| use core::{cmp, fmt, hash, mem, ptr, slice, usize}; |
| use core::iter::{FromIterator}; |
| use core::ops::{Deref, RangeBounds}; |
| |
| use alloc::{vec::Vec, string::String, boxed::Box, borrow::Borrow}; |
| |
| use crate::Buf; |
| use crate::buf::IntoIter; |
| use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering}; |
| |
| /// A reference counted contiguous slice of memory. |
| /// |
| /// `Bytes` is an efficient container for storing and operating on contiguous |
| /// slices of memory. It is intended for use primarily in networking code, but |
| /// could have applications elsewhere as well. |
| /// |
| /// `Bytes` values facilitate zero-copy network programming by allowing multiple |
| /// `Bytes` objects to point to the same underlying memory. This is managed by |
| /// using a reference count to track when the memory is no longer needed and can |
| /// be freed. |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let mut mem = Bytes::from("Hello world"); |
| /// let a = mem.slice(0..5); |
| /// |
| /// assert_eq!(a, "Hello"); |
| /// |
| /// let b = mem.split_to(6); |
| /// |
| /// assert_eq!(mem, "world"); |
| /// assert_eq!(b, "Hello "); |
| /// ``` |
| /// |
| /// # Memory layout |
| /// |
| /// The `Bytes` struct itself is fairly small, limited to 4 `usize` fields used |
| /// to track information about which segment of the underlying memory the |
| /// `Bytes` handle has access to. |
| /// |
| /// `Bytes` keeps both a pointer to the shared `Arc` containing the full memory |
| /// slice and a pointer to the start of the region visible by the handle. |
| /// `Bytes` also tracks the length of its view into the memory. |
| /// |
| /// # Sharing |
| /// |
| /// The memory itself is reference counted, and multiple `Bytes` objects may |
| /// point to the same region. Each `Bytes` handle point to different sections within |
| /// the memory region, and `Bytes` handle may or may not have overlapping views |
| /// into the memory. |
| /// |
| /// |
| /// ```text |
| /// |
| /// Arc ptrs +---------+ |
| /// ________________________ / | Bytes 2 | |
| /// / +---------+ |
| /// / +-----------+ | | |
| /// |_________/ | Bytes 1 | | | |
| /// | +-----------+ | | |
| /// | | | ___/ data | tail |
| /// | data | tail |/ | |
| /// v v v v |
| /// +-----+---------------------------------+-----+ |
| /// | Arc | | | | | |
| /// +-----+---------------------------------+-----+ |
| /// ``` |
| pub struct Bytes { |
| ptr: *const u8, |
| len: usize, |
| // inlined "trait object" |
| data: AtomicPtr<()>, |
| vtable: &'static Vtable, |
| } |
| |
| pub(crate) struct Vtable { |
| /// fn(data, ptr, len) |
| pub clone: unsafe fn(&AtomicPtr<()>, *const u8, usize) -> Bytes, |
| /// fn(data, ptr, len) |
| pub drop: unsafe fn(&mut AtomicPtr<()>, *const u8, usize), |
| } |
| |
| impl Bytes { |
| /// Creates a new empty `Bytes`. |
| /// |
| /// This will not allocate and the returned `Bytes` handle will be empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let b = Bytes::new(); |
| /// assert_eq!(&b[..], b""); |
| /// ``` |
| #[inline] |
| #[cfg(not(all(loom, test)))] |
| pub const fn new() -> Bytes { |
| // Make it a named const to work around |
| // "unsizing casts are not allowed in const fn" |
| const EMPTY: &[u8] = &[]; |
| Bytes::from_static(EMPTY) |
| } |
| |
| #[cfg(all(loom, test))] |
| pub fn new() -> Bytes { |
| const EMPTY: &[u8] = &[]; |
| Bytes::from_static(EMPTY) |
| } |
| |
| /// Creates a new `Bytes` from a static slice. |
| /// |
