all: split reusable components into workspace crates

utils/src/mmap.rs

@@ -0,0 +1,34 @@
+use {
+    crate::{oserror::OsError, ptr_ext::PtrExt},
+    std::ptr,
+    uapi::c,
+};
+
+pub struct Mmapped {
+    pub ptr: *const [u8],
+}
+
+pub fn mmap(
+    len: usize,
+    prot: c::c_int,
+    flags: c::c_int,
+    fd: c::c_int,
+    offset: c::off_t,
+) -> Result<Mmapped, OsError> {
+    let res = unsafe { c::mmap(ptr::null_mut(), len, prot, flags, fd, offset) };
+    if res == c::MAP_FAILED {
+        Err(OsError::default())
+    } else {
+        Ok(Mmapped {
+            ptr: ptr::slice_from_raw_parts(res.cast(), len),
+        })
+    }
+}
+
+impl Drop for Mmapped {
+    fn drop(&mut self) {
+        unsafe {
+            c::munmap(self.ptr.deref().as_ptr() as _, self.ptr.deref().len());
+        }
+    }
+}