gets and stuff

src/main.rs

@@ -1,72 +1,158 @@
-struct VM<'p> { program: &'p Program, block: u32, ip: u32, stack: Vec<Term>, status: Status }
-
-enum Status {
-    Running,
-    AwaitSyscall(Term),
-    Crash(&'static str),
-    Exit(Term),
+struct VM<'p> { 
+    program: &'p Program, 
+    block: u32, ip: u32, 
+    heap: Heap<'p>,
+    locals: Term,
+    stack: Vec<StackItem>, 
+    status: Status 
 }
 
-#[derive(Clone, Debug)]
-struct Term { atom: u32, args: Vec<Term>, }
-struct Program { blocks: Vec<Block> }
-struct Block { instructions: Vec<Instruction> }
+#[derive(Clone, Copy)]
+enum Status {
+    Running,
+    AwaitSyscall(u32),
+    Crash(&'static str),
+    Exit,
+}
 
+#[derive(Clone, Copy, Debug)]
+enum StackItem {
+    Term(Term),
+    Integer(u32),
+}
+impl StackItem {
+    fn term(self) -> Option<Term> {
+        if let StackItem::Term(t) = self { return Some(t) }
+        return None
+    }
+    
+    fn integer(self) -> Option<u32> {
+        if let StackItem::Integer(u) = self { return Some(u) }
+        return None
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+struct Term { index: u32 }  
+struct Program { 
+    blocks: Vec<BlockData>,
+    types: Vec<TypeData>,
+}
+struct BlockData { instructions: Vec<Instruction> }
+
+struct Block { index: u32 }
+
+#[derive(Debug)]
 enum Instruction {
-    // push Atom to stack, optionally with the current `stack` appended to it
-    Push { atom: u32, cc: bool },  
-    // do a binary operation between the top two stack items
-    BinOp { op: fn(Term, Term) -> Result<Term, &'static str> }, 
-    // expand the top stack item to the stack, failing if its len is not `len`
-    Expand { len: u32 },  
-    // jump to the given block. its stack is the top stack item
-    Call { block: u32 },  
-    // system call. pass the top stack item. get a stack item back
-    Syscall { syscall: u32 },
+    // push NULL to stack
+    PushNull, 
+    // push an integer to the stack
+    PushInteger(u32),
+
+    // push a new term to the stack with the given type
+    PushNew(Type),
+
+    // get the locals register
+    PushLocals,
+    // pop the locals register
+    PopLocals,
+
+    Op11(Op11), // [t1] -> [t2]
+    Op21(Op21), // [t1, t2] -> [t3]
+
+    // assert that the stack has n items and jump to the given block
+    Call { block: u32, n: u32, },  
+    // assert that the stack has n items, clear it, and execute a syscall
+    Syscall { syscall: u32, n: u32 },
+
     // kill the program
     Crash(&'static str),
     // end the program, popping the top stack item
     Exit
 }
 
+
+#[derive(Debug)]
+enum Op11 { Get(u32) }
+
+#[derive(Debug)]
+enum Op21 { Add, Set(u32) }
+
+const TY_NULL: Type = Type { id: 0x0 };
+const NULL: Term = Term { index: 0 };
+
 const SYSCALL_DBG: u32 = 0x1000;
 
