Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 1333 insertions, 0 deletions

diff --git a/vendor/weezl/src/decode.rs b/vendor/weezl/src/decode.rs
new file mode 100644
index 0000000..641a3a8
--- /dev/null
+++ b/vendor/weezl/src/decode.rs
@@ -0,0 +1,1333 @@
+//! A module for all decoding needs.
+#[cfg(feature = "std")]
+use crate::error::StreamResult;
+use crate::error::{BufferResult, LzwError, LzwStatus, VectorResult};
+use crate::{BitOrder, Code, StreamBuf, MAX_CODESIZE, MAX_ENTRIES, STREAM_BUF_SIZE};
+
+use crate::alloc::{boxed::Box, vec, vec::Vec};
+#[cfg(feature = "std")]
+use std::io::{self, BufRead, Write};
+
+/// The state for decoding data with an LZW algorithm.
+///
+/// The same structure can be utilized with streams as well as your own buffers and driver logic.
+/// It may even be possible to mix them if you are sufficiently careful not to lose or skip any
+/// already decode data in the process.
+///
+/// This is a sans-IO implementation, meaning that it only contains the state of the decoder and
+/// the caller will provide buffers for input and output data when calling the basic
+/// [`decode_bytes`] method. Nevertheless, a number of _adapters_ are provided in the `into_*`
+/// methods for decoding with a particular style of common IO.
+///
+/// * [`decode`] for decoding once without any IO-loop.
+/// * [`into_async`] for decoding with the `futures` traits for asynchronous IO.
+/// * [`into_stream`] for decoding with the standard `io` traits.
+/// * [`into_vec`] for in-memory decoding.
+///
+/// [`decode_bytes`]: #method.decode_bytes
+/// [`decode`]: #method.decode
+/// [`into_async`]: #method.into_async
+/// [`into_stream`]: #method.into_stream
+/// [`into_vec`]: #method.into_vec
+pub struct Decoder {
+    state: Box<dyn Stateful + Send + 'static>,
+}
+
+/// A decoding stream sink.
+///
+/// See [`Decoder::into_stream`] on how to create this type.
+///
+/// [`Decoder::into_stream`]: struct.Decoder.html#method.into_stream
+#[cfg_attr(
+    not(feature = "std"),
+    deprecated = "This type is only useful with the `std` feature."
+)]
+#[cfg_attr(not(feature = "std"), allow(dead_code))]
+pub struct IntoStream<'d, W> {
+    decoder: &'d mut Decoder,
+    writer: W,
+    buffer: Option<StreamBuf<'d>>,
+    default_size: usize,
+}
+
+/// An async decoding sink.
+///
+/// See [`Decoder::into_async`] on how to create this type.
+///
+/// [`Decoder::into_async`]: struct.Decoder.html#method.into_async
+#[cfg(feature = "async")]
+pub struct IntoAsync<'d, W> {
+    decoder: &'d mut Decoder,
+    writer: W,
+    buffer: Option<StreamBuf<'d>>,
+    default_size: usize,
+}
+
+/// A decoding sink into a vector.
+///
+/// See [`Decoder::into_vec`] on how to create this type.
+///
+/// [`Decoder::into_vec`]: struct.Decoder.html#method.into_vec
+pub struct IntoVec<'d> {
+    decoder: &'d mut Decoder,
+    vector: &'d mut Vec<u8>,
+}
+
+trait Stateful {
+    fn advance(&mut self, inp: &[u8], out: &mut [u8]) -> BufferResult;
+    fn has_ended(&self) -> bool;
+    /// Ignore an end code and continue decoding (no implied reset).
+    fn restart(&mut self);
+    /// Reset the decoder to the beginning, dropping all buffers etc.
+    fn reset(&mut self);
+}
+
+#[derive(Clone)]
+struct Link {
+    prev: Code,
+    byte: u8,
+}
+
+#[derive(Default)]
+struct MsbBuffer {
+    /// A buffer of individual bits. The oldest code is kept in the high-order bits.
+    bit_buffer: u64,
+    /// A precomputed mask for this code.
+    code_mask: u16,
+    /// The current code size.
+    code_size: u8,
+    /// The number of bits in the buffer.
+    bits: u8,
+}
+
+#[derive(Default)]
+struct LsbBuffer {
+    /// A buffer of individual bits. The oldest code is kept in the high-order bits.
+    bit_buffer: u64,
+    /// A precomputed mask for this code.
+    code_mask: u16,
+    /// The current code size.
+    code_size: u8,
+    /// The number of bits in the buffer.
+    bits: u8,
+}
+
+trait CodeBuffer {
+    fn new(min_size: u8) -> Self;
+    fn reset(&mut self, min_size: u8);
+    fn bump_code_size(&mut self);
+    /// Retrieve the next symbol, refilling if necessary.
+    fn next_symbol(&mut self, inp: &mut &[u8]) -> Option<Code>;
+    /// Refill the internal buffer.
+    fn refill_bits(&mut self, inp: &mut &[u8]);
+    /// Get the next buffered code word.
+    fn get_bits(&mut self) -> Option<Code>;
+    fn max_code(&self) -> Code;
+    fn code_size(&self) -> u8;
+}
+
+struct DecodeState<CodeBuffer> {
+    /// The original minimum code size.
+    min_size: u8,
+    /// The table of decoded codes.
+    table: Table,
+    /// The buffer of decoded data.
+    buffer: Buffer,
+    /// The link which we are still decoding and its original code.
+    last: Option<(Code, Link)>,
+    /// The next code entry.
+    next_code: Code,
+    /// Code to reset all tables.
+    clear_code: Code,
+    /// Code to signal the end of the stream.
+    end_code: Code,
+    /// A stored flag if the end code has already appeared.
+    has_ended: bool,
+    /// If tiff then bumps are a single code sooner.
+    is_tiff: bool,
+    /// Do we allow stream to start without an explicit reset code?
+    implicit_reset: bool,
+    /// The buffer for decoded words.
