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//! Safe wrappers around Erlang binaries.
//!
//! Rustler provides three binary types: [`Binary`], [`NewBinary`] and
//! [`OwnedBinary`]. All represent a contiguous region `u8`s, and they all use
//! the Erlang allocator. The primary difference between them is their ownership
//! semantics.
//!
//! The _owned_ in `OwnedBinary` refers to the fact that it owns the binary it
//! wraps. The _owner_ of an `OwnedBinary` is free to modify its contents. Ownership
//! lasts until it is dropped or consumed by converting it into a regular
//! `Binary`. An `OwnedBinary` cannot be copied or cloned and is thus always moved.
//!
//! The `Binary` type is an immutable shared-reference to a binary. `Binary`s are
//! cheap to copy: all copies of a `Binary` point to the original `Binary`'s
//! data. Additionally, a `Binary`'s lifetime is tied to that of the NIF's [`Env`],
//! preventing outstanding references to the data after a NIF returns.
//!
//! `NewBinary` is a way of creating a `Binary` without going via `OwnedBinary`.
//! This can improve performance, since `NewBinary`s can be allocated on the
//! heap if they are small. Unlike `OwnedBinary`, `NewBinary`s lifetime is tied
//! to that of the NIF's [`Env`]. `NewBinary` must be converted to a `Binary`
//! or directly to a `Term` before it can be passed to Erlang.
//!
//! # Examples
//!
//! Constructing an `OwnedBinary`:
//!
//! ```no_run
//! # use rustler::OwnedBinary;
//! {
//! let mut bin = OwnedBinary::new(5).expect("allocation failed");
//! bin.as_mut_slice().copy_from_slice("hello".as_bytes());
//! } // <- `bin` is dropped here
//! ```
//!
//! The following NIF takes a binary as its only parameter and returns a new binary
//! where each element is exclusive-or'ed with a constant:
//!
//! ```no_run
//! # use rustler::{Env, OwnedBinary, Binary, NifResult, Error};
//! #[rustler::nif]
//! fn xor_example<'a>(env: Env<'a>, bin: Binary<'a>) -> NifResult<Binary<'a>> {
//! let mut owned: OwnedBinary = bin.to_owned().ok_or(Error::Term(Box::new("no mem")))?;
//! for byte in owned.as_mut_slice() {
//! *byte ^= 0xAA;
//! }
//!
//! // Ownership of `owned`'s data is transferred to `env` on the
//! // following line, so no additional heap allocations are incurred.
//! Ok(Binary::from_owned(owned, env))
//! }
//! ```
//!
//! The contents of a newly-allocated `OwnedBinary` is not initialized to any
//! particular value. If your usage of the binary requires the it's data to be
//! zeroed, for example, then you must explicit zero it. In this example, we
//! manually zeroize the binary before passing it as slice to a third party
//! function.
//!
//! ```no_run
//! # fn some_third_party_api(buf: &mut [u8]) {
//! # for elem in buf {
//! # if *elem == 0 { *elem = 1 } else { panic!("Not a zero!") }
//! # }
//! # }
//! # use rustler::{Env, OwnedBinary, Binary, NifResult, Error};
//! #[rustler::nif]
//! fn wrapper_for_some_<'a>(env: Env<'a>) -> NifResult<Binary<'a>> {
//! let mut owned = OwnedBinary::new(100).ok_or(Error::Term(Box::new("no mem")))?;
//! for byte in owned.as_mut_slice() {
//! *byte = 0;
//! }
//!
//! // Some third party API which requires the slice to be all zeros on entry.
//! some_third_party_api(owned.as_mut_slice());
//!
//! // The imaginary API call presumedly filled in our binary with meaningful
//! // data, so let's return it.
//! Ok(Binary::from_owned(owned, env))
//! }
//!
//! ```
//!
//! [`Binary`]: struct.Binary.html
//! [`Env`]: ../../env/struct.Env.html
//! [`OwnedBinary`]: struct.OwnedBinary.html
use crate::{
wrapper::binary::{alloc, new_binary, realloc, ErlNifBinary},
Decoder, Encoder, Env, Error, NifResult, Term,
};
use std::{
borrow::{Borrow, BorrowMut},
hash::{Hash, Hasher},
io::Write,
mem::MaybeUninit,
ops::{Deref, DerefMut},
};
/// An mutable smart-pointer to an Erlang binary.
///
/// See [module-level doc](index.html) for more information.
pub struct OwnedBinary(ErlNifBinary);
impl<'a> OwnedBinary {
pub unsafe fn from_raw(inner: ErlNifBinary) -> OwnedBinary {
OwnedBinary(inner)
}
/// Allocates a new `OwnedBinary` with size `size`.
///
/// Memory is not initialized. If uninitialized memory is undesirable, set it
/// manually.
///
/// # Errors
///
/// If allocation fails, `None` is returned.
pub fn new(size: usize) -> Option<OwnedBinary> {
unsafe { alloc(size) }.map(OwnedBinary)
}
/// Copies `src`'s data into a new `OwnedBinary`.
