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    //! This module contains functionality for doing lz77 compression of data.
    #![macro_use]
    use std::cmp;
    use std::ops::{Range, RangeFrom};
    use std::iter::{self, Iterator};
    use std::slice::Iter;
    use std::fmt;

    use input_buffer::InputBuffer;
    use matching::longest_match;
    #[cfg(test)]
    use lzvalue::{LZValue, LZType};
    use huffman_table;
    use chained_hash_table::{ChainedHashTable, update_hash};
    #[cfg(test)]
    use compression_options::{HIGH_MAX_HASH_CHECKS, HIGH_LAZY_IF_LESS_THAN};
    use output_writer::{BufferStatus, DynamicWriter};
    use compress::Flush;
    use rle::process_chunk_greedy_rle;

    const MAX_MATCH: usize = huffman_table::MAX_MATCH as usize;
    const MIN_MATCH: usize = huffman_table::MIN_MATCH as usize;

    const NO_RLE: u16 = 43212;

    /// An enum describing whether we use lazy or greedy matching.
    #[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
    pub enum MatchingType {
        /// Use greedy matching: the matching algorithm simply uses a match right away
        /// if found.
        Greedy,
        /// Use lazy matching: after finding a match, the next input byte is checked, to see
        /// if there is a better match starting at that byte.
        ///
        /// As a special case, if max_hash_checks is set to 0, compression using only run-length
        /// (i.e maximum match distance of 1) is performed instead.
        Lazy,
    }

    impl fmt::Display for MatchingType {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                MatchingType::Greedy => write!(f, "Greedy matching"),
                MatchingType::Lazy => write!(f, "Lazy matching"),
            }
        }
    }

    /// A struct that contains the hash table, and keeps track of where we are in the input data
    pub struct LZ77State {
        /// Struct containing hash chains that will be used to find matches.
        hash_table: ChainedHashTable,
        /// True if this is the first window that is being processed.
        is_first_window: bool,
        /// Set to true when the last block has been processed.
        is_last_block: bool,
        /// How many bytes the last match in the previous window extended into the current one.
        overlap: usize,
        /// How many bytes of input the current block contains.
        current_block_input_bytes: u64,
        /// The maximum number of hash entries to search.
        max_hash_checks: u16,
        /// Only lazy match if we have a match length less than this.
        lazy_if_less_than: u16,
        /// Whether to use greedy or lazy parsing
        matching_type: MatchingType,
        /// Keep track of the previous match and byte in case the buffer is full when lazy matching.
        match_state: ChunkState,
        /// Keep track of how many bytes in the lookahead that was part of a match, but has not been
        /// added to the hash chain yet.
        bytes_to_hash: usize,
        /// Keep track of if sync flush was used. If this is the case, the two first bytes needs to be
        /// hashed.
        was_synced: bool,
    }

    impl LZ77State {
        /// Creates a new LZ77 state
        pub fn new(
            max_hash_checks: u16,
            lazy_if_less_than: u16,
            matching_type: MatchingType,
        ) -> LZ77State {
            LZ77State {
                hash_table: ChainedHashTable::new(),
                is_first_window: true,
                is_last_block: false,
                overlap: 0,
                current_block_input_bytes: 0,
                max_hash_checks: max_hash_checks,
                lazy_if_less_than: lazy_if_less_than,
                matching_type: matching_type,
                match_state: ChunkState::new(),
                bytes_to_hash: 0,
                was_synced: false,
            }
        }

        /// Resets the state excluding max_hash_checks and lazy_if_less_than
        pub fn reset(&mut self) {
            self.hash_table.reset();
            self.is_first_window = true;
            self.is_last_block = false;
            self.overlap = 0;
            self.current_block_input_bytes = 0;
            self.match_state = ChunkState::new();
            self.bytes_to_hash = 0
        }

        pub fn set_last(&mut self) {
            self.is_last_block = true;
        }

        /// Is this the last block we are outputting?
        pub fn is_last_block(&self) -> bool {
            self.is_last_block
        }

        /// How many bytes of input the current block contains.
        pub fn current_block_input_bytes(&self) -> u64 {
            self.current_block_input_bytes
        }

        /// Sets the number of input bytes for the current block to 0.
        pub fn reset_input_bytes(&mut self) {
            self.current_block_input_bytes = 0;
        }

        /// Is there a buffered byte that has not been output yet?
        pub fn pending_byte(&self) -> bool {
            self.match_state.add
        }