 
 fn main() {
-    host_program(&Program {
-        blocks: vec![
-            Block { instructions: vec![ 
-                Instruction::Expand { len: 0 },
-                Instruction::Push { atom: SYSCALL_DBG, cc: false },
-                Instruction::Push { atom: 0xdead0000, cc: false },
-                Instruction::Push { atom: 0x0000ba75, cc: false },
-                Instruction::BinOp { op: binop_add },
-                Instruction::BinOp { op: binop_append },
-                Instruction::Syscall { syscall: SYSCALL_DBG },
-                Instruction::Push { atom: 0x0, cc: false },
+    let mut program = Program::new();
+    let ty_locals = program.type_create(3);
+    program.block_create(
+        BlockData { 
+            instructions: vec![ 
+                Instruction::PushNew(ty_locals), Instruction::PopLocals, 
+                
+                Instruction::PushLocals, 
+                Instruction::PushInteger(0xdead0000), Instruction::Op21(Op21::Set(0)),
+                Instruction::PushInteger(0x0000ba75), Instruction::Op21(Op21::Set(1)),
+                // stack: [locals]
+
+                Instruction::Call { block: 1, n: 1 },
+            ]
+        }
+    );
+
+    program.block_create(
+        BlockData {
+            instructions: vec![
+                Instruction::PopLocals,
+
+                Instruction::PushLocals,
+                    Instruction::PushLocals, Instruction::Op11(Op11::Get(0)),
+                    Instruction::PushLocals, Instruction::Op11(Op11::Get(1)),
+                Instruction::Op21(Op21::Add),
+                Instruction::Op21(Op21::Set(2)),
+
+                Instruction::Call { block: 2, n: 1 }
+            ]
+        }
+    );
+
+    program.block_create(
+        BlockData { 
+            instructions: vec![
+                Instruction::PopLocals,
+
+                Instruction::PushLocals,
+                Instruction::Op11(Op11::Get(0)),
+                Instruction::Syscall { syscall: SYSCALL_DBG, n: 1 },
+
                 Instruction::Exit,
-            ]}
-        ]
-    }).unwrap();
+            ]
+        }
+    );
+
+    host_program(&program).unwrap()
 }
 
-fn host_program(p: &Program) -> Result<Term, String> {
+fn host_program(p: &Program) -> Result<(), String> {
     let mut vm = VM::start(p);
     loop {
         let status = vm.step();
         match status {
             Status::Running => {} 
-            Status::AwaitSyscall(sc) => {
-                match sc.atom {
+            Status::AwaitSyscall(ix) => {
+                match ix {
                     SYSCALL_DBG => { 
-                        println!("debug print: {:08x?}", sc.args[0].atom); 
-                        vm.complete_syscall(None)
+                        let top = vm.stack.pop().ok_or("should be an item on the stack")?;
+                        println!("debug print: {:08x?}", top);
+                        vm.complete_syscall()
                     }
-                    _ => { return Err(format!("unknown syscall: {}", sc.atom)) }
+                    _ => { return Err(format!("unknown syscall: {}", ix)) }
                 }
             }
             Status::Crash(err) => { return Err(err.to_string()); }
-            Status::Exit(t) => { return Ok(t.clone()); }
+            Status::Exit => { return Ok(()); }
         }
     }
 }
@@ -74,23 +160,26 @@ fn host_program(p: &Program) -> Result<Term, String> {
 
 impl<'p> VM<'p> {
     pub fn start(program: &'p Program) -> VM<'p> {
+        let mut heap = Heap::new(program);
+
         VM {
             program,
             block: 0,
             ip: 0,
-            stack: vec![Term { atom: 0, args: vec![] }],
+            heap,
+            locals: NULL,
+            stack: vec![],
             status: Status::Running,
-
         }
     }
 
-    pub fn step<'a>(&'a mut self) -> &'a Status {
+    pub fn step(&mut self) -> Status {
         let error = match self.internal_step() {
-            Ok(_) => { return &self.status; }
+            Ok(_) => { return self.status; }
             Err(e) => e
         };
         self.status = Status::Crash(error);
-        return &self.status
+        self.status
     }
     fn internal_step(&mut self) -> Result<(), &'static str> {
         if let Status::Running = self.status { } else { return Ok(()); }
@@ -100,52 +189,71 @@ impl<'p> VM<'p> {
                 .blocks.get(self.block as usize).ok_or("block must exist")?
                 .instructions.get(self.ip as usize).ok_or("instruction must exist")?;
         self.ip += 1;
+        println!("instruction: {:?}", instruction);
 
