Added trait `SystemError`: Allows errno codes to be attached to `Error` types. Added `ErrnoFormatter` struct for a confirugrably-buffered `fmt::Display` impl to print `strerror_r()` results on an errno code.

Fortune for mempipe's current commit: Future blessing − 末吉

src/ext.rs

@@ -4,4 +4,7 @@ use super::*;
 pub use loli::{
     DupExt,
     Dup2Ext,
+
+    SystemError,
+    SystemErrorExt,
 };

src/loli.rs

@@ -71,9 +71,197 @@ mod raw {
 
 // Errno error handling
 
+//TODO: Move all errno related stuff into a submodule inside `srd/loli/` to un-clutter this file; and add a `RawErrno`-like struct for errors that are *just* an errno value (that implements `SystemError`)
+
 /// A raw `errno` value
 pub type RawErrno = raw::c_int;
 
+/// Default max buffer size for formatting `errno` message codes.
+///
+/// This is the size used by glibc's `perror()`. It should cover all internationalised error messages.
+pub const DEFAULT_ERRNO_MESSAGE_BUFFER_SIZE: usize = 1024;
+
+/// Default buffer size short `errno` message code strings.
+///
+/// # Internationalisation
+/// This size covers all current English `errno` messages. However, if the program is ran with a non-ASCII locale, the size may exceed this by far. See `DEFAULT_ERRNO_MESSAGE_BUFFER_SIZE` for those cases.
+pub const DEFAULT_ASCII_ERRNO_MESSAGE_BUFFER_SIZE: usize = 64;
+
+/// An error type which also contains an `errno` code.
+pub trait SystemError: std::error::Error
+{
+    fn code(&self) -> RawErrno;
+    
+    #[inline(always)] 
+    fn fmt_message(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	errno_fmt_message::<1024>(self.code(), f)
+    }
+
+    #[inline] 
+    fn get_message(&self) -> ErrnoFormatter
+    {
+	ErrnoFormatter::new_default(self.code())
+    }
+
+    #[inline] 
+    fn message(&self) -> String
+    {
+	self.get_message().to_string()
+    }
+}
+
+/// Extension trait for `SystemError` types.
+///
+/// # Specific buffered sizes
+/// Provides user-configurable buffer sized methods for message formatting
+pub trait SystemErrorExt: SystemError
+{
+    fn fmt_message_with_buffer<const BUFFER_SIZE: usize>(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result;
+    fn get_message_with_buffer<const BUFFER_SIZE: usize>(&self) -> ErrnoFormatter<BUFFER_SIZE>;
+    fn message_with_buffer<const BUFFER_SIZE: usize>(&self) -> String;
+}
+
+impl<T: ?Sized> SystemErrorExt for T
+where T: SystemError
+{
+    #[inline] 
+    fn fmt_message_with_buffer<const BUFFER_SIZE: usize>(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	errno_fmt_message::<BUFFER_SIZE>(self.code(), f)
+    }
+
+    #[inline] 
+    fn get_message_with_buffer<const BUFFER_SIZE: usize>(&self) -> ErrnoFormatter<BUFFER_SIZE>
+    {
+	ErrnoFormatter::<BUFFER_SIZE>::new(self.code())
+    }
+    #[inline] 
+    fn message_with_buffer<const BUFFER_SIZE: usize>(&self) -> String
+    {
+	ErrnoFormatter::<BUFFER_SIZE>::new(self.code()).to_string()
+    }
+}
+
+/// String formatter for an `errno` value.
+///
+/// # `MESSAGE_BUFFER_SIZE`
+/// This structure contains only the `errno` code. The `MESSAGE_BUFFER_SIZE` const generic is used as a max size for formatting the error messages.
+/// It **must** be above 0.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Copy)]
+#[repr(transparent)]
+pub struct ErrnoFormatter<const MESSAGE_BUFFER_SIZE: usize = DEFAULT_ERRNO_MESSAGE_BUFFER_SIZE>(RawErrno);
+
+//TODO: Document the following
+
+impl ErrnoFormatter<DEFAULT_ASCII_ERRNO_MESSAGE_BUFFER_SIZE>
+{
+    #[inline(always)] 
