Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/wasi-common/src/sys/unix/linux/mod.rs

@@ -0,0 +1,42 @@
+pub(crate) mod hostcalls_impl;
+pub(crate) mod osfile;
+
+pub(crate) mod fdentry_impl {
+    use crate::{sys::host_impl, Result};
+    use std::os::unix::prelude::AsRawFd;
+
+    pub(crate) unsafe fn isatty(fd: &impl AsRawFd) -> Result<bool> {
+        use nix::errno::Errno;
+
+        let res = libc::isatty(fd.as_raw_fd());
+        if res == 1 {
+            // isatty() returns 1 if fd is an open file descriptor referring to a terminal...
+            Ok(true)
+        } else {
+            // ... otherwise 0 is returned, and errno is set to indicate the error.
+            match Errno::last() {
+                // While POSIX specifies ENOTTY if the passed
+                // fd is *not* a tty, on Linux, some implementations
+                // may return EINVAL instead.
+                //
+                // https://linux.die.net/man/3/isatty
+                Errno::ENOTTY | Errno::EINVAL => Ok(false),
+                x => Err(host_impl::errno_from_nix(x)),
+            }
+        }
+    }
+}
+
+pub(crate) mod host_impl {
+    pub(crate) const O_RSYNC: nix::fcntl::OFlag = nix::fcntl::OFlag::O_RSYNC;
+}
+
+pub(crate) mod fs_helpers {
+    pub(crate) fn utime_now() -> libc::c_long {
+        libc::UTIME_NOW
+    }
+
+    pub(crate) fn utime_omit() -> libc::c_long {
+        libc::UTIME_OMIT
+    }
+}