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#![no_std]

pub struct FastSliceBuffer<const LEN : usize, T> {
	pub data : [T; LEN],
	pub end : usize,
	pub length : usize,
}
impl<const LEN : usize> FastSliceBuffer<LEN, u8> {
    const LEN: usize = LEN;
    const INDEX_MAX: usize = LEN;
    #[inline(always)]
	pub fn capacity_remaining(&self) -> usize {
		Self::LEN - self.length
	}
	
	//Add to the end of the buffer
	//Copy N bytes in from source
    #[inline(never)]
	pub fn add_slice(&mut self, source : &[u8]) {
		let remaining = self.capacity_remaining();
		let num_elements_to_add = source.len().min(remaining);

if num_elements_to_add==0 {
            return;
        }
	
		//We will use exclusive ranges
		let begin_index = self.end;
		self.end += num_elements_to_add;
		self.length += num_elements_to_add;

//Copy as a single segment
		if self.end <= Self::LEN {
			self.data[begin_index..self.end].copy_from_slice(&source[0..num_elements_to_add]);
		}
		//Copy in a two segments
		else {
			let seg_length1 = Self::LEN - begin_index;
			self.data[begin_index..=Self::INDEX_MAX].copy_from_slice(&source[0..seg_length1]);

let seg_length2 = num_elements_to_add - seg_length1;
			self.data[0..seg_length2].copy_from_slice(&source[seg_length1..seg_length1+seg_length2]);
		}

if self.end >= Self::INDEX_MAX {
			self.end -= Self::LEN;
		}
	}
}

#[no_mangle]
pub fn testfunc(){
    let mut buffer = FastSliceBuffer::<16, u8> { data: [0u8;16], end: 16, length: 16};
    buffer.add_slice(&[12u8;10]);
}