| /// The returned `Bytes` will point directly to the static slice. There is |
| /// no allocating or copying. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let b = Bytes::from_static(b"hello"); |
| /// assert_eq!(&b[..], b"hello"); |
| /// ``` |
| #[inline] |
| #[cfg(not(all(loom, test)))] |
| pub const fn from_static(bytes: &'static [u8]) -> Bytes { |
| Bytes { |
| ptr: bytes.as_ptr(), |
| len: bytes.len(), |
| data: AtomicPtr::new(ptr::null_mut()), |
| vtable: &STATIC_VTABLE, |
| } |
| } |
| |
| #[cfg(all(loom, test))] |
| pub fn from_static(bytes: &'static [u8]) -> Bytes { |
| Bytes { |
| ptr: bytes.as_ptr(), |
| len: bytes.len(), |
| data: AtomicPtr::new(ptr::null_mut()), |
| vtable: &STATIC_VTABLE, |
| } |
| } |
| |
| /// Returns the number of bytes contained in this `Bytes`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let b = Bytes::from(&b"hello"[..]); |
| /// assert_eq!(b.len(), 5); |
| /// ``` |
| #[inline] |
| pub fn len(&self) -> usize { |
| self.len |
| } |
| |
| /// Returns true if the `Bytes` has a length of 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let b = Bytes::new(); |
| /// assert!(b.is_empty()); |
| /// ``` |
| #[inline] |
| pub fn is_empty(&self) -> bool { |
| self.len == 0 |
| } |
| |
| |
| ///Creates `Bytes` instance from slice, by copying it. |
| pub fn copy_from_slice(data: &[u8]) -> Self { |
| data.to_vec().into() |
| } |
| |
| /// Returns a slice of self for the provided range. |
| /// |
| /// This will increment the reference count for the underlying memory and |
| /// return a new `Bytes` handle set to the slice. |
| /// |
| /// This operation is `O(1)`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let a = Bytes::from(&b"hello world"[..]); |
| /// let b = a.slice(2..5); |
| /// |
| /// assert_eq!(&b[..], b"llo"); |
| /// ``` |
| /// |
| /// # Panics |
| /// |
| /// Requires that `begin <= end` and `end <= self.len()`, otherwise slicing |
| /// will panic. |
| pub fn slice(&self, range: impl RangeBounds<usize>) -> Bytes { |
| use core::ops::Bound; |
| |
| let len = self.len(); |
| |
| let begin = match range.start_bound() { |
| Bound::Included(&n) => n, |
| Bound::Excluded(&n) => n + 1, |
| Bound::Unbounded => 0, |
| }; |
| |
| let end = match range.end_bound() { |
| Bound::Included(&n) => n + 1, |
| Bound::Excluded(&n) => n, |
| Bound::Unbounded => len, |
| }; |
| |
| assert!( |
| begin <= end, |
| "range start must not be greater than end: {:?} <= {:?}", |
| begin, |
| end, |
| ); |
| assert!( |
| end <= len, |
| "range end out of bounds: {:?} <= {:?}", |
| end, |
| len, |
| ); |
| |
| if end == begin { |
| return Bytes::new(); |
| } |
| |
| |
| let mut ret = self.clone(); |
| |
| ret.len = end - begin; |
| ret.ptr = unsafe { ret.ptr.offset(begin as isize) }; |
| |
| ret |
| } |
| |
| /// Returns a slice of self that is equivalent to the given `subset`. |
| /// |
| /// When processing a `Bytes` buffer with other tools, one often gets a |
| /// `&[u8]` which is in fact a slice of the `Bytes`, i.e. a subset of it. |
| /// This function turns that `&[u8]` into another `Bytes`, as if one had |
| /// called `self.slice()` with the offsets that correspond to `subset`. |
| /// |
| /// This operation is `O(1)`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let bytes = Bytes::from(&b"012345678"[..]); |
| /// let as_slice = bytes.as_ref(); |
| /// let subset = &as_slice[2..6]; |
| /// let subslice = bytes.slice_ref(&subset); |
| /// assert_eq!(&subslice[..], b"2345"); |
| /// ``` |
| /// |
