Faster package count on Alpine Linux

src/linux/mod.rs

@@ -9,6 +9,7 @@ use crate::extra::path_extension;
 use crate::shared;
 use crate::traits::*;
 use itertools::Itertools;
+use nix::NixPath;
 use pciid_parser::Database;
 use regex::Regex;
 use std::fs;
@@ -855,6 +856,13 @@ impl LinuxPackageReadout {
     /// Returns the number of installed packages for systems
     /// that utilize `apk` as their package manager.
     fn count_apk() -> Option<usize> {
+
+        // faster method for alpine: count empty lines in /lib/apk/db/installed
+        if let Ok(content) = fs::read_to_string(Path::new("/lib/apk/db/installed")) {
+            return Some(content.lines().filter(|l| l.is_empty()).count());
+        }
+
+        // fallback to command invocation
         if !extra::which("apk") {
             return None;
         }