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    // Copyright 2019 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.

    //! Lookups of unicode properties using minimal perfect hashing.

    use crate::perfect_hash::mph_lookup;
    use crate::tables::*;

    /// Look up the canonical combining class for a codepoint.
    ///
    /// The value returned is as defined in the Unicode Character Database.
    pub fn canonical_combining_class(c: char) -> u8 {
        mph_lookup(
            c.into(),
            CANONICAL_COMBINING_CLASS_SALT,
            CANONICAL_COMBINING_CLASS_KV,
            u8_lookup_fk,
            u8_lookup_fv,
            0,
        )
    }

    pub(crate) fn composition_table(c1: char, c2: char) -> Option<char> {
        if c1 < '\u{10000}' && c2 < '\u{10000}' {
            mph_lookup(
                (c1 as u32) << 16 | (c2 as u32),
                COMPOSITION_TABLE_SALT,
                COMPOSITION_TABLE_KV,
                pair_lookup_fk,
                pair_lookup_fv_opt,
                None,
            )
        } else {
            composition_table_astral(c1, c2)
        }
    }

    pub(crate) fn canonical_fully_decomposed(c: char) -> Option<&'static [char]> {
        mph_lookup(
            c.into(),
            CANONICAL_DECOMPOSED_SALT,
            CANONICAL_DECOMPOSED_KV,
            pair_lookup_fk,
            pair_lookup_fv_opt,
            None,
        )
    }

    pub(crate) fn compatibility_fully_decomposed(c: char) -> Option<&'static [char]> {
        mph_lookup(
            c.into(),
            COMPATIBILITY_DECOMPOSED_SALT,
            COMPATIBILITY_DECOMPOSED_KV,
            pair_lookup_fk,
            pair_lookup_fv_opt,
            None,
        )
    }

    pub(crate) fn cjk_compat_variants_fully_decomposed(c: char) -> Option<&'static [char]> {
        mph_lookup(
            c.into(),
            CJK_COMPAT_VARIANTS_DECOMPOSED_SALT,
            CJK_COMPAT_VARIANTS_DECOMPOSED_KV,
            pair_lookup_fk,
            pair_lookup_fv_opt,
            None,
        )
    }

    /// Return whether the given character is a combining mark (`General_Category=Mark`)
    pub fn is_combining_mark(c: char) -> bool {
        mph_lookup(
            c.into(),
            COMBINING_MARK_SALT,
            COMBINING_MARK_KV,
            bool_lookup_fk,
            bool_lookup_fv,
            false,
        )
    }

    pub fn stream_safe_trailing_nonstarters(c: char) -> usize {
        mph_lookup(
            c.into(),
            TRAILING_NONSTARTERS_SALT,
            TRAILING_NONSTARTERS_KV,
            u8_lookup_fk,
            u8_lookup_fv,
            0,
        ) as usize
    }

    /// Extract the key in a 24 bit key and 8 bit value packed in a u32.
    #[inline]
    fn u8_lookup_fk(kv: u32) -> u32 {
        kv >> 8
    }

    /// Extract the value in a 24 bit key and 8 bit value packed in a u32.
    #[inline]
    fn u8_lookup_fv(kv: u32) -> u8 {
        (kv & 0xff) as u8
    }

    /// Extract the key for a boolean lookup.
    #[inline]
    fn bool_lookup_fk(kv: u32) -> u32 {
        kv
    }

    /// Extract the value for a boolean lookup.
    #[inline]
    fn bool_lookup_fv(_kv: u32) -> bool {
        true
    }

    /// Extract the key in a pair.
    #[inline]
    fn pair_lookup_fk<T>(kv: (u32, T)) -> u32 {
        kv.0
    }

    /// Extract the value in a pair, returning an option.
    #[inline]
    fn pair_lookup_fv_opt<T>(kv: (u32, T)) -> Option<T> {
        Some(kv.1)
    }