        /// Returns 1 if pending_byte is true, 0 otherwise.
        pub fn pending_byte_as_num(&self) -> usize {
            // This could be implemented by using `as usize` as the documentation states this would give
            // the same result, but not sure if that should be relied upon.
            if self.match_state.add {
                1
            } else {
                0
            }
        }
    }

    const DEFAULT_WINDOW_SIZE: usize = 32768;

    #[derive(Debug)]
    /// Status after calling `process_chunk`.
    pub enum ProcessStatus {
        /// All the input data was processed.
        Ok,
        /// The output buffer was full.
        ///
        /// The argument is the position of the next byte to be checked by `process_chunk`.
        BufferFull(usize),
    }

    #[derive(Debug)]
    /// A struct to keep track of status between calls of `process_chunk_lazy`
    ///
    /// This is needed as the output buffer might become full before having output all pending data.
    pub struct ChunkState {
        /// Length of the last match that was found, if any.
        current_length: u16,
        /// Distance of the last match that was found, if any.
        current_distance: u16,
        /// The previous byte checked in process_chunk.
        prev_byte: u8,
        /// The current byte being checked in process_chunk.
        cur_byte: u8,
        /// Whether prev_byte still needs to be output.
        add: bool,
    }

    impl ChunkState {
        pub fn new() -> ChunkState {
            ChunkState {
                current_length: 0,
                current_distance: 0,
                prev_byte: 0,
                cur_byte: 0,
                add: false,
            }
        }
    }

    pub fn buffer_full(position: usize) -> ProcessStatus {
        ProcessStatus::BufferFull(position)
    }

    fn process_chunk(
        data: &[u8],
        iterated_data: &Range<usize>,
        mut match_state: &mut ChunkState,
        hash_table: &mut ChainedHashTable,
        writer: &mut DynamicWriter,
        max_hash_checks: u16,
        lazy_if_less_than: usize,
        matching_type: MatchingType,
    ) -> (usize, ProcessStatus) {
        let avoid_rle = if cfg!(test) {
            // Avoid RLE if lazy_if_less than is a specific value.
            // This is used in some tests, ideally we should probably do this in a less clunky way,
            // but we use a value here that is higher than the maximum sensible one anyhow, and will
            // be truncated by deflate_state for calls from outside the library.
            lazy_if_less_than == NO_RLE as usize
        } else {
            false
        };
        match matching_type {
            MatchingType::Greedy => {
                process_chunk_greedy(data, iterated_data, hash_table, writer, max_hash_checks)
            }
            MatchingType::Lazy => {
                if max_hash_checks > 0 || avoid_rle {
                    process_chunk_lazy(
                        data,
                        iterated_data,
                        &mut match_state,
                        hash_table,
                        writer,
                        max_hash_checks,
                        lazy_if_less_than,
                    )
                } else {
                    // Use the RLE method if max_hash_checks is set to 0.
                    process_chunk_greedy_rle(data, iterated_data, writer)
                }
            }
        }
    }

    /// Add the specified number of bytes to the hash table from the iterators
    /// adding `start` to the position supplied to the hash table.
    fn add_to_hash_table(
        bytes_to_add: usize,
        insert_it: &mut iter::Zip<RangeFrom<usize>, Iter<u8>>,
        hash_it: &mut Iter<u8>,
        hash_table: &mut ChainedHashTable,
    ) {
        let taker = insert_it.by_ref().take(bytes_to_add);
        let mut hash_taker = hash_it.by_ref().take(bytes_to_add);
        // Update the hash manually here to keep it in a register.
        let mut hash = hash_table.current_hash();
        // Advance the iterators and add the bytes we jump over to the hash table and
        // checksum
        for (ipos, _) in taker {
            if let Some(&i_hash_byte) = hash_taker.next() {
                hash = update_hash(hash, i_hash_byte);
                hash_table.add_with_hash(ipos, hash);
            }
        }
        // Write the hash back once we are done.
        hash_table.set_hash(hash);
    }

    /// Write the specified literal `byte` to the writer `w`, and return
    /// `ProcessStatus::BufferFull($pos)` if the buffer is full after writing.
    ///
    /// `pos` should indicate the byte to start at in the next call to `process_chunk`,
    /// `is_hashed` should be set to true of the byte at pos has been added to the hash chain.
    macro_rules! write_literal{
        ($w:ident, $byte:expr, $pos:expr) => {
            let b_status = $w.write_literal($byte);

            if let BufferStatus::Full = b_status {
                return (0, buffer_full($pos));
            }
        };
    }

