//! A module for all encoding needs.
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};
#[cfg(feature = "std")]
use crate::error::StreamResult;
#[cfg(feature = "std")]
use std::io::{self, BufRead, Write};
/// The state for encoding 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 any written
/// data in the process.
///
/// This is a sans-IO implementation, meaning that it only contains the state of the encoder and
/// the caller will provide buffers for input and output data when calling the basic
/// [`encode_bytes`] method. Nevertheless, a number of _adapters_ are provided in the `into_*`
/// methods for enoding with a particular style of common IO.
///
/// * [`encode`] for encoding once without any IO-loop.
/// * [`into_async`] for encoding with the `futures` traits for asynchronous IO.
/// * [`into_stream`] for encoding with the standard `io` traits.
/// * [`into_vec`] for in-memory encoding.
///
/// [`encode_bytes`]: #method.encode_bytes
/// [`encode`]: #method.encode
/// [`into_async`]: #method.into_async
/// [`into_stream`]: #method.into_stream
/// [`into_vec`]: #method.into_vec
pub struct Encoder {
/// Internally dispatch via a dynamic trait object. This did not have any significant
/// performance impact as we batch data internally and this pointer does not change after
/// creation!
state: Box<dyn Stateful + Send + 'static>,
}
/// A encoding stream sink.
///
/// See [`Encoder::into_stream`] on how to create this type.
///
/// [`Encoder::into_stream`]: struct.Encoder.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> {
encoder: &'d mut Encoder,
writer: W,
buffer: Option<StreamBuf<'d>>,
default_size: usize,
}
/// An async decoding sink.
///
/// See [`Encoder::into_async`] on how to create this type.
///
/// [`Encoder::into_async`]: struct.Encoder.html#method.into_async
#[cfg(feature = "async")]
pub struct IntoAsync<'d, W> {
encoder: &'d mut Encoder,
writer: W,
buffer: Option<StreamBuf<'d>>,
default_size: usize,
}
/// A encoding sink into a vector.
///
/// See [`Encoder::into_vec`] on how to create this type.
///
/// [`Encoder::into_vec`]: struct.Encoder.html#method.into_vec
pub struct IntoVec<'d> {
encoder: &'d mut Encoder,
vector: &'d mut Vec<u8>,
}
trait Stateful {
fn advance(&mut self, inp: &[u8], out: &mut [u8]) -> BufferResult;
fn mark_ended(&mut self) -> bool;
/// Reset the state tracking if end code has been written.
fn restart(&mut self);
/// Reset the encoder to the beginning, dropping all buffers etc.
fn reset(&mut self);
}
struct EncodeState<B: Buffer> {
/// The configured minimal code size.
min_size: u8,
/// The current encoding symbol tree.
tree: Tree,
/// If we have pushed the end code.
has_ended: bool,
/// If tiff then bumps are a single code sooner.
is_tiff: bool,
/// The code corresponding to the currently read characters.
current_code: Code,
/// The clear code for resetting the dictionary.
clear_code: Code,
/// The bit buffer for encoding.
buffer: B,
}
struct MsbBuffer {
/// The current code length.
code_size: u8,
/// The buffer bits.
buffer: u64,
/// The number of valid buffer bits.
bits_in_buffer: u8,
}
struct LsbBuffer {
/// The current code length.
code_size: u8,
/// The buffer bits.
buffer: u64,
/// The number of valid buffer bits.
bits_in_buffer: u8,
}
trait Buffer {
fn new(size: u8) -> Self;
/// Reset the code size in the buffer.
fn reset(&mut self, min_size: u8);
/// Apply effects of a Clear Code.
fn clear(&mut self, min_size: u8);
/// Insert a code into the buffer.
fn buffer_code(&mut self, code: Code);
/// Push bytes if the buffer space is getting small.
fn push_out(&mut self, out: &mut &mut [u8]) -> bool;
/// Flush all full bytes, returning if at least one more byte remains.
fn flush_out(&mut self, out: &mut &mut [u8]) -> bool;
/// Pad the buffer to a full byte.
fn buffer_pad(&mut self);
/// Increase the maximum code size.
fn bump_code_size(&mut self);
/// Return the maximum code with the current code size.
fn max_code(&self) -> Code;
/// Return the current code size in bits.
fn code_size(&self) -> u8;
}
/// One tree node for at most each code.
/// To avoid using too much memory we keep nodes with few successors in optimized form. This form
/// doesn't offer lookup by indexing but instead does a linear search.