///
/// # Errors
///
/// If allocation fails, `None` is returned.
pub fn from_unowned(src: &Binary) -> Option<OwnedBinary> {
OwnedBinary::new(src.len()).map(|mut b| {
b.as_mut_slice().copy_from_slice(src);
b
})
}
/// Attempts to reallocate `self` with the new size.
///
/// Memory outside the range of the original binary will not be initialized. If
/// uninitialized memory is undesirable, set it manually.
///
/// # Errors
///
/// If reallocation fails, `false` is returned. Data remains intact on error.
#[must_use]
pub fn realloc(&mut self, size: usize) -> bool {
unsafe { realloc(&mut self.0, size) }
}
/// Attempts to reallocate `self` with the new size.
///
/// If reallocation fails, it will perform a copy instead.
///
/// Memory outside the range of the original binary will not be initialized. If
/// uninitialized memory is undesirable, set it manually.
pub fn realloc_or_copy(&mut self, size: usize) {
if !self.realloc(size) {
let mut new = OwnedBinary::new(size).unwrap();
if let Ok(num_written) = new.as_mut_slice().write(self.as_slice()) {
if !(num_written == self.len() || num_written == new.len()) {
panic!("Could not copy binary");
}
::std::mem::swap(&mut self.0, &mut new.0);
} else {
panic!("Could not copy binary");
}
}
}
/// Extracts a slice containing the entire binary.
pub fn as_slice(&self) -> &[u8] {
unsafe { ::std::slice::from_raw_parts(self.0.data, self.0.size) }
}
/// Extracts a mutable slice of the entire binary.
pub fn as_mut_slice(&mut self) -> &mut [u8] {
unsafe { ::std::slice::from_raw_parts_mut(self.0.data, self.0.size) }
}
/// Consumes `self` and returns an immutable `Binary`.
///
/// This method is the mirror of [`Binary::from_owned`], and they can be used
/// interchangeably.
///
/// [`Binary::from_owned`]: struct.Binary.html#method.from_owned
pub fn release(self, env: Env) -> Binary {
Binary::from_owned(self, env)
}
}
impl Borrow<[u8]> for OwnedBinary {
fn borrow(&self) -> &[u8] {
self.as_slice()
}
}
impl BorrowMut<[u8]> for OwnedBinary {
fn borrow_mut(&mut self) -> &mut [u8] {
self.as_mut_slice()
}
}
impl Deref for OwnedBinary {
type Target = [u8];
fn deref(&self) -> &[u8] {
self.as_slice()
}
}
impl DerefMut for OwnedBinary {
fn deref_mut(&mut self) -> &mut [u8] {
self.as_mut_slice()
}
}
impl Hash for OwnedBinary {
fn hash<H: Hasher>(&self, state: &mut H) {
self.as_slice().hash(state);
}
}
impl PartialEq for OwnedBinary {
fn eq(&self, other: &Self) -> bool {
self.as_slice() == other.as_slice()
}
}
impl Eq for OwnedBinary {}
impl PartialEq<Binary<'_>> for OwnedBinary {
fn eq(&self, other: &Binary) -> bool {
self.as_slice() == other.as_slice()
}
}
impl Drop for OwnedBinary {
fn drop(&mut self) {
unsafe { rustler_sys::enif_release_binary(&mut self.0) };
}
}
unsafe impl Send for OwnedBinary {}
/// An immutable smart-pointer to an Erlang binary.
///
/// See [module-level doc](index.html) for more information.
#[derive(Copy, Clone)]
pub struct Binary<'a> {
inner: ErlNifBinary,
term: Term<'a>,
}
impl<'a> Binary<'a> {
/// Consumes `owned` and returns an immutable `Binary`.
pub fn from_owned(owned: OwnedBinary, env: Env<'a>) -> Self {
// We are transferring ownership of `owned`'s data to the
// environment. Therefore, we need to prevent `owned`'s destructor being
// called at the end of this scope. The least error-prone solution (compared
// to `mem::forget()`) is to wrap `owned` in a `ManuallyDrop` and EXPLICITLY
// NOT CALL `ManuallyDrop::drop()`.
let mut owned = std::mem::ManuallyDrop::new(owned);
let term = unsafe {
Term::new(
env,
rustler_sys::enif_make_binary(env.as_c_arg(), &mut owned.0),
)
};
Binary {
inner: owned.0,
term,
}
}
/// Copies `self`'s data into a new `OwnedBinary`.
///
/// # Errors
///
/// If allocation fails, an error will be returned.
#[allow(clippy::wrong_self_convention)]
pub fn to_owned(&self) -> Option<OwnedBinary> {
OwnedBinary::from_unowned(self)
}
/// Creates a `Binary` from `term`.