    /// If the match is only 3 bytes long and the distance is more than 8 * 1024, it's likely to take
    /// up more space than it would save.
    #[inline]
    fn match_too_far(match_len: usize, match_dist: usize) -> bool {
        const TOO_FAR: usize = 8 * 1024;
        match_len == MIN_MATCH && match_dist > TOO_FAR
    }

    ///Create the iterators used when processing through a chunk of data.
    fn create_iterators<'a>(
        data: &'a [u8],
        iterated_data: &Range<usize>,
    ) -> (
        usize,
        iter::Zip<RangeFrom<usize>, Iter<'a, u8>>,
        Iter<'a, u8>,
    ) {
        let end = cmp::min(data.len(), iterated_data.end);
        let start = iterated_data.start;
        let current_chunk = &data[start..end];

        let insert_it = (start..).zip(current_chunk.iter());
        let hash_it = {
            let hash_start = if data.len() - start > 2 {
                start + 2
            } else {
                data.len()
            };
            (&data[hash_start..]).iter()
        };
        (end, insert_it, hash_it)
    }

    fn process_chunk_lazy(
        data: &[u8],
        iterated_data: &Range<usize>,
        state: &mut ChunkState,
        mut hash_table: &mut ChainedHashTable,
        writer: &mut DynamicWriter,
        max_hash_checks: u16,
        lazy_if_less_than: usize,
    ) -> (usize, ProcessStatus) {

        let (end, mut insert_it, mut hash_it) = create_iterators(data, iterated_data);

        const NO_LENGTH: u16 = 0;

        // The previous match length, if any.
        let mut prev_length = state.current_length;
        // The distance of the previous match if any.
        let mut prev_distance = state.current_distance;

        state.current_length = 0;
        state.current_distance = 0;

        // The number of bytes past end that was added due to finding a match that extends into
        // the lookahead window.
        let mut overlap = 0;

        // Set to true if we found a match that is equal to or longer than `lazy_if_less_than`,
        // indicating that we won't lazy match (check for a better match at the next byte).
        // If we had a good match, carry this over from the previous call.
        let mut ignore_next = prev_length as usize >= lazy_if_less_than;

        // This is to output the correct byte in case there is one pending to be output
        // from the previous call.
        state.prev_byte = state.cur_byte;

        // Iterate through the slice, adding literals or length/distance pairs
        while let Some((position, &b)) = insert_it.next() {
            state.cur_byte = b;
            if let Some(&hash_byte) = hash_it.next() {
                hash_table.add_hash_value(position, hash_byte);

                // Only lazy match if we have a match shorter than a set value
                // TODO: This should be cleaned up a bit
                if !ignore_next {
                    let (mut match_len, match_dist) = {
                        // If there already was a decent match at the previous byte
                        // and we are lazy matching, do less match checks in this step.
                        let max_hash_checks = if prev_length >= 32 {
                            max_hash_checks >> 2
                        } else {
                            max_hash_checks
                        };

                        // Check if we can find a better match here than the one we had at
                        // the previous byte.
                        longest_match(
                            data,
                            hash_table,
                            position,
                            prev_length as usize,
                            max_hash_checks,
                        )
                    };

                    // If the match is only 3 bytes long and very far back, it's probably not worth
                    // outputting.
                    if match_too_far(match_len, match_dist) {
                        match_len = NO_LENGTH as usize;
                    };

                    if match_len >= lazy_if_less_than {
                        // We found a decent match, so we won't check for a better one at the next byte.
                        ignore_next = true;
                    }
                    state.current_length = match_len as u16;
                    state.current_distance = match_dist as u16;
                } else {
                    // We already had a decent match, so we don't bother checking for another one.
                    state.current_length = NO_LENGTH;
                    state.current_distance = 0;
                    // Make sure we check again next time.
                    ignore_next = false;
                };

                if prev_length >= state.current_length && prev_length >= MIN_MATCH as u16 {
                    // The previous match was better so we add it.
                    // Casting note: length and distance is already bounded by the longest match
                    // function. Usize is just used for convenience.
                    let b_status =
                        writer.write_length_distance(prev_length as u16, prev_distance as u16);

                    // We add the bytes to the hash table and checksum.
                    // Since we've already added two of them, we need to add two less than
                    // the length.
                    let bytes_to_add = prev_length - 2;

                    add_to_hash_table(
                        bytes_to_add as usize,
                        &mut insert_it,
                        &mut hash_it,
                        &mut hash_table,
                    );

