use std::mem;

/// Struct that can be used to store a vector of bytes and sent
/// to JS
#[repr(C)]
#[derive(Debug)]
pub struct JsBytes {
    ptr: u32,
    len: u32,
}

impl JsBytes {
    /// Create a new `JsBytes` wrapper consuming the bytes
    pub fn new(mut bytes: Vec<u8>) -> *mut JsBytes {
        bytes.shrink_to_fit();
        let ptr = bytes.as_mut_ptr() as u32;
        let len = bytes.len() as u32;
        mem::forget(bytes);
        let boxed = Box::new(JsBytes { ptr, len });
        Box::into_raw(boxed)
    }

    /// Creates a `Vec` from a raw *mut JsBytes
    pub unsafe fn from_raw(ptr: *mut JsBytes) -> Vec<u8> {
        let boxed: Box<JsBytes> = Box::from_raw(ptr);
        Vec::from_raw_parts(boxed.ptr as *mut u8, boxed.len as usize, boxed.len as usize)
    }
}