// Copyright 2019 Octavian Oncescu

#![no_std]

//! A drop-in global allocator wrapper around the [mimalloc](https://github.com/microsoft/mimalloc) allocator.
//! Mimalloc is a general purpose, performance oriented allocator built by Microsoft.
//!
//! ## Usage
//! ```rust,ignore
//! use mimalloc::MiMalloc;
//!
//! #[global_allocator]
//! static GLOBAL: MiMalloc = MiMalloc;
//! ```
//!
//! ## Usage without secure mode
//! By default this library builds mimalloc in secure mode. This means that
//! heap allocations are encrypted, but this results in a 3% increase in overhead.
//!
//! To disable secure mode, in `Cargo.toml`:
//! ```rust,ignore
//! [dependencies]
//! mimalloc = { version = "*", default-features = false }
//! ```

extern crate libmimalloc_sys as ffi;

use core::alloc::{GlobalAlloc, Layout};
use core::ffi::c_void;
use ffi::*;

/// Drop-in mimalloc global allocator.
///
/// ## Usage
/// ```rust,ignore
/// use mimalloc::MiMalloc;
///
/// #[global_allocator]
/// static GLOBAL: MiMalloc = MiMalloc;
/// ```
pub struct MiMalloc;

unsafe impl GlobalAlloc for MiMalloc {
    #[inline]
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        mi_malloc_aligned(layout.size(), layout.align()) as *mut u8
    }

    #[inline]
    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
        mi_zalloc_aligned(layout.size(), layout.align()) as *mut u8
    }

    #[inline]
    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
        mi_free(ptr as *mut c_void);
    }

    #[inline]
    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
        mi_realloc_aligned(ptr as *mut c_void, new_size, layout.align()) as *mut u8
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_frees_allocated_memory() {
        unsafe {
            let layout = Layout::from_size_align(8, 8).unwrap();
            let alloc = MiMalloc;

            let ptr = alloc.alloc(layout);
            alloc.dealloc(ptr, layout);
        }
    }

    #[test]
    fn it_frees_allocated_big_memory() {
        unsafe {
            let layout = Layout::from_size_align(1 << 20, 32).unwrap();
            let alloc = MiMalloc;

            let ptr = alloc.alloc(layout);
            alloc.dealloc(ptr, layout);
        }
    }

    #[test]
    fn it_frees_zero_allocated_memory() {
        unsafe {
            let layout = Layout::from_size_align(8, 8).unwrap();
            let alloc = MiMalloc;

            let ptr = alloc.alloc_zeroed(layout);
            alloc.dealloc(ptr, layout);
        }
    }

    #[test]
    fn it_frees_zero_allocated_big_memory() {
        unsafe {
            let layout = Layout::from_size_align(1 << 20, 32).unwrap();
            let alloc = MiMalloc;

            let ptr = alloc.alloc_zeroed(layout);
            alloc.dealloc(ptr, layout);
        }
    }

    #[test]
    fn it_frees_reallocated_memory() {
        unsafe {
            let layout = Layout::from_size_align(8, 8).unwrap();
            let alloc = MiMalloc;

            let ptr = alloc.alloc(layout);
            let ptr = alloc.realloc(ptr, layout, 16);
            alloc.dealloc(ptr, layout);
        }
    }

    #[test]
    fn it_frees_reallocated_big_memory() {
        unsafe {
            let layout = Layout::from_size_align(1 << 20, 32).unwrap();
            let alloc = MiMalloc;

            let ptr = alloc.alloc(layout);
            let ptr = alloc.realloc(ptr, layout, 2 << 20);
            alloc.dealloc(ptr, layout);
        }
    }
}
