// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use libc::{c_void, c_char, size_t, uintptr_t, free, malloc, realloc};
use unstable::intrinsics::TyDesc;
use unstable::raw;
use sys::size_of;

extern {
    #[rust_stack]
    fn abort();
}

#[inline]
fn get_box_size(body_size: uint, body_align: uint) -> uint {
    let header_size = size_of::<raw::Box<()>>();
    // FIXME (#2699): This alignment calculation is suspicious. Is it right?
    let total_size = align_to(header_size, body_align) + body_size;
    total_size
}

// Rounds |size| to the nearest |alignment|. Invariant: |alignment| is a power
// of two.
#[inline]
fn align_to(size: uint, align: uint) -> uint {
    assert!(align != 0);
    (size + align - 1) & !(align - 1)
}

/// A wrapper around libc::malloc, aborting on out-of-memory
pub unsafe fn malloc_raw(size: uint) -> *c_void {
    #[fixed_stack_segment]; #[inline(never)];

    let p = malloc(size as size_t);
    if p.is_null() {
        // we need a non-allocating way to print an error here
        abort();
    }
    p
}

/// A wrapper around libc::realloc, aborting on out-of-memory
pub unsafe fn realloc_raw(ptr: *mut c_void, size: uint) -> *mut c_void {
    #[fixed_stack_segment]; #[inline(never)];

    let p = realloc(ptr, size as size_t);
    if p.is_null() {
        // we need a non-allocating way to print an error here
        abort();
    }
    p
}

/// The allocator for unique pointers without contained managed pointers.
#[cfg(not(test))]
#[lang="exchange_malloc"]
#[inline]
pub unsafe fn exchange_malloc(size: uintptr_t) -> *c_char {
    malloc_raw(size as uint) as *c_char
}

// FIXME: #7496
#[cfg(not(test))]
#[lang="closure_exchange_malloc"]
#[inline]
pub unsafe fn closure_exchange_malloc_(td: *c_char, size: uintptr_t) -> *c_char {
    closure_exchange_malloc(td, size)
}

#[inline]
pub unsafe fn closure_exchange_malloc(td: *c_char, size: uintptr_t) -> *c_char {
    let td = td as *TyDesc;
    let size = size as uint;

    assert!(td.is_not_null());

    let total_size = get_box_size(size, (*td).align);
    let p = malloc_raw(total_size as uint);

    let box = p as *mut raw::Box<()>;
    (*box).type_desc = td;

    box as *c_char
}

// NB: Calls to free CANNOT be allowed to fail, as throwing an exception from
// inside a landing pad may corrupt the state of the exception handler.
#[cfg(not(test))]
#[lang="exchange_free"]
#[inline]
pub unsafe fn exchange_free_(ptr: *c_char) {
    exchange_free(ptr)
}

pub unsafe fn exchange_free(ptr: *c_char) {
    #[fixed_stack_segment]; #[inline(never)];

    free(ptr as *c_void);
}

#[cfg(test)]
mod bench {
    use extra::test::BenchHarness;

    #[bench]
    fn alloc_owned_small(bh: &mut BenchHarness) {
        do bh.iter {
            ~10;
        }
    }

    #[bench]
    fn alloc_owned_big(bh: &mut BenchHarness) {
        do bh.iter {
            ~[10, ..1000];
        }
    }
}