+    pub const fn new_ascii(code: RawErrno) -> Self
+    {
+	Self(code)
+    }
+}
+
+impl ErrnoFormatter<DEFAULT_ERRNO_MESSAGE_BUFFER_SIZE>
+{
+    #[inline(always)] 
+    pub const fn new_default(code: RawErrno) -> Self
+    {
+	Self(code)
+    }
+}
+
+impl<const BUFF_SIZE: usize> ErrnoFormatter<BUFF_SIZE>
+{
+    #[inline(always)] 
+    pub const fn new(code: RawErrno) -> Self
+    {
+	Self(code)
+    }
+    
+    #[inline] 
+    pub const fn raw(self) -> RawErrno
+    {
+	self.0
+    }
+
+    #[inline] 
+    pub const fn buffer_size(self) -> usize
+    {
+	BUFF_SIZE
+    }
+
+    #[inline] 
+    pub const fn with_buffer_size<const NBUFF_SIZE: usize>(self) -> ErrnoFormatter<NBUFF_SIZE>
+    {
+	ErrnoFormatter::<NBUFF_SIZE>::new(self.0)
+    }
+    
+    pub fn try_to_string(&self) -> Result<String, Result<UString, RawErrno>>
+    {
+	match self.try_to_raw_string() {
+	    Ok(string) => string.into_string().map_err(|us| Ok(us)),
+	    Err(en) => Err(Err(en)),
+	}
+    }
+    
+    #[inline] 
+    pub fn try_to_raw_string(&self) -> Result<UString, RawErrno>
+    {
+	errno_ustring_buffer::<BUFF_SIZE>(self.0)
+    }
+
+    #[inline] 
+    pub fn try_to_c_string(&self) -> Result<CString, RawErrno>
+    {
+	errno_cstring_buffer::<BUFF_SIZE>(self.0)
+    }
+
+    #[inline]
+    pub fn to_raw_buffer(&self) -> Result<[u8; BUFF_SIZE], RawErrno>
+    {
+	errno_raw_buffer(self.0)
+    }
+}
+
+impl<const BUFF_SIZE: usize> fmt::Display for ErrnoFormatter<BUFF_SIZE>
+{
+    #[inline] 
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	errno_fmt_message::<BUFF_SIZE>(self.0, f)
+    }
+}
+
+
+fn errno_fmt_message<const BUFF_SIZE: usize>(code: RawErrno, f: &mut fmt::Formatter<'_>) -> fmt::Result
+{
+    if let Ok(buffer) = errno_raw_buffer::<BUFF_SIZE>(code)
+    {
+	if let Some(first) = buffer.split(|&b| b == 0).next()
+	{
+	    f.write_str(String::from_utf8_lossy(first).as_ref())
+	} else {
+	    #[cold]
+	    #[inline(never)] //XXX: Should we noinline this cold path? I think we should.
+	    fn _failed_path(code: RawErrno, f: &mut fmt::Formatter<'_>) -> fmt::Result
+	    {
+		write!(f, "<!unknown: empty message for errno {}>", code)
+	    }
+	    _failed_path(code, f)
+	}
+    } else {
+	#[cold]
+	#[inline(never)]
+	fn _failed_path(code: RawErrno, f: &mut fmt::Formatter<'_>) -> fmt::Result
+	{
+	    write!(f, "<!unknown: message extraction failed for errno {}>", code)
+	}
+	_failed_path(code, f)
+    }
+}
+
 fn errno_raw_buffer<const BUFF_SIZE: usize>(errno: RawErrno) -> Result<[u8; BUFF_SIZE], RawErrno>
 {
     use std::mem::MaybeUninit;
@@ -121,11 +309,11 @@ fn errno_lossy_string_buffer<const BUFF_SIZE: usize>(errno: RawErrno) -> Result<
 #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct DupError(RawErrno);
 
-impl DupError
+impl SystemError for DupError
 {
     /// The `errno` code for this error.
     #[inline] 
-    pub fn code(&self) -> RawErrno
+    fn code(&self) -> RawErrno
     {
 	self.0
     }
@@ -136,16 +324,8 @@ impl fmt::Display for DupError
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
     {
-	write!(f, "dup() failed with ")?;
-	
-	if let Ok(buffer) = errno_raw_buffer::<1024>(self.0) {
-	    let string = String::from_utf8_lossy(buffer.split(|&b| b == 0)
-						 .next()
-						 .unwrap_or(b"<empty error message buffer>"));
-	    write!(f, "{}: {}", self.0, string)
-	} else {
-	    write!(f, "{} <failed to extract code message at 1024 bytes buffer size>", self.0)
-	}
+	write!(f, "dup() failed with {}: ", self.0)?;
+	self.fmt_message(f)	
     }
 }
 
