Struct rocksdb::properties::PropName

pub struct PropName(/* private fields */);

A borrowed name of a RocksDB property.

The value is guaranteed to be a nul-terminated UTF-8 string. This means it can be converted to CStr and str at zero cost.

Implementations

impl PropName

pub fn as_c_str(&self) -> &CStr

Converts the value into a C string slice.

pub fn as_str(&self) -> &str

Converts the value into a string slice.

Nul byte terminating the underlying C string is not included in the returned slice.

Methods from Deref<Target = CStr>

pub fn as_ptr(&self) -> *const i8

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.

The type of the returned pointer is *const c_char, and whether it’s an alias for *const i8 or *const u8 is platform-specific.

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;

// Do not do this:
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 count_bytes(&self) -> usize

Returns the length of self. Like C’s strlen, this does not include the nul terminator.

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").unwrap();
assert_eq!(cstr.count_bytes(), 3);

let cstr = CStr::from_bytes_with_nul(b"\0").unwrap();
assert_eq!(cstr.count_bytes(), 0);

pub fn is_empty(&self) -> bool

Returns true if self.to_bytes() has a length of 0.

Examples

use std::ffi::CStr;

let cstr = CStr::from_bytes_with_nul(b"foo\0")?;
assert!(!cstr.is_empty());

let empty_cstr = CStr::from_bytes_with_nul(b"\0")?;
assert!(empty_cstr.is_empty());
assert!(c"".is_empty());

pub fn to_bytes(&self) -> &[u8]

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]

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 bytes(&self) -> Bytes<'_>

🔬This is a nightly-only experimental API. (cstr_bytes)

Iterates over the bytes in this C string.

The returned iterator will not contain the trailing nul terminator that this C string has.

Examples

#![feature(cstr_bytes)]
use std::ffi::CStr;

let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
assert!(cstr.bytes().eq(*b"foo"));

pub fn to_str(&self) -> Result<&str, Utf8Error>

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>

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(&str) with the result.

Examples

Calling to_string_lossy on a CStr containing valid UTF-8. The leading c on the string literal denotes a CStr.

use std::borrow::Cow;

assert_eq!(c"Hello World".to_string_lossy(), Cow::Borrowed("Hello World"));

Calling to_string_lossy on a CStr containing invalid UTF-8:

use std::borrow::Cow;

assert_eq!(
    c"Hello \xF0\x90\x80World".to_string_lossy(),
    Cow::Owned(String::from("Hello �World")) as Cow<'_, str>
);

Trait Implementations

impl AsRef<CStr> for PropName

fn as_ref(&self) -> &CStr

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<str> for PropName

fn as_ref(&self) -> &str

Converts this type into a shared reference of the (usually inferred) input type.

impl Borrow<PropName> for PropertyName

fn borrow(&self) -> &PropName

Immutably borrows from an owned value.

impl<'a> CStrLike for &'a PropName

type Baked = &'a CStr

type Error = Infallible

fn bake( self, ) -> Result<<&'a PropName as CStrLike>::Baked, <&'a PropName as CStrLike>::Error>

Bakes self into value which can be freely converted into &CStr.

fn into_c_string(self) -> Result<CString, <&'a PropName as CStrLike>::Error>

Consumers and converts value into an owned CString.

impl Debug for PropName

fn fmt(&self, fmtr: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Deref for PropName

type Target = CStr

The resulting type after dereferencing.

fn deref(&self) -> &<PropName as Deref>::Target

Dereferences the value.

impl Display for PropName

fn fmt(&self, fmtr: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Hash for PropName

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

impl Ord for PropName

fn cmp(&self, other: &PropName) -> Ordering

This method returns an Ordering between self and other.

impl PartialEq<CStr> for PropName

fn eq(&self, other: &CStr) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<PropName> for CStr

fn eq(&self, other: &PropName) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<PropName> for str

fn eq(&self, other: &PropName) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<str> for PropName

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq for PropName

fn eq(&self, other: &PropName) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for PropName

fn partial_cmp(&self, other: &PropName) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl ToOwned for PropName

type Owned = PropertyName

The resulting type after obtaining ownership.

fn to_owned(&self) -> <PropName as ToOwned>::Owned

Creates owned data from borrowed data, usually by cloning.

fn clone_into(&self, target: &mut <PropName as ToOwned>::Owned)

Uses borrowed data to replace owned data, usually by cloning.

impl Eq for PropName

impl StructuralPartialEq for PropName