1 files changed, 231 insertions, 0 deletions
diff --git a/third_party/rust/base64/src/chunked_encoder.rs b/third_party/rust/base64/src/chunked_encoder.rs
new file mode 100644
index 0000000000..0457259744
--- /dev/null
+++ b/third_party/rust/base64/src/chunked_encoder.rs
@@ -0,0 +1,231 @@
+#[cfg(any(feature = "alloc", feature = "std", test))]
+use alloc::string::String;
+use core::cmp;
+#[cfg(any(feature = "alloc", feature = "std", test))]
+use core::str;
+
+use crate::encode::add_padding;
+use crate::engine::{Config, Engine};
+
+/// The output mechanism for ChunkedEncoder's encoded bytes.
+pub trait Sink {
+    type Error;
+
+    /// Handle a chunk of encoded base64 data (as UTF-8 bytes)
+    fn write_encoded_bytes(&mut self, encoded: &[u8]) -> Result<(), Self::Error>;
+}
+
+const BUF_SIZE: usize = 1024;
+
+/// A base64 encoder that emits encoded bytes in chunks without heap allocation.
+pub struct ChunkedEncoder<'e, E: Engine + ?Sized> {
+    engine: &'e E,
+    max_input_chunk_len: usize,
+}
+
+impl<'e, E: Engine + ?Sized> ChunkedEncoder<'e, E> {
+    pub fn new(engine: &'e E) -> ChunkedEncoder<'e, E> {
+        ChunkedEncoder {
+            engine,
+            max_input_chunk_len: max_input_length(BUF_SIZE, engine.config().encode_padding()),
+        }
+    }
+
+    pub fn encode<S: Sink>(&self, bytes: &[u8], sink: &mut S) -> Result<(), S::Error> {
+        let mut encode_buf: [u8; BUF_SIZE] = [0; BUF_SIZE];
+        let mut input_index = 0;
+
+        while input_index < bytes.len() {
+            // either the full input chunk size, or it's the last iteration
+            let input_chunk_len = cmp::min(self.max_input_chunk_len, bytes.len() - input_index);
+
+            let chunk = &bytes[input_index..(input_index + input_chunk_len)];
+
+            let mut b64_bytes_written = self.engine.internal_encode(chunk, &mut encode_buf);
+
+            input_index += input_chunk_len;
+            let more_input_left = input_index < bytes.len();
+
+            if self.engine.config().encode_padding() && !more_input_left {
+                // no more input, add padding if needed. Buffer will have room because
+                // max_input_length leaves room for it.
+                b64_bytes_written += add_padding(bytes.len(), &mut encode_buf[b64_bytes_written..]);
+            }
+
+            sink.write_encoded_bytes(&encode_buf[0..b64_bytes_written])?;
+        }
+
+        Ok(())
+    }
+}
+
+/// Calculate the longest input that can be encoded for the given output buffer size.
+///
+/// If the config requires padding, two bytes of buffer space will be set aside so that the last
+/// chunk of input can be encoded safely.
+///
+/// The input length will always be a multiple of 3 so that no encoding state has to be carried over
+/// between chunks.
+fn max_input_length(encoded_buf_len: usize, padded: bool) -> usize {
+    let effective_buf_len = if padded {
+        // make room for padding
+        encoded_buf_len
+            .checked_sub(2)
+            .expect("Don't use a tiny buffer")
+    } else {
+        encoded_buf_len
+    };
+
+    // No padding, so just normal base64 expansion.
