Add From and TryFrom impls in libc_enum macro #1088
There are no files selected for viewing
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,12 +1,14 @@ | ||
| #[cfg(target_os = "dragonfly")] | ||
| extern crate cc; | ||
| extern crate version_check as rustc; | ||
|
|
||
| fn main() { | ||
| #[cfg(target_os = "dragonfly")] | ||
| cc::Build::new() | ||
| .file("src/errno_dragonfly.c") | ||
| .compile("liberrno_dragonfly.a"); | ||
|
|
||
| if rustc::is_min_version("1.34.0").unwrap_or(false) { | ||
| println!("cargo:rustc-cfg=try_from"); | ||
| } | ||
| } |
| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
|
@@ -2,8 +2,6 @@ | |
| /// with values from the libc crate. It is used the same way as the `bitflags!` macro, except | ||
| /// that only the name of the flag value has to be given. | ||
| /// | ||
| /// # Example | ||
| /// ``` | ||
| /// libc_bitflags!{ | ||
|
|
@@ -53,204 +51,121 @@ macro_rules! libc_bitflags { | |
| pub struct $BitFlags: $T { | ||
| $( | ||
| $(#[$inner $($args)*])* | ||
| const $Flag = ::libc::$Flag $(as $cast)*; | ||
| )+ | ||
| } | ||
| } | ||
| }; | ||
| } | ||
|
|
||
| /// The `libc_enum!` macro helps with a common use case of defining an enum exclusively using | ||
| /// values from the `libc` crate. The type after the enum name specifies the type of the constants | ||
| /// in `libc`. The macro will generate impls of `From` and `TryFrom` to convert between numeric and | ||
| /// enum values. | ||
| /// | ||
| /// `TryFrom` is only implemented for Rust >= 1.34.0, where the trait is stable. An equivalent | ||
| /// `try_from` inherent method is made available regardless of the Rust version. `TryInto` should | ||
| /// not be used as long as the MSRV for nix is less than 1.34.0. | ||
| /// | ||
| /// | ||
| /// Documentation for each variant must be provided before any cfg attributes. | ||
| /// | ||
| /// # Example | ||
| /// ``` | ||
| /// libc_enum! { | ||
| /// pub enum ProtFlags: c_int { | ||
| /// PROT_NONE, | ||
| /// PROT_READ, | ||
| /// PROT_WRITE, | ||
| /// PROT_EXEC, | ||
| /// /// Documentation before cfg attribute. | ||
| /// #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| /// PROT_GROWSDOWN, | ||
| /// #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| /// PROT_GROWSUP, | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// let flag: c_int = ProtFlags::PROT_NONE.into(); | ||
| /// let flag: ProtFlags = ProtFlags::try_from(::libc::PROT_NONE).unwrap(); | ||
| /// ``` | ||
| macro_rules! libc_enum { | ||
| // pub | ||
| ( | ||
| $(#[$enum_attr:meta])* | ||
| pub $(($($scope:tt)*))* enum $($def:tt)* | ||
| ) => { | ||
| libc_enum! { | ||
| @(pub $(($($scope)*))*) | ||
| $(#[$enum_attr])* | ||
| enum $($def)* | ||
| } | ||
| }; | ||
|
|
||
| // non-pub | ||
| ( | ||
| $(#[$enum_attr:meta])* | ||
| enum $($def:tt)* | ||
| ) => { | ||
| libc_enum! { | ||
| @() | ||
| $(#[$enum_attr])* | ||
| enum $($def)* | ||
| } | ||
| }; | ||
|
|
||
| ( | ||
| @($($vis:tt)*) | ||
| $(#[$enum_attr:meta])* | ||
| enum $enum:ident : $prim:ty { | ||
| $( | ||
| $(#[doc = $var_doc:tt])* | ||
|
There was a problem hiding this comment. Doc strings and cfg attributes are both different kinds of attributes. Could you simplify the macro by combining these two lines? There was a problem hiding this comment. The compiler emits a warning for "unused doc comment" when it sees a doc comment annotating a match arm, so I match them separately here so that I can use the |
||
| $(#[cfg($var_cfg:meta)])* | ||
| $entry:ident | ||
| ),* $(,)* | ||
| } | ||
| ) => { | ||
| $(#[$enum_attr])* | ||
| #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] | ||
| $($vis)* enum $enum { | ||
| $( | ||
| $(#[doc = $var_doc])* | ||
| $(#[cfg($var_cfg)])* | ||
| $entry = ::libc::$entry as isize | ||
|
There was a problem hiding this comment. why cast to There was a problem hiding this comment.
There was a problem hiding this comment. Given the way that these types will be used, I think that There was a problem hiding this comment. The problem is that in some places we're using a custom type as The reason we need to use a custom type is that in some cases the underlying type depends on the target machine. I'm not sure how we could get around that with the
Can you share an example where the repr makes a difference? |
||
| ),* | ||
| } | ||
|
|
||
| impl $enum { | ||
| pub fn try_from(value: $prim) -> std::result::Result<$enum, ::Error> { | ||
| match value { | ||
| $( | ||
| $(#[cfg($var_cfg)])* | ||
| ::libc::$entry => Ok($enum::$entry), | ||
| )* | ||
| // don't think this Error is the correct one | ||
|
There was a problem hiding this comment. I think that's a fine choice of error. There was a problem hiding this comment. The reason I doubt is that How about adding an There was a problem hiding this comment. Yeah, I understand. |
||
| _ => Err(::Error::invalid_argument()) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl std::convert::From<$enum> for $prim { | ||
| fn from(value: $enum) -> $prim { | ||
| match value { | ||
| $( | ||
| $(#[cfg($var_cfg)])* | ||
| $enum::$entry => ::libc::$entry, | ||
| )* | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(try_from)] | ||
| impl std::convert::TryFrom<$prim> for $enum { | ||
| type Error = ::Error; | ||
|
|
||
| fn try_from(value: $prim) -> std::result::Result<$enum, Self::Error> { | ||
| $enum::try_from(value) | ||
| } | ||
| } | ||
| }; | ||
| } | ||
|
|
||
Uh oh!
There was an error while loading. Please reload this page.