+    code_buffer: CodeBuffer,
+}
+
+struct Buffer {
+    bytes: Box<[u8]>,
+    read_mark: usize,
+    write_mark: usize,
+}
+
+struct Table {
+    inner: Vec<Link>,
+    depths: Vec<u16>,
+}
+
+impl Decoder {
+    /// Create a new decoder with the specified bit order and symbol size.
+    ///
+    /// The algorithm for dynamically increasing the code symbol bit width is compatible with the
+    /// original specification. In particular you will need to specify an `Lsb` bit oder to decode
+    /// the data portion of a compressed `gif` image.
+    ///
+    /// # Panics
+    ///
+    /// The `size` needs to be in the interval `0..=12`.
+    pub fn new(order: BitOrder, size: u8) -> Self {
+        type Boxed = Box<dyn Stateful + Send + 'static>;
+        super::assert_decode_size(size);
+        let state = match order {
+            BitOrder::Lsb => Box::new(DecodeState::<LsbBuffer>::new(size)) as Boxed,
+            BitOrder::Msb => Box::new(DecodeState::<MsbBuffer>::new(size)) as Boxed,
+        };
+
+        Decoder { state }
+    }
+
+    /// Create a TIFF compatible decoder with the specified bit order and symbol size.
+    ///
+    /// The algorithm for dynamically increasing the code symbol bit width is compatible with the
+    /// TIFF specification, which is a misinterpretation of the original algorithm for increasing
+    /// the code size. It switches one symbol sooner.
+    ///
+    /// # Panics
+    ///
+    /// The `size` needs to be in the interval `0..=12`.
+    pub fn with_tiff_size_switch(order: BitOrder, size: u8) -> Self {
+        type Boxed = Box<dyn Stateful + Send + 'static>;
+        super::assert_decode_size(size);
+        let state = match order {
+            BitOrder::Lsb => {
+                let mut state = Box::new(DecodeState::<LsbBuffer>::new(size));
+                state.is_tiff = true;
+                state as Boxed
+            }
+            BitOrder::Msb => {
+                let mut state = Box::new(DecodeState::<MsbBuffer>::new(size));
+                state.is_tiff = true;
+                state as Boxed
+            }
+        };
+
+        Decoder { state }
+    }
+
+    /// Decode some bytes from `inp` and write result to `out`.
+    ///
+    /// This will consume a prefix of the input buffer and write decoded output into a prefix of
+    /// the output buffer. See the respective fields of the return value for the count of consumed
+    /// and written bytes. For the next call You should have adjusted the inputs accordingly.
+    ///
+    /// The call will try to decode and write as many bytes of output as available. It will be
+    /// much more optimized (and avoid intermediate buffering) if it is allowed to write a large
+    /// contiguous chunk at once.
+    ///
+    /// See [`into_stream`] for high-level functions (that are only available with the `std`
+    /// feature).
+    ///
+    /// [`into_stream`]: #method.into_stream
+    pub fn decode_bytes(&mut self, inp: &[u8], out: &mut [u8]) -> BufferResult {
+        self.state.advance(inp, out)
+    }
+
+    /// Decode a single chunk of lzw encoded data.
+    ///
+    /// This method requires the data to contain an end marker, and returns an error otherwise.
+    ///
+    /// This is a convenience wrapper around [`into_vec`]. Use the `into_vec` adapter to customize
+    /// buffer size, to supply an existing vector, to control whether an end marker is required, or
+    /// to preserve partial data in the case of a decoding error.
+    ///
+    /// [`into_vec`]: #into_vec
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use weezl::{BitOrder, decode::Decoder};
+    ///
+    /// // Encoded that was created with an encoder.
+    /// let data = b"\x80\x04\x81\x94l\x1b\x06\xf0\xb0 \x1d\xc6\xf1\xc8l\x19 \x10";
+    /// let decoded = Decoder::new(BitOrder::Msb, 9)
+    ///     .decode(data)
+    ///     .unwrap();
+    /// assert_eq!(decoded, b"Hello, world");
+    /// ```
+    pub fn decode(&mut self, data: &[u8]) -> Result<Vec<u8>, LzwError> {
+        let mut output = vec![];
+        self.into_vec(&mut output).decode_all(data).status?;
+        Ok(output)
+    }
+
+    /// Construct a decoder into a writer.
+    #[cfg(feature = "std")]
+    pub fn into_stream<W: Write>(&mut self, writer: W) -> IntoStream<'_, W> {
+        IntoStream {
+            decoder: self,
+            writer,
+            buffer: None,
+            default_size: STREAM_BUF_SIZE,
+        }
+    }
+
+    /// Construct a decoder into an async writer.
+    #[cfg(feature = "async")]
+    pub fn into_async<W: futures::io::AsyncWrite>(&mut self, writer: W) -> IntoAsync<'_, W> {
+        IntoAsync {
+            decoder: self,
+            writer,
+            buffer: None,
+            default_size: STREAM_BUF_SIZE,
+        }
+    }
+
+    /// Construct a decoder into a vector.
+    ///
+    /// All decoded data is appended and the vector is __not__ cleared.
+    ///
+    /// Compared to `into_stream` this interface allows a high-level access to decoding without
+    /// requires the `std`-feature. Also, it can make full use of the extra buffer control that the
+    /// special target exposes.
+    pub fn into_vec<'lt>(&'lt mut self, vec: &'lt mut Vec<u8>) -> IntoVec<'lt> {
+        IntoVec {
+            decoder: self,
+            vector: vec,
+        }
+    }
+
+    /// Check if the decoding has finished.
+    ///
+    /// No more output is produced beyond the end code that marked the finish of the stream. The
+    /// decoder may have read additional bytes, including padding bits beyond the last code word
+    /// but also excess bytes provided.
+    pub fn has_ended(&self) -> bool {
+        self.state.has_ended()
+    }
+
+    /// Ignore an end code and continue.
+    ///
+    /// This will _not_ reset any of the inner code tables and not have the effect of a clear code.
