Make the offsets for SeekFrom's Hole and Data unsigned. (#1266)

* Make the offsets for `SeekFrom`'s `Hole` and `Data` unsigned.

These represent absolute offsets from the start of the file, so they
should be unsigned, for consistency with `Start`.

* Update tests.

Author: sunfishcode

src/backend/libc/fs/syscalls.rs

@@ -1293,9 +1293,17 @@ pub(crate) fn seek(fd: BorrowedFd<'_>, pos: SeekFrom) -> io::Result<u64> {
         SeekFrom::End(offset) => (c::SEEK_END, offset),
         SeekFrom::Current(offset) => (c::SEEK_CUR, offset),
         #[cfg(any(apple, freebsdlike, linux_kernel, solarish))]
-        SeekFrom::Data(offset) => (c::SEEK_DATA, offset),
+        SeekFrom::Data(pos) => {
+            let pos: u64 = pos;
+            // Silently cast; we'll get `EINVAL` if the value is negative.
+            (c::SEEK_DATA, pos as i64)
+        }
         #[cfg(any(apple, freebsdlike, linux_kernel, solarish))]
-        SeekFrom::Hole(offset) => (c::SEEK_HOLE, offset),
+        SeekFrom::Hole(pos) => {
+            let pos: u64 = pos;
+            // Silently cast; we'll get `EINVAL` if the value is negative.
+            (c::SEEK_HOLE, pos as i64)
+        }
     };
 
     // ESP-IDF and Vita don't support 64-bit offsets.

src/backend/linux_raw/fs/syscalls.rs

@@ -238,8 +238,16 @@ pub(crate) fn seek(fd: BorrowedFd<'_>, pos: SeekFrom) -> io::Result<u64> {
         }
         SeekFrom::End(offset) => (SEEK_END, offset),
         SeekFrom::Current(offset) => (SEEK_CUR, offset),
-        SeekFrom::Data(offset) => (SEEK_DATA, offset),
-        SeekFrom::Hole(offset) => (SEEK_HOLE, offset),
+        SeekFrom::Data(pos) => {
+            let pos: u64 = pos;
+            // Silently cast; we'll get `EINVAL` if the value is negative.
+            (SEEK_DATA, pos as i64)
+        }
+        SeekFrom::Hole(pos) => {
+            let pos: u64 = pos;
+            // Silently cast; we'll get `EINVAL` if the value is negative.
+            (SEEK_HOLE, pos as i64)
+        }
     };
     _seek(fd, offset, whence)
 }

src/fs/seek_from.rs

@@ -41,13 +41,13 @@ pub enum SeekFrom {
     ///
     /// [`Errno::NXIO`]: crate::io::Errno::NXIO
     #[cfg(any(apple, freebsdlike, linux_kernel, solarish))]
-    Data(i64),
+    Data(u64),
 
     /// Sets the offset to the current position plus the specified number of
     /// bytes, plus the distance to the next byte which is in a hole.
     ///
     /// If there is no hole past the offset, it will be set to the end of the
     /// file i.e. there is an implicit hole at the end of any file.
     #[cfg(any(apple, freebsdlike, linux_kernel, solarish))]
-    Hole(i64),
+    Hole(u64),
 }

tests/fs/seek.rs

@@ -43,18 +43,15 @@ fn test_seek_holes() {
     assert_eq!(seek(&file, SeekFrom::Start(0)), Ok(0));
     assert_eq!(seek(&file, SeekFrom::Current(0)), Ok(0));
     assert_eq!(seek(&file, SeekFrom::Hole(0)), Ok(hole_size));
-    assert_eq!(seek(&file, SeekFrom::Hole(hole_size as i64)), Ok(hole_size));
+    assert_eq!(seek(&file, SeekFrom::Hole(hole_size)), Ok(hole_size));
     assert_eq!(
-        seek(&file, SeekFrom::Hole(hole_size as i64 * 2)),
+        seek(&file, SeekFrom::Hole(hole_size * 2)),
         Ok(hole_size * 2 + 6)
     );
     assert_eq!(seek(&file, SeekFrom::Data(0)), Ok(0));
+    assert_eq!(seek(&file, SeekFrom::Data(hole_size)), Ok(hole_size * 2));
     assert_eq!(
-        seek(&file, SeekFrom::Data(hole_size as i64)),
-        Ok(hole_size * 2)
-    );
-    assert_eq!(
-        seek(&file, SeekFrom::Data(hole_size as i64 * 2)),
+        seek(&file, SeekFrom::Data(hole_size * 2)),
         Ok(hole_size * 2)
     );
 }