use crate::alloc::{GlobalAlloc, Layout, System};

use super::waitqueue::SpinMutex;

// Using a SpinMutex because we never want to exit the enclave waiting for the
// allocator.
//
// The current allocator here is the `dlmalloc` crate which we've got included
// in the rust-lang/rust repository as a submodule. The crate is a port of
// dlmalloc.c from C to Rust.
#[cfg_attr(test, linkage = "available_externally")]
#[export_name = "_ZN16__rust_internals3std3sys3sgx5alloc8DLMALLOCE"]
static DLMALLOC: SpinMutex<dlmalloc::Dlmalloc> = SpinMutex::new(dlmalloc::DLMALLOC_INIT);

#[stable(feature = "alloc_system_type", since = "1.28.0")]
unsafe impl GlobalAlloc for System {
    #[inline]
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        // SAFETY: the caller must uphold the safety contract for `malloc`
        unsafe { DLMALLOC.lock().malloc(layout.size(), layout.align()) }
    }

    #[inline]
    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
        // SAFETY: the caller must uphold the safety contract for `malloc`
        unsafe { DLMALLOC.lock().calloc(layout.size(), layout.align()) }
    }

    #[inline]
    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
        // SAFETY: the caller must uphold the safety contract for `malloc`
        unsafe { DLMALLOC.lock().free(ptr, layout.size(), layout.align()) }
    }

    #[inline]
    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
        // SAFETY: the caller must uphold the safety contract for `malloc`
        unsafe { DLMALLOC.lock().realloc(ptr, layout.size(), layout.align(), new_size) }
    }
}

// The following functions are needed by libunwind. These symbols are named
// in pre-link args for the target specification, so keep that in sync.
#[cfg(not(test))]
#[no_mangle]
pub unsafe extern "C" fn __rust_c_alloc(size: usize, align: usize) -> *mut u8 {
    unsafe { crate::alloc::alloc(Layout::from_size_align_unchecked(size, align)) }
}

#[cfg(not(test))]
#[no_mangle]
pub unsafe extern "C" fn __rust_c_dealloc(ptr: *mut u8, size: usize, align: usize) {
    unsafe { crate::alloc::dealloc(ptr, Layout::from_size_align_unchecked(size, align)) }
}