+    /// It will instead continue as if the end code had not been present. If no end code has
+    /// occurred then this is a no-op.
+    ///
+    /// You can test if an end code has occurred with [`has_ended`](#method.has_ended).
+    /// FIXME: clarify how this interacts with padding introduced after end code.
+    #[allow(dead_code)]
+    pub(crate) fn restart(&mut self) {
+        self.state.restart();
+    }
+
+    /// Reset all internal state.
+    ///
+    /// This produce a decoder as if just constructed with `new` but taking slightly less work. In
+    /// particular it will not deallocate any internal allocations. It will also avoid some
+    /// duplicate setup work.
+    pub fn reset(&mut self) {
+        self.state.reset();
+    }
+}
+
+#[cfg(feature = "std")]
+impl<'d, W: Write> IntoStream<'d, W> {
+    /// Decode data from a reader.
+    ///
+    /// This will read data until the stream is empty or an end marker is reached.
+    pub fn decode(&mut self, read: impl BufRead) -> StreamResult {
+        self.decode_part(read, false)
+    }
+
+    /// Decode data from a reader, requiring an end marker.
+    pub fn decode_all(mut self, read: impl BufRead) -> StreamResult {
+        self.decode_part(read, true)
+    }
+
+    /// Set the size of the intermediate decode buffer.
+    ///
+    /// A buffer of this size is allocated to hold one part of the decoded stream when no buffer is
+    /// available and any decoding method is called. No buffer is allocated if `set_buffer` has
+    /// been called. The buffer is reused.
+    ///
+    /// # Panics
+    /// This method panics if `size` is `0`.
+    pub fn set_buffer_size(&mut self, size: usize) {
+        assert_ne!(size, 0, "Attempted to set empty buffer");
+        self.default_size = size;
+    }
+
+    /// Use a particular buffer as an intermediate decode buffer.
+    ///
+    /// Calling this sets or replaces the buffer. When a buffer has been set then it is used
+    /// instead of dynamically allocating a buffer. Note that the size of the buffer is critical
+    /// for efficient decoding. Some optimization techniques require the buffer to hold one or more
+    /// previous decoded words. There is also additional overhead from `write` calls each time the
+    /// buffer has been filled.
+    ///
+    /// # Panics
+    /// This method panics if the `buffer` is empty.
+    pub fn set_buffer(&mut self, buffer: &'d mut [u8]) {
+        assert_ne!(buffer.len(), 0, "Attempted to set empty buffer");
+        self.buffer = Some(StreamBuf::Borrowed(buffer));
+    }
+
+    fn decode_part(&mut self, mut read: impl BufRead, must_finish: bool) -> StreamResult {
+        let IntoStream {
+            decoder,
+            writer,
+            buffer,
+            default_size,
+        } = self;
+
+        enum Progress {
+            Ok,
+            Done,
+        }
+
+        let mut bytes_read = 0;
+        let mut bytes_written = 0;
+
+        // Converting to mutable refs to move into the `once` closure.
+        let read_bytes = &mut bytes_read;
+        let write_bytes = &mut bytes_written;
+
+        let outbuf: &mut [u8] =
+            match { buffer.get_or_insert_with(|| StreamBuf::Owned(vec![0u8; *default_size])) } {
+                StreamBuf::Borrowed(slice) => &mut *slice,
+                StreamBuf::Owned(vec) => &mut *vec,
+            };
+        assert!(!outbuf.is_empty());
+
+        let once = move || {
+            // Try to grab one buffer of input data.
+            let data = read.fill_buf()?;
+
+            // Decode as much of the buffer as fits.
+            let result = decoder.decode_bytes(data, &mut outbuf[..]);
+            // Do the bookkeeping and consume the buffer.
+            *read_bytes += result.consumed_in;
+            *write_bytes += result.consumed_out;
+            read.consume(result.consumed_in);
+
+            // Handle the status in the result.
+            let done = result.status.map_err(|err| {
+                io::Error::new(io::ErrorKind::InvalidData, &*format!("{:?}", err))
+            })?;
+
+            // Check if we had any new data at all.
+            if let LzwStatus::NoProgress = done {
+                debug_assert_eq!(
+                    result.consumed_out, 0,
+                    "No progress means we have not decoded any data"
+                );
+                // In particular we did not finish decoding.
+                if must_finish {
+                    return Err(io::Error::new(
+                        io::ErrorKind::UnexpectedEof,
+                        "No more data but no end marker detected",
+                    ));
+                } else {
+                    return Ok(Progress::Done);
+                }
+            }
+
+            // And finish by writing our result.
+            // TODO: we may lose data on error (also on status error above) which we might want to
+            // deterministically handle so that we don't need to restart everything from scratch as
+            // the only recovery strategy. Any changes welcome.
+            writer.write_all(&outbuf[..result.consumed_out])?;
+
+            Ok(if let LzwStatus::Done = done {
+                Progress::Done
+            } else {
+                Progress::Ok
+            })
+        };
+
+        // Decode chunks of input data until we're done.
+        let status = core::iter::repeat_with(once)
+            // scan+fuse can be replaced with map_while
+            .scan((), |(), result| match result {
+                Ok(Progress::Ok) => Some(Ok(())),
+                Err(err) => Some(Err(err)),
+                Ok(Progress::Done) => None,
+            })
+            .fuse()
+            .collect();
+
+        StreamResult {
+            bytes_read,
+            bytes_written,
+            status,
+        }
+    }
+}
+
+impl IntoVec<'_> {
+    /// Decode data from a slice.
+    ///
+    /// This will read data until the slice is empty or an end marker is reached.
+    pub fn decode(&mut self, read: &[u8]) -> VectorResult {
+        self.decode_part(read, false)
+    }
+
+    /// Decode data from a slice, requiring an end marker.
+    pub fn decode_all(mut self, read: &[u8]) -> VectorResult {
+        self.decode_part(read, true)
+    }
+
+    fn grab_buffer(&mut self) -> (&mut [u8], &mut Decoder) {
+        const CHUNK_SIZE: usize = 1 << 12;
+        let decoder = &mut self.decoder;
+        let length = self.vector.len();
+
+        // Use the vector to do overflow checks and w/e.