                    // If the match is longer than the current window, we have note how many
                    // bytes we overlap, since we don't need to do any matching on these bytes
                    // in the next call of this function.
                    // We don't have to worry about setting overlap to 0 if this is false, as the
                    // function will stop after this condition is true, and overlap is not altered
                    // elsewhere.
                    if position + prev_length as usize > end {
                        // We need to subtract 1 since the byte at pos is also included.
                        overlap = position + prev_length as usize - end - 1;
                    };

                    state.add = false;

                    // Note that there is no current match.
                    state.current_length = 0;
                    state.current_distance = 0;

                    if let BufferStatus::Full = b_status {
                        // MATCH(lazy)
                        return (overlap, buffer_full(position + prev_length as usize - 1));
                    }

                    ignore_next = false;

                } else if state.add {
                    // We found a better match (or there was no previous match)
                    // so output the previous byte.
                    // BETTER OR NO MATCH
                    write_literal!(writer, state.prev_byte, position + 1);
                } else {
                    state.add = true
                }

                prev_length = state.current_length;
                prev_distance = state.current_distance;
                state.prev_byte = b;
            } else {
                // If there is a match at this point, it will not have been added, so we need to add it.
                if prev_length >= MIN_MATCH as u16 {
                    let b_status =
                        writer.write_length_distance(prev_length as u16, prev_distance as u16);

                    state.current_length = 0;
                    state.current_distance = 0;
                    state.add = false;

                    // As this will be a 3-length match at the end of the input data, there can't be any
                    // overlap.
                    // TODO: Not sure if we need to signal that the buffer is full here.
                    // It's only needed in the case of syncing.
                    if let BufferStatus::Full = b_status {
                        // TODO: These bytes should be hashed when doing a sync flush.
                        // This can't be done here as the new input data does not exist yet.
                        return (0, buffer_full(end));
                    } else {
                        return (0, ProcessStatus::Ok);
                    }
                };

                if state.add {
                    // We may still have a leftover byte at this point, so we add it here if needed.
                    state.add = false;

                    // ADD
                    write_literal!(writer, state.prev_byte, position + 1);

                };

                // We are at the last two bytes we want to add, so there is no point
                // searching for matches here.

                // AFTER ADD
                write_literal!(writer, b, position + 1);
            }
        }
        (overlap, ProcessStatus::Ok)
    }

    fn process_chunk_greedy(
        data: &[u8],
        iterated_data: &Range<usize>,
        mut hash_table: &mut ChainedHashTable,
        writer: &mut DynamicWriter,
        max_hash_checks: u16,
    ) -> (usize, ProcessStatus) {

        let (end, mut insert_it, mut hash_it) = create_iterators(data, iterated_data);

        const NO_LENGTH: usize = 0;

        // The number of bytes past end that was added due to finding a match that extends into
        // the lookahead window.
        let mut overlap = 0;

        // Iterate through the slice, adding literals or length/distance pairs.
        while let Some((position, &b)) = insert_it.next() {
            if let Some(&hash_byte) = hash_it.next() {
                hash_table.add_hash_value(position, hash_byte);

                // TODO: This should be cleaned up a bit.
                let (match_len, match_dist) =
                    { longest_match(data, hash_table, position, NO_LENGTH, max_hash_checks) };

                if match_len >= MIN_MATCH as usize && !match_too_far(match_len, match_dist) {
                    // Casting note: length and distance is already bounded by the longest match
                    // function. Usize is just used for convenience.
                    let b_status = writer.write_length_distance(match_len as u16, match_dist as u16);

                    // We add the bytes to the hash table and checksum.
                    // Since we've already added one of them, we need to add one less than
                    // the length.
                    let bytes_to_add = match_len - 1;
                    add_to_hash_table(
                        bytes_to_add,
                        &mut insert_it,
                        &mut hash_it,
                        &mut hash_table,
                    );

                    // If the match is longer than the current window, we have note how many
                    // bytes we overlap, since we don't need to do any matching on these bytes
                    // in the next call of this function.
                    if position + match_len > end {
                        // We need to subtract 1 since the byte at pos is also included.
                        overlap = position + match_len - end;
                    };

                    if let BufferStatus::Full = b_status {
                        // MATCH
                        return (overlap, buffer_full(position + match_len));
                    }

                } else {
                    // NO MATCH
                    write_literal!(writer, b, position + 1);
                }
            } else {
                // We are at the last two bytes we want to add, so there is no point
                // searching for matches here.
                // END
                write_literal!(writer, b, position + 1);
            }
        }
        (overlap, ProcessStatus::Ok)
    }

    #[derive(Eq, PartialEq, Clone, Copy, Debug)]
    pub enum LZ77Status {
        /// Waiting for more input before doing any processing
        NeedInput,
        /// The output buffer is full, so the current block needs to be ended so the
        /// buffer can be flushed.
        EndBlock,
        /// All pending data has been processed.
        Finished,
    }

