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#![no_std]
#![feature(lang_items)]
#![allocator]
#![feature(allocator)]

#[no_mangle]
pub extern "C" fn __rust_allocate(size: usize, align: usize) -> *mut u8 {
    unsafe { imp::allocate(size, align) }
}

#[no_mangle]
pub extern "C" fn __rust_deallocate(ptr: *mut u8, old_size: usize, align: usize) {
    unsafe { imp::deallocate(ptr, old_size, align) }
}

#[no_mangle]
pub extern "C" fn __rust_reallocate(ptr: *mut u8,
                                    old_size: usize,
                                    size: usize,
                                    align: usize)
                                    -> *mut u8 {
    unsafe { imp::reallocate(ptr, old_size, size, align) }
}

#[no_mangle]
pub extern "C" fn __rust_reallocate_inplace(ptr: *mut u8,
                                            old_size: usize,
                                            size: usize,
                                            align: usize)
                                            -> usize {
    unsafe { imp::reallocate_inplace(ptr, old_size, size, align) }
}

#[no_mangle]
pub extern "C" fn __rust_usable_size(size: usize, align: usize) -> usize {
    imp::usable_size(size, align)
}

mod imp {

    extern "C" {
        fn malloc(size: usize) -> *mut u8;
        fn realloc(ptr: *mut u8, size: usize) -> *mut u8;
        fn free(ptr: *mut u8);
    }

    pub unsafe fn allocate(size: usize, _: usize) -> *mut u8 {
        malloc(size)
    }

    pub unsafe fn reallocate(ptr: *mut u8, _: usize, size: usize, _: usize) -> *mut u8 {
        realloc(ptr, size)
    }

    pub unsafe fn reallocate_inplace(_ptr: *mut u8,
                                     old_size: usize,
                                     _size: usize,
                                     _align: usize)
                                     -> usize {
        old_size
    }

    pub unsafe fn deallocate(ptr: *mut u8, _: usize, _: usize) {
        free(ptr)
    }

    pub fn usable_size(size: usize, _align: usize) -> usize {
        size
    }
}