.

.gitignore

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+/target

Cargo.toml

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+[package]
+name = "picolog"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+itertools = "*"
+log = {  version = "*", features = ["std"] }

src/lib.rs

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+use std::io::{stdout, Write};
+use itertools::{Itertools, Position};
+use log::*;
+
+//╶───╴Initializers╶─────────────────────────────────────────────────────────╴
+
+pub fn init() -> Result<(), SetLoggerError>{
+    init_with_filter(LevelFilter::Info, |_|true)
+}
+
+pub fn init_with_level(max_level_filter: LevelFilter) -> Result<(), SetLoggerError>{
+    init_with_filter(max_level_filter, |_|true)
+}
+
+pub fn init_with_filter(
+    max_level_filter: LevelFilter,
+    filter: impl Fn(&Metadata) -> bool + Send + Sync + 'static
+) -> Result<(), SetLoggerError> {
+    set_boxed_logger(Box::new(PicoLogger {
+        filter,
+    }))?;
+    set_max_level(max_level_filter);
+    Ok(())
+}
+
+//╶───╴PicoLogger╶───────────────────────────────────────────────────────────╴
+
+pub struct PicoLogger<F: Fn(&Metadata) -> bool + Send + Sync> {
+    filter: F
+}
+
+impl<F: Fn(&Metadata) -> bool + Send + Sync> Log for PicoLogger<F> {
+    fn enabled(&self, metadata: &Metadata) -> bool { (self.filter)(metadata) }
+    fn log(&self, record: &Record) { _=format(record); }
+    fn flush(&self) {}
+}
+
+//╶───╴Formatting╶───────────────────────────────────────────────────────────╴
+
+fn format(record: &Record) -> std::io::Result<()> {
+    let mut buffer = stdout();
+    let buffer = &mut buffer;
+    write!(buffer, "{GRAY}")?;
+
+    // module name
+    let mp = rtrunc(record.module_path().unwrap_or(""), 12);
+    write!(buffer, "{mp:>12} ")?;
+
+    // file path
+    let fp = rtrunc(record.file().unwrap_or(""), 12);
+    write!(buffer, "{fp:>12}:{:<4}", record.line().unwrap_or(0))?;
+
+    // write the record level
+    match record.level() {
+        Level::Error    => write!(buffer, "[{RED}Errr{GRAY}] "),
+        Level::Warn     => write!(buffer, "[{YELLOW}Warn{GRAY}] "),
+        Level::Info     => write!(buffer, "[{BLUE}Info{GRAY}] "),
+        Level::Debug    => write!(buffer, "[{PURPLE}Dbug{GRAY}] "),
+        Level::Trace    => write!(buffer, "[{GREEN}Trce{GRAY}] "),
+    }?;
+
+    // write the actual message
+    use std::fmt::Write;
+    let mut splicer = LineSplicer(buffer);
+    _=write!(splicer, "{}", record.args());
+
+    // finalize
+    write!(buffer, "\n")?;
+    buffer.flush()
+}
+
+struct LineSplicer<'a>(&'a mut dyn Write);
+impl<'a> std::fmt::Write for LineSplicer<'a> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        for (p, part) in s.split("\n").with_position() {
+            match p {
+                Position::First     => write!(self.0, "\n          {GRAY}╷{RESET} "),
+                Position::Middle    => write!(self.0, "\n          {GRAY}│{RESET} "),
+                Position::Last      => write!(self.0, "\n          {GRAY}╵{RESET} "),
+                Position::Only      => write!(self.0, "{RESET}"),
+            }.map_err(|_|std::fmt::Error)?;
+            self.0.write(part.as_bytes())
+                .map_err(|_|std::fmt::Error)?;
+        }
+        Ok(())
+    }
+}
+
+//╶───╴Utility╶──────────────────────────────────────────────────────────────╴
+
+const RESET         : &str = "\x1B[0m";
+const RED           : &str = "\x1B[0;31m";
+const GREEN         : &str = "\x1B[0;32m";
+const YELLOW        : &str = "\x1B[0;33m";
+const BLUE          : &str = "\x1B[0;34m";
+const PURPLE        : &str = "\x1B[0;35m";
+const GRAY          : &str = "\x1B[0;90m";
+
+/// truncate strings to a maximum length, right aligned
+fn rtrunc(string: &str, max_len: usize) -> &str {
+    let len = string.chars().count();
+    if len <= max_len { return string; }
+
+    let crop = string.char_indices()
+        .nth(len - max_len)
+        .unwrap_or((0,'\0')).0;
+    &string[crop..]
+}

src/main.rs

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+include!("lib.rs");
+
+fn main() {
+    _=init_with_level(LevelFilter::Trace);
+    trace!("trace");
+    debug!("debug");
+    info!("info");
+    warn!("warn");
+    error!("error");
+
+    info!("multiline\ndemo");
+    info!("one\ntwo\nthree\nfour");
+
+}