Struct arccstr::ArcCStr [−][src]
pub struct ArcCStr { /* fields omitted */ }
Expand description
A thread-safe reference-counted null-terminated string.
The type ArcCStr
provides shared ownership of a C-style null-terminated string allocated in
the heap. Invoking clone
on ArcCStr
produces a new pointer to the same value in the heap.
When the last ArcCStr
pointer to a given string is destroyed, the pointed-to string is also
destroyed. Behind the scenes, ArcCStr
works much like Arc
.
Strings pointed to using ArcCStr
are meant to be immutable, and there therefore no
mechanism is provided to get a mutable reference to the underlying string, even if there are no
other pointers to the string in question.
ArcCStr
uses atomic operations for reference counting, so ArcCStr
s can be sent freely
between threads. In other words, ArcCStr
implements cheap Send
for strings using the fact
that CStr
is Sync
. ArcCStr
tries to minimize the space overhead of this feature by
sharing the string data. The disadvantage of this approach is that it requires atomic
operations that are more expensive than ordinary memory accesses. Thus, if you have many
threads accessing the same data, you may see contention. However, in the common case, using
ArcCStr
should still be faster than cloning the full string.
ArcCStr
automatically dereferences to CStr
(via the Deref
trait), so you can call
CStr
’s methods on a value of type ArcCStr
. To avoid name clashes with CStr
’s methods,
the methods of ArcCStr
itself are associated functions, called using function-like
syntax:
use arccstr::ArcCStr; use std::convert::TryFrom; let mut my_arc = ArcCStr::try_from("foobar").unwrap(); ArcCStr::strong_count(&my_arc);
Examples
Sharing some immutable strings between threads:
use std::convert::TryFrom; use arccstr::ArcCStr; use std::thread; let five = ArcCStr::try_from("5").unwrap(); for _ in 0..10 { let five = ArcCStr::clone(&five); thread::spawn(move || { println!("{:?}", five); }); }
Implementations
impl ArcCStr
[src]
impl ArcCStr
[src]pub fn strong_count(this: &Self) -> usize
[src]
pub fn strong_count(this: &Self) -> usize
[src]Gets the number of pointers to this string.
Safety
This method by itself is safe, but using it correctly requires extra care. Another thread can change the strong count at any time, including potentially between calling this method and acting on the result.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); let _also_five = ArcCStr::clone(&five); // This assertion is deterministic because we haven't shared // the `ArcCStr` between threads. assert_eq!(2, ArcCStr::strong_count(&five));
pub fn ptr_eq(this: &Self, other: &Self) -> bool
[src]
pub fn ptr_eq(this: &Self, other: &Self) -> bool
[src]Returns true if the two ArcCStr
s point to the same value (not
just values that compare as equal).
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); let same_five = ArcCStr::clone(&five); let other_five = ArcCStr::try_from("5").unwrap(); assert!(ArcCStr::ptr_eq(&five, &same_five)); assert!(!ArcCStr::ptr_eq(&five, &other_five));
Methods from Deref<Target = CStr>
pub const fn as_ptr(&self) -> *const i8
1.0.0 (const: 1.32.0)[src]
pub const fn as_ptr(&self) -> *const i8
1.0.0 (const: 1.32.0)[src]Returns the inner pointer to this C string.
The returned pointer will be valid for as long as self
is, and points
to a contiguous region of memory terminated with a 0 byte to represent
the end of the string.
WARNING
The returned pointer is read-only; writing to it (including passing it to C code that writes to it) causes undefined behavior.
It is your responsibility to make sure that the underlying memory is not
freed too early. For example, the following code will cause undefined
behavior when ptr
is used inside the unsafe
block:
use std::ffi::CString; let ptr = CString::new("Hello").expect("CString::new failed").as_ptr(); unsafe { // `ptr` is dangling *ptr; }
This happens because the pointer returned by as_ptr
does not carry any
lifetime information and the CString
is deallocated immediately after
the CString::new("Hello").expect("CString::new failed").as_ptr()
expression is evaluated.
