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// sink.rs
// Copyright © 2024-2026 RustLogs (RLG). All rights reserved.
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT
//! Platform-native logging sinks.
//!
//! [`PlatformSink`] routes formatted log payloads to the best available
//! output: `os_log` on macOS, `journald` on Linux, or stdout/file as fallback.
//! Construct via [`PlatformSink::native()`] or [`PlatformSink::from_config()`].
use std::io::Write;
#[cfg(unix)]
use std::os::unix::net::UnixDatagram;
#[cfg(not(unix))]
#[allow(dead_code)]
#[derive(Debug)]
pub struct UnixDatagram;
#[cfg(not(unix))]
#[allow(dead_code)]
impl UnixDatagram {
pub fn send(&self, _: &[u8]) -> std::io::Result<usize> {
Ok(0)
}
}
/// Unified interface for platform-native log output.
#[derive(Debug)]
#[allow(variant_size_differences)]
pub enum PlatformSink {
/// Standard output fallback.
Stdout,
/// File sink fallback.
File(std::fs::File),
/// Native OS Log on macOS.
OsLog,
/// Systemd Journald socket on Linux.
Journald(Option<UnixDatagram>),
}
#[cfg(any(target_os = "macos", test))]
#[allow(unsafe_code)]
mod macos_ffi {
use std::os::raw::{c_char, c_void};
#[allow(dead_code)]
pub(super) type os_log_t = *mut c_void;
#[repr(transparent)]
#[allow(dead_code)]
pub(super) struct os_log_type_t(pub(super) u8);
#[allow(dead_code)]
pub(super) const OS_LOG_TYPE_DEFAULT: os_log_type_t =
os_log_type_t(0x00);
#[allow(dead_code)]
pub(super) const OS_LOG_TYPE_INFO: os_log_type_t =
os_log_type_t(0x01);
#[allow(dead_code)]
pub(super) const OS_LOG_TYPE_DEBUG: os_log_type_t =
os_log_type_t(0x02);
#[allow(dead_code)]
pub(super) const OS_LOG_TYPE_ERROR: os_log_type_t =
os_log_type_t(0x10);
#[allow(dead_code)]
pub(super) const OS_LOG_TYPE_FAULT: os_log_type_t =
os_log_type_t(0x11);
unsafe extern "C" {
#[allow(dead_code)]
pub(super) fn os_log_create(
subsystem: *const c_char,
category: *const c_char,
) -> os_log_t;
#[allow(dead_code)]
pub(super) fn _os_log_impl(
dso: *mut c_void,
log: os_log_t,
log_type: os_log_type_t,
format: *const c_char,
buf: *const u8,
size: u32,
);
}
}
impl PlatformSink {
/// Build a sink from the given [`Config`](crate::config::Config).
///
/// Inspects `logging_destinations` in order:
/// - `File(path)` → open for append
/// - `Stdout` → stdout
/// - `Network(_)` → skipped (not yet implemented)
///
/// Falls back to [`PlatformSink::native()`] if no destination matches.
#[must_use]
pub fn from_config(config: &crate::config::Config) -> Self {
for dest in &config.logging_destinations {
match dest {
crate::config::LoggingDestination::File(path) => {
if let Ok(file) = std::fs::OpenOptions::new()
.create(true)
.append(true)
.open(path)
{
return Self::File(file);
}
}
crate::config::LoggingDestination::Stdout => {
return Self::Stdout;
}
crate::config::LoggingDestination::Network(_) => {
// Network sinks not yet implemented — fall through.
}
}
}
Self::native()
}
/// Detect and return the best native sink for the current OS.
#[must_use]
#[allow(clippy::missing_const_for_fn)]
pub fn native() -> Self {
// Allow explicit fallback to stdout via environment variable.
if std::env::var("RLG_FALLBACK_STDOUT").is_ok()
|| std::env::var("GITHUB_ACTIONS").is_ok()
{
return Self::Stdout;
}
#[cfg(target_os = "macos")]
{
Self::OsLog
}
#[cfg(target_os = "linux")]
{
Self::detect_journald()
}
#[cfg(not(any(target_os = "macos", target_os = "linux")))]
{
Self::Stdout
}
}
/// Detect the `journald` socket on Linux.
#[cfg(target_os = "linux")]
fn detect_journald() -> Self {
Self::try_journald_socket("/run/systemd/journal/socket")
}
/// Connect a `UnixDatagram` to the given socket path.
#[cfg(target_os = "linux")]
fn try_journald_socket(path: &str) -> Self {
UnixDatagram::unbound()
.ok()
.and_then(|socket| {
socket.connect(path).ok().map(|()| socket)
})
.map_or(Self::Journald(None), |s| Self::Journald(Some(s)))
}
/// Write a formatted log payload to this sink.
#[allow(unused_variables)]
#[allow(clippy::too_many_lines)]
pub fn emit(&mut self, level: &str, payload: &[u8]) {
match self {
Self::Stdout => {
let _ = std::io::stdout().write_all(payload);
let _ = std::io::stdout().write_all(b"\n");
}
Self::File(f) => {
let _ = f.write_all(payload);
let _ = f.write_all(b"\n");
}
Self::OsLog => {
#[cfg(target_os = "macos")]
{
if std::env::var("RLG_FALLBACK_STDOUT").is_ok()
|| std::env::var("GITHUB_ACTIONS").is_ok()
{
let _ = (level, payload);
} else {
#[cfg(not(any(test, miri)))]
{
use macos_ffi::*;
use std::ffi::CString;
let subsystem =
CString::new("com.rlg.logger").unwrap();
let category =
CString::new("default").unwrap();
// SAFETY: The pointers passed to `os_log_create` and `_os_log_impl` are derived from
// valid, null-terminated `CString`s. The `buf` pointer is valid for `size` bytes.
