Fix cap-std compilation on WASI.

This gets cap-primitives and cap-std to the point where they compile on
WASI. There are a few TODOs, and some of this will need to be revisited
as WASI evolves and adds `chmod` support, but this should suffice for
now.

Fixes #195.

Author: sunfishcode

cap-primitives/src/fs/dir_options.rs

@@ -1,3 +1,4 @@
+#[cfg(not(target_os = "wasi"))]
 use crate::fs::DirOptionsExt;
 
 /// Options and flags which can be used to configure how a directory is
@@ -6,6 +7,7 @@ use crate::fs::DirOptionsExt;
 /// This is to `create_dir` what to `OpenOptions` is to `open`.
 #[derive(Debug, Clone)]
 pub struct DirOptions {
+    #[cfg(not(target_os = "wasi"))]
     #[allow(dead_code)]
     pub(crate) ext: DirOptionsExt,
 }
@@ -16,6 +18,7 @@ impl DirOptions {
     #[inline]
     pub const fn new() -> Self {
         Self {
+            #[cfg(not(target_os = "wasi"))]
             ext: DirOptionsExt::new(),
         }
     }

cap-primitives/src/fs/metadata.rs

@@ -259,6 +259,44 @@ impl std::os::unix::fs::MetadataExt for Metadata {
     }
 }
 
+#[cfg(target_os = "wasi")]
+impl std::os::wasi::fs::MetadataExt for Metadata {
+    #[inline]
+    fn dev(&self) -> u64 {
+        self.ext.dev()
+    }
+
+    #[inline]
+    fn ino(&self) -> u64 {
+        self.ext.ino()
+    }
+
+    #[inline]
+    fn nlink(&self) -> u64 {
+        self.ext.nlink()
+    }
+
+    #[inline]
+    fn size(&self) -> u64 {
+        self.ext.size()
+    }
+
+    #[inline]
+    fn atim(&self) -> u64 {
+        self.ext.atim()
+    }
+
+    #[inline]
+    fn mtim(&self) -> u64 {
+        self.ext.mtim()
+    }
+
+    #[inline]
+    fn ctim(&self) -> u64 {
+        self.ext.ctim()
+    }
+}
+
 #[cfg(target_os = "vxworks")]
 impl std::os::vxworks::fs::MetadataExt for Metadata {
     #[inline]

cap-primitives/src/fs/mod.rs

@@ -32,6 +32,7 @@ mod remove_file;
 mod remove_open_dir;
 mod rename;
 mod reopen;
+#[cfg(not(target_os = "wasi"))]
 mod set_permissions;
 mod set_times;
 mod stat;
@@ -85,6 +86,7 @@ pub use remove_file::remove_file;
 pub use remove_open_dir::{remove_open_dir, remove_open_dir_all};
 pub use rename::rename;
 pub use reopen::reopen;
+#[cfg(not(target_os = "wasi"))]
 pub use set_permissions::set_permissions;
 pub use set_times::{set_times, set_times_nofollow};
 pub use stat::stat;

cap-primitives/src/fs/open_options.rs

@@ -178,6 +178,41 @@ impl std::os::unix::fs::OpenOptionsExt for OpenOptions {
     }
 }
 
+#[cfg(target_os = "wasi")]
+impl std::os::wasi::fs::OpenOptionsExt for OpenOptions {
+    fn lookup_flags(&mut self, _: u32) -> &mut Self {
+        todo!()
+    }
+    fn directory(&mut self, dir_required: bool) -> &mut Self {
+        self.dir_required = dir_required;
+        self
+    }
+    fn dsync(&mut self, _: bool) -> &mut Self {
+        todo!()
+    }
+    fn nonblock(&mut self, _: bool) -> &mut Self {
+        todo!()
+    }
+    fn rsync(&mut self, _: bool) -> &mut Self {
+        todo!()
+    }
+    fn sync(&mut self, _: bool) -> &mut Self {
+        todo!()
+    }
+    fn fs_rights_base(&mut self, _: u64) -> &mut Self {
+        todo!()
+    }
+    fn fs_rights_inheriting(&mut self, _: u64) -> &mut Self {
+        todo!()
+    }
+    fn open_at<P>(&self, dirfd: &std::fs::File, path: P) -> Result<std::fs::File, std::io::Error>
+    where
+        P: AsRef<std::path::Path>,
+    {
+        crate::fs::open(dirfd, path.as_ref(), self)
+    }
+}
+
 #[cfg(target_os = "vxworks")]
 impl std::os::vxworks::fs::OpenOptionsExt for OpenOptions {
     #[inline]

cap-primitives/src/fs/permissions.rs

@@ -1,4 +1,4 @@
-#[cfg(any(unix, target_os = "vxworks"))]
+#[cfg(not(windows))]
 use crate::fs::PermissionsExt;
 #[cfg(unix)]
 use rustix::fs::RawMode;
@@ -52,6 +52,15 @@ impl Permissions {
         Ok(fs::Permissions::from_mode(self.ext.mode()))
     }
 
