lp_solvers/
util.rs

1//! Utilities to help with building problems
2use std::borrow::Cow;
3use std::collections::hash_map::DefaultHasher;
4use std::collections::HashMap;
5use std::hash::{Hash, Hasher};
6
7/// Useful to generate a list of unique valid variable names
8#[derive(Debug, Default)]
9pub struct UniqueNameGenerator {
10    names: HashMap<u64, usize>,
11}
12
13impl UniqueNameGenerator {
14    /// Create a new variable. Returns a valid variable name, never returned before by this generator.
15    ///
16    /// ```
17    /// use lp_solvers::util::UniqueNameGenerator;
18    ///
19    /// let mut gen = UniqueNameGenerator::default();
20    /// assert_eq!(gen.add_variable("x"), "x");
21    /// assert_eq!(gen.add_variable("y"), "y");
22    /// assert_eq!(gen.add_variable("z"), "z");
23    /// assert_eq!(gen.add_variable("!#?/"), "v"); // "!#?/" is not a valid variable name
24    /// assert_eq!(gen.add_variable("x"), "x2"); // A variable with name x is already present
25    /// ```
26    pub fn add_variable<'a>(&mut self, name: &'a str) -> Cow<'a, str> {
27        let mut stem = stem(name);
28        let hash = calculate_hash(&stem);
29        let n = self.names.entry(hash).or_insert(0);
30        *n += 1;
31        if *n >= 2 {
32            stem = Cow::Owned(stem.into_owned() + &n.to_string());
33        }
34        stem
35    }
36}
37
38fn stem(name: &str) -> Cow<'_, str> {
39    if name.contains(|c: char| !c.is_ascii_alphabetic()) || name.is_empty() {
40        let mut owned = name.replace(|c: char| !c.is_ascii_alphabetic(), "");
41        if owned.is_empty() {
42            owned.push('v');
43        }
44        Cow::Owned(owned)
45    } else {
46        Cow::Borrowed(name)
47    }
48}
49
50fn calculate_hash(t: &str) -> u64 {
51    let mut s = DefaultHasher::new();
52    t.hash(&mut s);
53    s.finish()
54}
55
56pub(crate) fn buf_contains(haystack: &[u8], needle: &str) -> bool {
57    let needle = needle.as_bytes();
58    haystack
59        .windows(needle.len())
60        .any(|window| window == needle)
61}
lp_solvers/util.rs

lp_solvers/
util.rs