// We check `log_handle` for null before passing it to `_os_log_impl`.
#[allow(unsafe_code)]
unsafe {
let log_handle = os_log_create(
subsystem.as_ptr(),
category.as_ptr(),
);
if log_handle.is_null() {
// Fallback to stdout if os_log_create fails
let _ = std::io::stdout()
.write_all(payload);
let _ = std::io::stdout()
.write_all(b"\n");
return;
}
let log_type = match level {
"ERROR" | "FATAL" => {
OS_LOG_TYPE_ERROR
}
"CRITICAL" => OS_LOG_TYPE_FAULT,
"WARN" => OS_LOG_TYPE_DEFAULT,
"INFO" => OS_LOG_TYPE_INFO,
"DEBUG" | "TRACE" | "VERBOSE" => {
OS_LOG_TYPE_DEBUG
}
_ => OS_LOG_TYPE_DEFAULT,
};
let format =
CString::new("%{public}s").unwrap();
// Strip null bytes from payload before creating CString
let clean_payload: Vec<u8> = payload
.iter()
.copied()
.filter(|&b| b != 0)
.collect();
let msg = CString::new(clean_payload)
.unwrap_or_default();
_os_log_impl(
std::ptr::null_mut(),
log_handle,
log_type,
format.as_ptr(),
msg.as_ptr().cast::<u8>(),
msg.as_bytes().len() as u32,
);
}
}
#[cfg(any(test, miri))]
{
let _ = (level, payload);
}
}
}
#[cfg(not(target_os = "macos"))]
{
let _ = (level, payload);
}
}
Self::Journald(socket_opt) => {
if let Some(socket) = socket_opt {
#[cfg(any(test, miri))]
let _ = socket;
let priority = match level {
"ERROR" | "FATAL" | "CRITICAL" => "3",
"WARN" => "4",
"INFO" => "6",
"DEBUG" | "TRACE" | "VERBOSE" => "7",
_ => "5",
};
// Journald expects newline-separated key-value pairs
let mut journal_payload =
Vec::with_capacity(payload.len() + 32);
journal_payload.extend_from_slice(b"PRIORITY=");
journal_payload
.extend_from_slice(priority.as_bytes());
journal_payload.extend_from_slice(b"\nMESSAGE=");
journal_payload.extend_from_slice(payload);
journal_payload.extend_from_slice(b"\n");
if std::env::var("RLG_FALLBACK_STDOUT").is_ok()
|| std::env::var("GITHUB_ACTIONS").is_ok()
{
let _ = journal_payload;
} else {
#[cfg(all(
target_os = "linux",
not(any(test, miri))
))]
let _ = socket.send(&journal_payload);
#[cfg(any(
not(target_os = "linux"),
test,
miri
))]
{
let _ = journal_payload;
}
}
} else {
let _ = std::io::stdout().write_all(payload);
let _ = std::io::stdout().write_all(b"\n");
}
}
}
}
}
#[cfg(all(test, not(miri)))]
mod tests {
use super::*;
use serial_test::serial;
#[test]
#[cfg_attr(miri, ignore)]
fn test_platform_sink_stdout() {
let mut sink = PlatformSink::Stdout;
sink.emit("INFO", b"test stdout");
}
#[test]
#[cfg_attr(miri, ignore)]
#[allow(unsafe_code)]
#[serial]
fn test_platform_sink_fallback_env_var() {
// SAFETY: Test-only; no other threads depend on this env var.
unsafe { std::env::set_var("RLG_FALLBACK_STDOUT", "1") };
let sink = PlatformSink::native();
assert!(matches!(sink, PlatformSink::Stdout));
// SAFETY: Test-only cleanup.
unsafe { std::env::remove_var("RLG_FALLBACK_STDOUT") };
}
#[test]
#[cfg_attr(miri, ignore)]
#[allow(unsafe_code)]
#[serial]
fn test_platform_sink_native_journald_path() {
// SAFETY: Test-only env var cleanup so native() reaches platform code.
unsafe {
std::env::remove_var("RLG_FALLBACK_STDOUT");
std::env::remove_var("GITHUB_ACTIONS");
}
let sink = PlatformSink::native();
#[cfg(target_os = "linux")]
assert!(matches!(sink, PlatformSink::Journald(_)));
#[cfg(target_os = "macos")]
assert!(matches!(sink, PlatformSink::OsLog));
#[cfg(not(any(target_os = "linux", target_os = "macos")))]
assert!(matches!(sink, PlatformSink::Stdout));
// SAFETY: Restore fallback for other tests.
unsafe { std::env::set_var("RLG_FALLBACK_STDOUT", "1") };
}
#[test]
#[cfg_attr(miri, ignore)]
#[cfg(target_os = "linux")]
fn test_try_journald_socket_failure() {
let sink =
PlatformSink::try_journald_socket("/nonexistent/path");
assert!(matches!(sink, PlatformSink::Journald(None)));
}
#[test]
#[cfg_attr(miri, ignore)]
fn test_platform_sink_journald_coverage() {
#[cfg(unix)]
{
let (sock1, _sock2) = UnixDatagram::pair().unwrap();
let mut sink = PlatformSink::Journald(Some(sock1));
sink.emit("INFO", b"test journald");
}
let mut sink_none = PlatformSink::Journald(None);
sink_none.emit("INFO", b"test journald fallback");
}
}