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denoland-deno/serde_v8/magic/bytestring.rs

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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
use super::transl8::{FromV8, ToV8};
use crate::magic::transl8::impl_magic;
use crate::Error;
use smallvec::SmallVec;
use std::mem::size_of;
const USIZE2X: usize = size_of::<usize>() * 2;
#[derive(
PartialEq,
Eq,
Clone,
Debug,
Default,
derive_more::Deref,
derive_more::DerefMut,
derive_more::AsRef,
derive_more::AsMut,
)]
#[as_mut(forward)]
#[as_ref(forward)]
pub struct ByteString(SmallVec<[u8; USIZE2X]>);
impl_magic!(ByteString);
// const-assert that Vec<u8> and SmallVec<[u8; size_of::<usize>() * 2]> have a same size.
// Note from https://docs.rs/smallvec/latest/smallvec/#union -
// smallvec can still be larger than Vec if the inline buffer is
// larger than two machine words.
const _: () =
assert!(size_of::<Vec<u8>>() == size_of::<SmallVec<[u8; USIZE2X]>>());
impl ToV8 for ByteString {
fn to_v8<'a>(
&self,
scope: &mut v8::HandleScope<'a>,
) -> Result<v8::Local<'a, v8::Value>, crate::Error> {
let v =
v8::String::new_from_one_byte(scope, self, v8::NewStringType::Normal)
.unwrap();
Ok(v.into())
}
}
impl FromV8 for ByteString {
fn from_v8(
scope: &mut v8::HandleScope,
value: v8::Local<v8::Value>,
) -> Result<Self, crate::Error> {
let v8str = v8::Local::<v8::String>::try_from(value)
.map_err(|_| Error::ExpectedString)?;
if !v8str.contains_only_onebyte() {
return Err(Error::ExpectedLatin1);
}
let len = v8str.length();
let mut buffer = SmallVec::with_capacity(len);
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#[allow(clippy::uninit_vec)]
// SAFETY: we set length == capacity (see previous line),
// before immediately writing into that buffer and sanity check with an assert
unsafe {
buffer.set_len(len);
let written = v8str.write_one_byte(
scope,
&mut buffer,
0,
v8::WriteOptions::NO_NULL_TERMINATION,
);
assert!(written == len);
}
Ok(Self(buffer))
}
}
// smallvec does not impl From/Into traits
// like Vec<u8> does. So here we are.
impl From<Vec<u8>> for ByteString {
fn from(vec: Vec<u8>) -> Self {
ByteString(SmallVec::from_vec(vec))
}
}
#[allow(clippy::from_over_into)]
impl Into<Vec<u8>> for ByteString {
fn into(self) -> Vec<u8> {
self.0.into_vec()
}
}
impl From<&[u8]> for ByteString {
fn from(s: &[u8]) -> Self {
ByteString(SmallVec::from_slice(s))
}
}
impl From<&str> for ByteString {
fn from(s: &str) -> Self {
let v: Vec<u8> = s.into();
ByteString::from(v)
}
}
impl From<String> for ByteString {
fn from(s: String) -> Self {
ByteString::from(s.into_bytes())
}
}