yanix: Provide faccessat.

Author: sunfishcode

crates/wasi-common/yanix/src/file.rs

@@ -31,6 +31,15 @@ bitflags! {
     }
 }
 
+bitflags! {
+    pub struct Access: libc::c_int {
+        const R_OK = libc::R_OK;
+        const W_OK = libc::W_OK;
+        const X_OK = libc::X_OK;
+        const F_OK = libc::F_OK;
+    }
+}
+
 bitflags! {
     pub struct AtFlags: libc::c_int {
         const REMOVEDIR = libc::AT_REMOVEDIR;
@@ -315,6 +324,22 @@ pub unsafe fn fstat(fd: RawFd) -> Result<stat> {
     Ok(filestat.assume_init())
 }
 
+pub unsafe fn faccessat<P: AsRef<Path>>(
+    dirfd: RawFd,
+    path: P,
+    access: Access,
+    flags: AtFlags,
+) -> Result<()> {
+    let path = cstr(path)?;
+    from_result(libc::faccessat(
+        dirfd as libc::c_int,
+        path.as_ptr(),
+        access.bits(),
+        flags.bits(),
+    ))?;
+    Ok(())
+}
+
 /// `fionread()` function, equivalent to `ioctl(fd, FIONREAD, *bytes)`.
 pub unsafe fn fionread(fd: RawFd) -> Result<u32> {
     let mut nread: libc::c_int = 0;