    #[cfg(test)]
    pub fn lz77_compress_block_finish(
        data: &[u8],
        state: &mut LZ77State,
        buffer: &mut InputBuffer,
        mut writer: &mut DynamicWriter,
    ) -> (usize, LZ77Status) {
        let (consumed, status, _) =
            lz77_compress_block(data, state, buffer, &mut writer, Flush::Finish);
        (consumed, status)
    }

    /// Compress a slice with lz77 compression.
    ///
    /// This function processes one window at a time, and returns when there is no input left,
    /// or it determines it's time to end a block.
    ///
    /// Returns the number of bytes of the input that were consumed, a status describing
    /// whether there is no input, it's time to finish, or it's time to end the block, and the position
    /// of the first byte in the input buffer that has not been output (but may have been checked for
    /// matches).
    pub fn lz77_compress_block(
        data: &[u8],
        state: &mut LZ77State,
        buffer: &mut InputBuffer,
        mut writer: &mut DynamicWriter,
        flush: Flush,
    ) -> (usize, LZ77Status, usize) {
        // Currently we only support the maximum window size
        let window_size = DEFAULT_WINDOW_SIZE;

        // Indicates whether we should try to process all the data including the lookahead, or if we
        // should wait until we have at least one window size of data before doing anything.
        let finish = flush == Flush::Finish || flush == Flush::Sync;
        let sync = flush == Flush::Sync;

        let mut current_position = 0;

        // The current status of the encoding.
        let mut status = LZ77Status::EndBlock;

        // Whether warm up the hash chain with the two first values.
        let mut add_initial = true;

        // If we have synced, add the two first bytes to the hash as they couldn't be added before.
        if state.was_synced {
            if buffer.current_end() > 2 {
                let pos_add = buffer.current_end() - 2;
                for (n, &b) in data.iter().take(2).enumerate() {
                    state.hash_table.add_hash_value(n + pos_add, b);
                }
                add_initial = false;
            }
            state.was_synced = false;
        }

        // Add data to the input buffer and keep a reference to the slice of data not added yet.
        let mut remaining_data = buffer.add_data(data);

        loop {
            // Note if there is a pending byte from the previous call to process_chunk,
            // so we get the block input size right.
            let pending_previous = state.pending_byte_as_num();

            assert!(writer.buffer_length() <= (window_size * 2));
            // The process is a bit different for the first 32k bytes.
            // TODO: There is a lot of duplicate code between the two branches here, we should be able
            // to simplify this.
            if state.is_first_window {
                // Don't do anything until we are either flushing, or we have at least one window of
                // data.
                if buffer.current_end() >= (window_size * 2) + MAX_MATCH || finish {

                    if buffer.get_buffer().len() >= 2 && add_initial &&
                        state.current_block_input_bytes == 0
                    {
                        let b = buffer.get_buffer();
                        // Warm up the hash with the two first values, so we can find  matches at
                        // index 0.
                        state.hash_table.add_initial_hash_values(b[0], b[1]);
                        add_initial = false;
                    }

                    let first_chunk_end = cmp::min(window_size, buffer.current_end());

                    let start = state.overlap;

                    let (overlap, p_status) = process_chunk(
                        buffer.get_buffer(),
                        &(start..first_chunk_end),
                        &mut state.match_state,
                        &mut state.hash_table,
                        &mut writer,
                        state.max_hash_checks,
                        state.lazy_if_less_than as usize,
                        state.matching_type,
                    );

                    state.overlap = overlap;
                    state.bytes_to_hash = overlap;

                    // If the buffer is full, we want to end the block.
                    if let ProcessStatus::BufferFull(written) = p_status {
                        state.overlap = if overlap > 0 { overlap } else { written };
                        status = LZ77Status::EndBlock;
                        current_position = written - state.pending_byte_as_num();
                        state.current_block_input_bytes +=
                            (written - start + overlap + pending_previous -
                                 state.pending_byte_as_num()) as u64;
                        break;
                    }

                    // Update the length of how many input bytes the current block is representing,
                    // taking into account pending bytes.
                    state.current_block_input_bytes +=
                        (first_chunk_end - start + overlap + pending_previous -
                             state.pending_byte_as_num()) as u64;

