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