bool_trie.rs.html -- source
Description: Source to the Rust file `src/libcore/unicode/bool_trie.rs`.
Keywords: rust, rustlang, rust-lang

     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

    // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    /// BoolTrie is a trie for representing a set of Unicode codepoints. It is
    /// implemented with postfix compression (sharing of identical child nodes),
    /// which gives both compact size and fast lookup.
    ///
    /// The space of Unicode codepoints is divided into 3 subareas, each
    /// represented by a trie with different depth. In the first (0..0x800), there
    /// is no trie structure at all; each u64 entry corresponds to a bitvector
    /// effectively holding 64 bool values.
    ///
    /// In the second (0x800..0x10000), each child of the root node represents a
    /// 64-wide subrange, but instead of storing the full 64-bit value of the leaf,
    /// the trie stores an 8-bit index into a shared table of leaf values. This
    /// exploits the fact that in reasonable sets, many such leaves can be shared.
    ///
    /// In the third (0x10000..0x110000), each child of the root node represents a
    /// 4096-wide subrange, and the trie stores an 8-bit index into a 64-byte slice
    /// of a child tree. Each of these 64 bytes represents an index into the table
    /// of shared 64-bit leaf values. This exploits the sparse structure in the
    /// non-BMP range of most Unicode sets.
    pub struct BoolTrie {
        // 0..0x800 (corresponding to 1 and 2 byte utf-8 sequences)
        pub r1: [u64; 32],   // leaves

        // 0x800..0x10000 (corresponding to 3 byte utf-8 sequences)
        pub r2: [u8; 992],      // first level
        pub r3: &'static [u64],  // leaves

        // 0x10000..0x110000 (corresponding to 4 byte utf-8 sequences)
        pub r4: [u8; 256],       // first level
        pub r5: &'static [u8],   // second level
        pub r6: &'static [u64],  // leaves
    }
    impl BoolTrie {
        pub fn lookup(&self, c: char) -> bool {
            let c = c as u32;
            if c < 0x800 {
                trie_range_leaf(c, self.r1[(c >> 6) as usize])
            } else if c < 0x10000 {
                let child = self.r2[(c >> 6) as usize - 0x20];
                trie_range_leaf(c, self.r3[child as usize])
            } else {
                let child = self.r4[(c >> 12) as usize - 0x10];
                let leaf = self.r5[((child as usize) << 6) + ((c >> 6) as usize & 0x3f)];
                trie_range_leaf(c, self.r6[leaf as usize])
            }
        }
    }

    pub struct SmallBoolTrie {
        pub(crate) r1: &'static [u8],  // first level
        pub(crate) r2: &'static [u64],  // leaves
    }

    impl SmallBoolTrie {
        pub fn lookup(&self, c: char) -> bool {
            let c = c as u32;
            match self.r1.get((c >> 6) as usize) {
                Some(&child) => trie_range_leaf(c, self.r2[child as usize]),
                None => false,
            }
        }
    }

    fn trie_range_leaf(c: u32, bitmap_chunk: u64) -> bool {
        ((bitmap_chunk >> (c & 63)) & 1) != 0
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g. `str,u8` or `String,struct:Vec,test`)