retina 0.4.18

high-level RTSP multimedia streaming library
Documentation 
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// Copyright (C) The Retina Authors
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Formatter for byte data that is expected to be mostly ASCII.

use std::fmt;

/// Holds something that's supposed to be mostly ASCII.
///
/// Some SDP values are allowed to be UTF-8-encoded ISO-10646 characters, but mostly it's
/// supposed to be valid ASCII. This has a `Debug` impl that is fairly readable for ASCII
/// characters and can be copy'n'pasted into Python's `codecs.decode(..., 'string_escape'`)`
/// or the like.
pub(crate) struct MostlyAscii<'a> {
    pub bytes: &'a [u8],
    pub escape_newline: bool,
}

impl<'a> MostlyAscii<'a> {
    pub fn new(bytes: &'a [u8]) -> Self {
        Self {
            bytes,
            escape_newline: false,
        }
    }
}

impl fmt::Debug for MostlyAscii<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "\"")?;
        for &b in self.bytes {
            match b {
                b'"' => write!(f, "\"")?,
                b'\r' => write!(f, "\\r")?,
                b'\n' if self.escape_newline => write!(f, "\\n")?,
                // Note: when escape_newline is false, newlines are written in unescaped form.
                b' ' | b'\n' | 0x20..=0x7E => write!(f, "{}", b as char)?,
                _ => write!(f, "\\x{b:02X}")?,
            }
        }
        write!(f, "\"")?;
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn basic_ascii() {
        let m = MostlyAscii::new(b"hello world");
        assert_eq!(format!("{m:?}"), "\"hello world\"");
    }

    #[test]
    fn newline_unescaped() {
        let m = MostlyAscii::new(b"line1\nline2");
        assert_eq!(format!("{m:?}"), "\"line1\nline2\"");
    }

    #[test]
    fn newline_escaped() {
        let m = MostlyAscii {
            bytes: b"line1\nline2",
            escape_newline: true,
        };
        assert_eq!(format!("{m:?}"), "\"line1\\nline2\"");
    }

    #[test]
    fn cr_always_escaped() {
        let m = MostlyAscii::new(b"line1\r\nline2");
        assert_eq!(format!("{m:?}"), "\"line1\\r\nline2\"");
    }

    #[test]
    fn non_ascii() {
        let m = MostlyAscii::new(b"hello\x80\xFF");
        assert_eq!(format!("{m:?}"), "\"hello\\x80\\xFF\"");
    }
}