base64/
display.rs

Help
1//! Enables base64'd output anywhere you might use a `Display` implementation, like a format string.
2//!
3//! ```
4//! use base64::{display::Base64Display, engine::general_purpose::STANDARD};
5//!
6//! let data = vec![0x0, 0x1, 0x2, 0x3];
7//! let wrapper = Base64Display::new(&data, &STANDARD);
8//!
9//! assert_eq!("base64: AAECAw==", format!("base64: {}", wrapper));
10//! ```
11
12use super::chunked_encoder::ChunkedEncoder;
13use crate::engine::Engine;
14use core::fmt::{Display, Formatter};
15use core::{fmt, str};
16
17/// A convenience wrapper for base64'ing bytes into a format string without heap allocation.
18pub struct Base64Display<'a, 'e, E: Engine> {
19    bytes: &'a [u8],
20    chunked_encoder: ChunkedEncoder<'e, E>,
21}
22
23impl<'a, 'e, E: Engine> Base64Display<'a, 'e, E> {
24    /// Create a `Base64Display` with the provided engine.
25    pub fn new(bytes: &'a [u8], engine: &'e E) -> Base64Display<'a, 'e, E> {
26        Base64Display {
27            bytes,
28            chunked_encoder: ChunkedEncoder::new(engine),
29        }
30    }
31}
32
33impl<'a, 'e, E: Engine> Display for Base64Display<'a, 'e, E> {
34    fn fmt(&self, formatter: &mut Formatter) -> Result<(), fmt::Error> {
35        let mut sink = FormatterSink { f: formatter };
36        self.chunked_encoder.encode(self.bytes, &mut sink)
37    }
38}
39
40struct FormatterSink<'a, 'b: 'a> {
41    f: &'a mut Formatter<'b>,
42}
43
44impl<'a, 'b: 'a> super::chunked_encoder::Sink for FormatterSink<'a, 'b> {
45    type Error = fmt::Error;
46
47    fn write_encoded_bytes(&mut self, encoded: &[u8]) -> Result<(), Self::Error> {
48        // Avoid unsafe. If max performance is needed, write your own display wrapper that uses
49        // unsafe here to gain about 10-15%.
50        self.f
51            .write_str(str::from_utf8(encoded).expect("base64 data was not utf8"))
52    }
53}
54
55#[cfg(test)]
56mod tests {
57    use super::super::chunked_encoder::tests::{
58        chunked_encode_matches_normal_encode_random, SinkTestHelper,
59    };
60    use super::*;
61    use crate::engine::general_purpose::STANDARD;
62
63    #[test]
64    fn basic_display() {
65        assert_eq!(
66            "~$Zm9vYmFy#*",
67            format!("~${}#*", Base64Display::new(b"foobar", &STANDARD))
68        );
69        assert_eq!(
70            "~$Zm9vYmFyZg==#*",
71            format!("~${}#*", Base64Display::new(b"foobarf", &STANDARD))
72        );
73    }
74
75    #[test]
76    fn display_encode_matches_normal_encode() {
77        let helper = DisplaySinkTestHelper;
78        chunked_encode_matches_normal_encode_random(&helper);
79    }
80
81    struct DisplaySinkTestHelper;
82
83    impl SinkTestHelper for DisplaySinkTestHelper {
84        fn encode_to_string<E: Engine>(&self, engine: &E, bytes: &[u8]) -> String {
85            format!("{}", Base64Display::new(bytes, engine))
86        }
87    }
88}
base64/display.rs

base64/
display.rs
