whitespacers/
program.rs

1use num_bigint::BigInt;
2
3use std::cmp::Reverse;
4use std::rc::Rc;
5use std::ops::Range;
6use std::collections::HashMap;
7
8use crate::label::Label;
9
10pub use crate::Program;
11
12#[derive(Debug, Clone)]
13pub struct SourceLoc {
14    pub line: usize,
15    pub column: usize,
16    pub span: Range<usize>,
17    pub label: Option<Rc<Label>>
18}
19
20#[derive(Debug, Clone)]
21pub enum Command {
22    Push {value: Integer},
23    PushBig {value: BigInteger},
24    Duplicate,
25    Copy {index: usize},
26    Swap,
27    Discard,
28    Slide {amount: usize},
29    Add,
30    Subtract,
31    Multiply,
32    Divide,
33    Modulo,
34    Set,
35    Get,
36    Label,
37    Call {index: usize},
38    Jump {index: usize},
39    JumpIfZero {index: usize},
40    JumpIfNegative {index: usize},
41    EndSubroutine,
42    EndProgram,
43    PrintChar,
44    PrintNum,
45    InputChar,
46    InputNum
47}
48
49pub type Integer = isize;
50
51pub type BigInteger = BigInt;
52
53#[derive(Debug, Clone)]
54pub enum SizedInteger {
55    Big(BigInteger),
56    Small(Integer)
57}
58
59impl Program {
60    /// Remove source location information from the program.
61    pub fn strip(&mut self) {
62        self.source = None;
63        self.locs = None;
64    }
65
66    /// Rewrites labels to ensure the resulting program is as small as possible.
67    pub fn minify(&mut self) {
68        // get the source locs, otherwise, invent some new sourcelocs.
69        let locs = if let Some(ref mut locs) = self.locs {
70            locs
71        } else {
72            self.locs = Some(self.commands.iter().map(|_| SourceLoc {line: 0, column: 0, span: 0..0, label: None}).collect());
73            self.locs.as_mut().unwrap()
74        };
75
76        // create an index => times_used map
77        let mut label_count = HashMap::<usize, usize>::new();
78        for (i, op) in self.commands.iter().enumerate() {
79            match *op {
80                Command::Label => *label_count.entry(i + 1).or_insert(0) += 1,
81                Command::Call {index}
82                | Command::Jump {index}
83                | Command::JumpIfZero {index}
84                | Command::JumpIfNegative {index} => *label_count.entry(index).or_insert(0) += 1,
85                _ => ()
86            }
87        }
88
89        // turn the map into a list of (index, times_used) that is sorted by times_used,
90        // breaking ties by earlier location
91        let mut label_count: Vec<_> = label_count.into_iter().collect();
92        label_count.sort_by_key(|&(index, count)| (Reverse(count), index));
93
94        // create an allocator that produces unique labels, starting from the smallest possible label
95        let mut length = 0usize;
96        let mut value = 0usize;
97        let mut new_label = || {
98            // create label
99            let mut label = Label::new();
100            for i in (0..length).rev() {
101                label.push(value & (1 << i) != 0);
102            }
103            // increment state
104            value += 1;
105            if value == (1 << length) {
106                length += 1;
107                value = 0;
108            }
109            Rc::new(label)
110        };
111
112        // from the sorted list, create a map of index => new_label
113        let label_map: HashMap<_, _> = label_count.iter().map(|&(i, _)| (i, new_label())).collect();
114
115        // and edit locs using them.
116        for ((i, op), loc) in self.commands.iter().enumerate().zip(locs) {
117            match *op {
118                Command::Label => loc.label = Some(label_map[&(i + 1)].clone()),
119                Command::Call {index}
120                | Command::Jump {index}
121                | Command::JumpIfZero {index}
122                | Command::JumpIfNegative {index} => loc.label = Some(label_map[&index].clone()),
123                _ => ()
124            }
125        }
126    }
127}
whitespacers/program.rs

whitespacers/
program.rs
