1 files changed, 88 insertions, 0 deletions
diff --git a/third_party/rust/base64/src/display.rs b/third_party/rust/base64/src/display.rs
new file mode 100644
index 0000000000..fc292f1b00
--- /dev/null
+++ b/third_party/rust/base64/src/display.rs
@@ -0,0 +1,88 @@
+//! 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))
+        }
+    }
+}