                    // We are at the first window so we don't need to slide the hash table yet.
                    // If finishing or syncing, we stop here.
                    if first_chunk_end >= buffer.current_end() && finish {
                        current_position = first_chunk_end - state.pending_byte_as_num();
                        if !sync {
                            state.set_last();
                            state.is_first_window = false;
                        } else {
                            state.overlap = first_chunk_end;
                            state.was_synced = true;
                        }
                        debug_assert!(
                            !state.pending_byte(),
                            "Bug! Ended compression wit a pending byte!"
                        );
                        status = LZ77Status::Finished;
                        break;
                    }
                    // Otherwise, continue.
                    state.is_first_window = false;
                } else {
                    status = LZ77Status::NeedInput;
                    break;
                }
            } else if buffer.current_end() >= (window_size * 2) + MAX_MATCH || finish {
                if buffer.current_end() >= window_size + 2 {
                    for (n, &h) in buffer.get_buffer()[window_size + 2..]
                        .iter()
                        .enumerate()
                        .take(state.bytes_to_hash)
                    {
                        state.hash_table.add_hash_value(window_size + n, h);
                    }
                    state.bytes_to_hash = 0;
                }
                // This isn't the first chunk, so we start reading at one window in in the
                // buffer plus any additional overlap from earlier.
                let start = window_size + state.overlap;

                // Determine where we have to stop iterating to slide the buffer and hash,
                // or stop because we are at the end of the input data.
                let end = cmp::min(window_size * 2, buffer.current_end());

                let (overlap, p_status) = process_chunk(
                    buffer.get_buffer(),
                    &(start..end),
                    &mut state.match_state,
                    &mut state.hash_table,
                    &mut writer,
                    state.max_hash_checks,
                    state.lazy_if_less_than as usize,
                    state.matching_type,
                );

                state.bytes_to_hash = overlap;

                if let ProcessStatus::BufferFull(written) = p_status {
                    state.current_block_input_bytes +=
                        (written - start + pending_previous - state.pending_byte_as_num()) as u64;

                    // If the buffer is full, return and end the block.
                    // If overlap is non-zero, the buffer was full after outputting the last byte,
                    // otherwise we have to skip to the point in the buffer where we stopped in the
                    // next call.
                    state.overlap = if overlap > 0 {
                        // If we are at the end of the window, make sure we slide the buffer and the
                        // hash table.
                        if state.max_hash_checks > 0 {
                            state.hash_table.slide(window_size);
                        }
                        remaining_data = buffer.slide(remaining_data.unwrap_or(&[]));
                        overlap
                    } else {
                        written - window_size
                    };

                    current_position = written - state.pending_byte_as_num();

                    // Status is already EndBlock at this point.
                    // status = LZ77Status::EndBlock;
                    break;
                }

                state.current_block_input_bytes +=
                    (end - start + overlap + pending_previous - state.pending_byte_as_num()) as u64;

                // The buffer is not full, but we still need to note if there is any overlap into the
                // next window.
                state.overlap = overlap;

                if remaining_data.is_none() && finish && end == buffer.current_end() {
                    current_position = buffer.current_end();
                    debug_assert!(
                        !state.pending_byte(),
                        "Bug! Ended compression wit a pending byte!"
                    );

                    // We stopped before or at the window size, so we are at the end.
                    if !sync {
                        // If we are finishing and not syncing, we simply indicate that we are done.
                        state.set_last();
                    } else {
                        // For sync flushing we need to slide the buffer and the hash chains so that the
                        // next call to this function starts at the right place.

                        // There won't be any overlap, since when syncing, we process to the end of the.
                        // pending data.
                        state.overlap = buffer.current_end() - window_size;
                        state.was_synced = true;
                    }
                    status = LZ77Status::Finished;
                    break;
                } else {
                    // We are not at the end, so slide and continue.
                    // We slide the hash table back to make space for new hash values
                    // We only need to remember 2^15 bytes back (the maximum distance allowed by the
                    // deflate spec).
                    if state.max_hash_checks > 0 {
                        state.hash_table.slide(window_size);
                    }

                    // Also slide the buffer, discarding data we no longer need and adding new data.
                    remaining_data = buffer.slide(remaining_data.unwrap_or(&[]));
                }
            } else {
                // The caller has not indicated that they want to finish or flush, and there is less
                // than a window + lookahead of new data, so we wait for more.
                status = LZ77Status::NeedInput;
                break;
            }

        }

        (
            data.len() - remaining_data.unwrap_or(&[]).len(),
            status,
            current_position,
        )
    }

    #[cfg(test)]
    pub fn decompress_lz77(input: &[LZValue]) -> Vec<u8> {
        decompress_lz77_with_backbuffer(input, &[])
    }

