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use super::arc_block::ArcBlock;
use std::alloc::Layout;
#[derive(Debug)]
#[repr(C)]
pub struct ArcBuffer {
block: ArcBlock,
}
#[repr(C)]
struct ArcBufferInner {
length: usize,
first_byte: u8,
}
impl ArcBuffer {
pub fn new(length: usize) -> Self {
Self {
block: if length == 0 {
ArcBlock::null()
} else {
let mut block = ArcBlock::new(
Layout::new::<usize>()
.extend(Layout::array::<u8>(length).unwrap())
.unwrap()
.0
.pad_to_align(),
);
unsafe { *(block.ptr_mut() as *mut usize) = length }
block
},
}
}
pub fn as_slice(&self) -> &[u8] {
unsafe {
if self.block.is_null() {
std::slice::from_raw_parts(core::ptr::NonNull::dangling().as_ptr(), 0)
} else {
let inner = &*(self.block.ptr() as *const ArcBufferInner);
std::slice::from_raw_parts(&inner.first_byte, inner.length)
}
}
}
pub fn as_slice_mut(&mut self) -> &mut [u8] {
unsafe {
if self.block.is_null() {
std::slice::from_raw_parts_mut(core::ptr::NonNull::dangling().as_ptr(), 0)
} else {
let inner = &mut *(self.block.ptr() as *mut ArcBufferInner);
std::slice::from_raw_parts_mut(&mut inner.first_byte, inner.length)
}
}
}
}
impl Default for ArcBuffer {
fn default() -> Self {
Self::new(0)
}
}
impl Clone for ArcBuffer {
fn clone(&self) -> Self {
Self {
block: self.block.clone(),
}
}
}
impl Drop for ArcBuffer {
fn drop(&mut self) {
self.block.drop::<()>();
}
}
impl From<&[u8]> for ArcBuffer {
fn from(slice: &[u8]) -> Self {
let mut buffer = Self::new(slice.len());
buffer.as_slice_mut().copy_from_slice(slice);
buffer
}
}
#[cfg(test)]
mod tests {
use super::*;
fn drop<T>(_: T) {}
#[test]
fn create_buffer() {
ArcBuffer::new(42);
}
#[test]
fn create_zero_sized_buffer() {
ArcBuffer::new(0);
}
#[test]
fn clone() {
let arc = ArcBuffer::new(42);
drop(arc.clone());
drop(arc);
}
#[test]
fn convert_from_vec() {
ArcBuffer::from(vec![0u8; 42].as_slice());
}
#[test]
fn convert_from_string() {
ArcBuffer::from("hello".as_bytes());
}
}