#[derive(Default)]
struct Tree {
simples: Vec<Simple>,
complex: Vec<Full>,
keys: Vec<CompressedKey>,
}
#[derive(Clone, Copy)]
enum FullKey {
NoSuccessor,
Simple(u16),
Full(u16),
}
#[derive(Clone, Copy)]
struct CompressedKey(u16);
const SHORT: usize = 16;
#[derive(Clone, Copy)]
struct Simple {
codes: [Code; SHORT],
chars: [u8; SHORT],
count: u8,
}
#[derive(Clone, Copy)]
struct Full {
char_continuation: [Code; 256],
}
impl Encoder {
/// Create a new encoder 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 encode
/// the data portion of a compressed `gif` image.
///
/// # Panics
///
/// The `size` needs to be in the interval `2..=12`.
pub fn new(order: BitOrder, size: u8) -> Self {
type Boxed = Box<dyn Stateful + Send + 'static>;
super::assert_encode_size(size);
let state = match order {
BitOrder::Lsb => Box::new(EncodeState::<LsbBuffer>::new(size)) as Boxed,
BitOrder::Msb => Box::new(EncodeState::<MsbBuffer>::new(size)) as Boxed,
};
Encoder { state }
}
/// Create a TIFF compatible encoder 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 `2..=12`.
pub fn with_tiff_size_switch(order: BitOrder, size: u8) -> Self {
type Boxed = Box<dyn Stateful + Send + 'static>;
super::assert_encode_size(size);
let state = match order {
BitOrder::Lsb => {
let mut state = Box::new(EncodeState::<LsbBuffer>::new(size));
state.is_tiff = true;
state as Boxed
}
BitOrder::Msb => {
let mut state = Box::new(EncodeState::<MsbBuffer>::new(size));
state.is_tiff = true;
state as Boxed
}
};
Encoder { state }
}
/// Encode some bytes from `inp` into `out`.
///
/// See [`into_stream`] for high-level functions (this interface is only available with the
/// `std` feature) and [`finish`] for marking the input data as complete.
///
/// When some input byte is invalid, i.e. is not smaller than `1 << size`, then that byte and
/// all following ones will _not_ be consumed and the `status` of the result will signal an
/// error. The result will also indicate that all bytes up to but not including the offending
/// byte have been consumed. You may try again with a fixed byte.
///
/// [`into_stream`]: #method.into_stream
/// [`finish`]: #method.finish
pub fn encode_bytes(&mut self, inp: &[u8], out: &mut [u8]) -> BufferResult {
self.state.advance(inp, out)
}
/// Encode a single chunk of data.
///
/// This method will add an end marker to the encoded chunk.
///
/// 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, encode::Encoder};
///
/// let data = b"Hello, world";
/// let encoded = Encoder::new(BitOrder::Msb, 9)
/// .encode(data)
/// .expect("All bytes valid for code size");
/// ```
pub fn encode(&mut self, data: &[u8]) -> Result<Vec<u8>, LzwError> {
let mut output = Vec::new();
self.into_vec(&mut output).encode_all(data).status?;
Ok(output)
}
/// Construct a encoder into a writer.
#[cfg(feature = "std")]
pub fn into_stream<W: Write>(&mut self, writer: W) -> IntoStream<'_, W> {
IntoStream {
encoder: self,
writer,
buffer: None,
default_size: STREAM_BUF_SIZE,
}
}
/// Construct a encoder into an async writer.
#[cfg(feature = "async")]
pub fn into_async<W: futures::io::AsyncWrite>(&mut self, writer: W) -> IntoAsync<'_, W> {
IntoAsync {
encoder: self,
writer,
buffer: None,
default_size: STREAM_BUF_SIZE,
}
}
/// Construct an encoder into a vector.
///
/// All encoded data is appended and the vector is __not__ cleared.
///
/// Compared to `into_stream` this interface allows a high-level access to encoding 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 {
encoder: self,
vector: vec,
}
}
/// Mark the encoding as in the process of finishing.
///
/// The next following call to `encode_bytes` which is able to consume the complete input will
/// also try to emit an end code. It's not recommended, but also not unsound, to use different
/// byte slices in different calls from this point forward and thus to 'delay' the actual end
/// of the data stream. The behaviour after the end marker has been written is unspecified but
/// sound.
pub fn finish(&mut self) {
self.state.mark_ended();
}
/// Undo marking this data stream as ending.
/// 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 an encoder 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> {
/// Encode data from a reader.
