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//! Enables base64'd output anywhere you might use a `Display` implementation, like a format string.
//!
//! ```
//! use base64::{display::Base64Display, engine::general_purpose::STANDARD};
//!
//! let data = vec![0x0, 0x1, 0x2, 0x3];
//! let wrapper = Base64Display::new(&data, &STANDARD);
//!
//! assert_eq!("base64: AAECAw==", format!("base64: {}", wrapper));
//! ```
use super::chunked_encoder::ChunkedEncoder;
use crate::engine::Engine;
use core::fmt::{Display, Formatter};
use core::{fmt, str};
/// A convenience wrapper for base64'ing bytes into a format string without heap allocation.
pub struct Base64Display<'a, 'e, E: Engine> {
bytes: &'a [u8],
chunked_encoder: ChunkedEncoder<'e, E>,
}
impl<'a, 'e, E: Engine> Base64Display<'a, 'e, E> {
/// Create a `Base64Display` with the provided engine.
pub fn new(bytes: &'a [u8], engine: &'e E) -> Base64Display<'a, 'e, E> {
Base64Display {
bytes,
chunked_encoder: ChunkedEncoder::new(engine),
}
}
}
impl<'a, 'e, E: Engine> Display for Base64Display<'a, 'e, E> {
fn fmt(&self, formatter: &mut Formatter) -> Result<(), fmt::Error> {
let mut sink = FormatterSink { f: formatter };
self.chunked_encoder.encode(self.bytes, &mut sink)
}
}
struct FormatterSink<'a, 'b: 'a> {
f: &'a mut Formatter<'b>,
}
impl<'a, 'b: 'a> super::chunked_encoder::Sink for FormatterSink<'a, 'b> {
type Error = fmt::Error;
fn write_encoded_bytes(&mut self, encoded: &[u8]) -> Result<(), Self::Error> {
// Avoid unsafe. If max performance is needed, write your own display wrapper that uses
// unsafe here to gain about 10-15%.
self.f
.write_str(str::from_utf8(encoded).expect("base64 data was not utf8"))
}
}
#[cfg(test)]
mod tests {
use super::super::chunked_encoder::tests::{
chunked_encode_matches_normal_encode_random, SinkTestHelper,
};
use super::*;
use crate::engine::general_purpose::STANDARD;
#[test]
fn basic_display() {
assert_eq!(
"~$Zm9vYmFy#*",
format!("~${}#*", Base64Display::new(b"foobar", &STANDARD))
);
assert_eq!(
"~$Zm9vYmFyZg==#*",
format!("~${}#*", Base64Display::new(b"foobarf", &STANDARD))
);
}
#[test]
fn display_encode_matches_normal_encode() {
let helper = DisplaySinkTestHelper;
chunked_encode_matches_normal_encode_random(&helper);
}
struct DisplaySinkTestHelper;
impl SinkTestHelper for DisplaySinkTestHelper {
fn encode_to_string<E: Engine>(&self, engine: &E, bytes: &[u8]) -> String {
format!("{}", Base64Display::new(bytes, engine))
}
}
}