| /// # Panics |
| /// |
| /// Requires that the given `sub` slice is in fact contained within the |
| /// `Bytes` buffer; otherwise this function will panic. |
| pub fn slice_ref(&self, subset: &[u8]) -> Bytes { |
| // Empty slice and empty Bytes may have their pointers reset |
| // so explicitly allow empty slice to be a subslice of any slice. |
| if subset.is_empty() { |
| return Bytes::new(); |
| } |
| |
| let bytes_p = self.as_ptr() as usize; |
| let bytes_len = self.len(); |
| |
| let sub_p = subset.as_ptr() as usize; |
| let sub_len = subset.len(); |
| |
| assert!( |
| sub_p >= bytes_p, |
| "subset pointer ({:p}) is smaller than self pointer ({:p})", |
| sub_p as *const u8, |
| bytes_p as *const u8, |
| ); |
| assert!( |
| sub_p + sub_len <= bytes_p + bytes_len, |
| "subset is out of bounds: self = ({:p}, {}), subset = ({:p}, {})", |
| bytes_p as *const u8, |
| bytes_len, |
| sub_p as *const u8, |
| sub_len, |
| ); |
| |
| let sub_offset = sub_p - bytes_p; |
| |
| self.slice(sub_offset..(sub_offset + sub_len)) |
| } |
| |
| /// Splits the bytes into two at the given index. |
| /// |
| /// Afterwards `self` contains elements `[0, at)`, and the returned `Bytes` |
| /// contains elements `[at, len)`. |
| /// |
| /// This is an `O(1)` operation that just increases the reference count and |
| /// sets a few indices. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let mut a = Bytes::from(&b"hello world"[..]); |
| /// let b = a.split_off(5); |
| /// |
| /// assert_eq!(&a[..], b"hello"); |
| /// assert_eq!(&b[..], b" world"); |
| /// ``` |
| /// |
| /// # Panics |
| /// |
| /// Panics if `at > len`. |
| #[must_use = "consider Bytes::truncate if you don't need the other half"] |
| pub fn split_off(&mut self, at: usize) -> Bytes { |
| assert!( |
| at <= self.len(), |
| "split_off out of bounds: {:?} <= {:?}", |
| at, |
| self.len(), |
| ); |
| |
| if at == self.len() { |
| return Bytes::new(); |
| } |
| |
| if at == 0 { |
| return mem::replace(self, Bytes::new()); |
| } |
| |
| let mut ret = self.clone(); |
| |
| self.len = at; |
| |
| unsafe { ret.inc_start(at) }; |
| |
| ret |
| } |
| |
| /// Splits the bytes into two at the given index. |
| /// |
| /// Afterwards `self` contains elements `[at, len)`, and the returned |
| /// `Bytes` contains elements `[0, at)`. |
| /// |
| /// This is an `O(1)` operation that just increases the reference count and |
| /// sets a few indices. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let mut a = Bytes::from(&b"hello world"[..]); |
| /// let b = a.split_to(5); |
| /// |
| /// assert_eq!(&a[..], b" world"); |
| /// assert_eq!(&b[..], b"hello"); |
| /// ``` |
| /// |
| /// # Panics |
| /// |
| /// Panics if `at > len`. |
| #[must_use = "consider Bytes::advance if you don't need the other half"] |
| pub fn split_to(&mut self, at: usize) -> Bytes { |
| assert!( |
| at <= self.len(), |
| "split_to out of bounds: {:?} <= {:?}", |
| at, |
| self.len(), |
| ); |
| |
| if at == self.len() { |
| return mem::replace(self, Bytes::new()); |
| } |
| |
| if at == 0 { |
| return Bytes::new(); |
| } |
| |
| |
| let mut ret = self.clone(); |
| |
| unsafe { self.inc_start(at) }; |
| |
| ret.len = at; |
| ret |
| } |
| |
| /// Shortens the buffer, keeping the first `len` bytes and dropping the |
| /// rest. |
| /// |
| /// If `len` is greater than the buffer's current length, this has no |
| /// effect. |
| /// |
| /// The [`split_off`] method can emulate `truncate`, but this causes the |
