feat(app): add caching mechanism for kernel parameters

Cargo.lock

@@ -110,6 +110,27 @@ dependencies = [
  "lazy_static",
 ]
 
+[[package]]
+name = "dirs-next"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b98cf8ebf19c3d1b223e151f99a4f9f0690dca41414773390fc824184ac833e1"
+dependencies = [
+ "cfg-if",
+ "dirs-sys-next",
+]
+
+[[package]]
+name = "dirs-sys-next"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ebda144c4fe02d1f7ea1a7d9641b6fc6b580adcfa024ae48797ecdeb6825b4d"
+dependencies = [
+ "libc",
+ "redox_users",
+ "winapi",
+]
+
 [[package]]
 name = "either"
 version = "1.6.1"
@@ -131,6 +152,17 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcd999463524c52659517fe2cea98493cfe485d10565e7b0fb07dbba7ad2753"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "globset"
 version = "0.4.8"
@@ -182,6 +214,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "itoa"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b71991ff56294aa922b450139ee08b3bfc70982c6b2c7562771375cf73542dd4"
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
@@ -277,6 +315,25 @@ dependencies = [
  "num_cpus",
 ]
 
+[[package]]
+name = "redox_syscall"
+version = "0.2.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8383f39639269cde97d255a32bdb68c047337295414940c68bdd30c2e13203ff"
+dependencies = [
+ "bitflags",
+]
+
+[[package]]
+name = "redox_users"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "528532f3d801c87aec9def2add9ca802fe569e44a544afe633765267840abe64"
+dependencies = [
+ "getrandom",
+ "redox_syscall",
+]
+
 [[package]]
 name = "regex"
 version = "1.5.4"
@@ -294,6 +351,12 @@ version = "0.6.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f497285884f3fcff424ffc933e56d7cbca511def0c9831a7f9b5f6153e3cc89b"
 
+[[package]]
+name = "ryu"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c9613b5a66ab9ba26415184cfc41156594925a9cf3a2057e57f31ff145f6568"
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
@@ -309,6 +372,37 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "serde"
+version = "1.0.130"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f12d06de37cf59146fbdecab66aa99f9fe4f78722e3607577a5375d66bd0c913"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.130"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7bc1a1ab1961464eae040d96713baa5a724a8152c1222492465b54322ec508b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "serde_json"
+version = "1.0.72"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0ffa0837f2dfa6fb90868c2b5468cad482e175f7dad97e7421951e663f2b527"
+dependencies = [
+ "itoa",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.78"
@@ -347,8 +441,11 @@ name = "systeroid-core"
 version = "0.1.0"
 dependencies = [
  "colored",
+ "dirs-next",
  "lazy_static",
  "rayon",
+ "serde",
+ "serde_json",
  "sysctl",
  "systeroid-parser",
  "thiserror",
@@ -415,6 +512,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.10.2+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"
+
 [[package]]
 name = "winapi"
 version = "0.3.9"

systeroid-core/Cargo.toml

@@ -10,6 +10,9 @@ thiserror = "1.0.29"
 lazy_static = "1.4.0"
 rayon = "1.5.1"
 colored = "2.0.0"
+serde = { version = "1.0.130", features = ["derive"] }
+serde_json = "1.0.69"
+dirs-next = "2.0.0"
 
 [dependencies.systeroid-parser]
 version = "0.1.0"

systeroid-core/src/cache.rs

@@ -0,0 +1,55 @@
+use crate::error::{Error, Result};
+use serde::de::DeserializeOwned;
+use serde::Serialize;
+use std::fs::{self, File};
+use std::io::Write;
+use std::path::PathBuf;
+use systeroid_parser::reader;
+
+/// Cache manager for handling the R/W operations of labeled data.
+#[derive(Debug)]
+pub struct Cache {
+    /// Cache directory.
+    cache_dir: PathBuf,
+}
+
+impl Cache {
+    /// Initializes the cache storage.
+    pub fn init() -> Result<Self> {
+        Ok(Self {
+            cache_dir: dirs_next::cache_dir().ok_or_else(|| {
+                Error::CacheError(String::from("cannot access the cache directory"))
+            })?,
+        })
+    }
+
+    /// Returns the path of given labeled data.
+    fn get_cache_path(&self, label: &str) -> PathBuf {
+        self.cache_dir
+            .join(env!("CARGO_PKG_NAME"))
+            .join(label)
+            .with_extension("json")
+    }
+
+    /// Returns `true` if the labeled data is present in the cache.
+    pub fn exists(&self, label: &str) -> bool {
+        self.get_cache_path(label).exists()
+    }
+
+    /// Reads the given labeled data from the cache.
+    pub fn read<Data: DeserializeOwned>(&self, label: &str) -> Result<Data> {
+        let raw_data = reader::read_to_string(self.get_cache_path(label))?;
+        Ok(serde_json::from_str(&raw_data)?)
+    }
+
+    /// Writes the given data to the cache.
+    pub fn write<Data: ?Sized + Serialize>(&self, data: &Data, label: &str) -> Result<()> {
+        let cache_path = self.get_cache_path(label);
+        if !cache_path.exists() {
+            fs::create_dir_all(self.cache_dir.join(env!("CARGO_PKG_NAME")))?;
+        };
+        let mut file = File::create(&cache_path)?;
+        file.write_all(serde_json::to_string(data)?.as_bytes())?;
+        Ok(())
+    }
+}

systeroid-core/src/error.rs

@@ -9,6 +9,12 @@ pub enum Error {
     /// Error that may occur whenever a lock is acquired.
     #[error("thread lock error: `{0}`")]
     ThreadLockError(String),
+    /// Error that may occur when accessing the cached data.
+    #[error("cache error: `{0}`")]
+    CacheError(String),
+    /// Error that may occur while de/serializing JSON data.
+    #[error("JSON de/serialization error: `{0}`")]
+    SerdeJsonError(#[from] serde_json::Error),
     /// Error that may occur while parsing documents.
     #[error("parser error: `{0}`")]
     ParseError(#[from] systeroid_parser::error::Error),

systeroid-core/src/lib.rs

@@ -19,3 +19,6 @@ pub mod config;
 
