add musl and glibc wrappers for getdents{,64}

src/unix/linux_like/linux/gnu/mod.rs

@@ -1346,6 +1346,13 @@ extern "C" {
     pub fn mempcpy(dest: *mut c_void, src: *const c_void, n: size_t) -> *mut c_void;
 }
 
+extern "C" {
+    // There is no glibc wrapper for the getdents system call, and getdents64() is only available
+    // from 2.30 onwards.
+    /// `buffer` points to a buffer of [`crate::dirent64`] structs.
+    pub fn getdents64(fd: c_int, buffer: *mut c_void, nbytes: usize) -> isize;
+}
+
 cfg_if! {
     if #[cfg(any(
         target_arch = "x86",

src/unix/linux_like/linux/musl/lfs64.rs

@@ -198,6 +198,11 @@ pub unsafe extern "C" fn readdir64_r(
     crate::readdir_r(dirp, entry as *mut _, result as *mut _)
 }
 
+#[inline]
+pub unsafe extern "C" fn getdents64(fd: c_int, buf: *mut crate::dirent64, len: usize) -> c_int {
+    crate::getdents(fd, buf as *mut _, len)
+}
+
 #[inline]
 pub unsafe extern "C" fn sendfile64(
     out_fd: c_int,

src/unix/linux_like/linux/musl/mod.rs

@@ -37,6 +37,15 @@ cfg_if! {
     }
 }
 
+#[repr(C)]
+pub struct posix_dent {
+    pub d_ino: ino_t,
+    pub d_off: off_t,
+    pub d_reclen: c_ushort,
+    pub d_type: c_uchar,
+    pub d_name: *mut c_char,
+}
+
 impl siginfo_t {
     pub unsafe fn si_addr(&self) -> *mut c_void {
         #[repr(C)]
@@ -971,6 +980,12 @@ extern "C" {
     pub fn utmpxname(file: *const c_char) -> c_int;
 }
 
+extern "C" {
+    pub fn posix_getdents(fd: c_int, buf: *mut c_void, len: usize, flags: c_int) -> isize;
+
+    pub fn getdents(fd: c_int, buf: *mut crate::dirent, len: usize) -> c_int;
+}
+
 // Alias <foo> to <foo>64 to mimic glibc's LFS64 support
 mod lfs64;
 pub use self::lfs64::*;