log4rs 1.4.0

A highly configurable multi-output logging implementation for the `log` facade
Documentation 
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//! The ANSI writer.
//!
//! Requires the `ansi_writer` feature.

use crate::encode::{self, Color, Style};
use std::{fmt, io};

/// An `encode::Write`r that wraps an `io::Write`r, emitting ANSI escape codes
/// for text style.
#[derive(Clone, Eq, PartialEq, Hash, Debug)]
pub struct AnsiWriter<W>(pub W);

impl<W: io::Write> io::Write for AnsiWriter<W> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.0.write(buf)
    }

    fn flush(&mut self) -> io::Result<()> {
        self.0.flush()
    }

    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        self.0.write_all(buf)
    }

    fn write_fmt(&mut self, fmt: fmt::Arguments) -> io::Result<()> {
        self.0.write_fmt(fmt)
    }
}

impl<W: io::Write> encode::Write for AnsiWriter<W> {
    fn set_style(&mut self, style: &Style) -> io::Result<()> {
        let mut buf = [0; 12];
        buf[0] = b'\x1b';
        buf[1] = b'[';
        buf[2] = b'0';
        let mut idx = 3;

        if let Some(text) = style.text {
            buf[idx] = b';';
            buf[idx + 1] = b'3';
            buf[idx + 2] = color_byte(text);
            idx += 3;
        }

        if let Some(background) = style.background {
            buf[idx] = b';';
            buf[idx + 1] = b'4';
            buf[idx + 2] = color_byte(background);
            idx += 3;
        }

        if let Some(intense) = style.intense {
            buf[idx] = b';';
            if intense {
                buf[idx + 1] = b'1';
                idx += 2;
            } else {
                buf[idx + 1] = b'2';
                buf[idx + 2] = b'2';
                idx += 3;
            }
        }
        buf[idx] = b'm';
        self.0.write_all(&buf[..=idx])
    }
}

fn color_byte(c: Color) -> u8 {
    match c {
        Color::Black => b'0',
        Color::Red => b'1',
        Color::Green => b'2',
        Color::Yellow => b'3',
        Color::Blue => b'4',
        Color::Magenta => b'5',
        Color::Cyan => b'6',
        Color::White => b'7',
    }
}

#[cfg(test)]
mod test {
    use std::io::{self, Write};

    use super::*;
    use crate::encode::{Color, Style, Write as EncodeWrite};

    #[test]
    fn basic() {
        let stdout = io::stdout();
        let mut w = AnsiWriter(stdout.lock());

        w.write_all(b"normal ").unwrap();
        w.set_style(
            Style::new()
                .text(Color::Red)
                .background(Color::Blue)
                .intense(true),
        )
        .unwrap();
        w.write_all(b"styled").unwrap();
        w.set_style(Style::new().text(Color::Green)).unwrap();
        w.write_all(b" styled2").unwrap();
        w.set_style(&Style::new()).unwrap();
        w.write_all(b" normal\n").unwrap();
        w.flush().unwrap();
    }
}