pub trait CStrLike {
type Baked: Deref<Target = CStr>;
type Error: Debug + Display;
// Required methods
fn bake(self) -> Result<Self::Baked, Self::Error>;
fn into_c_string(self) -> Result<CString, Self::Error>;
}Expand description
Value which can be converted into a C string.
The trait is used as argument to functions which wish to accept either
&str or &CStr arguments while internally need to interact with
C APIs. Accepting &str may be more convenient for users but requires
conversion into CString internally which requires allocation. With this
trait, latency-conscious users may choose to prepare CStr in advance and
then pass it directly without having to incur the conversion cost.
To use the trait, function should accept impl CStrLike and after baking
the argument (with CStrLike::bake method) it can use it as a &CStr
(since the baked result dereferences into CStr).
§Example
use std::ffi::{CStr, CString};
use rocksdb::CStrLike;
fn strlen(arg: impl CStrLike) -> std::result::Result<usize, String> {
let baked = arg.bake().map_err(|err| err.to_string())?;
Ok(unsafe { libc::strlen(baked.as_ptr()) })
}
const FOO: &str = "foo";
const BAR: &CStr = unsafe { CStr::from_bytes_with_nul_unchecked(b"bar\0") };
assert_eq!(Ok(3), strlen(FOO));
assert_eq!(Ok(3), strlen(BAR));Required Associated Types§
Required Methods§
sourcefn bake(self) -> Result<Self::Baked, Self::Error>
fn bake(self) -> Result<Self::Baked, Self::Error>
Bakes self into value which can be freely converted into &CStr.
This may require allocation and may fail if self has invalid value.
sourcefn into_c_string(self) -> Result<CString, Self::Error>
fn into_c_string(self) -> Result<CString, Self::Error>
Consumers and converts value into an owned CString.
If Self is already a CString simply returns it; if it’s a reference
to a CString then the value is cloned. In other cases this may
require allocation and may fail if self has invalid value.