+        self.vector.reserve(CHUNK_SIZE);
+        // FIXME: decoding into uninit buffer?
+        self.vector.resize(length + CHUNK_SIZE, 0u8);
+
+        (&mut self.vector[length..], decoder)
+    }
+
+    fn decode_part(&mut self, part: &[u8], must_finish: bool) -> VectorResult {
+        let mut result = VectorResult {
+            consumed_in: 0,
+            consumed_out: 0,
+            status: Ok(LzwStatus::Ok),
+        };
+
+        enum Progress {
+            Ok,
+            Done,
+        }
+
+        // Converting to mutable refs to move into the `once` closure.
+        let read_bytes = &mut result.consumed_in;
+        let write_bytes = &mut result.consumed_out;
+        let mut data = part;
+
+        // A 64 MB buffer is quite large but should get alloc_zeroed.
+        // Note that the decoded size can be up to quadratic in code block.
+        let once = move || {
+            // Grab a new output buffer.
+            let (outbuf, decoder) = self.grab_buffer();
+
+            // Decode as much of the buffer as fits.
+            let result = decoder.decode_bytes(data, &mut outbuf[..]);
+            // Do the bookkeeping and consume the buffer.
+            *read_bytes += result.consumed_in;
+            *write_bytes += result.consumed_out;
+            data = &data[result.consumed_in..];
+
+            let unfilled = outbuf.len() - result.consumed_out;
+            let filled = self.vector.len() - unfilled;
+            self.vector.truncate(filled);
+
+            // Handle the status in the result.
+            match result.status {
+                Err(err) => Err(err),
+                Ok(LzwStatus::NoProgress) if must_finish => Err(LzwError::InvalidCode),
+                Ok(LzwStatus::NoProgress) | Ok(LzwStatus::Done) => Ok(Progress::Done),
+                Ok(LzwStatus::Ok) => Ok(Progress::Ok),
+            }
+        };
+
+        // Decode chunks of input data until we're done.
+        let status: Result<(), _> = core::iter::repeat_with(once)
+            // scan+fuse can be replaced with map_while
+            .scan((), |(), result| match result {
+                Ok(Progress::Ok) => Some(Ok(())),
+                Err(err) => Some(Err(err)),
+                Ok(Progress::Done) => None,
+            })
+            .fuse()
+            .collect();
+
+        if let Err(err) = status {
+            result.status = Err(err);
+        }
+
+        result
+    }
+}
+
+// This is implemented in a separate file, so that 1.34.2 does not parse it. Otherwise, it would
+// trip over the usage of await, which is a reserved keyword in that edition/version. It only
+// contains an impl block.
+#[cfg(feature = "async")]
+#[path = "decode_into_async.rs"]
+mod impl_decode_into_async;
+
+impl<C: CodeBuffer> DecodeState<C> {
+    fn new(min_size: u8) -> Self {
+        DecodeState {
+            min_size,
+            table: Table::new(),
+            buffer: Buffer::new(),
+            last: None,
+            clear_code: 1 << min_size,
+            end_code: (1 << min_size) + 1,
+            next_code: (1 << min_size) + 2,
+            has_ended: false,
+            is_tiff: false,
+            implicit_reset: true,
+            code_buffer: CodeBuffer::new(min_size),
+        }
+    }
+
+    fn init_tables(&mut self) {
+        self.code_buffer.reset(self.min_size);
+        self.next_code = (1 << self.min_size) + 2;
+        self.table.init(self.min_size);
+    }
+
+    fn reset_tables(&mut self) {
+        self.code_buffer.reset(self.min_size);
+        self.next_code = (1 << self.min_size) + 2;
+        self.table.clear(self.min_size);
+    }
+}
+
+impl<C: CodeBuffer> Stateful for DecodeState<C> {
+    fn has_ended(&self) -> bool {
+        self.has_ended
+    }
+
+    fn restart(&mut self) {
+        self.has_ended = false;
+    }
+
+    fn reset(&mut self) {
+        self.table.init(self.min_size);
+        self.buffer.read_mark = 0;
+        self.buffer.write_mark = 0;
+        self.last = None;
+        self.restart();
+        self.code_buffer = CodeBuffer::new(self.min_size);
+    }
+
+    fn advance(&mut self, mut inp: &[u8], mut out: &mut [u8]) -> BufferResult {
+        // Skip everything if there is nothing to do.
+        if self.has_ended {
+            return BufferResult {
+                consumed_in: 0,
+                consumed_out: 0,
+                status: Ok(LzwStatus::Done),
+            };
+        }
+
+        // Rough description:
+        // We will fill the output slice as much as possible until either there is no more symbols
+        // to decode or an end code has been reached. This requires an internal buffer to hold a
+        // potential tail of the word corresponding to the last symbol. This tail will then be
+        // decoded first before continuing with the regular decoding. The same buffer is required
+        // to persist some symbol state across calls.
+        //
+        // We store the words corresponding to code symbols in an index chain, bytewise, where we
+        // push each decoded symbol. (TODO: wuffs shows some success with 8-byte units). This chain
+        // is traversed for each symbol when it is decoded and bytes are placed directly into the
+        // output slice. In the special case (new_code == next_code) we use an existing decoded
+        // version that is present in either the out bytes of this call or in buffer to copy the
+        // repeated prefix slice.
+        // TODO: I played with a 'decoding cache' to remember the position of long symbols and
+        // avoid traversing the chain, doing a copy of memory instead. It did however not lead to
+        // a serious improvement. It's just unlikely to both have a long symbol and have that
+        // repeated twice in the same output buffer.