| /// excess bytes to be returned instead of dropped. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let mut buf = Bytes::from(&b"hello world"[..]); |
| /// buf.truncate(5); |
| /// assert_eq!(buf, b"hello"[..]); |
| /// ``` |
| /// |
| /// [`split_off`]: #method.split_off |
| #[inline] |
| pub fn truncate(&mut self, len: usize) { |
| if len < self.len { |
| // The Vec "promotable" vtables do not store the capacity, |
| // so we cannot truncate while using this repr. We *have* to |
| // promote using `split_off` so the capacity can be stored. |
| if self.vtable as *const Vtable == &PROMOTABLE_EVEN_VTABLE || |
| self.vtable as *const Vtable == &PROMOTABLE_ODD_VTABLE { |
| drop(self.split_off(len)); |
| } else { |
| self.len = len; |
| } |
| } |
| } |
| |
| /// Clears the buffer, removing all data. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use bytes::Bytes; |
| /// |
| /// let mut buf = Bytes::from(&b"hello world"[..]); |
| /// buf.clear(); |
| /// assert!(buf.is_empty()); |
| /// ``` |
| #[inline] |
| pub fn clear(&mut self) { |
| self.truncate(0); |
| } |
| |
| #[inline] |
| pub(crate) unsafe fn with_vtable(ptr: *const u8, len: usize, data: AtomicPtr<()>, vtable: &'static Vtable) -> Bytes { |
| Bytes { |
| ptr, |
| len, |
| data, |
| vtable, |
| } |
| } |
| |
| // private |
| |
| #[inline] |
| fn as_slice(&self) -> &[u8] { |
| unsafe { |
| slice::from_raw_parts(self.ptr, self.len) |
| } |
| } |
| |
| #[inline] |
| unsafe fn inc_start(&mut self, by: usize) { |
| // should already be asserted, but debug assert for tests |
| debug_assert!(self.len >= by, "internal: inc_start out of bounds"); |
| self.len -= by; |
| self.ptr = self.ptr.offset(by as isize); |
| } |
| } |
| |
| // Vtable must enforce this behavior |
| unsafe impl Send for Bytes {} |
| unsafe impl Sync for Bytes {} |
| |
| impl Drop for Bytes { |
| #[inline] |
| fn drop(&mut self) { |
| unsafe { |
| (self.vtable.drop)(&mut self.data, self.ptr, self.len) |
| } |
| } |
| } |
| |
| impl Clone for Bytes { |
| #[inline] |
| fn clone(&self) -> Bytes { |
| unsafe { |
| (self.vtable.clone)(&self.data, self.ptr, self.len) |
| } |
| } |
| } |
| |
| impl Buf for Bytes { |
| #[inline] |
| fn remaining(&self) -> usize { |
| self.len() |
| } |
| |
| #[inline] |
| fn bytes(&self) -> &[u8] { |
| self.as_slice() |
| } |
| |
| #[inline] |
| fn advance(&mut self, cnt: usize) { |
| assert!( |
| cnt <= self.len(), |
| "cannot advance past `remaining`: {:?} <= {:?}", |
| cnt, |
| self.len(), |
| ); |
| |
| unsafe { |
| self.inc_start(cnt); |
| } |
| } |
| |
| fn to_bytes(&mut self) -> crate::Bytes { |
| core::mem::replace(self, Bytes::new()) |
| } |
| } |
| |
| impl Deref for Bytes { |
| type Target = [u8]; |
| |
| #[inline] |
| fn deref(&self) -> &[u8] { |
| self.as_slice() |
| } |
| } |
| |
| impl AsRef<[u8]> for Bytes { |
| #[inline] |
| fn as_ref(&self) -> &[u8] { |
| self.as_slice() |
| } |
| } |
| |
| impl hash::Hash for Bytes { |
| fn hash<H>(&self, state: &mut H) where H: hash::Hasher { |
| self.as_slice().hash(state); |
| } |
| } |
| |
| impl Borrow<[u8]> for Bytes { |
| fn borrow(&self) -> &[u8] { |
| self.as_slice() |
| } |
| } |
| |
| impl IntoIterator for Bytes { |
| type Item = u8; |
| type IntoIter = IntoIter<Bytes>; |
| |
| fn into_iter(self) -> Self::IntoIter { |
| IntoIter::new(self) |
| } |
| } |
| |
| impl<'a> IntoIterator for &'a Bytes { |
| type Item = &'a u8; |
| type IntoIter = core::slice::Iter<'a, u8>; |
| |
| fn into_iter(self) -> Self::IntoIter { |
| self.as_slice().into_iter() |
| } |