+    (effective_buf_len / 4) * 3
+}
+
+// A really simple sink that just appends to a string
+#[cfg(any(feature = "alloc", feature = "std", test))]
+pub(crate) struct StringSink<'a> {
+    string: &'a mut String,
+}
+
+#[cfg(any(feature = "alloc", feature = "std", test))]
+impl<'a> StringSink<'a> {
+    pub(crate) fn new(s: &mut String) -> StringSink {
+        StringSink { string: s }
+    }
+}
+
+#[cfg(any(feature = "alloc", feature = "std", test))]
+impl<'a> Sink for StringSink<'a> {
+    type Error = ();
+
+    fn write_encoded_bytes(&mut self, s: &[u8]) -> Result<(), Self::Error> {
+        self.string.push_str(str::from_utf8(s).unwrap());
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use rand::{
+        distributions::{Distribution, Uniform},
+        Rng, SeedableRng,
+    };
+
+    use crate::{
+        alphabet::STANDARD,
+        engine::general_purpose::{GeneralPurpose, GeneralPurposeConfig, PAD},
+        tests::random_engine,
+    };
+
+    use super::*;
+
+    #[test]
+    fn chunked_encode_empty() {
+        assert_eq!("", chunked_encode_str(&[], PAD));
+    }
+
+    #[test]
+    fn chunked_encode_intermediate_fast_loop() {
+        // > 8 bytes input, will enter the pretty fast loop
+        assert_eq!("Zm9vYmFyYmF6cXV4", chunked_encode_str(b"foobarbazqux", PAD));
+    }
+
+    #[test]
+    fn chunked_encode_fast_loop() {
+        // > 32 bytes input, will enter the uber fast loop
+        assert_eq!(
+            "Zm9vYmFyYmF6cXV4cXV1eGNvcmdlZ3JhdWx0Z2FycGx5eg==",
+            chunked_encode_str(b"foobarbazquxquuxcorgegraultgarplyz", PAD)
+        );
+    }
+
+    #[test]
+    fn chunked_encode_slow_loop_only() {
+        // < 8 bytes input, slow loop only
+        assert_eq!("Zm9vYmFy", chunked_encode_str(b"foobar", PAD));
+    }
+
+    #[test]
+    fn chunked_encode_matches_normal_encode_random_string_sink() {
+        let helper = StringSinkTestHelper;
+        chunked_encode_matches_normal_encode_random(&helper);
+    }
+
+    #[test]
+    fn max_input_length_no_pad() {
+        assert_eq!(768, max_input_length(1024, false));
+    }
+
+    #[test]
+    fn max_input_length_with_pad_decrements_one_triple() {
+        assert_eq!(765, max_input_length(1024, true));
+    }
+
+    #[test]
+    fn max_input_length_with_pad_one_byte_short() {
+        assert_eq!(765, max_input_length(1025, true));
+    }
+
+    #[test]
+    fn max_input_length_with_pad_fits_exactly() {
+        assert_eq!(768, max_input_length(1026, true));
+    }
+
+    #[test]
+    fn max_input_length_cant_use_extra_single_encoded_byte() {
+        assert_eq!(300, max_input_length(401, false));
+    }
+
+    pub fn chunked_encode_matches_normal_encode_random<S: SinkTestHelper>(sink_test_helper: &S) {
+        let mut input_buf: Vec<u8> = Vec::new();
+        let mut output_buf = String::new();
+        let mut rng = rand::rngs::SmallRng::from_entropy();
+        let input_len_range = Uniform::new(1, 10_000);
+
+        for _ in 0..5_000 {
+            input_buf.clear();
+            output_buf.clear();
+
+            let buf_len = input_len_range.sample(&mut rng);
+            for _ in 0..buf_len {
+                input_buf.push(rng.gen());
+            }
+
+            let engine = random_engine(&mut rng);
+
+            let chunk_encoded_string = sink_test_helper.encode_to_string(&engine, &input_buf);
+            engine.encode_string(&input_buf, &mut output_buf);
+
+            assert_eq!(output_buf, chunk_encoded_string, "input len={}", buf_len);
+        }
+    }
+
+    fn chunked_encode_str(bytes: &[u8], config: GeneralPurposeConfig) -> String {
+        let mut s = String::new();
+
+        let mut sink = StringSink::new(&mut s);
+        let engine = GeneralPurpose::new(&STANDARD, config);
+        let encoder = ChunkedEncoder::new(&engine);
+        encoder.encode(bytes, &mut sink).unwrap();
+
+        s
+    }
+
+    // An abstraction around sinks so that we can have tests that easily to any sink implementation
+    pub trait SinkTestHelper {
+        fn encode_to_string<E: Engine>(&self, engine: &E, bytes: &[u8]) -> String;
+    }
+
+    struct StringSinkTestHelper;
+
+    impl SinkTestHelper for StringSinkTestHelper {
+        fn encode_to_string<E: Engine>(&self, engine: &E, bytes: &[u8]) -> String {
+            let encoder = ChunkedEncoder::new(engine);
+            let mut s = String::new();
+            let mut sink = StringSink::new(&mut s);
+            encoder.encode(bytes, &mut sink).unwrap();
+
+            s
+        }
+    }
+}