+        //
+        // You will also find the (to my knowledge novel) concept of a _decoding burst_ which
+        // gained some >~10% speedup in tests. This is motivated by wanting to use out-of-order
+        // execution as much as possible and for this reason have the least possible stress on
+        // branch prediction. Our decoding table already gives us a lookahead on symbol lengths but
+        // only for re-used codes, not novel ones. This lookahead also makes the loop termination
+        // when restoring each byte of the code word perfectly predictable! So a burst is a chunk
+        // of code words which are all independent of each other, have known lengths _and_ are
+        // guaranteed to fit into the out slice without requiring a buffer. One burst can be
+        // decoded in an extremely tight loop.
+        //
+        // TODO: since words can be at most (1 << MAX_CODESIZE) = 4096 bytes long we could avoid
+        // that intermediate buffer at the expense of not always filling the output buffer
+        // completely. Alternatively we might follow its chain of precursor states twice. This may
+        // be even cheaper if we store more than one byte per link so it really should be
+        // evaluated.
+        // TODO: if the caller was required to provide the previous last word we could also avoid
+        // the buffer for cases where we need it to restore the next code! This could be built
+        // backwards compatible by only doing it after an opt-in call that enables the behaviour.
+
+        // Record initial lengths for the result that is returned.
+        let o_in = inp.len();
+        let o_out = out.len();
+
+        // The code_link is the previously decoded symbol.
+        // It's used to link the new code back to its predecessor.
+        let mut code_link = None;
+        // The status, which is written to on an invalid code.
+        let mut status = Ok(LzwStatus::Ok);
+
+        match self.last.take() {
+            // No last state? This is the first code after a reset?
+            None => {
+                match self.next_symbol(&mut inp) {
+                    // Plainly invalid code.
+                    Some(code) if code > self.next_code => status = Err(LzwError::InvalidCode),
+                    // next_code would require an actual predecessor.
+                    Some(code) if code == self.next_code => status = Err(LzwError::InvalidCode),
+                    // No more symbols available and nothing decoded yet.
+                    // Assume that we didn't make progress, this may get reset to Done if we read
+                    // some bytes from the input.
+                    None => status = Ok(LzwStatus::NoProgress),
+                    // Handle a valid code.
+                    Some(init_code) => {
+                        if init_code == self.clear_code {
+                            self.init_tables();
+                        } else if init_code == self.end_code {
+                            self.has_ended = true;
+                            status = Ok(LzwStatus::Done);
+                        } else if self.table.is_empty() {
+                            if self.implicit_reset {
+                                self.init_tables();
+
+                                self.buffer.fill_reconstruct(&self.table, init_code);
+                                let link = self.table.at(init_code).clone();
+                                code_link = Some((init_code, link));
+                            } else {
+                                // We require an explicit reset.
+                                status = Err(LzwError::InvalidCode);
+                            }
+                        } else {
+                            // Reconstruct the first code in the buffer.
+                            self.buffer.fill_reconstruct(&self.table, init_code);
+                            let link = self.table.at(init_code).clone();
+                            code_link = Some((init_code, link));
+                        }
+                    }
+                }
+            }
+            // Move the tracking state to the stack.
+            Some(tup) => code_link = Some(tup),
+        };
+
+        // Track an empty `burst` (see below) means we made no progress.
+        let mut burst_required_for_progress = false;
+        // Restore the previous state, if any.
+        if let Some((code, link)) = code_link.take() {
+            code_link = Some((code, link));
+            let remain = self.buffer.buffer();
+            // Check if we can fully finish the buffer.
+            if remain.len() > out.len() {
+                if out.is_empty() {
+                    status = Ok(LzwStatus::NoProgress);
+                } else {
+                    out.copy_from_slice(&remain[..out.len()]);
+                    self.buffer.consume(out.len());
+                    out = &mut [];
+                }
+            } else if remain.is_empty() {
+                status = Ok(LzwStatus::NoProgress);
+                burst_required_for_progress = true;
+            } else {
+                let consumed = remain.len();
+                out[..consumed].copy_from_slice(remain);
+                self.buffer.consume(consumed);
+                out = &mut out[consumed..];
+                burst_required_for_progress = false;
+            }
+        }
+
+        // The tracking state for a burst.
+        // These are actually initialized later but compiler wasn't smart enough to fully optimize
+        // out the init code so that appears outside th loop.
+        // TODO: maybe we can make it part of the state but it's dubious if that really gives a
+        // benefit over stack usage? Also the slices stored here would need some treatment as we
+        // can't infect the main struct with a lifetime.
+        let mut burst = [0; 6];
+        let mut bytes = [0u16; 6];
+        let mut target: [&mut [u8]; 6] = Default::default();
+        // A special reference to out slice which holds the last decoded symbol.
+        let mut last_decoded: Option<&[u8]> = None;
+
+        while let Some((mut code, mut link)) = code_link.take() {
+            if out.is_empty() && !self.buffer.buffer().is_empty() {
+                code_link = Some((code, link));
+                break;
+            }
+
+            let mut burst_size = 0;
+            // Ensure the code buffer is full, we're about to request some codes.
+            // Note that this also ensures at least one code is in the buffer if any input is left.
+            self.refill_bits(&mut inp);
+            // A burst is a sequence of decodes that are completely independent of each other. This
+            // is the case if neither is an end code, a clear code, or a next code, i.e. we have
+            // all of them in the decoding table and thus known their depths, and additionally if
+            // we can decode them directly into the output buffer.
+            for b in &mut burst {
+                // TODO: does it actually make a perf difference to avoid reading new bits here?
+                *b = match self.get_bits() {
+                    None => break,
+                    Some(code) => code,
+                };
+
+                // We can commit the previous burst code, and will take a slice from the output
+                // buffer. This also avoids the bounds check in the tight loop later.
+                if burst_size > 0 {
+                    let len = bytes[burst_size - 1];
+                    let (into, tail) = out.split_at_mut(usize::from(len));
+                    target[burst_size - 1] = into;
+                    out = tail;
+                }
+
+                // Check that we don't overflow the code size with all codes we burst decode.