+    #[cfg(target_os = "wasi")]
+    #[inline]
+    #[allow(clippy::unnecessary_wraps)]
+    fn _into_std(self, file: &fs::File) -> io::Result<fs::Permissions> {
+        let mut permissions = file.metadata()?.permissions();
+        permissions.set_readonly(self.readonly());
+        Ok(permissions)
+    }
+
     #[cfg(windows)]
     #[inline]
     fn _into_std(self, file: &fs::File) -> io::Result<fs::Permissions> {

cap-primitives/src/rustix/fs/copy_impl.rs

@@ -25,6 +25,7 @@ fn open_from(start: &fs::File, path: &Path) -> io::Result<(fs::File, fs::Metadat
     Ok((reader, metadata))
 }
 
+#[cfg(not(target_os = "wasi"))]
 fn open_to_and_set_permissions(
     start: &fs::File,
     path: &Path,
@@ -54,6 +55,25 @@ fn open_to_and_set_permissions(
     Ok((writer, writer_metadata))
 }
 
+#[cfg(target_os = "wasi")]
+fn open_to_and_set_permissions(
+    start: &fs::File,
+    path: &Path,
+    reader_metadata: fs::Metadata,
+) -> io::Result<(fs::File, fs::Metadata)> {
+    let writer = open(
+        start,
+        path,
+        OpenOptions::new()
+            // create the file with the correct mode right away
+            .write(true)
+            .create(true)
+            .truncate(true),
+    )?;
+    let writer_metadata = writer.metadata()?;
+    Ok((writer, writer_metadata))
+}
+
 #[cfg(not(any(
     target_os = "linux",
     target_os = "android",

cap-primitives/src/rustix/fs/create_dir_unchecked.rs

@@ -10,9 +10,10 @@ pub(crate) fn create_dir_unchecked(
     path: &Path,
     options: &DirOptions,
 ) -> io::Result<()> {
-    Ok(mkdirat(
-        start,
-        path,
-        Mode::from_bits(options.ext.mode as RawMode).unwrap(),
-    )?)
+    #[cfg(not(target_os = "wasi"))]
+    let raw_mode = options.ext.mode as RawMode;
+    #[cfg(target_os = "wasi")]
+    let raw_mode = 0;
+
+    Ok(mkdirat(start, path, Mode::from_bits(raw_mode).unwrap())?)
 }

cap-primitives/src/rustix/fs/dir_utils.rs

@@ -6,7 +6,7 @@ use std::ops::Deref;
 #[cfg(unix)]
 use std::os::unix::{ffi::OsStrExt, fs::OpenOptionsExt};
 #[cfg(target_os = "wasi")]
-use std::os::wasi::{ffi::OsStrExt, fs::OpenOptionsExt};
+use std::os::wasi::ffi::OsStrExt;
 use std::path::Path;
 #[cfg(racy_asserts)]
 use std::{ffi::OsString, os::unix::ffi::OsStringExt, path::PathBuf};
@@ -104,10 +104,13 @@ pub(crate) fn open_ambient_dir_impl(path: &Path, _: AmbientAuthority) -> io::Res
     // `O_DIRECTORY` manually.
     let flags = OFlags::DIRECTORY | target_o_path();
 
-    fs::OpenOptions::new()
-        .read(true)
-        .custom_flags(flags.bits() as i32)
-        .open(&path)
+    let mut options = fs::OpenOptions::new();
+    options.read(true);
+
+    #[cfg(not(target_os = "wasi"))]
+    options.custom_flags(flags.bits() as i32);
+
+    options.open(&path)
 }
 
 /// Use `O_PATH` on platforms which have it, or none otherwise.
@@ -131,6 +134,7 @@ pub(crate) const fn target_o_path() -> OFlags {
         target_os = "macos",
         target_os = "netbsd",
         target_os = "openbsd",
+        target_os = "wasi",
     ))]
     {
         OFlags::empty()

cap-primitives/src/rustix/fs/file_path.rs

@@ -6,8 +6,6 @@ use std::ffi::OsString;
 use std::fs;
 #[cfg(unix)]
 use std::os::unix::ffi::OsStringExt;
-#[cfg(target_os = "wasi")]
-use std::os::wasi::ffi::OsStringExt;
 use std::path::PathBuf;
 
 pub(crate) fn file_path_by_ttyname_or_seaching(file: &fs::File) -> Option<PathBuf> {

cap-primitives/src/rustix/fs/file_type_ext.rs

@@ -44,12 +44,16 @@ impl FileTypeExt {
             FileType::ext(Self::BlockDevice)
         } else if std.is_char_device() {
             FileType::ext(Self::CharDevice)
-        } else if std.is_fifo() {
-            FileType::ext(Self::Fifo)
-        } else if std.is_socket() {
-            FileType::ext(Self::Socket)
         } else {
-            FileType::unknown()
+            #[cfg(not(target_os = "wasi"))]
+            if std.is_fifo() {
+                return FileType::ext(Self::Fifo);
+            }
+            if std.is_socket() {
+                FileType::ext(Self::Socket)
+            } else {
+                FileType::unknown()
+            }
         }
     }