capnp 0.25.4

// Copyright (c) 2013-2017 Sandstorm Development Group, Inc. and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// THE SOFTWARE.

//! Helper type for generated Struct and List constants.
//!
//! `constant::Reader` does not do bounds-checking, so it is unsafe to
//! manually construct one of these.

use core::marker::PhantomData;

use crate::any_pointer;
use crate::private::layout::PointerReader;
use crate::traits::Owned;
use crate::Result;

#[derive(Copy, Clone)]
pub struct Reader<T> {
    pub(crate) phantom: PhantomData<T>,
    pub(crate) arena: &'static crate::private::arena::GeneratedCodeArena,
}

impl<T> Reader<T>
where
    T: Owned,
{
    /// Constructs a new `constant::Reader`.
    pub const fn new(arena: &'static crate::private::arena::GeneratedCodeArena) -> Self {
        Self {
            phantom: PhantomData,
            arena,
        }
    }

    /// Retrieve the value.
    pub fn get(&self) -> Result<<T as Owned>::Reader<'static>> {
        any_pointer::Reader::new(PointerReader::get_root_from_arena(self.arena)?).get_as()
    }
}