1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
use super::chunk;
use super::errors::*;
use super::interner::Interner;
use super::opcode::OpCode;
use super::value::{LoxString, Value};
pub struct VM {
chunk: chunk::Chunk,
// TODO(tazjin): Accessing array elements constantly is not ideal,
// lets see if something clever can be done with iterators.
ip: usize,
stack: Vec<Value>,
strings: Interner,
}
impl VM {
fn push(&mut self, value: Value) {
self.stack.push(value)
}
fn pop(&mut self) -> Value {
self.stack.pop().expect("fatal error: stack empty!")
}
}
macro_rules! with_type {
( $self:ident, $val:ident, $type:pat, $body:expr ) => {
match $val {
$type => $body,
_ => {
return Err(Error {
line: $self.chunk.get_line($self.ip - 1),
kind: ErrorKind::TypeError(format!(
"Expected type {}, but found value: {:?}",
stringify!($type),
$val,
)),
})
}
}
};
}
macro_rules! binary_op {
( $vm:ident, $type:tt, $op:tt ) => {
binary_op!($vm, $type, $type, $op)
};
( $vm:ident, $in_type:tt, $out_type:tt, $op:tt ) => {{
let b = $vm.pop();
let a = $vm.pop();
with_type!($vm, b, Value::$in_type(val_b), {
with_type!($vm, a, Value::$in_type(val_a), {
$vm.push(Value::$out_type(val_a $op val_b))
})
})
}};
}
impl VM {
fn run(&mut self) -> LoxResult<Value> {
loop {
let op = &self.chunk.code[self.ip];
#[cfg(feature = "disassemble")]
chunk::disassemble_instruction(&self.chunk, self.ip);
self.ip += 1;
match op {
OpCode::OpReturn => {
let val = self.pop();
return Ok(self.return_value(val));
}
OpCode::OpConstant(idx) => {
let c = self.chunk.constant(*idx).clone();
self.push(c);
}
OpCode::OpNil => self.push(Value::Nil),
OpCode::OpTrue => self.push(Value::Bool(true)),
OpCode::OpFalse => self.push(Value::Bool(false)),
OpCode::OpNot => {
let v = self.pop();
self.push(Value::Bool(v.is_falsey()));
}
OpCode::OpEqual => {
let b = self.pop();
let a = self.pop();
self.push(Value::Bool(a == b));
}
OpCode::OpLess => binary_op!(self, Number, Bool, <),
OpCode::OpGreater => binary_op!(self, Number, Bool, >),
OpCode::OpNegate => {
let v = self.pop();
with_type!(
self,
v,
Value::Number(num),
self.push(Value::Number(-num))
);
}
OpCode::OpSubtract => binary_op!(self, Number, -),
OpCode::OpMultiply => binary_op!(self, Number, *),
OpCode::OpDivide => binary_op!(self, Number, /),
OpCode::OpAdd => {
let b = self.pop();
let a = self.pop();
match (a, b) {
(Value::String(s_a), Value::String(s_b)) => {
let mut new_s = self.resolve_str(&s_a).to_string();
new_s.push_str(self.resolve_str(&s_b));
self.push(Value::String(new_s.into()));
}
(Value::Number(n_a), Value::Number(n_b)) =>
self.push(Value::Number(n_a + n_b)),
_ => return Err(Error {
line: self.chunk.get_line(self.ip - 1),
kind: ErrorKind::TypeError(
"'+' operator only works on strings and numbers".into()
),
})
}
}
}
#[cfg(feature = "disassemble")]
println!("=> {:?}", self.stack);
}
}
// For some types of values (e.g. interned strings), returns
// should no longer include any references into the interpreter.
fn return_value(&self, val: Value) -> Value {
match val {
Value::String(string @ LoxString::Interned(_)) => {
Value::String(self.resolve_str(&string).to_string().into())
}
_ => val,
}
}
fn resolve_str<'a>(&'a self, string: &'a LoxString) -> &'a str {
match string {
LoxString::Heap(s) => s.as_str(),
LoxString::Interned(id) => self.strings.lookup(*id),
}
}
}
pub fn interpret(strings: Interner, chunk: chunk::Chunk) -> LoxResult<Value> {
let mut vm = VM {
chunk,
strings,
ip: 0,
stack: vec![],
};
vm.run()
}
|
