diff --git a/RELEASE-NOTES.md b/RELEASE-NOTES.md index 51c1616..d9c787a 100644 --- a/RELEASE-NOTES.md +++ b/RELEASE-NOTES.md @@ -2,6 +2,7 @@ - Implement `source` instead of `cause` on Error types - Roll back MSRV to 1.48.0 so Debian can continue to live in a time warp +- Slightly faster chunked encoding for short inputs # 0.21.2 @@ -17,7 +18,6 @@ - `Engine.internal_decode` return type changed - Update MSRV to 1.60.0 - # 0.21.0 ## Migration diff --git a/src/chunked_encoder.rs b/src/chunked_encoder.rs index bc3810a..69bc745 100644 --- a/src/chunked_encoder.rs +++ b/src/chunked_encoder.rs @@ -1,12 +1,12 @@ +use crate::{ + encode::add_padding, + engine::{Config, Engine}, +}; #[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; @@ -15,72 +15,37 @@ pub trait Sink { 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()), - } + ChunkedEncoder { engine } } pub fn encode(&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(b64_bytes_written, &mut encode_buf[b64_bytes_written..]); + const BUF_SIZE: usize = 1024; + const CHUNK_SIZE: usize = BUF_SIZE / 4 * 3; + + let mut buf = [0; BUF_SIZE]; + for chunk in bytes.chunks(CHUNK_SIZE) { + let mut len = self.engine.internal_encode(chunk, &mut buf); + if chunk.len() != CHUNK_SIZE && self.engine.config().encode_padding() { + // Final, potentially partial, chunk. + // Only need to consider if padding is needed on a partial chunk since full chunk + // is a multiple of 3, which therefore won't be padded. + // Pad output to multiple of four bytes if required by config. + len += add_padding(len, &mut buf[len..]); } - - sink.write_encoded_bytes(&encode_buf[0..b64_bytes_written])?; + sink.write_encoded_bytes(&buf[..len])?; } 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> { @@ -152,38 +117,13 @@ pub mod tests { 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(sink_test_helper: &S) { let mut input_buf: Vec = 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 { + for _ in 0..20_000 { input_buf.clear(); output_buf.clear();