| use crate::engine::Engine; |
| use std::{ |
| cmp, fmt, io, |
| io::{ErrorKind, Result}, |
| }; |
| |
| pub(crate) const BUF_SIZE: usize = 1024; |
| /// The most bytes whose encoding will fit in `BUF_SIZE` |
| const MAX_INPUT_LEN: usize = BUF_SIZE / 4 * 3; |
| // 3 bytes of input = 4 bytes of base64, always (because we don't allow line wrapping) |
| const MIN_ENCODE_CHUNK_SIZE: usize = 3; |
| |
| /// A `Write` implementation that base64 encodes data before delegating to the wrapped writer. |
| /// |
| /// Because base64 has special handling for the end of the input data (padding, etc), there's a |
| /// `finish()` method on this type that encodes any leftover input bytes and adds padding if |
| /// appropriate. It's called automatically when deallocated (see the `Drop` implementation), but |
| /// any error that occurs when invoking the underlying writer will be suppressed. If you want to |
| /// handle such errors, call `finish()` yourself. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::io::Write; |
| /// use base64::engine::general_purpose; |
| /// |
| /// // use a vec as the simplest possible `Write` -- in real code this is probably a file, etc. |
| /// let mut enc = base64::write::EncoderWriter::new(Vec::new(), &general_purpose::STANDARD); |
| /// |
| /// // handle errors as you normally would |
| /// enc.write_all(b"asdf").unwrap(); |
| /// |
| /// // could leave this out to be called by Drop, if you don't care |
| /// // about handling errors or getting the delegate writer back |
| /// let delegate = enc.finish().unwrap(); |
| /// |
| /// // base64 was written to the writer |
| /// assert_eq!(b"YXNkZg==", &delegate[..]); |
| /// |
| /// ``` |
| /// |
| /// # Panics |
| /// |
| /// Calling `write()` (or related methods) or `finish()` after `finish()` has completed without |
| /// error is invalid and will panic. |
| /// |
| /// # Errors |
| /// |
| /// Base64 encoding itself does not generate errors, but errors from the wrapped writer will be |
| /// returned as per the contract of `Write`. |
| /// |
| /// # Performance |
| /// |
| /// It has some minor performance loss compared to encoding slices (a couple percent). |
| /// It does not do any heap allocation. |
| /// |
| /// # Limitations |
| /// |
| /// Owing to the specification of the `write` and `flush` methods on the `Write` trait and their |
| /// implications for a buffering implementation, these methods may not behave as expected. In |
| /// particular, calling `write_all` on this interface may fail with `io::ErrorKind::WriteZero`. |
| /// See the documentation of the `Write` trait implementation for further details. |
| pub struct EncoderWriter<'e, E: Engine, W: io::Write> { |
| engine: &'e E, |
| /// Where encoded data is written to. It's an Option as it's None immediately before Drop is |
| /// called so that finish() can return the underlying writer. None implies that finish() has |
| /// been called successfully. |
| delegate: Option<W>, |
| /// Holds a partial chunk, if any, after the last `write()`, so that we may then fill the chunk |
| /// with the next `write()`, encode it, then proceed with the rest of the input normally. |
| extra_input: [u8; MIN_ENCODE_CHUNK_SIZE], |
| /// How much of `extra` is occupied, in `[0, MIN_ENCODE_CHUNK_SIZE]`. |
| extra_input_occupied_len: usize, |
| /// Buffer to encode into. May hold leftover encoded bytes from a previous write call that the underlying writer |
| /// did not write last time. |
| output: [u8; BUF_SIZE], |
| /// How much of `output` is occupied with encoded data that couldn't be written last time |
| output_occupied_len: usize, |
| /// panic safety: don't write again in destructor if writer panicked while we were writing to it |
| panicked: bool, |
| } |
| |
| impl<'e, E: Engine, W: io::Write> fmt::Debug for EncoderWriter<'e, E, W> { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| write!( |
| f, |
| "extra_input: {:?} extra_input_occupied_len:{:?} output[..5]: {:?} output_occupied_len: {:?}", |
| self.extra_input, |
| self.extra_input_occupied_len, |