         match instruction {
-            &Instruction::Push { atom, cc } => {
-                let mut term = Term { atom, args: vec![] };
-                if cc { term.args.extend(self.stack.drain(..)) }
-                self.stack.push(term)
+            &Instruction::PushNull => {
+                self.stack.push(StackItem::Term(NULL))
             }
-            Instruction::BinOp { op } => {
+
+            &Instruction::PushInteger(int) => {
+                self.stack.push(StackItem::Integer(int))
+            }
+
+            &Instruction::PushNew(ty) => {
+                let t = self.heap.term_create(ty);
+                self.stack.push(StackItem::Term(t))
+            }
+
+            Instruction::PushLocals => {
+                self.stack.push(StackItem::Term(self.locals))
+            }
+            
+            Instruction::PopLocals => {
+                let t0 = self.stack.pop().ok_or("t0 must be present")?.term().ok_or("t0 must be a term")?;
+                self.locals = t0;
+            }
+
+            Instruction::Op11(op) => {
+                let t0 = self.stack.pop().ok_or("t0 must be present")?;
+                self.stack.push(op.perform(&mut self.heap, t0)?);
+            }
+
+            Instruction::Op21(op) => {
                 let t1 = self.stack.pop().ok_or("t1 must be present")?;
                 let t0 = self.stack.pop().ok_or("t0 must be present")?;
-                self.stack.push(op(t0, t1)?);
+                self.stack.push(op.perform(&mut self.heap, t0, t1)?);
             }
-            &Instruction::Expand { len } => {
-                let term = self.stack.pop().ok_or("term must be present")?;
-                if term.args.len() != len as usize { panic!("term must have {} args", len) }
-            }
-            &Instruction::Call { block } => {
-                let invocation = self.stack.pop().ok_or("invocation must be present")?;
-                if invocation.atom != block { panic!("invocation doesn't match block"); }
-                self.stack.clear();
-                self.stack.push(invocation);
+
+            &Instruction::Call { block, n } => {
+                if self.stack.len() != n as usize {
+                    return Err("stack has wrong number of elements");
+                }
+                self.locals = NULL;
                 self.block = block;
                 self.ip = 0;
 
             }
-            &Instruction::Syscall { syscall } => {
-                let invocation = self.stack.pop().ok_or("invocation must be present")?;
-                if invocation.atom != syscall { panic!("invocation doesn't match syscall"); }
-                self.status = Status::AwaitSyscall(invocation)
+            &Instruction::Syscall { syscall, n } => {
+                if self.stack.len() != n as usize {
+                    return Err("stack has wrong number of elements");
+                }
+                self.status = Status::AwaitSyscall(syscall)
             }
             Instruction::Crash(c) => {
                 panic!("crashed: {}", c)
             }
             Instruction::Exit => {
-                let exit = self.stack.pop().ok_or("exit arg must be present")?;
-                self.status = Status::Exit(exit)
+                self.status = Status::Exit
             }
         }
 
         Ok(())
     }
 
-    pub fn complete_syscall(&mut self, result: Option<Term>) {
+    pub fn complete_syscall(&mut self) {
         match &self.status {
             Status::AwaitSyscall(_) => {
-                if let Some(t) = result { self.stack.push(t); }
                 self.status = Status::Running;
             }, // continue
             _ => { 
@@ -155,12 +263,138 @@ impl<'p> VM<'p> {
     }
 }
 
+impl Op11 {
+    fn perform(&self, heap: &mut Heap, v0: StackItem) -> Result<StackItem, &'static str> {
+        match self {
+            &Op11::Get(ix) => {
+                let t0 = v0.term().ok_or("must be a term")?;
+                Ok(heap.term_get_arg(t0, ix))
+            }
+       }
+    }
 
-fn binop_append(mut t0: Term, mut t1: Term) -> Result<Term, &'static str> {
-    t0.args.push(t1); Ok(t0)
 }
 