+                if let Some(potential_code) = self.next_code.checked_add(burst_size as u16) {
+                    burst_size += 1;
+                    if potential_code == self.code_buffer.max_code() - Code::from(self.is_tiff) {
+                        break;
+                    }
+                } else {
+                    // next_code overflowed
+                    break;
+                }
+
+                // A burst code can't be special.
+                if *b == self.clear_code || *b == self.end_code || *b >= self.next_code {
+                    break;
+                }
+
+                // Read the code length and check that we can decode directly into the out slice.
+                let len = self.table.depths[usize::from(*b)];
+                if out.len() < usize::from(len) {
+                    break;
+                }
+
+                bytes[burst_size - 1] = len;
+            }
+
+            // No code left, and no more bytes to fill the buffer.
+            if burst_size == 0 {
+                if burst_required_for_progress {
+                    status = Ok(LzwStatus::NoProgress);
+                }
+                code_link = Some((code, link));
+                break;
+            }
+
+            burst_required_for_progress = false;
+            // Note that the very last code in the burst buffer doesn't actually belong to the
+            // burst itself. TODO: sometimes it could, we just don't differentiate between the
+            // breaks and a loop end condition above. That may be a speed advantage?
+            let (&new_code, burst) = burst[..burst_size].split_last().unwrap();
+
+            // The very tight loop for restoring the actual burst.
+            for (&burst, target) in burst.iter().zip(&mut target[..burst_size - 1]) {
+                let cha = self.table.reconstruct(burst, target);
+                // TODO: this pushes into a Vec, maybe we can make this cleaner.
+                // Theoretically this has a branch and llvm tends to be flaky with code layout for
+                // the case of requiring an allocation (which can't occur in practice).
+                let new_link = self.table.derive(&link, cha, code);
+                self.next_code += 1;
+                code = burst;
+                link = new_link;
+            }
+
+            // Update the slice holding the last decoded word.
+            if let Some(new_last) = target[..burst_size - 1].last_mut() {
+                let slice = core::mem::replace(new_last, &mut []);
+                last_decoded = Some(&*slice);
+            }
+
+            // Now handle the special codes.
+            if new_code == self.clear_code {
+                self.reset_tables();
+                last_decoded = None;
+                continue;
+            }
+
+            if new_code == self.end_code {
+                self.has_ended = true;
+                status = Ok(LzwStatus::Done);
+                last_decoded = None;
+                break;
+            }
+
+            if new_code > self.next_code {
+                status = Err(LzwError::InvalidCode);
+                last_decoded = None;
+                break;
+            }
+
+            let required_len = if new_code == self.next_code {
+                self.table.depths[usize::from(code)] + 1
+            } else {
+                self.table.depths[usize::from(new_code)]
+            };
+
+            let cha;
+            let is_in_buffer;
+            // Check if we will need to store our current state into the buffer.
+            if usize::from(required_len) > out.len() {
+                is_in_buffer = true;
+                if new_code == self.next_code {
+                    // last_decoded will be Some if we have restored any code into the out slice.
+                    // Otherwise it will still be present in the buffer.
+                    if let Some(last) = last_decoded.take() {
+                        self.buffer.bytes[..last.len()].copy_from_slice(last);
+                        self.buffer.write_mark = last.len();
+                        self.buffer.read_mark = last.len();
+                    }
+
+                    cha = self.buffer.fill_cscsc();
+                } else {
+                    // Restore the decoded word into the buffer.
+                    last_decoded = None;
+                    cha = self.buffer.fill_reconstruct(&self.table, new_code);
+                }
+            } else {
+                is_in_buffer = false;
+                let (target, tail) = out.split_at_mut(usize::from(required_len));
+                out = tail;
+
+                if new_code == self.next_code {
+                    // Reconstruct high.
+                    let source = match last_decoded.take() {
+                        Some(last) => last,
+                        None => &self.buffer.bytes[..self.buffer.write_mark],
+                    };
+                    cha = source[0];
+                    target[..source.len()].copy_from_slice(source);
+                    target[source.len()..][0] = source[0];
+                } else {
+                    cha = self.table.reconstruct(new_code, target);
+                }
+
+                // A new decoded word.
+                last_decoded = Some(target);
+            }
+
+            let new_link;
+            // Each newly read code creates one new code/link based on the preceding code if we
+            // have enough space to put it there.
+            if !self.table.is_full() {
+                let link = self.table.derive(&link, cha, code);
+
+                if self.next_code == self.code_buffer.max_code() - Code::from(self.is_tiff)
+                    && self.code_buffer.code_size() < MAX_CODESIZE
+                {
+                    self.bump_code_size();
+                }
+
+                self.next_code += 1;
+                new_link = link;
+            } else {
+                // It's actually quite likely that the next code will be a reset but just in case.
+                // FIXME: this path hasn't been tested very well.
+                new_link = link.clone();
+            }
+
+            // store the information on the decoded word.
+            code_link = Some((new_code, new_link));
+
+            // Can't make any more progress with decoding.
+            if is_in_buffer {
+                break;
+            }
+        }
+
+        // We need to store the last word into the buffer in case the first code in the next
+        // iteration is the next_code.
+        if let Some(tail) = last_decoded {
+            self.buffer.bytes[..tail.len()].copy_from_slice(tail);
+            self.buffer.write_mark = tail.len();
+            self.buffer.read_mark = tail.len();
+        }
+
+        // Ensure we don't indicate that no progress was made if we read some bytes from the input
+        // (which is progress).
+        if o_in > inp.len() {
+            if let Ok(LzwStatus::NoProgress) = status {
+                status = Ok(LzwStatus::Ok);
+            }
+        }
+
+        // Store the code/link state.
