ucd_trie/
lib.rs

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1/*!
2The ucd-trie crate provides a compressed trie set specifically tailored for
3Unicode codepoints. The principle use case for such a trie is to represent
4properties defined by Unicode that correspond to sets of Unicode codepoints.
5(These properties are formally called boolean properties or "single valued"
6properties. See
7[UTR#23 S3.3](https://www.unicode.org/reports/tr23/#PropertyTypeDefinitions)
8for more details.)
9
10This crate has two principle types: `TrieSetOwned` and `TrieSetSlice`,
11corresponding to a similar split as there is between `Vec<T>` and `&[T]`.
12`TrieSetOwned` is the only way to construct a trie from a set of Unicode
13codepoints.
14
15The intended use of this library is to embed a static instance of
16`TrieSetSlice` into your source code, and then use its methods as defined in
17this crate to test membership. (The `ucd-generate` tool can likely generate
18this code for you.)
19
20Finally, while this crate uses the standard library by default, it provides
21`no_std` functionality by disabling the `std` feature. When `no_std` is
22enabled, then `TrieSetOwned` is not provided. Instead, only `TrieSetSlice` is
23provided, which means `no_std` crates can still embed tries into their code.
24*/
25
26#![deny(missing_docs)]
27#![cfg_attr(not(feature = "std"), no_std)]
28
29use core::fmt;
30
31#[cfg(feature = "std")]
32pub use crate::owned::{Error, Result, TrieSetOwned};
33
34#[cfg(test)]
35#[allow(dead_code)]
36mod general_category;
37#[cfg(feature = "std")]
38mod owned;
39
40const CHUNK_SIZE: usize = 64;
41
42/// A type alias for `TrieSetSlice<'static>`.
43pub type TrieSet = TrieSetSlice<'static>;
44
45/// A borrowed trie set.
46#[derive(Clone, Copy)]
47pub struct TrieSetSlice<'a> {
48    /// first tree, one level
49    #[doc(hidden)]
50    pub tree1_level1: &'a [u64],
51    /// second tree, first level
52    #[doc(hidden)]
53    pub tree2_level1: &'a [u8],
54    /// second tree, second level
55    #[doc(hidden)]
56    pub tree2_level2: &'a [u64],
57    /// third tree, first level
58    #[doc(hidden)]
59    pub tree3_level1: &'a [u8],
60    /// third tree, second level
61    #[doc(hidden)]
62    pub tree3_level2: &'a [u8],
63    /// third tree, third level
64    #[doc(hidden)]
65    pub tree3_level3: &'a [u64],
66}
67
68impl<'a> fmt::Debug for TrieSetSlice<'a> {
69    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
70        write!(f, "TrieSetSlice(...)")
71    }
72}
73
74impl<'a> TrieSetSlice<'a> {
75    /// Returns true if and only if the given Unicode scalar value is in this
76    /// set.
77    pub fn contains_char(&self, c: char) -> bool {
78        self.contains(c as usize)
79    }
80
81    /// Returns true if and only if the given codepoint is in this set.
82    ///
83    /// If the given value exceeds the codepoint range (i.e., it's greater
84    /// than `0x10FFFF`), then this returns false.
85    pub fn contains_u32(&self, cp: u32) -> bool {
86        if cp > 0x10FFFF {
87            return false;
88        }
89        self.contains(cp as usize)
90    }
91
92    #[inline(always)]
93    fn contains(&self, cp: usize) -> bool {
94        if cp < 0x800 {
95            self.chunk_contains(cp, self.tree1_level1[cp >> 6])
96        } else if cp < 0x10000 {
97            let leaf = match self.tree2_level1.get((cp >> 6) - 0x20) {
98                None => return false,
99                Some(&leaf) => leaf,
100            };
101            self.chunk_contains(cp, self.tree2_level2[leaf as usize])
102        } else {
103            let child = match self.tree3_level1.get((cp >> 12) - 0x10) {
104                None => return false,
105                Some(&child) => child,
106            };
107            let i = ((child as usize) * CHUNK_SIZE) + ((cp >> 6) & 0b111111);
108            let leaf = self.tree3_level2[i];
109            self.chunk_contains(cp, self.tree3_level3[leaf as usize])
110        }
111    }
112
113    #[inline(always)]
114    fn chunk_contains(&self, cp: usize, chunk: u64) -> bool {
115        ((chunk >> (cp & 0b111111)) & 1) == 1
116    }
117}
ucd_trie/lib.rs

ucd_trie/
lib.rs
