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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
use std::ops::Deref;
use std::ops::DerefMut;
use std::ops::Range;
use super::transl8::FromV8;
/// A ZeroCopyBuf encapsulates a slice that's been borrowed from a JavaScript
/// ArrayBuffer object. JavaScript objects can normally be garbage collected,
/// but the existence of a ZeroCopyBuf inhibits this until it is dropped. It
/// behaves much like an Arc<[u8]>.
///
/// # Cloning
/// Cloning a ZeroCopyBuf does not clone the contents of the buffer,
/// it creates a new reference to that buffer.
///
/// To actually clone the contents of the buffer do
/// `let copy = Vec::from(&*zero_copy_buf);`
#[derive(Clone)]
pub struct ZeroCopyBuf {
pub(crate) store: v8::SharedRef<v8::BackingStore>,
pub(crate) range: Range<usize>,
}
unsafe impl Send for ZeroCopyBuf {}
impl ZeroCopyBuf {
pub fn from_buffer(
buffer: v8::Local<v8::ArrayBuffer>,
range: Range<usize>,
) -> Result<Self, v8::DataError> {
let store = buffer.get_backing_store();
if store.is_shared() {
return Err(v8::DataError::BadType {
actual: "shared ArrayBufferView",
expected: "non-shared ArrayBufferView",
});
}
Ok(Self { store, range })
}
fn as_slice(&self) -> &[u8] {
unsafe { &*(&self.store[self.range.clone()] as *const _ as *const [u8]) }
}
#[allow(clippy::cast_ref_to_mut)]
fn as_slice_mut(&mut self) -> &mut [u8] {
unsafe { &mut *(&self.store[self.range.clone()] as *const _ as *mut [u8]) }
}
}
pub(crate) fn to_ranged_buffer<'s>(
scope: &mut v8::HandleScope<'s>,
value: v8::Local<v8::Value>,
) -> Result<(v8::Local<'s, v8::ArrayBuffer>, Range<usize>), v8::DataError> {
if value.is_array_buffer_view() {
let view: v8::Local<v8::ArrayBufferView> = value.try_into()?;
let (offset, len) = (view.byte_offset(), view.byte_length());
let buffer = view.buffer(scope).ok_or(v8::DataError::NoData {
expected: "view to have a buffer",
})?;
let buffer = v8::Local::new(scope, buffer); // recreate handle to avoid lifetime issues
return Ok((buffer, offset..offset + len));
}
let b: v8::Local<v8::ArrayBuffer> = value.try_into()?;
let b = v8::Local::new(scope, b); // recreate handle to avoid lifetime issues
Ok((b, 0..b.byte_length()))
}
impl FromV8 for ZeroCopyBuf {
fn from_v8(
scope: &mut v8::HandleScope,
value: v8::Local<v8::Value>,
) -> Result<Self, crate::Error> {
to_ranged_buffer(scope, value)
.and_then(|(b, r)| Self::from_buffer(b, r))
.map_err(|_| crate::Error::ExpectedBuffer)
}
}
impl Deref for ZeroCopyBuf {
type Target = [u8];
fn deref(&self) -> &[u8] {
self.as_slice()
}
}
impl DerefMut for ZeroCopyBuf {
fn deref_mut(&mut self) -> &mut [u8] {
self.as_slice_mut()
}
}
impl AsRef<[u8]> for ZeroCopyBuf {
fn as_ref(&self) -> &[u8] {
self.as_slice()
}
}
impl AsMut<[u8]> for ZeroCopyBuf {
fn as_mut(&mut self) -> &mut [u8] {
self.as_slice_mut()
}
}
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