 /// Display options.
 pub mod display;
+
+/// Cache manager.
+pub mod cache;

systeroid-core/src/sysctl.rs

@@ -4,6 +4,7 @@ use crate::error::Result;
 use crate::parsers::parse_kernel_docs;
 use colored::*;
 use rayon::prelude::*;
+use serde::{Deserialize, Serialize};
 use std::convert::TryFrom;
 use std::fmt::{self, Display, Formatter};
 use std::io::Write;
@@ -12,7 +13,7 @@ use std::result::Result as StdResult;
 use sysctl::{Ctl, CtlFlags, CtlIter, Sysctl as SysctlImpl};
 
 /// Sections of the sysctl documentation.
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, Serialize, Deserialize)]
 pub enum Section {
     /// Documentation for `/proc/sys/abi/*`
     Abi,
@@ -76,7 +77,7 @@ impl Section {
 }
 
 /// Representation of a kernel parameter.
-#[derive(Debug)]
+#[derive(Serialize, Deserialize, Debug)]
 pub struct Parameter {
     /// Name of the kernel parameter.
     pub name: String,
@@ -260,6 +261,22 @@ impl Sysctl {
         parameter
     }
 
+    /// Updates the parameters using the given list.
+    ///
+    /// Keeps the original values.
+    pub fn update_params(&mut self, mut parameters: Vec<Parameter>) {
+        parameters.par_iter_mut().for_each(|parameter| {
+            if let Some(param) = self
+                .parameters
+                .par_iter()
+                .find_any(|param| param.name == parameter.name)
+            {
+                parameter.value = param.value.to_string();
+            }
+        });
+        self.parameters = parameters;
+    }
+
     /// Updates the descriptions of the kernel parameters.
     pub fn update_docs(&mut self, kernel_docs: &Path) -> Result<()> {
         let documents = parse_kernel_docs(kernel_docs)?;

systeroid/src/app.rs

@@ -2,10 +2,14 @@ use std::env;
 use std::io::{self, Stdout};
 use std::path::PathBuf;
 use std::process::{Command, Stdio};
+use systeroid_core::cache::Cache;
 use systeroid_core::config::AppConfig;
 use systeroid_core::error::Result;
 use systeroid_core::parsers::KERNEL_DOCS_PATH;
-use systeroid_core::sysctl::Sysctl;
+use systeroid_core::sysctl::{Parameter, Sysctl};
+
+/// Label for caching the kernel parameters.
+const PARAMETERS_CACHE_LABEL: &str = "parameters";
 
 /// Application controller.
 #[derive(Debug)]
@@ -14,19 +18,21 @@ pub struct App<'a> {
     sysctl: &'a mut Sysctl,
     /// Configuration.
     config: &'a AppConfig,
+    /// Cache.
+    cache: Cache,
     /// Standard output.
     stdout: Stdout,
 }
 
 impl<'a> App<'a> {
     /// Constructs a new instance.
-    pub fn new(sysctl: &'a mut Sysctl, config: &'a AppConfig) -> Self {
-        let stdout = io::stdout();
-        Self {
+    pub fn new(sysctl: &'a mut Sysctl, config: &'a AppConfig) -> Result<Self> {
+        Ok(Self {
             sysctl,
             config,
-            stdout,
-        }
+            cache: Cache::init()?,
+            stdout: io::stdout(),
+        })
     }
 
     /// Displays all of the available kernel modules.
@@ -39,16 +45,23 @@ impl<'a> App<'a> {
 
     /// Updates the documentation for kernel parameters.
     pub fn update_documentation(&mut self, kernel_docs: Option<&PathBuf>) -> Result<()> {
+        if self.cache.exists(PARAMETERS_CACHE_LABEL) && kernel_docs.is_none() {
+            self.sysctl
+                .update_params(self.cache.read::<Vec<Parameter>>(PARAMETERS_CACHE_LABEL)?);
+            return Ok(());
+        }
         let mut kernel_docs_path = KERNEL_DOCS_PATH.clone();
         if let Some(path) = kernel_docs {
             kernel_docs_path.insert(0, path);
         }
         if let Some(path) = kernel_docs_path.iter().find(|path| path.exists()) {
-            self.sysctl.update_docs(path)
+            self.sysctl.update_docs(path)?;
+            self.cache
+                .write(&self.sysctl.parameters, PARAMETERS_CACHE_LABEL)?;
         } else {
             eprintln!("warning: `Linux kernel documentation cannot be found. Please specify a path via '-d' argument`",);
-            Ok(())
         }
+        Ok(())
     }
 
     /// Displays the documentation of a parameter.

systeroid/src/lib.rs

@@ -21,7 +21,7 @@ pub fn run(args: Args) -> Result<()> {
     config.app.display_type = args.display_type;
     config.app.no_color = env::var("NO_COLOR").is_ok();
     let mut sysctl = Sysctl::init(config.sysctl)?;
-    let mut app = App::new(&mut sysctl, &config.app);
+    let mut app = App::new(&mut sysctl, &config.app)?;
 
     if let Some(param) = args.param_to_explain {
         app.update_documentation(args.kernel_docs.as_ref())?;