65 lines
2.2 KiB
Rust
65 lines
2.2 KiB
Rust
// Copyright 2014 The Servo Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/// A static `PhfStrSet`
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///
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/// This trait is implemented by static sets of interned strings generated using
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/// `string_cache_codegen`, and `EmptyStaticAtomSet` for when strings will be added dynamically.
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///
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/// It is used by the methods of [`Atom`] to check if a string is present in the static set.
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///
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/// [`Atom`]: struct.Atom.html
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pub trait StaticAtomSet: Ord {
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/// Get the location of the static string set in the binary.
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fn get() -> &'static PhfStrSet;
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/// Get the index of the empty string, which is in every set and is used for `Atom::default`.
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fn empty_string_index() -> u32;
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}
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/// A string set created using a [perfect hash function], specifically
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/// [Hash, Displace and Compress].
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///
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/// See the CHD document for the meaning of the struct fields.
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///
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/// [perfect hash function]: https://en.wikipedia.org/wiki/Perfect_hash_function
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/// [Hash, Displace and Compress]: http://cmph.sourceforge.net/papers/esa09.pdf
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pub struct PhfStrSet {
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#[doc(hidden)]
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pub key: u64,
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#[doc(hidden)]
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pub disps: &'static [(u32, u32)],
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#[doc(hidden)]
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pub atoms: &'static [&'static str],
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#[doc(hidden)]
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pub hashes: &'static [u32],
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}
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/// An empty static atom set for when only dynamic strings will be added
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#[derive(PartialEq, Eq, PartialOrd, Ord)]
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pub struct EmptyStaticAtomSet;
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impl StaticAtomSet for EmptyStaticAtomSet {
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fn get() -> &'static PhfStrSet {
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// The name is a lie: this set is not empty (it contains the empty string)
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// but that’s only to avoid divisions by zero in rust-phf.
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static SET: PhfStrSet = PhfStrSet {
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key: 0,
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disps: &[(0, 0)],
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atoms: &[""],
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// "" SipHash'd, and xored with u64_hash_to_u32.
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hashes: &[0x3ddddef3],
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};
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&SET
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}
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fn empty_string_index() -> u32 {
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0
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}
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}
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