Struct rocksdb::properties::PropertyName

source ·

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

Expand description

An owned name of a RocksDB property.

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

Implementations§

source §

impl PropertyName

source

pub fn into_c_string(self) -> CString

Converts the value into a C string.

source

pub fn into_string(self) -> String

Converts the property name into a string.

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

Methods from Deref<Target = PropName>§

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pub fn as_c_str(&self) -> &CStr

Converts the value into a C string slice.

source

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>§

1.0.0 · source

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.

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pub fn count_bytes(&self) -> usize

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

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

#![feature(cstr_count_bytes)]

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);

1.71.0 · source

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());

1.0.0 · source

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");

1.0.0 · source

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");

1.4.0 · source

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"));

1.4.0 · source

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:

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>
);