To fix the problem, bind the CString
to a local variable:
use std::ffi::CString; let hello = CString::new("Hello").expect("CString::new failed"); let ptr = hello.as_ptr(); unsafe { // `ptr` is valid because `hello` is in scope *ptr; }
This way, the lifetime of the CString
in hello
encompasses
the lifetime of ptr
and the unsafe
block.
pub fn to_bytes(&self) -> &[u8]
1.0.0[src]
pub fn to_bytes(&self) -> &[u8]
1.0.0[src]Converts this C string to a byte slice.
The returned slice will not contain the trailing nul terminator that this C string has.
Note: This method is currently implemented as a constant-time cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.
Examples
use std::ffi::CStr; let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); assert_eq!(cstr.to_bytes(), b"foo");
pub fn to_bytes_with_nul(&self) -> &[u8]
1.0.0[src]
pub fn to_bytes_with_nul(&self) -> &[u8]
1.0.0[src]Converts this C string to a byte slice containing the trailing 0 byte.
This function is the equivalent of CStr::to_bytes
except that it
will retain the trailing nul terminator instead of chopping it off.
Note: This method is currently implemented as a 0-cost cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.
Examples
use std::ffi::CStr; let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); assert_eq!(cstr.to_bytes_with_nul(), b"foo\0");
pub fn to_str(&self) -> Result<&str, Utf8Error>
1.4.0[src]
pub fn to_str(&self) -> Result<&str, Utf8Error>
1.4.0[src]Yields a &str
slice if the CStr
contains valid UTF-8.
If the contents of the CStr
are valid UTF-8 data, this
function will return the corresponding &str
slice. Otherwise,
it will return an error with details of where UTF-8 validation failed.
Examples
use std::ffi::CStr; let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); assert_eq!(cstr.to_str(), Ok("foo"));
pub fn to_string_lossy(&self) -> Cow<'_, str>
1.4.0[src]
pub fn to_string_lossy(&self) -> Cow<'_, str>
1.4.0[src]Converts a CStr
into a Cow
<
str
>
.
If the contents of the CStr
are valid UTF-8 data, this
function will return a Cow
::
Borrowed
(
&str
)
with the corresponding &str
slice. Otherwise, it will
replace any invalid UTF-8 sequences with
U+FFFD REPLACEMENT CHARACTER
and return a
Cow
::
Owned
(
String
)
with the result.
Examples
Calling to_string_lossy
on a CStr
containing valid UTF-8:
use std::borrow::Cow; use std::ffi::CStr; let cstr = CStr::from_bytes_with_nul(b"Hello World\0") .expect("CStr::from_bytes_with_nul failed"); assert_eq!(cstr.to_string_lossy(), Cow::Borrowed("Hello World"));
Calling to_string_lossy
on a CStr
containing invalid UTF-8:
use std::borrow::Cow; use std::ffi::CStr; let cstr = CStr::from_bytes_with_nul(b"Hello \xF0\x90\x80World\0") .expect("CStr::from_bytes_with_nul failed"); assert_eq!( cstr.to_string_lossy(), Cow::Owned(String::from("Hello �World")) as Cow<'_, str> );
Trait Implementations
impl Clone for ArcCStr
[src]
impl Clone for ArcCStr
[src]fn clone(&self) -> ArcCStr
[src]
fn clone(&self) -> ArcCStr
[src]Makes a clone of the ArcCStr
pointer.
This creates another pointer to the same underlying string, increasing the reference count.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); ArcCStr::clone(&five);
fn clone_from(&mut self, source: &Self)
1.0.0[src]
fn clone_from(&mut self, source: &Self)
1.0.0[src]Performs copy-assignment from source
. Read more
impl<'de> Deserialize<'de> for ArcCStr
[src]
impl<'de> Deserialize<'de> for ArcCStr
[src]fn deserialize<D>(deserializer: D) -> Result<ArcCStr, D::Error> where
D: Deserializer<'de>,
[src]
fn deserialize<D>(deserializer: D) -> Result<ArcCStr, D::Error> where
D: Deserializer<'de>,
[src]Deserialize this value from the given Serde deserializer. Read more
impl Drop for ArcCStr
[src]
impl Drop for ArcCStr
[src]fn drop(&mut self)
[src]
fn drop(&mut self)
[src]Drops the ArcCStr
.
