melib/utils: add hostname() utility function

Signed-off-by: Manos Pitsidianakis <manos@pitsidianak.is>

meli/src/conf.rs

@@ -1262,7 +1262,7 @@ mod dotaddressable {
 
 #[test]
 fn test_config_parse() {
-    use std::{fmt::Write, fs, io::prelude::*, path::PathBuf};
+    use std::{fmt::Write, fs, path::PathBuf};
 
     struct ConfigFile {
         path: PathBuf,
@@ -1319,11 +1319,8 @@ send_mail = 'false'
 
     impl ConfigFile {
         fn new(content: &str) -> std::result::Result<Self, std::io::Error> {
-            let mut f = fs::File::open("/dev/urandom")?;
-            let mut buf = [0u8; 16];
-            f.read_exact(&mut buf)?;
             let mut filename = String::with_capacity(2 * 16);
-            for byte in &buf {
+            for byte in melib::utils::random::random_u64().to_be_bytes() {
                 write!(&mut filename, "{:02X}", byte).unwrap();
             }
             let mut path = std::env::temp_dir();

melib/Cargo.toml

@@ -37,7 +37,7 @@ libc = { version = "0.2.125", features = ["extra_traits"] }
 libloading = "^0.7"
 log = { version = "0.4", features = ["std"] }
 native-tls = { version = "0.2.3", default-features = false, optional = true }
-nix = { version = "0.27", default-features = false, features = ["fs", "socket", "dir"] }
+nix = { version = "0.27", default-features = false, features = ["fs", "socket", "dir", "hostname"] }
 nom = { version = "7" }
 notify = { version = "4.0.15", optional = true }
 polling = "2.8"

melib/src/error.rs

@@ -390,6 +390,13 @@ impl ErrorKind {
     is_variant! { is_value_error, ValueError }
 }
 
+#[macro_export]
+macro_rules! src_err_arc_wrap {
+    ($err:expr) => {{
+        (Box::new($err) as Box<dyn std::error::Error + Send + Sync + 'static>).into()
+    }};
+}
+
 #[derive(Clone, Debug)]
 pub struct Error {
     pub summary: Cow<'static, str>,

melib/src/maildir/backend.rs

@@ -39,6 +39,7 @@ use crate::{
 
 extern crate notify;
 use std::{
+    borrow::Cow,
     collections::{hash_map::DefaultHasher, HashMap, HashSet},
     ffi::OsStr,
     fs,
@@ -1247,26 +1248,25 @@ impl MaildirType {
         }
         path.push("cur");
         {
-            let mut rand_buf = [0u8; 16];
-            let mut f =
-                fs::File::open("/dev/urandom").expect("Could not open /dev/urandom for reading");
-            f.read_exact(&mut rand_buf)
-                .expect("Could not read from /dev/urandom/");
-            let mut hostn_buf = String::with_capacity(256);
-            let mut f =
-                fs::File::open("/etc/hostname").expect("Could not open /etc/hostname for reading");
-            f.read_to_string(&mut hostn_buf)
-                .expect("Could not read from /etc/hostname");
-            let timestamp = std::time::SystemTime::now()
-                .duration_since(std::time::SystemTime::UNIX_EPOCH)
-                .unwrap()
-                .as_millis();
+            type BeBytes128 = [u8; 16];
+            debug_assert_eq!(std::mem::size_of::<u64>(), 8);
+            debug_assert_eq!(
+                std::mem::size_of::<BeBytes128>(),
+                2 * std::mem::size_of::<[u8; 8]>()
+            );
+            let mut rand_num: BeBytes128 = [0u8; 16];
+            rand_num[0..8].copy_from_slice(&crate::utils::random::random_u64().to_be_bytes());
+            rand_num[8..].copy_from_slice(&crate::utils::random::random_u64().to_be_bytes());
+            let hostname = crate::utils::hostname::hostname()
+                .ok()
+                .and_then(|osstr| osstr.into_string().ok().map(Cow::Owned))
+                .unwrap_or(Cow::Borrowed("localhost"));
             let mut filename = format!(
                 "{}.{:x}_{}.{}:2,",
-                timestamp,
-                u128::from_be_bytes(rand_buf),
+                crate::utils::random::clock_millis(),
+                u128::from_be_bytes(rand_num),
                 std::process::id(),
-                hostn_buf.trim()
+                hostname.trim()
             );
             if let Some(flags) = flags {
                 if !(flags & Flag::DRAFT).is_empty() {

melib/src/utils/mod.rs

@@ -207,3 +207,31 @@ impl std::ops::Not for SortOrder {
         }
     }
 }
+
+pub mod hostname {
+    //! Get local hostname.
+    use crate::error::{Error, ErrorKind, IntoError, Result};
+    use crate::src_err_arc_wrap;
+    use std::io::Read;
+
+    /// Get local hostname with the `gethostname()` libc function.
+    pub fn hostname() -> Result<std::ffi::OsString> {
+        let retval = nix::unistd::gethostname().map_err(|err| {
+            Error::new("Could not discover local hostname")
+                .set_source(Some(src_err_arc_wrap! {err}))
+                .set_err_kind(ErrorKind::OSError)
+        });
+        if retval.is_err() {
+            let mut hostn_buf = String::with_capacity(256);
+            if matches!(
+                std::fs::File::open("/etc/hostname")
+                    .ok()
+                    .and_then(|mut f| f.read_to_string(&mut hostn_buf).ok()),
+                Some(n) if n > 0
+            ) {
+                return Ok(hostn_buf.into());
+            }
+        }
+        retval
+    }
+}

melib/src/utils/random.rs

@@ -69,3 +69,10 @@ pub fn clock() -> u64 {
         .unwrap()
         .as_secs()
 }
+
+pub fn clock_millis() -> u128 {
+    SystemTime::now()
+        .duration_since(SystemTime::UNIX_EPOCH)
+        .unwrap()
+        .as_millis()
+}