+        self.last = code_link;
+
+        BufferResult {
+            consumed_in: o_in.wrapping_sub(inp.len()),
+            consumed_out: o_out.wrapping_sub(out.len()),
+            status,
+        }
+    }
+}
+
+impl<C: CodeBuffer> DecodeState<C> {
+    fn next_symbol(&mut self, inp: &mut &[u8]) -> Option<Code> {
+        self.code_buffer.next_symbol(inp)
+    }
+
+    fn bump_code_size(&mut self) {
+        self.code_buffer.bump_code_size()
+    }
+
+    fn refill_bits(&mut self, inp: &mut &[u8]) {
+        self.code_buffer.refill_bits(inp)
+    }
+
+    fn get_bits(&mut self) -> Option<Code> {
+        self.code_buffer.get_bits()
+    }
+}
+
+impl CodeBuffer for MsbBuffer {
+    fn new(min_size: u8) -> Self {
+        MsbBuffer {
+            code_size: min_size + 1,
+            code_mask: (1u16 << (min_size + 1)) - 1,
+            bit_buffer: 0,
+            bits: 0,
+        }
+    }
+
+    fn reset(&mut self, min_size: u8) {
+        self.code_size = min_size + 1;
+        self.code_mask = (1 << self.code_size) - 1;
+    }
+
+    fn next_symbol(&mut self, inp: &mut &[u8]) -> Option<Code> {
+        if self.bits < self.code_size {
+            self.refill_bits(inp);
+        }
+
+        self.get_bits()
+    }
+
+    fn bump_code_size(&mut self) {
+        self.code_size += 1;
+        self.code_mask = (self.code_mask << 1) | 1;
+    }
+
+    fn refill_bits(&mut self, inp: &mut &[u8]) {
+        let wish_count = (64 - self.bits) / 8;
+        let mut buffer = [0u8; 8];
+        let new_bits = match inp.get(..usize::from(wish_count)) {
+            Some(bytes) => {
+                buffer[..usize::from(wish_count)].copy_from_slice(bytes);
+                *inp = &inp[usize::from(wish_count)..];
+                wish_count * 8
+            }
+            None => {
+                let new_bits = inp.len() * 8;
+                buffer[..inp.len()].copy_from_slice(inp);
+                *inp = &[];
+                new_bits as u8
+            }
+        };
+        self.bit_buffer |= u64::from_be_bytes(buffer) >> self.bits;
+        self.bits += new_bits;
+    }
+
+    fn get_bits(&mut self) -> Option<Code> {
+        if self.bits < self.code_size {
+            return None;
+        }
+
+        let mask = u64::from(self.code_mask);
+        let rotbuf = self.bit_buffer.rotate_left(self.code_size.into());
+        self.bit_buffer = rotbuf & !mask;
+        self.bits -= self.code_size;
+        Some((rotbuf & mask) as u16)
+    }
+
+    fn max_code(&self) -> Code {
+        self.code_mask
+    }
+
+    fn code_size(&self) -> u8 {
+        self.code_size
+    }
+}
+
+impl CodeBuffer for LsbBuffer {
+    fn new(min_size: u8) -> Self {
+        LsbBuffer {
+            code_size: min_size + 1,
+            code_mask: (1u16 << (min_size + 1)) - 1,
+            bit_buffer: 0,
+            bits: 0,
+        }
+    }
+
+    fn reset(&mut self, min_size: u8) {
+        self.code_size = min_size + 1;
+        self.code_mask = (1 << self.code_size) - 1;
+    }
+
+    fn next_symbol(&mut self, inp: &mut &[u8]) -> Option<Code> {
+        if self.bits < self.code_size {
+            self.refill_bits(inp);
+        }
+
+        self.get_bits()
+    }
+
+    fn bump_code_size(&mut self) {
+        self.code_size += 1;
+        self.code_mask = (self.code_mask << 1) | 1;
+    }
+
+    fn refill_bits(&mut self, inp: &mut &[u8]) {
+        let wish_count = (64 - self.bits) / 8;
+        let mut buffer = [0u8; 8];
+        let new_bits = match inp.get(..usize::from(wish_count)) {
+            Some(bytes) => {
+                buffer[..usize::from(wish_count)].copy_from_slice(bytes);
+                *inp = &inp[usize::from(wish_count)..];
+                wish_count * 8
+            }
+            None => {
+                let new_bits = inp.len() * 8;
+                buffer[..inp.len()].copy_from_slice(inp);
+                *inp = &[];
+                new_bits as u8
+            }
+        };
+        self.bit_buffer |= u64::from_be_bytes(buffer).swap_bytes() << self.bits;
+        self.bits += new_bits;
+    }
+
+    fn get_bits(&mut self) -> Option<Code> {
+        if self.bits < self.code_size {
+            return None;
+        }
+
+        let mask = u64::from(self.code_mask);
+        let code = self.bit_buffer & mask;
+        self.bit_buffer >>= self.code_size;
+        self.bits -= self.code_size;
+        Some(code as u16)
+    }
+
+    fn max_code(&self) -> Code {
+        self.code_mask
+    }
+
+    fn code_size(&self) -> u8 {
+        self.code_size
+    }
+}
+
+impl Buffer {
+    fn new() -> Self {
+        Buffer {
+            bytes: vec![0; MAX_ENTRIES].into_boxed_slice(),
+            read_mark: 0,
+            write_mark: 0,
+        }
+    }
+
+    /// When encoding a sequence `cScSc` where `c` is any character and `S` is any string
+    /// this results in two codes `AB`, `A` encoding `cS` and `B` encoding `cSc`. Supposing
+    /// the buffer is already filled with the reconstruction of `A`, we can easily fill it
+    /// with the reconstruction of `B`.