This will decrement the reference count. If the reference count reaches zero then we also deallocate the underlying string.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let foo = ArcCStr::try_from("foo").unwrap(); let foo2 = ArcCStr::clone(&foo); drop(foo); // "foo" is still in memory drop(foo2); // "foo" is deallocated
impl Ord for ArcCStr
[src]
impl Ord for ArcCStr
[src]fn cmp(&self, other: &ArcCStr) -> Ordering
[src]
fn cmp(&self, other: &ArcCStr) -> Ordering
[src]Comparison for two ArcCStr
s.
The two are compared by calling cmp()
on their underlying strings.
Examples
use arccstr::ArcCStr; use std::cmp::Ordering; use std::convert::TryFrom; let five = ArcCStr::try_from("5").unwrap(); assert_eq!(Ordering::Less, five.cmp(&ArcCStr::try_from("6").unwrap()));
impl PartialEq<ArcCStr> for ArcCStr
[src]
impl PartialEq<ArcCStr> for ArcCStr
[src]fn eq(&self, other: &ArcCStr) -> bool
[src]
fn eq(&self, other: &ArcCStr) -> bool
[src]Equality for two ArcCStr
s.
Two ArcCStr
s are equal if their underlying strings are equal.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5"); assert_eq!(five, ArcCStr::try_from("5")); assert_ne!(five, ArcCStr::try_from("6"));
impl PartialOrd<ArcCStr> for ArcCStr
[src]
impl PartialOrd<ArcCStr> for ArcCStr
[src]fn partial_cmp(&self, other: &ArcCStr) -> Option<Ordering>
[src]
fn partial_cmp(&self, other: &ArcCStr) -> Option<Ordering>
[src]Partial comparison for two ArcCStr
s.
The two are compared by calling partial_cmp()
on their underlying strings.
Examples
use arccstr::ArcCStr; use std::cmp::Ordering; use std::convert::TryFrom; let five = ArcCStr::try_from("5").unwrap(); assert_eq!(Some(Ordering::Less), five.partial_cmp(&ArcCStr::try_from("6").unwrap()));
fn lt(&self, other: &ArcCStr) -> bool
[src]
fn lt(&self, other: &ArcCStr) -> bool
[src]Less-than comparison for two ArcCStr
s.
The two are compared by calling <
on their inner values.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); assert!(five < ArcCStr::try_from("6").unwrap());
fn le(&self, other: &ArcCStr) -> bool
[src]
fn le(&self, other: &ArcCStr) -> bool
[src]‘Less than or equal to’ comparison for two ArcCStr
s.
The two are compared by calling <=
on their underlying strings.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); assert!(five <= ArcCStr::try_from("5").unwrap());
fn gt(&self, other: &ArcCStr) -> bool
[src]
fn gt(&self, other: &ArcCStr) -> bool
[src]Greater-than comparison for two ArcCStr
s.
The two are compared by calling >
on their underlying strings.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); assert!(five > ArcCStr::try_from("4").unwrap());
fn ge(&self, other: &ArcCStr) -> bool
[src]
fn ge(&self, other: &ArcCStr) -> bool
[src]‘Greater than or equal to’ comparison for two ArcCStr
s.
The two are compared by calling >=
on their underlying strings.
Examples
use std::convert::TryFrom; use arccstr::ArcCStr; let five = ArcCStr::try_from("5").unwrap(); assert!(five >= ArcCStr::try_from("5").unwrap());
impl Eq for ArcCStr
[src]
impl Send for ArcCStr
[src]
impl Sync for ArcCStr
[src]
Auto Trait Implementations
Blanket Implementations
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]pub fn borrow_mut(&mut self) -> &mut T
[src]
pub fn borrow_mut(&mut self) -> &mut T
[src]Mutably borrows from an owned value. Read more
impl<T> ToOwned for T where
T: Clone,
[src]
impl<T> ToOwned for T where
T: Clone,
[src]type Owned = T
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
[src]
pub fn to_owned(&self) -> T
[src]Creates owned data from borrowed data, usually by cloning. Read more
pub fn clone_into(&self, target: &mut T)
[src]
pub fn clone_into(&self, target: &mut T)
[src]🔬 This is a nightly-only experimental API. (toowned_clone_into
)
recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
impl<T> DeserializeOwned for T where
T: for<'de> Deserialize<'de>,
[src]
T: for<'de> Deserialize<'de>,