-fn binop_add(mut t0: Term, mut t1: Term) -> Result<Term, &'static str> {
-    t0.atom += t1.atom;
-    Ok(t0)
+impl Op21 {
+    fn perform(&self, heap: &mut Heap, v0: StackItem, v1: StackItem) -> Result<StackItem, &'static str> {
+        match self {
+            Op21::Add => {
+                let i0 = v0.integer().ok_or("must be an integer")?;
+                let i1 = v1.integer().ok_or("must be an integer")?;
+                Ok(StackItem::Integer(i0.wrapping_add(i1)))
+            }
+            &Op21::Set(ix) => {
+                let t0 = v0.term().ok_or("must be a term")?;
+                heap.term_set_arg(t0, ix, v1);
+                Ok(v0)
+            }
+        }
+    }
+}
+
+
+impl Program {
+    fn new() -> Program {
+        let mut p = Self {
+            blocks: vec![],
+            types: vec![],
+        };
+        let ty_null = p.type_create(0);
+        assert_eq!(TY_NULL, ty_null);
+        return p
+    }
+
+    fn type_create(&mut self, len: u32) -> Type {
+        let index = self.types.len();
+        self.types.push(TypeData { len });
+        Type { id: index as u32 }
+    }
+
+    fn type_get(&self, ty: Type) -> &TypeData {
+        return self.types.get(ty.id as usize).expect("type should have existed")
+    }
+
+    fn block_create(&mut self, block: BlockData) -> Block {
+        let index = self.blocks.len();
+        self.blocks.push(block);
+        Block { index: index as u32 }
+    }
+}
+
+struct Heap<'p> { 
+    program: &'p Program,
+    data: Vec<HeapItem> 
+}
+
+#[derive(Debug)]
+enum HeapItem {
+    Type(Type),
+    StackItem(StackItem),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+struct Type {
+    id: u32
+}
+
+struct TypeData {
+    len: u32
+}
+
+impl<'p> Heap<'p> {
+    fn new(p: &'p Program) -> Self {
+        let mut h = Heap {
+            program: p,
+            data: vec![],
+        };
+        let null = h.term_create(TY_NULL);
+        assert_eq!(NULL.index, null.index);
+        h
+    }
+
+    fn term_create(&mut self, ty: Type) -> Term {
+        let td = self.program.type_get(ty);
+        let index = self.data.len() as u32;
+        self.data.push(HeapItem::Type(ty));
+        for _ in 0..td.len {
+            self.data.push(HeapItem::StackItem(StackItem::Term(NULL)));
+        }
+        Term { index }
+    }
+
+    fn term_get_type(&self, term: Term) -> Type {
+        let header = self.data.get(term.index as usize).expect("term should have been valid");
+        if let &HeapItem::Type(ty) = header {
+            ty
+        } else {
+            panic!("header is invalid: {:?}", header)
+        }
+    }
+
+    fn term_get_arg(&self, term: Term, ix: u32) -> StackItem {
+        let ty = self.term_get_type(term);
+        let td = self.program.type_get(ty);
+
+        if ix < td.len {
+            let value = self.data.get((term.index + ix + 1) as usize).expect("should have been present");
+            match value {
+                &HeapItem::StackItem(si) => si,
+                _ => panic!("should have been a StackItem")
+            }
+        } else {
+            panic!("invalid ix: {}", ix)
+        }
+    }
+
+    fn term_set_arg(&mut self, term: Term, ix: u32, arg: StackItem) {
+        let ty = self.term_get_type(term);
+        let td = self.program.type_get(ty);
+
+        if ix < td.len {
+            let slot = self.data.get_mut((term.index + ix + 1) as usize).expect("should have been present");
+            *slot = HeapItem::StackItem(arg)
+        } else {
+            panic!("invalid ix: {}", ix)
+        }
+    }
 }