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//! Helper utilities
//!
// TODO RPC: Consider replacing this with a derive-deftly template.
//
/// Define an `impl From<fromty> for toty`` that wraps its input as
/// `toty::variant(Arc::new(e))``
macro_rules! define_from_for_arc {
{ $fromty:ty => $toty:ty [$variant:ident] } => {
impl From<$fromty> for $toty {
fn from(e: $fromty) -> $toty {
Self::$variant(std::sync::Arc::new(e))
}
}
};
}
use std::ffi::{CStr, CString, NulError};
pub(crate) use define_from_for_arc;
/// A string that is guaranteed to be UTF-8 and NUL-terminated,
/// for fast access as either type.
//
// TODO RPC: Rename so we can expose it more sensibly.
#[derive(Clone, Debug)]
pub struct Utf8CString {
/// The body of this string.
///
/// # Safety
///
/// INVARIANT: This string must be valid UTF-8.
///
/// (We do not _yet_ depend on this invariant for safety in our rust code, but we do promise in
/// our C ffi that it will hold.)
string: Box<CStr>,
}
impl AsRef<CStr> for Utf8CString {
fn as_ref(&self) -> &CStr {
&self.string
}
}
impl AsRef<str> for Utf8CString {
fn as_ref(&self) -> &str {
// TODO: We might someday decide to implement this using unsafe methods, to avoid walking
// over the string to enforce properties that are already there.
self.string.to_str().expect("Utf8CString was not UTF-8‽")
}
}
// TODO: In theory we could have an unchecked version of this function, if we are 100%
// sure that serde_json will reject every string that contains a NUL. But let's not do
// that unless the NUL check shows up in profiles.
impl TryFrom<String> for Utf8CString {
type Error = NulError;
fn try_from(value: String) -> Result<Self, Self::Error> {
// Safety: Since `value` is a `String`, it is guaranteed to be UTF-8.
Ok(Utf8CString {
string: CString::new(value)?.into_boxed_c_str(),
})
}
}
/// Ffi-related functionality for Utf8CStr
#[cfg(feature = "ffi")]
pub(crate) mod ffi {
use std::ffi::c_char;
impl super::Utf8CString {
/// Expose this Utf8CStr as a C string.
pub(crate) fn as_ptr(&self) -> *const c_char {
self.string.as_ptr()
}
}
}
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