| } |
| |
| impl FromIterator<u8> for Bytes { |
| fn from_iter<T: IntoIterator<Item = u8>>(into_iter: T) -> Self { |
| Vec::from_iter(into_iter).into() |
| } |
| } |
| |
| // impl Eq |
| |
| impl PartialEq for Bytes { |
| fn eq(&self, other: &Bytes) -> bool { |
| self.as_slice() == other.as_slice() |
| } |
| } |
| |
| impl PartialOrd for Bytes { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| self.as_slice().partial_cmp(other.as_slice()) |
| } |
| } |
| |
| impl Ord for Bytes { |
| fn cmp(&self, other: &Bytes) -> cmp::Ordering { |
| self.as_slice().cmp(other.as_slice()) |
| } |
| } |
| |
| impl Eq for Bytes {} |
| |
| impl PartialEq<[u8]> for Bytes { |
| fn eq(&self, other: &[u8]) -> bool { |
| self.as_slice() == other |
| } |
| } |
| |
| impl PartialOrd<[u8]> for Bytes { |
| fn partial_cmp(&self, other: &[u8]) -> Option<cmp::Ordering> { |
| self.as_slice().partial_cmp(other) |
| } |
| } |
| |
| impl PartialEq<Bytes> for [u8] { |
| fn eq(&self, other: &Bytes) -> bool { |
| *other == *self |
| } |
| } |
| |
| impl PartialOrd<Bytes> for [u8] { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other) |
| } |
| } |
| |
| impl PartialEq<str> for Bytes { |
| fn eq(&self, other: &str) -> bool { |
| self.as_slice() == other.as_bytes() |
| } |
| } |
| |
| impl PartialOrd<str> for Bytes { |
| fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> { |
| self.as_slice().partial_cmp(other.as_bytes()) |
| } |
| } |
| |
| impl PartialEq<Bytes> for str { |
| fn eq(&self, other: &Bytes) -> bool { |
| *other == *self |
| } |
| } |
| |
| impl PartialOrd<Bytes> for str { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other) |
| } |
| } |
| |
| impl PartialEq<Vec<u8>> for Bytes { |
| fn eq(&self, other: &Vec<u8>) -> bool { |
| *self == &other[..] |
| } |
| } |
| |
| impl PartialOrd<Vec<u8>> for Bytes { |
| fn partial_cmp(&self, other: &Vec<u8>) -> Option<cmp::Ordering> { |
| self.as_slice().partial_cmp(&other[..]) |
| } |
| } |
| |
| impl PartialEq<Bytes> for Vec<u8> { |
| fn eq(&self, other: &Bytes) -> bool { |
| *other == *self |
| } |
| } |
| |
| impl PartialOrd<Bytes> for Vec<u8> { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other) |
| } |
| } |
| |
| impl PartialEq<String> for Bytes { |
| fn eq(&self, other: &String) -> bool { |
| *self == &other[..] |
| } |
| } |
| |
| impl PartialOrd<String> for Bytes { |
| fn partial_cmp(&self, other: &String) -> Option<cmp::Ordering> { |
| self.as_slice().partial_cmp(other.as_bytes()) |
| } |
| } |
| |
| impl PartialEq<Bytes> for String { |
| fn eq(&self, other: &Bytes) -> bool { |
| *other == *self |
| } |
| } |
| |
| impl PartialOrd<Bytes> for String { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other) |
| } |
| } |
| |
| impl PartialEq<Bytes> for &[u8] { |
| fn eq(&self, other: &Bytes) -> bool { |
| *other == *self |
| } |
| } |
| |
| impl PartialOrd<Bytes> for &[u8] { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other) |
| } |
| } |
| |
| impl PartialEq<Bytes> for &str { |
| fn eq(&self, other: &Bytes) -> bool { |
| *other == *self |
| } |
| } |
| |
| impl PartialOrd<Bytes> for &str { |
| fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> { |
| <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other) |
| } |
| } |
| |
| impl<'a, T: ?Sized> PartialEq<&'a T> for Bytes |
| where Bytes: PartialEq<T> |
| { |
| fn eq(&self, other: &&'a T) -> bool { |
| *self == **other |
| } |
| } |
| |
| impl<'a, T: ?Sized> PartialOrd<&'a T> for Bytes |
| where Bytes: PartialOrd<T> |
| { |