///
/// This will drain the supplied reader. It will not encode an end marker after all data has
/// been processed.
pub fn encode(&mut self, read: impl BufRead) -> StreamResult {
self.encode_part(read, false)
}
/// Encode data from a reader and an end marker.
pub fn encode_all(mut self, read: impl BufRead) -> StreamResult {
self.encode_part(read, true)
}
/// Set the size of the intermediate encode buffer.
///
/// A buffer of this size is allocated to hold one part of the encoded stream when no buffer is
/// available and any encoding 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 encode buffer.
///
/// Calling this sets or replaces the buffer. When a buffer has been set then it is used
/// instead of a dynamically allocating a buffer. Note that the size of the buffer is relevant
/// for efficient encoding as there is 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 encode_part(&mut self, mut read: impl BufRead, finish: bool) -> StreamResult {
let IntoStream {
encoder,
writer,
buffer,
default_size,
} = self;
enum Progress {
Ok,
Done,
}
let mut bytes_read = 0;
let mut bytes_written = 0;
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 || {
let data = read.fill_buf()?;
if data.is_empty() {
if finish {
encoder.finish();
} else {
return Ok(Progress::Done);
}
}
let result = encoder.encode_bytes(data, &mut outbuf[..]);
*read_bytes += result.consumed_in;
*write_bytes += result.consumed_out;
read.consume(result.consumed_in);
let done = result.status.map_err(|err| {
io::Error::new(io::ErrorKind::InvalidData, &*format!("{:?}", err))
})?;
if let LzwStatus::Done = done {
writer.write_all(&outbuf[..result.consumed_out])?;
return Ok(Progress::Done);
}
if let LzwStatus::NoProgress = done {
return Err(io::Error::new(
io::ErrorKind::UnexpectedEof,
"No more data but no end marker detected",
));
}
writer.write_all(&outbuf[..result.consumed_out])?;
Ok(Progress::Ok)
};
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<'_> {
/// Encode data from a slice.
pub fn encode(&mut self, read: &[u8]) -> VectorResult {
self.encode_part(read, false)
}
/// Decode data from a reader, adding an end marker.
pub fn encode_all(mut self, read: &[u8]) -> VectorResult {
self.encode_part(read, true)
}
fn grab_buffer(&mut self) -> (&mut [u8], &mut Encoder) {
const CHUNK_SIZE: usize = 1 << 12;
let decoder = &mut self.encoder;
let length = self.vector.len();
// Use the vector to do overflow checks and w/e.
self.vector.reserve(CHUNK_SIZE);
// FIXME: encoding into uninit buffer?
self.vector.resize(length + CHUNK_SIZE, 0u8);
(&mut self.vector[length..], decoder)
}
fn encode_part(&mut self, part: &[u8], 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, encoder) = self.grab_buffer();
if finish {
encoder.finish();
}
// Decode as much of the buffer as fits.
let result = encoder.encode_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.
let done = result.status?;
if let LzwStatus::Done = done {
Ok(Progress::Done)
} else {
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 = "encode_into_async.rs"]
mod impl_encode_into_async;
impl<B: Buffer> EncodeState<B> {
fn new(min_size: u8) -> Self {
let clear_code = 1 << min_size;
let mut tree = Tree::default();
tree.init(min_size);
let mut state = EncodeState {
min_size,
tree,
has_ended: false,
is_tiff: false,
current_code: clear_code,
clear_code,
buffer: B::new(min_size),
};
state.buffer_code(clear_code);
state
}
}
impl<B: Buffer> Stateful for EncodeState<B> {
fn advance(&mut self, mut inp: &[u8], mut out: &mut [u8]) -> BufferResult {
let c_in = inp.len();
let c_out = out.len();
let mut status = Ok(LzwStatus::Ok);
'encoding: loop {
if self.push_out(&mut out) {
break;
}
if inp.is_empty() && self.has_ended {
let end = self.end_code();
if self.current_code != end {
if self.current_code != self.clear_code {
self.buffer_code(self.current_code);
// When reading this code, the decoder will add an extra entry to its table
// before reading th end code. Thusly, it may increase its code size based
// on this additional entry.
if self.tree.keys.len() + usize::from(self.is_tiff)
> usize::from(self.buffer.max_code())
&& self.buffer.code_size() < MAX_CODESIZE
{
self.buffer.bump_code_size();
}
}
self.buffer_code(end);
self.current_code = end;
self.buffer_pad();
}
break;
}
let mut next_code = None;
let mut bytes = inp.iter();
while let Some(&byte) = bytes.next() {
if self.min_size < 8 && byte >= 1 << self.min_size {
status = Err(LzwError::InvalidCode);
break 'encoding;
}
inp = bytes.as_slice();
match self.tree.iterate(self.current_code, byte) {
Ok(code) => self.current_code = code,
Err(_) => {
next_code = Some(self.current_code);
self.current_code = u16::from(byte);
break;
}
}
}
match next_code {
// No more bytes, no code produced.