    #[cfg(test)]
    pub fn decompress_lz77_with_backbuffer(input: &[LZValue], back_buffer: &[u8]) -> Vec<u8> {
        let mut output = Vec::new();
        for p in input {
            match p.value() {
                LZType::Literal(l) => output.push(l),
                LZType::StoredLengthDistance(l, d) => {
                    // We found a match, so we have to get the data that the match refers to.
                    let d = d as usize;
                    let prev_output_len = output.len();
                    // Get match data from the back buffer if the match extends that far.
                    let consumed = if d > output.len() {
                        let into_back_buffer = d - output.len();

                        assert!(
                            into_back_buffer <= back_buffer.len(),
                            "ERROR: Attempted to refer to a match in non-existing data!\
                             into_back_buffer: {}, back_buffer len {}, d {}, l {:?}",
                            into_back_buffer,
                            back_buffer.len(),
                            d,
                            l
                        );
                        let start = back_buffer.len() - into_back_buffer;
                        let end = cmp::min(back_buffer.len(), start + l.actual_length() as usize);
                        output.extend_from_slice(&back_buffer[start..end]);

                        end - start
                    } else {
                        0
                    };

                    // Get match data from the currently decompressed data.
                    let start = prev_output_len.saturating_sub(d);
                    let mut n = 0;
                    while n < (l.actual_length() as usize).saturating_sub(consumed) {
                        let b = output[start + n];
                        output.push(b);
                        n += 1;
                    }
                }
            }
        }
        output
    }

    #[cfg(test)]
    pub struct TestStruct {
        state: LZ77State,
        buffer: InputBuffer,
        writer: DynamicWriter,
    }

    #[cfg(test)]
    impl TestStruct {
        fn new() -> TestStruct {
            TestStruct::with_config(
                HIGH_MAX_HASH_CHECKS,
                HIGH_LAZY_IF_LESS_THAN,
                MatchingType::Lazy,
            )
        }

        fn with_config(
            max_hash_checks: u16,
            lazy_if_less_than: u16,
            matching_type: MatchingType,
        ) -> TestStruct {
            TestStruct {
                state: LZ77State::new(max_hash_checks, lazy_if_less_than, matching_type),
                buffer: InputBuffer::empty(),
                writer: DynamicWriter::new(),
            }
        }

        fn compress_block(&mut self, data: &[u8], flush: bool) -> (usize, LZ77Status, usize) {
            lz77_compress_block(
                data,
                &mut self.state,
                &mut self.buffer,
                &mut self.writer,
                if flush { Flush::Finish } else { Flush::None },
            )
        }
    }

    #[cfg(test)]
    pub fn lz77_compress(data: &[u8]) -> Option<Vec<LZValue>> {
        lz77_compress_conf(
            data,
            HIGH_MAX_HASH_CHECKS,
            HIGH_LAZY_IF_LESS_THAN,
            MatchingType::Lazy,
        )
    }

    /// Compress a slice, not storing frequency information
    ///
    /// This is a convenience function for compression with fixed huffman values
    /// Only used in tests for now
    #[cfg(test)]
    pub fn lz77_compress_conf(
        data: &[u8],
        max_hash_checks: u16,
        lazy_if_less_than: u16,
        matching_type: MatchingType,
    ) -> Option<Vec<LZValue>> {
        let mut test_boxed = Box::new(TestStruct::with_config(
            max_hash_checks,
            lazy_if_less_than,
            matching_type,
        ));
        let mut out = Vec::<LZValue>::with_capacity(data.len() / 3);
        {
            let test = test_boxed.as_mut();
            let mut slice = data;

            while !test.state.is_last_block {
                let bytes_written = lz77_compress_block_finish(
                    slice,
                    &mut test.state,
                    &mut test.buffer,
                    &mut test.writer,
                ).0;
                slice = &slice[bytes_written..];
                out.extend(test.writer.get_buffer());
                test.writer.clear();
            }

        }

        Some(out)
    }

    #[cfg(test)]
    mod test {
        use super::*;

        use lzvalue::{LZValue, LZType, lit, ld};
        use chained_hash_table::WINDOW_SIZE;
        use compression_options::DEFAULT_LAZY_IF_LESS_THAN;
        use test_utils::get_test_data;
        use output_writer::MAX_BUFFER_LENGTH;

