file_model: Use binary search to find index

Binary search is a fast method to sort for an item within
a sorted list. We have a sorted list, so we can take advantage
of binary search instead of having a linear traversal through
the list.

Because binary search requires a sorted list, we need to use
the same logic for sorting and searching. Here we factor out
the filename comparison logic into `util::compare_by_name()`.
In the future we may want to have a module for sorting algorithm
logic and checking what sorting algortihm Nautilus uses.

src/file_model.rs

@@ -101,13 +101,7 @@ impl LpFileModel {
             });
 
             // Then sort by name.
-            vec.sort_by(|file_a, file_b| {
+            vec.sort_by(util::compare_by_name);
-                let name_a = util::get_file_display_name(file_a).unwrap_or_default();
-                let name_b = util::get_file_display_name(file_b).unwrap_or_default();
-
-                util::utf8_collate_key_for_filename(&name_a)
-                    .cmp(&util::utf8_collate_key_for_filename(&name_b))
-            });
 
             model.imp().directory.set(directory.clone()).unwrap();
         }
@@ -127,6 +121,8 @@ impl LpFileModel {
     pub fn index_of(&self, file: &gio::File) -> Option<u32> {
         let imp = self.imp();
         let vec = imp.inner.borrow();
-        vec.iter().position(|f| f.equal(file)).map(|p| p as u32)
+        vec.binary_search_by(|a| util::compare_by_name(a, file))
+            .ok()
+            .map(|i| i as u32)
     }
 }

src/util.rs

@@ -3,6 +3,10 @@ use crate::deps::*;
 use gio::prelude::*;
 use glib::translate::*;
 
+use anyhow::Context;
+
+use std::fmt::Write;
+
 pub fn utf8_collate_key_for_filename(filename: &str) -> String {
     unsafe {
         from_glib_full(glib::ffi::g_utf8_collate_key_for_filename(
@@ -18,14 +22,11 @@ pub fn get_file_display_name(file: &gio::File) -> Option<String> {
     Some(info.display_name().to_string())
 }
 
-pub fn query_attributes(
+pub fn query_attributes(file: &gio::File, attributes: Vec<&str>) -> anyhow::Result<gio::FileInfo> {
-    file: &gio::File,
-    attributes: Vec<&str>,
-) -> Result<gio::FileInfo, glib::Error> {
     let mut attributes = attributes;
     let mut attr_str = String::from(attributes.remove(0));
     for attr in attributes {
-        attr_str.push_str(&format!(",{}", attr));
+        write!(attr_str, ",{}", attr)?;
     }
 
     file.query_info(
@@ -33,4 +34,12 @@ pub fn query_attributes(
         gio::FileQueryInfoFlags::empty(),
         gio::Cancellable::NONE,
     )
+    .context("Failed to query string")
+}
+
+pub fn compare_by_name(file_a: &gio::File, file_b: &gio::File) -> std::cmp::Ordering {
+    let name_a = get_file_display_name(file_a).unwrap_or_default();
+    let name_b = get_file_display_name(file_b).unwrap_or_default();
+
+    utf8_collate_key_for_filename(&name_a).cmp(&utf8_collate_key_for_filename(&name_b))
 }