freertos-std 0.0.1

A Clone of the Rust Standard Library for FreeRTOS
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use crate::alloc::{GlobalAlloc, Layout, System};

extern "C" {
    pub fn pvPortMalloc( xSize : u32 ) -> *mut u8 ;
    pub fn vPortFree( pv : *mut u8 );
}


#[stable(feature = "alloc_system_type", since = "1.28.0")]
unsafe impl GlobalAlloc for System {
    #[inline]
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        let size_to_alloc = layout.size() + layout.align();
        let allocated_ptr = unsafe {
            pvPortMalloc(size_to_alloc as u32)
        };

        // find padding and aligned_pointer
        // make sure that at least one byte is available in padding to store
        // the padding value (hence the .offset(1))
        let padding = allocated_ptr.offset(1).align_offset(layout.align()) + 1;
        let aligned_ptr = allocated_ptr.offset(padding as isize);

        // store padding just before the aligned_ptr
        unsafe {
            *aligned_ptr.offset(-1) = padding as u8;
        }

        aligned_ptr
    }

    #[inline]
    unsafe fn dealloc(&self, aligned_ptr: *mut u8, _layout: Layout) {
        unsafe {
            let padding = *aligned_ptr.offset(-1) as isize;
            let original_ptr = aligned_ptr.offset(-1 * padding);
            vPortFree(original_ptr);
        }
    }

}