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    use crate::marker::PhantomData;
    use crate::slice;

    use libc::{c_void, iovec};

    #[derive(Copy, Clone)]
    #[repr(transparent)]
    pub struct IoSlice<'a> {
        vec: iovec,
        _p: PhantomData<&'a [u8]>,
    }

    impl<'a> IoSlice<'a> {
        #[inline]
        pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
            IoSlice {
                vec: iovec { iov_base: buf.as_ptr() as *mut u8 as *mut c_void, iov_len: buf.len() },
                _p: PhantomData,
            }
        }

        #[inline]
        pub fn advance(&mut self, n: usize) {
            if self.vec.iov_len < n {
                panic!("advancing IoSlice beyond its length");
            }

            unsafe {
                self.vec.iov_len -= n;
                self.vec.iov_base = self.vec.iov_base.add(n);
            }
        }

        #[inline]
        pub fn as_slice(&self) -> &[u8] {
            unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
        }
    }

    #[repr(transparent)]
    pub struct IoSliceMut<'a> {
        vec: iovec,
        _p: PhantomData<&'a mut [u8]>,
    }

    impl<'a> IoSliceMut<'a> {
        #[inline]
        pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
            IoSliceMut {
                vec: iovec { iov_base: buf.as_mut_ptr() as *mut c_void, iov_len: buf.len() },
                _p: PhantomData,
            }
        }

        #[inline]
        pub fn advance(&mut self, n: usize) {
            if self.vec.iov_len < n {
                panic!("advancing IoSliceMut beyond its length");
            }

            unsafe {
                self.vec.iov_len -= n;
                self.vec.iov_base = self.vec.iov_base.add(n);
            }
        }

        #[inline]
        pub fn as_slice(&self) -> &[u8] {
            unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
        }

        #[inline]
        pub fn as_mut_slice(&mut self) -> &mut [u8] {
            unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
        }
    }