| &self.output[0..5], |
| self.output_occupied_len |
| ) |
| } |
| } |
| |
| impl<'e, E: Engine, W: io::Write> EncoderWriter<'e, E, W> { |
| /// Create a new encoder that will write to the provided delegate writer. |
| pub fn new(delegate: W, engine: &'e E) -> EncoderWriter<'e, E, W> { |
| EncoderWriter { |
| engine, |
| delegate: Some(delegate), |
| extra_input: [0u8; MIN_ENCODE_CHUNK_SIZE], |
| extra_input_occupied_len: 0, |
| output: [0u8; BUF_SIZE], |
| output_occupied_len: 0, |
| panicked: false, |
| } |
| } |
| |
| /// Encode all remaining buffered data and write it, including any trailing incomplete input |
| /// triples and associated padding. |
| /// |
| /// Once this succeeds, no further writes or calls to this method are allowed. |
| /// |
| /// This may write to the delegate writer multiple times if the delegate writer does not accept |
| /// all input provided to its `write` each invocation. |
| /// |
| /// If you don't care about error handling, it is not necessary to call this function, as the |
| /// equivalent finalization is done by the Drop impl. |
| /// |
| /// Returns the writer that this was constructed around. |
| /// |
| /// # Errors |
| /// |
| /// The first error that is not of `ErrorKind::Interrupted` will be returned. |
| pub fn finish(&mut self) -> Result<W> { |
| // If we could consume self in finish(), we wouldn't have to worry about this case, but |
| // finish() is retryable in the face of I/O errors, so we can't consume here. |
| if self.delegate.is_none() { |
| panic!("Encoder has already had finish() called"); |
| }; |
| |
| self.write_final_leftovers()?; |
| |
| let writer = self.delegate.take().expect("Writer must be present"); |
| |
| Ok(writer) |
| } |
| |
| /// Write any remaining buffered data to the delegate writer. |
| fn write_final_leftovers(&mut self) -> Result<()> { |
| if self.delegate.is_none() { |
| // finish() has already successfully called this, and we are now in drop() with a None |
| // writer, so just no-op |
| return Ok(()); |
| } |
| |
| self.write_all_encoded_output()?; |
| |
| if self.extra_input_occupied_len > 0 { |
| let encoded_len = self |
| .engine |
| .encode_slice( |
| &self.extra_input[..self.extra_input_occupied_len], |
| &mut self.output[..], |
| ) |
| .expect("buffer is large enough"); |
| |
| self.output_occupied_len = encoded_len; |
| |
| self.write_all_encoded_output()?; |
| |
| // write succeeded, do not write the encoding of extra again if finish() is retried |
| self.extra_input_occupied_len = 0; |
| } |
| |
| Ok(()) |
| } |
| |
| /// Write as much of the encoded output to the delegate writer as it will accept, and store the |
| /// leftovers to be attempted at the next write() call. Updates `self.output_occupied_len`. |
| /// |
| /// # Errors |
| /// |
| /// Errors from the delegate writer are returned. In the case of an error, |
| /// `self.output_occupied_len` will not be updated, as errors from `write` are specified to mean |
| /// that no write took place. |
| fn write_to_delegate(&mut self, current_output_len: usize) -> Result<()> { |
| self.panicked = true; |
| let res = self |
| .delegate |
| .as_mut() |
| .expect("Writer must be present") |
| .write(&self.output[..current_output_len]); |
| self.panicked = false; |
| |
| res.map(|consumed| { |
| debug_assert!(consumed <= current_output_len); |
| |
| if consumed < current_output_len { |
| self.output_occupied_len = current_output_len.checked_sub(consumed).unwrap(); |
| // If we're blocking on I/O, the minor inefficiency of copying bytes to the |
| // start of the buffer is the least of our concerns... |
| // TODO Rotate moves more than we need to; copy_within now stable. |
| self.output.rotate_left(consumed); |
| } else { |
| self.output_occupied_len = 0; |
| } |
| }) |
| } |
| |
| /// Write all buffered encoded output. If this returns `Ok`, `self.output_occupied_len` is `0`. |
| /// |
| /// This is basically write_all for the remaining buffered data but without the undesirable |
| /// abort-on-`Ok(0)` behavior. |
| /// |