+    fn fill_cscsc(&mut self) -> u8 {
+        self.bytes[self.write_mark] = self.bytes[0];
+        self.write_mark += 1;
+        self.read_mark = 0;
+        self.bytes[0]
+    }
+
+    // Fill the buffer by decoding from the table
+    fn fill_reconstruct(&mut self, table: &Table, code: Code) -> u8 {
+        self.write_mark = 0;
+        self.read_mark = 0;
+        let depth = table.depths[usize::from(code)];
+        let mut memory = core::mem::replace(&mut self.bytes, Box::default());
+
+        let out = &mut memory[..usize::from(depth)];
+        let last = table.reconstruct(code, out);
+
+        self.bytes = memory;
+        self.write_mark = usize::from(depth);
+        last
+    }
+
+    fn buffer(&self) -> &[u8] {
+        &self.bytes[self.read_mark..self.write_mark]
+    }
+
+    fn consume(&mut self, amt: usize) {
+        self.read_mark += amt;
+    }
+}
+
+impl Table {
+    fn new() -> Self {
+        Table {
+            inner: Vec::with_capacity(MAX_ENTRIES),
+            depths: Vec::with_capacity(MAX_ENTRIES),
+        }
+    }
+
+    fn clear(&mut self, min_size: u8) {
+        let static_count = usize::from(1u16 << u16::from(min_size)) + 2;
+        self.inner.truncate(static_count);
+        self.depths.truncate(static_count);
+    }
+
+    fn init(&mut self, min_size: u8) {
+        self.inner.clear();
+        self.depths.clear();
+        for i in 0..(1u16 << u16::from(min_size)) {
+            self.inner.push(Link::base(i as u8));
+            self.depths.push(1);
+        }
+        // Clear code.
+        self.inner.push(Link::base(0));
+        self.depths.push(0);
+        // End code.
+        self.inner.push(Link::base(0));
+        self.depths.push(0);
+    }
+
+    fn at(&self, code: Code) -> &Link {
+        &self.inner[usize::from(code)]
+    }
+
+    fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    fn is_full(&self) -> bool {
+        self.inner.len() >= MAX_ENTRIES
+    }
+
+    fn derive(&mut self, from: &Link, byte: u8, prev: Code) -> Link {
+        let link = from.derive(byte, prev);
+        let depth = self.depths[usize::from(prev)] + 1;
+        self.inner.push(link.clone());
+        self.depths.push(depth);
+        link
+    }
+
+    fn reconstruct(&self, code: Code, out: &mut [u8]) -> u8 {
+        let mut code_iter = code;
+        let table = &self.inner[..=usize::from(code)];
+        let len = code_iter;
+        for ch in out.iter_mut().rev() {
+            //(code, cha) = self.table[k as usize];
+            // Note: This could possibly be replaced with an unchecked array access if
+            //  - value is asserted to be < self.next_code() in push
+            //  - min_size is asserted to be < MAX_CODESIZE
+            let entry = &table[usize::from(code_iter)];
+            code_iter = core::cmp::min(len, entry.prev);
+            *ch = entry.byte;
+        }
+        out[0]
+    }
+}
+
+impl Link {
+    fn base(byte: u8) -> Self {
+        Link { prev: 0, byte }
+    }
+
+    // TODO: this has self type to make it clear we might depend on the old in a future
+    // optimization. However, that has no practical purpose right now.
+    fn derive(&self, byte: u8, prev: Code) -> Self {
+        Link { prev, byte }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::alloc::vec::Vec;
+    #[cfg(feature = "std")]
+    use crate::StreamBuf;
+    use crate::{decode::Decoder, BitOrder};
+
+    #[test]
+    fn invalid_code_size_low() {
+        let _ = Decoder::new(BitOrder::Msb, 0);
+        let _ = Decoder::new(BitOrder::Msb, 1);
+    }
+
+    #[test]
+    #[should_panic]
+    fn invalid_code_size_high() {
+        let _ = Decoder::new(BitOrder::Msb, 14);
+    }
+
+    fn make_encoded() -> Vec<u8> {
+        const FILE: &'static [u8] = include_bytes!(concat!(
+            env!("CARGO_MANIFEST_DIR"),
+            "/benches/binary-8-msb.lzw"
+        ));
+        return Vec::from(FILE);
+    }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn into_stream_buffer_no_alloc() {
+        let encoded = make_encoded();
+        let mut decoder = Decoder::new(BitOrder::Msb, 8);
+
+        let mut output = vec![];
+        let mut buffer = [0; 512];
+        let mut istream = decoder.into_stream(&mut output);
+        istream.set_buffer(&mut buffer[..]);
+        istream.decode(&encoded[..]).status.unwrap();
+
+        match istream.buffer {
+            Some(StreamBuf::Borrowed(_)) => {}
+            None => panic!("Decoded without buffer??"),
+            Some(StreamBuf::Owned(_)) => panic!("Unexpected buffer allocation"),
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn into_stream_buffer_small_alloc() {
+        struct WriteTap<W: std::io::Write>(W);
+        const BUF_SIZE: usize = 512;
+
+        impl<W: std::io::Write> std::io::Write for WriteTap<W> {
+            fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+                assert!(buf.len() <= BUF_SIZE);
+                self.0.write(buf)
+            }
+            fn flush(&mut self) -> std::io::Result<()> {
+                self.0.flush()
+            }
+        }
+
+        let encoded = make_encoded();
+        let mut decoder = Decoder::new(BitOrder::Msb, 8);
+
+        let mut output = vec![];
+        let mut istream = decoder.into_stream(WriteTap(&mut output));
+        istream.set_buffer_size(512);
+        istream.decode(&encoded[..]).status.unwrap();
+
+        match istream.buffer {
+            Some(StreamBuf::Owned(vec)) => assert!(vec.len() <= BUF_SIZE),
+            Some(StreamBuf::Borrowed(_)) => panic!("Unexpected borrowed buffer, where from?"),
+            None => panic!("Decoded without buffer??"),
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn reset() {
+        let encoded = make_encoded();
+        let mut decoder = Decoder::new(BitOrder::Msb, 8);
+        let mut reference = None;
+
+        for _ in 0..2 {
+            let mut output = vec![];
+            let mut buffer = [0; 512];
+            let mut istream = decoder.into_stream(&mut output);
+            istream.set_buffer(&mut buffer[..]);
+            istream.decode_all(&encoded[..]).status.unwrap();
+
+            decoder.reset();
+            if let Some(reference) = &reference {
+                assert_eq!(output, *reference);
+            } else {
+                reference = Some(output);
+            }
+        }
+    }
+}