| fn partial_cmp(&self, other: &&'a T) -> Option<cmp::Ordering> { |
| self.partial_cmp(&**other) |
| } |
| } |
| |
| // impl From |
| |
| impl Default for Bytes { |
| #[inline] |
| fn default() -> Bytes { |
| Bytes::new() |
| } |
| } |
| |
| impl From<&'static [u8]> for Bytes { |
| fn from(slice: &'static [u8]) -> Bytes { |
| Bytes::from_static(slice) |
| } |
| } |
| |
| impl From<&'static str> for Bytes { |
| fn from(slice: &'static str) -> Bytes { |
| Bytes::from_static(slice.as_bytes()) |
| } |
| } |
| |
| impl From<Vec<u8>> for Bytes { |
| fn from(vec: Vec<u8>) -> Bytes { |
| // into_boxed_slice doesn't return a heap allocation for empty vectors, |
| // so the pointer isn't aligned enough for the KIND_VEC stashing to |
| // work. |
| if vec.is_empty() { |
| return Bytes::new(); |
| } |
| |
| let slice = vec.into_boxed_slice(); |
| let len = slice.len(); |
| let ptr = slice.as_ptr(); |
| drop(Box::into_raw(slice)); |
| |
| if ptr as usize & 0x1 == 0 { |
| let data = ptr as usize | KIND_VEC; |
| Bytes { |
| ptr, |
| len, |
| data: AtomicPtr::new(data as *mut _), |
| vtable: &PROMOTABLE_EVEN_VTABLE, |
| } |
| } else { |
| Bytes { |
| ptr, |
| len, |
| data: AtomicPtr::new(ptr as *mut _), |
| vtable: &PROMOTABLE_ODD_VTABLE, |
| } |
| } |
| } |
| } |
| |
| impl From<String> for Bytes { |
| fn from(s: String) -> Bytes { |
| Bytes::from(s.into_bytes()) |
| } |
| } |
| |
| // ===== impl Vtable ===== |
| |
| impl fmt::Debug for Vtable { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("Vtable") |
| .field("clone", &(self.clone as *const ())) |
| .field("drop", &(self.drop as *const ())) |
| .finish() |
| } |
| } |
| |
| // ===== impl StaticVtable ===== |
| |
| const STATIC_VTABLE: Vtable = Vtable { |
| clone: static_clone, |
| drop: static_drop, |
| }; |
| |
| unsafe fn static_clone(_: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes { |
| let slice = slice::from_raw_parts(ptr, len); |
| Bytes::from_static(slice) |
| } |
| |
| unsafe fn static_drop(_: &mut AtomicPtr<()>, _: *const u8, _: usize) { |
| // nothing to drop for &'static [u8] |
| } |
| |
| // ===== impl PromotableVtable ===== |
| |
| static PROMOTABLE_EVEN_VTABLE: Vtable = Vtable { |
| clone: promotable_even_clone, |
| drop: promotable_even_drop, |
| }; |
| |
| static PROMOTABLE_ODD_VTABLE: Vtable = Vtable { |
| clone: promotable_odd_clone, |
| drop: promotable_odd_drop, |
| }; |
| |
| unsafe fn promotable_even_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes { |
| let shared = data.load(Ordering::Acquire); |
| let kind = shared as usize & KIND_MASK; |
| |
| if kind == KIND_ARC { |
| shallow_clone_arc(shared as _, ptr, len) |
| } else { |
| debug_assert_eq!(kind, KIND_VEC); |
| let buf = (shared as usize & !KIND_MASK) as *mut u8; |
| shallow_clone_vec(data, shared, buf, ptr, len) |
| } |
| } |
| |
| unsafe fn promotable_even_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) { |
| let shared = *data.get_mut(); |
| let kind = shared as usize & KIND_MASK; |
| |
| if kind == KIND_ARC { |
| release_shared(shared as *mut Shared); |
| } else { |
| debug_assert_eq!(kind, KIND_VEC); |
| let buf = (shared as usize & !KIND_MASK) as *mut u8; |
| drop(rebuild_boxed_slice(buf, ptr, len)); |
| } |
| } |
| |
| unsafe fn promotable_odd_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes { |
| let shared = data.load(Ordering::Acquire); |
| let kind = shared as usize & KIND_MASK; |
| |
| if kind == KIND_ARC { |
| shallow_clone_arc(shared as _, ptr, len) |
| } else { |