| /// # Errors |
| /// |
| /// Any error emitted by the delegate writer abort the write loop and is returned, unless it's |
| /// `Interrupted`, in which case the error is ignored and writes will continue. |
| fn write_all_encoded_output(&mut self) -> Result<()> { |
| while self.output_occupied_len > 0 { |
| let remaining_len = self.output_occupied_len; |
| match self.write_to_delegate(remaining_len) { |
| // try again on interrupts ala write_all |
| Err(ref e) if e.kind() == ErrorKind::Interrupted => {} |
| // other errors return |
| Err(e) => return Err(e), |
| // success no-ops because remaining length is already updated |
| Ok(_) => {} |
| }; |
| } |
| |
| debug_assert_eq!(0, self.output_occupied_len); |
| Ok(()) |
| } |
| |
| /// Unwraps this `EncoderWriter`, returning the base writer it writes base64 encoded output |
| /// to. |
| /// |
| /// Normally this method should not be needed, since `finish()` returns the inner writer if |
| /// it completes successfully. That will also ensure all data has been flushed, which the |
| /// `into_inner()` function does *not* do. |
| /// |
| /// Calling this method after `finish()` has completed successfully will panic, since the |
| /// writer has already been returned. |
| /// |
| /// This method may be useful if the writer implements additional APIs beyond the `Write` |
| /// trait. Note that the inner writer might be in an error state or have an incomplete |
| /// base64 string written to it. |
| pub fn into_inner(mut self) -> W { |
| self.delegate |
| .take() |
| .expect("Encoder has already had finish() called") |
| } |
| } |
| |
| impl<'e, E: Engine, W: io::Write> io::Write for EncoderWriter<'e, E, W> { |
| /// Encode input and then write to the delegate writer. |
| /// |
| /// Under non-error circumstances, this returns `Ok` with the value being the number of bytes |
| /// of `input` consumed. The value may be `0`, which interacts poorly with `write_all`, which |
| /// interprets `Ok(0)` as an error, despite it being allowed by the contract of `write`. See |
| /// <https://github.com/rust-lang/rust/issues/56889> for more on that. |
| /// |
| /// If the previous call to `write` provided more (encoded) data than the delegate writer could |
| /// accept in a single call to its `write`, the remaining data is buffered. As long as buffered |
| /// data is present, subsequent calls to `write` will try to write the remaining buffered data |
| /// to the delegate and return either `Ok(0)` -- and therefore not consume any of `input` -- or |
| /// an error. |
| /// |
| /// # Errors |
| /// |
| /// Any errors emitted by the delegate writer are returned. |
| fn write(&mut self, input: &[u8]) -> Result<usize> { |
| if self.delegate.is_none() { |
| panic!("Cannot write more after calling finish()"); |
| } |
| |
| if input.is_empty() { |
| return Ok(0); |
| } |
| |
| // The contract of `Write::write` places some constraints on this implementation: |
| // - a call to `write()` represents at most one call to a wrapped `Write`, so we can't |
| // iterate over the input and encode multiple chunks. |
| // - Errors mean that "no bytes were written to this writer", so we need to reset the |
| // internal state to what it was before the error occurred |
| |
| // before reading any input, write any leftover encoded output from last time |
| if self.output_occupied_len > 0 { |
| let current_len = self.output_occupied_len; |
| return self |
| .write_to_delegate(current_len) |
| // did not read any input |
| .map(|_| 0); |
| } |
| |
| debug_assert_eq!(0, self.output_occupied_len); |
| |
| // how many bytes, if any, were read into `extra` to create a triple to encode |
| let mut extra_input_read_len = 0; |
| let mut input = input; |
| |
| let orig_extra_len = self.extra_input_occupied_len; |
| |
| let mut encoded_size = 0; |
| // always a multiple of MIN_ENCODE_CHUNK_SIZE |
| let mut max_input_len = MAX_INPUT_LEN; |
| |
| // process leftover un-encoded input from last write |
| if self.extra_input_occupied_len > 0 { |
