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// Copyright 2021, The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Provides a universal logger interface that allows logging both on-device (using android_logger)
//! and on-host (using env_logger).
//! On-host, this allows the use of the RUST_LOG environment variable as documented in
//! https://docs.rs/env_logger.
use std::ffi::CString;
use std::sync::atomic::{AtomicBool, Ordering};
static LOGGER_INITIALIZED: AtomicBool = AtomicBool::new(false);
type FormatFn = Box<dyn Fn(&log::Record) -> String + Sync + Send>;
/// Logger configuration, opportunistically mapped to configuration parameters for android_logger
/// or env_logger where available.
#[derive(Default)]
pub struct Config<'a> {
log_level: Option<log::Level>,
custom_format: Option<FormatFn>,
filter: Option<&'a str>,
#[allow(dead_code)] // Field is only used on device, and ignored on host.
tag: Option<CString>,
}
/// Based on android_logger::Config
impl<'a> Config<'a> {
/// Change the minimum log level.
///
/// All values above the set level are logged. For example, if
/// `Warn` is set, the `Error` is logged too, but `Info` isn't.
pub fn with_min_level(mut self, level: log::Level) -> Self {
self.log_level = Some(level);
self
}
/// Set a log tag. Only used on device.
pub fn with_tag_on_device<S: Into<Vec<u8>>>(mut self, tag: S) -> Self {
self.tag = Some(CString::new(tag).expect("Can't convert tag to CString"));
self
}
/// Set the format function for formatting the log output.
/// ```
/// # use universal_logger::Config;
/// universal_logger::init(
/// Config::default()
/// .with_min_level(log::Level::Trace)
/// .format(|record| format!("my_app: {}", record.args()))
/// )
/// ```
pub fn format<F>(mut self, format: F) -> Self
where
F: Fn(&log::Record) -> String + Sync + Send + 'static,
{
self.custom_format = Some(Box::new(format));
self
}
/// Set a filter, using the format specified in https://docs.rs/env_logger.
pub fn with_filter(mut self, filter: &'a str) -> Self {
self.filter = Some(filter);
self
}
}
/// Initializes logging on host. Returns false if logging is already initialized.
/// Config values take precedence over environment variables for host logging.
#[cfg(not(target_os = "android"))]
pub fn init(config: Config) -> bool {
// Return immediately if the logger is already initialized.
if LOGGER_INITIALIZED.fetch_or(true, Ordering::SeqCst) {
return false;
}
let mut builder = env_logger::Builder::from_default_env();
if let Some(log_level) = config.log_level {
builder.filter_level(log_level.to_level_filter());
}
if let Some(custom_format) = config.custom_format {
use std::io::Write; // Trait used by write!() macro, but not in Android code
builder.format(move |f, r| {
let formatted = custom_format(r);
writeln!(f, "{}", formatted)
});
}
if let Some(filter_str) = config.filter {
builder.parse_filters(filter_str);
}
builder.init();
true
}
/// Initializes logging on device. Returns false if logging is already initialized.
#[cfg(target_os = "android")]
pub fn init(config: Config) -> bool {
// Return immediately if the logger is already initialized.
if LOGGER_INITIALIZED.fetch_or(true, Ordering::SeqCst) {
return false;
}
// We do not have access to the private variables in android_logger::Config, so we have to use
// the builder instead.
let mut builder = android_logger::Config::default();
if let Some(log_level) = config.log_level {
builder = builder.with_min_level(log_level);
}
if let Some(custom_format) = config.custom_format {
builder = builder.format(move |f, r| {
let formatted = custom_format(r);
write!(f, "{}", formatted)
});
}
if let Some(filter_str) = config.filter {
let filter = env_logger::filter::Builder::new().parse(filter_str).build();
builder = builder.with_filter(filter);
}
if let Some(tag) = config.tag {
builder = builder.with_tag(tag);
}
android_logger::init_once(builder);
true
}
/// Note that the majority of tests checking behavior are under the tests/ folder, as they all
/// require independent initialization steps. The local test module just performs some basic crash
/// testing without performing initialization.
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_with_min_level() {
let config = Config::default()
.with_min_level(log::Level::Trace)
.with_min_level(log::Level::Error);
assert_eq!(config.log_level, Some(log::Level::Error));
}
#[test]
fn test_with_filter() {
let filter = "debug,hello::crate=trace";
let config = Config::default().with_filter(filter);
assert_eq!(config.filter.unwrap(), filter)
}
#[test]
fn test_with_tag_on_device() {
let config = Config::default().with_tag_on_device("my_app");
assert_eq!(config.tag.unwrap(), CString::new("my_app").unwrap());
}
#[test]
fn test_format() {
let config = Config::default().format(|record| format!("my_app: {}", record.args()));
assert!(config.custom_format.is_some());
}
}
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