| debug_assert_eq!(kind, KIND_VEC); |
| shallow_clone_vec(data, shared, shared as *mut u8, ptr, len) |
| } |
| } |
| |
| unsafe fn promotable_odd_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) { |
| let shared = *data.get_mut(); |
| let kind = shared as usize & KIND_MASK; |
| |
| if kind == KIND_ARC { |
| release_shared(shared as *mut Shared); |
| } else { |
| debug_assert_eq!(kind, KIND_VEC); |
| |
| drop(rebuild_boxed_slice(shared as *mut u8, ptr, len)); |
| } |
| } |
| |
| unsafe fn rebuild_boxed_slice(buf: *mut u8, offset: *const u8, len: usize) -> Box<[u8]> { |
| let cap = (offset as usize - buf as usize) + len; |
| Box::from_raw(slice::from_raw_parts_mut(buf, cap)) |
| } |
| |
| // ===== impl SharedVtable ===== |
| |
| struct Shared { |
| // holds vec for drop, but otherwise doesnt access it |
| _vec: Vec<u8>, |
| ref_cnt: AtomicUsize, |
| } |
| |
| // Assert that the alignment of `Shared` is divisible by 2. |
| // This is a necessary invariant since we depend on allocating `Shared` a |
| // shared object to implicitly carry the `KIND_ARC` flag in its pointer. |
| // This flag is set when the LSB is 0. |
| const _: [(); 0 - mem::align_of::<Shared>() % 2] = []; // Assert that the alignment of `Shared` is divisible by 2. |
| |
| static SHARED_VTABLE: Vtable = Vtable { |
| clone: shared_clone, |
| drop: shared_drop, |
| }; |
| |
| const KIND_ARC: usize = 0b0; |
| const KIND_VEC: usize = 0b1; |
| const KIND_MASK: usize = 0b1; |
| |
| unsafe fn shared_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes { |
| let shared = data.load(Ordering::Acquire); |
| shallow_clone_arc(shared as _, ptr, len) |
| } |
| |
| unsafe fn shared_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) { |
| let shared = *data.get_mut(); |
| release_shared(shared as *mut Shared); |
| } |
| |
| unsafe fn shallow_clone_arc(shared: *mut Shared, ptr: *const u8, len: usize) -> Bytes { |
| let old_size = (*shared).ref_cnt.fetch_add(1, Ordering::Relaxed); |
| |
| if old_size > usize::MAX >> 1 { |
| crate::abort(); |
| } |
| |
| Bytes { |
| ptr, |
| len, |
| data: AtomicPtr::new(shared as _), |
| vtable: &SHARED_VTABLE, |
| } |
| } |
| |
| #[cold] |
| unsafe fn shallow_clone_vec(atom: &AtomicPtr<()>, ptr: *const (), buf: *mut u8, offset: *const u8, len: usize) -> Bytes { |
| // If the buffer is still tracked in a `Vec<u8>`. It is time to |
| // promote the vec to an `Arc`. This could potentially be called |
| // concurrently, so some care must be taken. |
| |
| // First, allocate a new `Shared` instance containing the |
| // `Vec` fields. It's important to note that `ptr`, `len`, |
| // and `cap` cannot be mutated without having `&mut self`. |
| // This means that these fields will not be concurrently |
| // updated and since the buffer hasn't been promoted to an |
| // `Arc`, those three fields still are the components of the |
| // vector. |
| let vec = rebuild_boxed_slice(buf, offset, len).into_vec(); |
| let shared = Box::new(Shared { |
| _vec: vec, |
| // Initialize refcount to 2. One for this reference, and one |
| // for the new clone that will be returned from |
| // `shallow_clone`. |
| ref_cnt: AtomicUsize::new(2), |
| }); |
| |
| let shared = Box::into_raw(shared); |
| |
| // The pointer should be aligned, so this assert should |
| // always succeed. |
| debug_assert!( |
| 0 == (shared as usize & KIND_MASK), |
| "internal: Box<Shared> should have an aligned pointer", |
| ); |
| |
| // Try compare & swapping the pointer into the `arc` field. |