None => break,
Some(code) => {
self.buffer_code(code);
if self.tree.keys.len() + usize::from(self.is_tiff)
> usize::from(self.buffer.max_code()) + 1
&& self.buffer.code_size() < MAX_CODESIZE
{
self.buffer.bump_code_size();
}
if self.tree.keys.len() > MAX_ENTRIES {
self.buffer_code(self.clear_code);
self.tree.reset(self.min_size);
self.buffer.clear(self.min_size);
}
}
}
}
if inp.is_empty() && self.current_code == self.end_code() {
if !self.flush_out(&mut out) {
status = Ok(LzwStatus::Done);
}
}
BufferResult {
consumed_in: c_in - inp.len(),
consumed_out: c_out - out.len(),
status,
}
}
fn mark_ended(&mut self) -> bool {
core::mem::replace(&mut self.has_ended, true)
}
fn restart(&mut self) {
self.has_ended = false;
}
fn reset(&mut self) {
self.restart();
self.current_code = self.clear_code;
self.tree.reset(self.min_size);
self.buffer.reset(self.min_size);
self.buffer_code(self.clear_code);
}
}
impl<B: Buffer> EncodeState<B> {
fn push_out(&mut self, out: &mut &mut [u8]) -> bool {
self.buffer.push_out(out)
}
fn flush_out(&mut self, out: &mut &mut [u8]) -> bool {
self.buffer.flush_out(out)
}
fn end_code(&self) -> Code {
self.clear_code + 1
}
fn buffer_pad(&mut self) {
self.buffer.buffer_pad();
}
fn buffer_code(&mut self, code: Code) {
self.buffer.buffer_code(code);
}
}
impl Buffer for MsbBuffer {
fn new(min_size: u8) -> Self {
MsbBuffer {
code_size: min_size + 1,
buffer: 0,
bits_in_buffer: 0,
}
}
fn reset(&mut self, min_size: u8) {
self.code_size = min_size + 1;
self.buffer = 0;
self.bits_in_buffer = 0;
}
fn clear(&mut self, min_size: u8) {
self.code_size = min_size + 1;
}
fn buffer_code(&mut self, code: Code) {
let shift = 64 - self.bits_in_buffer - self.code_size;
self.buffer |= u64::from(code) << shift;
self.bits_in_buffer += self.code_size;
}
fn push_out(&mut self, out: &mut &mut [u8]) -> bool {
if self.bits_in_buffer + 2 * self.code_size < 64 {
return false;
}
self.flush_out(out)
}
fn flush_out(&mut self, out: &mut &mut [u8]) -> bool {
let want = usize::from(self.bits_in_buffer / 8);
let count = want.min((*out).len());
let (bytes, tail) = core::mem::replace(out, &mut []).split_at_mut(count);
*out = tail;
for b in bytes {
*b = ((self.buffer & 0xff00_0000_0000_0000) >> 56) as u8;
self.buffer <<= 8;
self.bits_in_buffer -= 8;
}
count < want
}
fn buffer_pad(&mut self) {
let to_byte = self.bits_in_buffer.wrapping_neg() & 0x7;
self.bits_in_buffer += to_byte;
}
fn bump_code_size(&mut self) {
self.code_size += 1;
}
fn max_code(&self) -> Code {
(1 << self.code_size) - 1
}
fn code_size(&self) -> u8 {
self.code_size
}
}
impl Buffer for LsbBuffer {
fn new(min_size: u8) -> Self {
LsbBuffer {
code_size: min_size + 1,
buffer: 0,
bits_in_buffer: 0,
}
}
fn reset(&mut self, min_size: u8) {
self.code_size = min_size + 1;
self.buffer = 0;
self.bits_in_buffer = 0;
}
fn clear(&mut self, min_size: u8) {
self.code_size = min_size + 1;
}
fn buffer_code(&mut self, code: Code) {
self.buffer |= u64::from(code) << self.bits_in_buffer;
self.bits_in_buffer += self.code_size;
}
fn push_out(&mut self, out: &mut &mut [u8]) -> bool {
if self.bits_in_buffer + 2 * self.code_size < 64 {
return false;
}
self.flush_out(out)
}
fn flush_out(&mut self, out: &mut &mut [u8]) -> bool {
let want = usize::from(self.bits_in_buffer / 8);
let count = want.min((*out).len());
let (bytes, tail) = core::mem::replace(out, &mut []).split_at_mut(count);
*out = tail;
for b in bytes {
*b = (self.buffer & 0x0000_0000_0000_00ff) as u8;
self.buffer >>= 8;
self.bits_in_buffer -= 8;
}
count < want
}
fn buffer_pad(&mut self) {
let to_byte = self.bits_in_buffer.wrapping_neg() & 0x7;
self.bits_in_buffer += to_byte;
}
fn bump_code_size(&mut self) {
self.code_size += 1;
}
fn max_code(&self) -> Code {
(1 << self.code_size) - 1
}
fn code_size(&self) -> u8 {
self.code_size
}
}
impl Tree {
fn init(&mut self, min_size: u8) {
// We need a way to represent the state of a currently empty buffer. We use the clear code
// for this, thus create one complex mapping that leads to the one-char base codes.
