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/***********************************************************************************************************************
 * Copyright (c) 2019 by the authors
 *
 * Author: André Borrmann
 * License: Apache License 2.0
 **********************************************************************************************************************/
#![doc(html_root_url = "https://docs.rs/ruspiro-allocator/0.3.0")]
#![no_std]
#![feature(alloc_error_handler)]
//! # Custom Allocator for HEAP memory allocations
//!
//! This crate provides a custom allocator for heap memory. If any baremetal crate uses functions and structures from
//! the ``alloc`` crate an allocator need to be provided as well. However, this crate does not export any public
//! API to be used. It only encapsulates the memeory allocator that shall be linked into the binary.
//!
//! # Usage
//!
//! To link the custom allocator with your project just add the usage to your main crate rust file like so:
//! ```
//! extern crate ruspiro_allocator;
//! ```
//! Wherever you define the usage of the ``ruspiro-allocator`` crate within your project does not matter. But as soon
//! as this is done the dynamic structures requiring heap memory allocations from the ``alloc`` crate could be used like
//! so:
//! ```
//! #[macro_use]
//! extern crate alloc;
//! use alloc::vec::*;
//! use alloc::boxed::*;
//!
//! fn main() {
//!     let mut v: Vec<u32> = vec![10, 20];
//!     let b: Box<u16> = Box::new(10);
//!     v.push(12);
//! }
//! ```
//!

/// this specifies the custom memory allocator to use whenever heap memory need to be allocated or freed
#[global_allocator]
static ALLOCATOR: RusPiRoAllocator = RusPiRoAllocator;

use core::alloc::{GlobalAlloc, Layout};
use ruspiro_lock::Spinlock;

// define a global static guard to secure concurrent cross core access to the allocator
static GUARD: Spinlock = Spinlock::new();

struct RusPiRoAllocator;

unsafe impl GlobalAlloc for RusPiRoAllocator {
    #[inline]
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        GUARD.aquire();
        let mem = m_alloca(layout.size() as u32, layout.align() as u16);
        GUARD.release();

        mem
    }

    #[inline]
    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
        GUARD.aquire();
        m_freea(ptr);
        GUARD.release();
    }

    #[inline]
    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
        GUARD.aquire();
        let ptr = m_alloca(layout.size() as u32, layout.align() as u16);
        GUARD.release();

        m_memset(ptr, 0x0, layout.size() as u32);
        ptr
    }
}

#[alloc_error_handler]
fn alloc_error_handler(_: Layout) -> ! {
    // TODO: how to handle memory allocation errors?
    loop {}
}

extern "C" {
    // external functions pre-compiled with the build script from c or assembly files
    fn m_alloca(size: u32, align: u16) -> *mut u8;
    fn m_freea(ptr: *mut u8);
    fn m_memset(ptr: *mut u8, value: u32, size: u32);
}