| debug_assert!(self.extra_input_occupied_len < 3); |
| if input.len() + self.extra_input_occupied_len >= MIN_ENCODE_CHUNK_SIZE { |
| // Fill up `extra`, encode that into `output`, and consume as much of the rest of |
| // `input` as possible. |
| // We could write just the encoding of `extra` by itself but then we'd have to |
| // return after writing only 4 bytes, which is inefficient if the underlying writer |
| // would make a syscall. |
| extra_input_read_len = MIN_ENCODE_CHUNK_SIZE - self.extra_input_occupied_len; |
| debug_assert!(extra_input_read_len > 0); |
| // overwrite only bytes that weren't already used. If we need to rollback extra_len |
| // (when the subsequent write errors), the old leading bytes will still be there. |
| self.extra_input[self.extra_input_occupied_len..MIN_ENCODE_CHUNK_SIZE] |
| .copy_from_slice(&input[0..extra_input_read_len]); |
| |
| let len = self.engine.internal_encode( |
| &self.extra_input[0..MIN_ENCODE_CHUNK_SIZE], |
| &mut self.output[..], |
| ); |
| debug_assert_eq!(4, len); |
| |
| input = &input[extra_input_read_len..]; |
| |
| // consider extra to be used up, since we encoded it |
| self.extra_input_occupied_len = 0; |
| // don't clobber where we just encoded to |
| encoded_size = 4; |
| // and don't read more than can be encoded |
| max_input_len = MAX_INPUT_LEN - MIN_ENCODE_CHUNK_SIZE; |
| |
| // fall through to normal encoding |
| } else { |
| // `extra` and `input` are non empty, but `|extra| + |input| < 3`, so there must be |
| // 1 byte in each. |
| debug_assert_eq!(1, input.len()); |
| debug_assert_eq!(1, self.extra_input_occupied_len); |
| |
| self.extra_input[self.extra_input_occupied_len] = input[0]; |
| self.extra_input_occupied_len += 1; |
| return Ok(1); |
| }; |
| } else if input.len() < MIN_ENCODE_CHUNK_SIZE { |
| // `extra` is empty, and `input` fits inside it |
| self.extra_input[0..input.len()].copy_from_slice(input); |
| self.extra_input_occupied_len = input.len(); |
| return Ok(input.len()); |
| }; |
| |
| // either 0 or 1 complete chunks encoded from extra |
| debug_assert!(encoded_size == 0 || encoded_size == 4); |
| debug_assert!( |
| // didn't encode extra input |
| MAX_INPUT_LEN == max_input_len |
| // encoded one triple |
| || MAX_INPUT_LEN == max_input_len + MIN_ENCODE_CHUNK_SIZE |
| ); |
| |
| // encode complete triples only |
| let input_complete_chunks_len = input.len() - (input.len() % MIN_ENCODE_CHUNK_SIZE); |
| let input_chunks_to_encode_len = cmp::min(input_complete_chunks_len, max_input_len); |
| debug_assert_eq!(0, max_input_len % MIN_ENCODE_CHUNK_SIZE); |
| debug_assert_eq!(0, input_chunks_to_encode_len % MIN_ENCODE_CHUNK_SIZE); |
| |
| encoded_size += self.engine.internal_encode( |
| &input[..(input_chunks_to_encode_len)], |
| &mut self.output[encoded_size..], |
| ); |
| |
| // not updating `self.output_occupied_len` here because if the below write fails, it should |
| // "never take place" -- the buffer contents we encoded are ignored and perhaps retried |
| // later, if the consumer chooses. |
| |
| self.write_to_delegate(encoded_size) |
| // no matter whether we wrote the full encoded buffer or not, we consumed the same |
| // input |
| .map(|_| extra_input_read_len + input_chunks_to_encode_len) |
| .map_err(|e| { |
| // in case we filled and encoded `extra`, reset extra_len |
| self.extra_input_occupied_len = orig_extra_len; |
| |
| e |
| }) |
| } |
| |
| /// Because this is usually treated as OK to call multiple times, it will *not* flush any |
| /// incomplete chunks of input or write padding. |
| /// # Errors |
| /// |
| /// The first error that is not of [`ErrorKind::Interrupted`] will be returned. |
| fn flush(&mut self) -> Result<()> { |
| self.write_all_encoded_output()?; |
| self.delegate |
| .as_mut() |
| .expect("Writer must be present") |
| .flush() |
| } |
| } |
| |
| impl<'e, E: Engine, W: io::Write> Drop for EncoderWriter<'e, E, W> { |
| fn drop(&mut self) { |
| if !self.panicked { |
| // like `BufWriter`, ignore errors during drop |
| let _ = self.write_final_leftovers(); |
| } |
| } |
| } |
