faster read permission checking

src/file_browser.rs

@@ -19,6 +19,7 @@ use crate::fail::{HResult, HError, ErrorLog};
 use crate::widget::{Events, WidgetCore};
 use crate::proclist::ProcView;
 use crate::bookmarks::BMPopup;
+use crate::term;
 use crate::term::ScreenExt;
 use crate::foldview::LogView;
 use crate::coordinates::Coordinates;
@@ -271,9 +272,16 @@ impl FileBrowser {
     }
 
     pub fn main_widget_goto(&mut self, dir: &File) -> HResult<()> {
-        if dir.read_dir().is_err() {
-            self.show_status("Can't enter! Permission denied!").log();
-            return Ok(());
+        match dir.is_readable() {
+            Ok(true) => {},
+            Ok(false) => {
+                let status =
+                    format!("{}Stop right there, cowboy! Check your permisions!",
+                            term::color_red());
+                self.show_status(&status).log();
+                return Ok(());
+            }
+            err @ Err(_) => err.log()
         }
 
         let dir = dir.clone();

src/files.rs

@@ -9,7 +9,10 @@ use std::ffi::{OsStr, OsString};
 
 use lscolors::LsColors;
 use mime_detective;
-use users;
+use users::{get_current_username,
+            get_current_groupname,
+            get_user_by_uid,
+            get_group_by_gid};
 use chrono::TimeZone;
 use failure::Error;
 use notify::DebouncedEvent;
@@ -553,6 +556,35 @@ impl File {
         Ok(())
     }
 
+    pub fn is_readable(&self) -> HResult<bool> {
+        let meta = self.meta()?;
+        let current_user = get_current_username()?.to_string_lossy().to_string();
+        let current_group = get_current_groupname()?.to_string_lossy().to_string();
+        let file_user = get_user_by_uid(meta.uid())?
+            .name()
+            .to_string_lossy()
+            .to_string();
+        let file_group = get_group_by_gid(meta.gid())?
+            .name()
+            .to_string_lossy()
+            .to_string();
+        let perms = meta.mode();
+
+        let user_readable = perms & 0o400;
+        let group_readable = perms & 0o040;
+        let other_readable = perms & 0o004;
+
+        if current_user == file_user && user_readable > 0 {
+            Ok(true)
+        } else if current_group == file_group && group_readable > 0 {
+            Ok(true)
+        } else if other_readable > 0 {
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    }
+
     pub fn pretty_print_permissions(&self) -> HResult<String> {
         let perms: usize = format!("{:o}", self.meta()?.mode()).parse().unwrap();
         let perms: usize  = perms % 800;