| // `Release` is used synchronize with other threads that |
| // will load the `arc` field. |
| // |
| // If the `compare_and_swap` fails, then the thread lost the |
| // race to promote the buffer to shared. The `Acquire` |
| // ordering will synchronize with the `compare_and_swap` |
| // that happened in the other thread and the `Shared` |
| // pointed to by `actual` will be visible. |
| let actual = atom.compare_and_swap(ptr as _, shared as _, Ordering::AcqRel); |
| |
| if actual as usize == ptr as usize { |
| // The upgrade was successful, the new handle can be |
| // returned. |
| return Bytes { |
| ptr: offset, |
| len, |
| data: AtomicPtr::new(shared as _), |
| vtable: &SHARED_VTABLE, |
| }; |
| } |
| |
| // The upgrade failed, a concurrent clone happened. Release |
| // the allocation that was made in this thread, it will not |
| // be needed. |
| let shared = Box::from_raw(shared); |
| mem::forget(*shared); |
| |
| // Buffer already promoted to shared storage, so increment ref |
| // count. |
| shallow_clone_arc(actual as _, offset, len) |
| } |
| |
| unsafe fn release_shared(ptr: *mut Shared) { |
| // `Shared` storage... follow the drop steps from Arc. |
| if (*ptr).ref_cnt.fetch_sub(1, Ordering::Release) != 1 { |
| return; |
| } |
| |
| // This fence is needed to prevent reordering of use of the data and |
| // deletion of the data. Because it is marked `Release`, the decreasing |
| // of the reference count synchronizes with this `Acquire` fence. This |
| // means that use of the data happens before decreasing the reference |
| // count, which happens before this fence, which happens before the |
| // deletion of the data. |
| // |
| // As explained in the [Boost documentation][1], |
| // |
| // > It is important to enforce any possible access to the object in one |
| // > thread (through an existing reference) to *happen before* deleting |
| // > the object in a different thread. This is achieved by a "release" |
| // > operation after dropping a reference (any access to the object |
| // > through this reference must obviously happened before), and an |
| // > "acquire" operation before deleting the object. |
| // |
| // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html) |
| atomic::fence(Ordering::Acquire); |
| |
| // Drop the data |
| Box::from_raw(ptr); |
| } |
| |
| // compile-fails |
| |
| /// ```compile_fail |
| /// use bytes::Bytes; |
| /// #[deny(unused_must_use)] |
| /// { |
| /// let mut b1 = Bytes::from("hello world"); |
| /// b1.split_to(6); |
| /// } |
| /// ``` |
| fn _split_to_must_use() {} |
| |
| /// ```compile_fail |
| /// use bytes::Bytes; |
| /// #[deny(unused_must_use)] |
| /// { |
| /// let mut b1 = Bytes::from("hello world"); |
| /// b1.split_off(6); |
| /// } |
| /// ``` |
| fn _split_off_must_use() {} |
| |
| // fuzz tests |
| #[cfg(all(test, loom))] |
| mod fuzz { |
| use std::sync::Arc; |
| use loom::thread; |
| |
| use super::Bytes; |
| #[test] |
| fn bytes_cloning_vec() { |
| loom::model(|| { |
| let a = Bytes::from(b"abcdefgh".to_vec()); |
| let addr = a.as_ptr() as usize; |
| |
| // test the Bytes::clone is Sync by putting it in an Arc |
| let a1 = Arc::new(a); |
| let a2 = a1.clone(); |
| |
| let t1 = thread::spawn(move || { |
| let b: Bytes = (*a1).clone(); |
| assert_eq!(b.as_ptr() as usize, addr); |
| }); |
| |
| let t2 = thread::spawn(move || { |
| let b: Bytes = (*a2).clone(); |
| assert_eq!(b.as_ptr() as usize, addr); |
| }); |
| |
| t1.join().unwrap(); |
| t2.join().unwrap(); |
| }); |
| } |
| } |