self.keys
.resize((1 << min_size) + 2, FullKey::NoSuccessor.into());
self.complex.push(Full {
char_continuation: [0; 256],
});
let map_of_begin = self.complex.last_mut().unwrap();
for ch in 0u16..256 {
map_of_begin.char_continuation[usize::from(ch)] = ch;
}
self.keys[1 << min_size] = FullKey::Full(0).into();
}
fn reset(&mut self, min_size: u8) {
self.simples.clear();
self.keys.truncate((1 << min_size) + 2);
// Keep entry for clear code.
self.complex.truncate(1);
// The first complex is not changed..
for k in self.keys[..(1 << min_size) + 2].iter_mut() {
*k = FullKey::NoSuccessor.into();
}
self.keys[1 << min_size] = FullKey::Full(0).into();
}
fn at_key(&self, code: Code, ch: u8) -> Option<Code> {
let key = self.keys[usize::from(code)];
match FullKey::from(key) {
FullKey::NoSuccessor => None,
FullKey::Simple(idx) => {
let nexts = &self.simples[usize::from(idx)];
let successors = nexts
.codes
.iter()
.zip(nexts.chars.iter())
.take(usize::from(nexts.count));
for (&scode, &sch) in successors {
if sch == ch {
return Some(scode);
}
}
None
}
FullKey::Full(idx) => {
let full = &self.complex[usize::from(idx)];
let precode = full.char_continuation[usize::from(ch)];
if usize::from(precode) < MAX_ENTRIES {
Some(precode)
} else {
None
}
}
}
}
/// Iterate to the next char.
/// Return Ok when it was already in the tree or creates a new entry for it and returns Err.
fn iterate(&mut self, code: Code, ch: u8) -> Result<Code, Code> {
if let Some(next) = self.at_key(code, ch) {
Ok(next)
} else {
Err(self.append(code, ch))
}
}
fn append(&mut self, code: Code, ch: u8) -> Code {
let next: Code = self.keys.len() as u16;
let key = self.keys[usize::from(code)];
// TODO: with debug assertions, check for non-existence
match FullKey::from(key) {
FullKey::NoSuccessor => {
let new_key = FullKey::Simple(self.simples.len() as u16);
self.simples.push(Simple::default());
let simples = self.simples.last_mut().unwrap();
simples.codes[0] = next;
simples.chars[0] = ch;
simples.count = 1;
self.keys[usize::from(code)] = new_key.into();
}
FullKey::Simple(idx) if usize::from(self.simples[usize::from(idx)].count) < SHORT => {
let nexts = &mut self.simples[usize::from(idx)];
let nidx = usize::from(nexts.count);
nexts.chars[nidx] = ch;
nexts.codes[nidx] = next;
nexts.count += 1;
}
FullKey::Simple(idx) => {
let new_key = FullKey::Full(self.complex.len() as u16);
let simples = &self.simples[usize::from(idx)];
self.complex.push(Full {
char_continuation: [Code::max_value(); 256],
});
let full = self.complex.last_mut().unwrap();
for (&pch, &pcont) in simples.chars.iter().zip(simples.codes.iter()) {
full.char_continuation[usize::from(pch)] = pcont;
}
self.keys[usize::from(code)] = new_key.into();
}
FullKey::Full(idx) => {
let full = &mut self.complex[usize::from(idx)];
full.char_continuation[usize::from(ch)] = next;
}
}
self.keys.push(FullKey::NoSuccessor.into());
next
}
}
impl Default for FullKey {
fn default() -> Self {
FullKey::NoSuccessor
}
}
impl Default for Simple {
fn default() -> Self {
Simple {
codes: [0; SHORT],
chars: [0; SHORT],
count: 0,
}
}
}
impl From<CompressedKey> for FullKey {
fn from(CompressedKey(key): CompressedKey) -> Self {
match (key >> MAX_CODESIZE) & 0xf {
