// Copyright (c) 2021, BlockProject 3D
//
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//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright notice,
//       this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright notice,
//       this list of conditions and the following disclaimer in the documentation
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//       may be used to endorse or promote products derived from this software
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// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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//! Contains various utilities to be used by other modules
//!
//! *this module is not intended for direct use*

use std::num::Wrapping;

/// Hash text using BPX defined hash function for strings
///
/// # Arguments
///
/// * `s` - the string to compute hash for
pub fn hash(s: &str) -> u64
{
    let mut val: Wrapping<u64> = Wrapping(5381);

    for v in s.as_bytes() {
        val = ((val << 5) + val) + Wrapping(*v as u64);
    }
    return val.0;
}

/// Extension to include get_or_insert_with but with support for Result and errors
pub trait OptionExtension<T>
{
    fn get_or_insert_with_err<TError, F: FnOnce() -> Result<T, TError>>(&mut self, f: F) -> Result<&mut T, TError>;
}

impl<T> OptionExtension<T> for Option<T>
{
    fn get_or_insert_with_err<TError, F: FnOnce() -> Result<T, TError>>(&mut self, f: F) -> Result<&mut T, TError>
    {
        if let None = *self {
            *self = Some(f()?);
        }

        match self {
            Some(v) => Ok(v),
            // SAFETY: a `None` variant for `self` would have been replaced by a `Some`
            // variant in the code above.
            None => unsafe { std::hint::unreachable_unchecked() }
        }
    }
}