///
/// # Errors
///
/// If `term` is not a binary, an error will be returned.
pub fn from_term(term: Term<'a>) -> Result<Self, Error> {
let mut binary = MaybeUninit::uninit();
if unsafe {
rustler_sys::enif_inspect_binary(
term.get_env().as_c_arg(),
term.as_c_arg(),
binary.as_mut_ptr(),
)
} == 0
{
return Err(Error::BadArg);
}
Ok(Binary {
inner: unsafe { binary.assume_init() },
term,
})
}
/// Creates a `Binary` from `term`.
///
/// # Errors
///
/// If `term` is not an `iolist`, an error will be returned.
pub fn from_iolist(term: Term<'a>) -> Result<Self, Error> {
let mut binary = MaybeUninit::uninit();
if unsafe {
rustler_sys::enif_inspect_iolist_as_binary(
term.get_env().as_c_arg(),
term.as_c_arg(),
binary.as_mut_ptr(),
)
} == 0
{
return Err(Error::BadArg);
}
Ok(Binary {
inner: unsafe { binary.assume_init() },
term,
})
}
/// Returns an Erlang term representation of `self`.
#[allow(clippy::wrong_self_convention)]
pub fn to_term<'b>(&self, env: Env<'b>) -> Term<'b> {
self.term.in_env(env)
}
/// Extracts a slice containing the entire binary.
pub fn as_slice(&self) -> &'a [u8] {
unsafe { ::std::slice::from_raw_parts(self.inner.data, self.inner.size) }
}
/// Returns a new view into the same binary.
///
/// This method is analogous to subslicing (e.g. `some_data[offset..length]`) in
/// that it does not copy nor allocate data.
///
/// # Errors
///
/// If `offset + length` is out of bounds, an error will be returned.
pub fn make_subbinary(&self, offset: usize, length: usize) -> NifResult<Binary<'a>> {
let min_len = length.checked_add(offset);
if min_len.ok_or(Error::BadArg)? > self.inner.size {
return Err(Error::BadArg);
}
let raw_term = unsafe {
rustler_sys::enif_make_sub_binary(
self.term.get_env().as_c_arg(),
self.term.as_c_arg(),
offset,
length,
)
};
let term = unsafe { Term::new(self.term.get_env(), raw_term) };
// This should never fail, as we are always passing in a binary term.
Ok(Binary::from_term(term).ok().unwrap())
}
}
impl<'a> Borrow<[u8]> for Binary<'a> {
fn borrow(&self) -> &[u8] {
self.as_slice()
}
}
impl<'a> Deref for Binary<'a> {
type Target = [u8];
fn deref(&self) -> &[u8] {
self.as_slice()
}
}
impl<'a> Decoder<'a> for Binary<'a> {
fn decode(term: Term<'a>) -> Result<Self, Error> {
Binary::from_term(term)
}
}
impl<'a> Encoder for Binary<'a> {
fn encode<'b>(&self, env: Env<'b>) -> Term<'b> {
self.to_term(env)
}
}
impl Hash for Binary<'_> {
fn hash<H: Hasher>(&self, state: &mut H) {
self.as_slice().hash(state);
}
}
impl PartialEq for Binary<'_> {
fn eq(&self, other: &Self) -> bool {
self.as_slice() == other.as_slice()
}
}
impl Eq for Binary<'_> {}
impl PartialEq<OwnedBinary> for Binary<'_> {
fn eq(&self, other: &OwnedBinary) -> bool {
self.as_slice() == other.as_slice()
}
}
/// ## Binary terms
impl<'a> Term<'a> {
pub fn into_binary(self) -> NifResult<Binary<'a>> {
Binary::from_term(self)
}
}
/// An newly-created, mutable Erlang binary.
///
/// See [module-level doc](index.html) for more information.
pub struct NewBinary<'a> {
buf: *mut u8,
size: usize,
// safety: we must not expose `term` until it is no longer possible to get a
// &mut ref to `buf`.
term: Term<'a>,
}
impl<'a> NewBinary<'a> {
/// Allocates a new `NewBinary`
pub fn new(env: Env<'a>, size: usize) -> Self {
let (buf, term) = unsafe { new_binary(env, size) };
NewBinary { buf, term, size }
}
/// Extracts a slice containing the entire binary.
pub fn as_slice(&self) -> &[u8] {
unsafe { ::std::slice::from_raw_parts(self.buf, self.size) }
}
/// Extracts a mutable slice of the entire binary.
pub fn as_mut_slice(&mut self) -> &mut [u8] {
unsafe { ::std::slice::from_raw_parts_mut(self.buf, self.size) }
}
}
impl<'a> From<NewBinary<'a>> for Binary<'a> {
fn from(new_binary: NewBinary<'a>) -> Self {
Binary::from_term(new_binary.term).unwrap()
}
}
impl<'a> From<NewBinary<'a>> for Term<'a> {
fn from(new_binary: NewBinary<'a>) -> Self {
new_binary.term
}
}
impl<'a> Deref for NewBinary<'a> {
type Target = [u8];
fn deref(&self) -> &[u8] {
self.as_slice()
}
}
impl<'a> DerefMut for NewBinary<'a> {
fn deref_mut(&mut self) -> &mut [u8] {
self.as_mut_slice()
}
}