0 => FullKey::Full(key & 0xfff),
1 => FullKey::Simple(key & 0xfff),
_ => FullKey::NoSuccessor,
}
}
}
impl From<FullKey> for CompressedKey {
fn from(full: FullKey) -> Self {
CompressedKey(match full {
FullKey::NoSuccessor => 0x2000,
FullKey::Simple(code) => 0x1000 | code,
FullKey::Full(code) => code,
})
}
}
#[cfg(test)]
mod tests {
use super::{BitOrder, Encoder, LzwError, LzwStatus};
use crate::alloc::vec::Vec;
use crate::decode::Decoder;
#[cfg(feature = "std")]
use crate::StreamBuf;
#[test]
fn invalid_input_rejected() {
const BIT_LEN: u8 = 2;
let ref input = [0, 1 << BIT_LEN /* invalid */, 0];
let ref mut target = [0u8; 128];
let mut encoder = Encoder::new(BitOrder::Msb, BIT_LEN);
encoder.finish();
// We require simulation of normality, that is byte-for-byte compression.
let result = encoder.encode_bytes(input, target);
assert!(if let Err(LzwError::InvalidCode) = result.status {
true
} else {
false
});
assert_eq!(result.consumed_in, 1);
let fixed = encoder.encode_bytes(&[1, 0], &mut target[result.consumed_out..]);
assert!(if let Ok(LzwStatus::Done) = fixed.status {
true
} else {
false
});
assert_eq!(fixed.consumed_in, 2);
// Okay, now test we actually fixed it.
let ref mut compare = [0u8; 4];
let mut todo = &target[..result.consumed_out + fixed.consumed_out];
let mut free = &mut compare[..];
let mut decoder = Decoder::new(BitOrder::Msb, BIT_LEN);
// Decode with up to 16 rounds, far too much but inconsequential.
for _ in 0..16 {
if decoder.has_ended() {
break;
}
let result = decoder.decode_bytes(todo, free);
assert!(result.status.is_ok());
todo = &todo[result.consumed_in..];
free = &mut free[result.consumed_out..];
}
let remaining = { free }.len();
let len = compare.len() - remaining;
assert_eq!(todo, &[]);
assert_eq!(compare[..len], [0, 1, 0]);
}
#[test]
#[should_panic]
fn invalid_code_size_low() {
let _ = Encoder::new(BitOrder::Msb, 1);
}
#[test]
#[should_panic]
fn invalid_code_size_high() {
let _ = Encoder::new(BitOrder::Msb, 14);
}
fn make_decoded() -> Vec<u8> {
const FILE: &'static [u8] =
include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/Cargo.lock"));
return Vec::from(FILE);
}
#[test]
#[cfg(feature = "std")]
fn into_stream_buffer_no_alloc() {
let encoded = make_decoded();
let mut encoder = Encoder::new(BitOrder::Msb, 8);
let mut output = vec![];
let mut buffer = [0; 512];
let mut istream = encoder.into_stream(&mut output);
istream.set_buffer(&mut buffer[..]);
istream.encode(&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_decoded();
let mut encoder = Encoder::new(BitOrder::Msb, 8);
let mut output = vec![];
let mut istream = encoder.into_stream(WriteTap(&mut output));
istream.set_buffer_size(512);
istream.encode(&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_decoded();
let mut encoder = Encoder::new(BitOrder::Msb, 8);
let mut reference = None;
for _ in 0..2 {
let mut output = vec![];
let mut buffer = [0; 512];
let mut istream = encoder.into_stream(&mut output);
istream.set_buffer(&mut buffer[..]);
istream.encode_all(&encoded[..]).status.unwrap();
encoder.reset();
if let Some(reference) = &reference {
assert_eq!(output, *reference);
} else {
reference = Some(output);
}
}
}
}