@@ -199,6 +379,8 @@ fn errno_if_nz(rv: raw::c_int) -> Result<(), RawErrno>
 
 // Wrapper traits
 
+//TODO: Move wrapper traits into a seperate module in src/loli/ to unclutter this file
+
 /// Extension methods for `dup()`ing file descriptors
 pub trait DupExt: Sized
 {
@@ -233,7 +415,10 @@ where T: FromRawFd + AsRawFd
     }
 }
 
-//TODO: Document the following, and make it work like CStr/CString
+//TODO: Document the following, and make sure it works like CStr/CString (minus the nul-termination bs)
+
+//TODO: Move UStr/UString and related stuffs into a seperate module in src/loli/ to unclutter this file
+
 
 /// A reference to an unmanaged string that may contain non-utf8 characters.
 ///
@@ -422,6 +607,14 @@ impl UString
 	})
     }
     
+    pub fn try_into_string(self) -> Result<String, std::string::FromUtf8Error>
+    {
+	let vec = Vec::from(self.0);
+	String::from_utf8(vec)/*.map_err(|e| {
+	    Self(e.into_bytes().into())
+    })*/
+    }
+
     /// Allocate a new owned `CString` from this nul-terminated unmanaged string.
     ///
     /// # Safety
@@ -486,8 +679,9 @@ fn deref(&self) -> &Self::Target {
 &self.0[..]
     }
 }
+
 XXX: Is DerefMut needed, too?
-XXX: What about AsMut?
+XXX: What about AsMut? I think those two are unsafe, especially if the &mut UStr comes from an &mut str. There are unsafe methods for this anyway.
  */
 
 impl AsRef<UStr> for UString
@@ -510,7 +704,7 @@ impl Deref for UString
     }
 }
 
-//XXX: Should we allow mutation of the `ustr` here? I think so, because we don't allow mutation of the underlying [u8]
+//Should we allow mutation of the `ustr` here? I think so, because we don't allow mutation of the underlying [u8]
 impl AsMut<UStr> for UString
 {
     #[inline(always)] 
@@ -527,6 +721,91 @@ impl DerefMut for UString
     }
 }
 
+// UStr/ing <--?> CStr/ing
+
+impl From<CString> for UString
+{
+    #[inline] 
+    fn from(from: CString) -> Self
+    {
+	Self::from_c_string(from)
+    }
+}
+
+impl<'a> From<&'a CStr> for &'a UStr
+{
+    #[inline] 
+    fn from(from: &'a CStr) -> Self
+    {
+	UStr::from_c_str(from)
+    }
+}
+
+impl TryFrom<UString> for CString
+{
+    type Error = std::ffi::FromVecWithNulError;
+
+    #[inline] 
+    fn try_from(from: UString) -> Result<Self, Self::Error>
+    {
+	from.into_c_string()
+    }
+}
+
+impl<'a> TryFrom<&'a UStr> for &'a CStr
+{
+    type Error = std::ffi::FromBytesWithNulError;
+
+    #[inline] 
+    fn try_from(from: &'a UStr) -> Result<Self, Self::Error>
+    {
+	from.as_c_str()
+    }
+}
+
+// UStr/ing <--?> str/ing
+
+impl From<String> for UString
+{
+    #[inline] 
+    fn from(from: String) -> Self
+    {
+	Self::new(from.into_bytes())
+    }
+}
+
+impl<'a> From<&'a str> for &'a UStr
+{
+    #[inline] 
+    fn from(from: &'a str) -> Self
+    {
+	UStr::new(from.as_bytes())
+    }
+}
+// No From<&'_ mut str> for &'_ mut UStr: The bytes belonging to the &'_ str may be modified in safe code if this were allowed.
+
+impl TryFrom<UString> for String
+{
+    type Error = std::string::FromUtf8Error;
+
+    #[inline] 
+    fn try_from(from: UString) -> Result<Self, Self::Error>
+    {
+	from.try_into_string()
+    }
+}
+
+impl<'a> TryFrom<&'a UStr> for &'a str
+{
+    type Error = std::str::Utf8Error;
+
+    #[inline] 
+    fn try_from(from: &'a UStr) -> Result<Self, Self::Error>
+    {
+	from.to_str()
+    }
+}
+
 #[cfg(test)]
 mod tests
 {