fix and clean up comments surrounding file seeking

Author: Tropix126

library/std/src/sys/pal/vexos/fs.rs

@@ -339,33 +339,19 @@ impl File {
             SeekFrom::Start(offset) => unsafe {
                 map_fresult(vex_sdk::vexFileSeek(self.fd.0, try_convert_offset(offset)?, SEEK_SET))?
             },
-
-            // VEXos does not allow seeking with negative offsets.
-            // That means we need to calculate the offset from the start for both of these.
             SeekFrom::End(offset) => unsafe {
-                // If our offset is positive, everything is easy
                 if offset >= 0 {
                     map_fresult(vex_sdk::vexFileSeek(
                         self.fd.0,
                         try_convert_offset(offset)?,
                         SEEK_END,
                     ))?
                 } else {
-                    // Get the position of the end of the file...
+                    // `vexFileSeek` does not support seeking with negative offset, meaning
+                    // we have to calculate the offset from the end of the file ourselves.
                     map_fresult(vex_sdk::vexFileSeek(
                         self.fd.0,
-                        try_convert_offset(offset)?,
-                        SEEK_END,
-                    ))?;
-                    // The number returned by the VEX SDK tell is stored as a 32 bit interger,
-                    // and therefore this conversion cannot fail.
-                    let position = self.tell()? as i64;
-
-                    // Offset from that position
-                    let new_position = position + offset;
-                    map_fresult(vex_sdk::vexFileSeek(
-                        self.fd.0,
-                        try_convert_offset(new_position)?,
+                        try_convert_offset(self.file_attr().size + offset)?,
                         SEEK_SET,
                     ))?
                 }
@@ -378,12 +364,11 @@ impl File {
                         SEEK_CUR,
                     ))?
                 } else {
-                    let position = self.tell()? as i64;
-
-                    let new_position = position + offset;
+                    // `vexFileSeek` does not support seeking with negative offset, meaning
+                    // we have to calculate the offset from the stream position ourselves.
                     map_fresult(vex_sdk::vexFileSeek(
                         self.fd.0,
-                        try_convert_offset(new_position)?,
+                        try_convert_offset((self.tell()? as i64) + offset)?,
                         SEEK_SET,
                     ))?
                 }