        /// Helper function to print the output from the lz77 compression function
        fn print_output(input: &[LZValue]) {
            let mut output = vec![];
            for l in input {
                match l.value() {
                    LZType::Literal(l) => output.push(l),
                    LZType::StoredLengthDistance(l, d) => {
                        output.extend(format!("<L {}>", l.actual_length()).into_bytes());
                        output.extend(format!("<D {}>", d).into_bytes())
                    }
                }
            }

            println!("\"{}\"", String::from_utf8(output).unwrap());
        }

        /// Test that a short string from an example on SO compresses correctly
        #[test]
        fn compress_short() {
            let test_bytes = String::from("Deflate late").into_bytes();
            let res = lz77_compress(&test_bytes).unwrap();

            let decompressed = decompress_lz77(&res);

            assert_eq!(test_bytes, decompressed);
            assert_eq!(*res.last().unwrap(), LZValue::length_distance(4, 5));
        }

        /// Test that compression is working for a longer file
        #[test]
        fn compress_long() {
            let input = get_test_data();
            let compressed = lz77_compress(&input).unwrap();
            assert!(compressed.len() < input.len());

            let decompressed = decompress_lz77(&compressed);
            println!("compress_long length: {}", input.len());

            // This is to check where the compression fails, if it were to
            for (n, (&a, &b)) in input.iter().zip(decompressed.iter()).enumerate() {
                if a != b {
                    println!("First difference at {}, input: {}, output: {}", n, a, b);
                    break;
                }
            }
            assert_eq!(input.len(), decompressed.len());
            assert!(&decompressed == &input);
        }

        /// Check that lazy matching is working as intended
        #[test]
        fn lazy() {
            // We want to match on `badger` rather than `nba` as it is longer
            // let data = b" nba nbadg badger nbadger";
            let data = b"nba badger nbadger";
            let compressed = lz77_compress(data).unwrap();
            let test = compressed[compressed.len() - 1];
            if let LZType::StoredLengthDistance(l, _) = test.value() {
                assert_eq!(l.actual_length(), 6);
            } else {
                print_output(&compressed);
                panic!();
            }
        }

        fn roundtrip(data: &[u8]) {
            let compressed = super::lz77_compress(&data).unwrap();
            let decompressed = decompress_lz77(&compressed);
            assert!(decompressed == data);
        }

        // Check that data with the exact window size is working properly
        #[test]
        #[allow(unused)]
        fn exact_window_size() {
            use std::io::Write;
            let mut data = vec![0; WINDOW_SIZE];
            roundtrip(&data);
            {
                data.write(&[22; WINDOW_SIZE]);
            }
            roundtrip(&data);
            {
                data.write(&[55; WINDOW_SIZE]);
            }
            roundtrip(&data);
        }

        /// Test that matches at the window border are working correctly
        #[test]
        fn border() {
            use chained_hash_table::WINDOW_SIZE;
            let mut data = vec![35; WINDOW_SIZE];
            data.extend(b"Test");
            let compressed = super::lz77_compress(&data).unwrap();
            assert!(compressed.len() < data.len());
            let decompressed = decompress_lz77(&compressed);

            assert_eq!(decompressed.len(), data.len());
            assert!(decompressed == data);
        }

        #[test]
        fn border_multiple_blocks() {
            use chained_hash_table::WINDOW_SIZE;
            let mut data = vec![0; (WINDOW_SIZE * 2) + 50];
            data.push(1);
            let compressed = super::lz77_compress(&data).unwrap();
            assert!(compressed.len() < data.len());
            let decompressed = decompress_lz77(&compressed);
            assert_eq!(decompressed.len(), data.len());
            assert!(decompressed == data);
        }

        #[test]
        fn compress_block_status() {
            use input_buffer::InputBuffer;

            let data = b"Test data data";
            let mut writer = DynamicWriter::new();

            let mut buffer = InputBuffer::empty();
            let mut state = LZ77State::new(4096, DEFAULT_LAZY_IF_LESS_THAN, MatchingType::Lazy);
            let status = lz77_compress_block_finish(data, &mut state, &mut buffer, &mut writer);
            assert_eq!(status.1, LZ77Status::Finished);
            assert!(&buffer.get_buffer()[..data.len()] == data);
            assert_eq!(buffer.current_end(), data.len());
        }

        #[test]
        fn compress_block_multiple_windows() {
            use input_buffer::InputBuffer;
            use output_writer::DynamicWriter;

            let data = get_test_data();
            assert!(data.len() > (WINDOW_SIZE * 2) + super::MAX_MATCH);
            let mut writer = DynamicWriter::new();

            let mut buffer = InputBuffer::empty();
            let mut state = LZ77State::new(0, DEFAULT_LAZY_IF_LESS_THAN, MatchingType::Lazy);
            let (bytes_consumed, status) =
                lz77_compress_block_finish(&data, &mut state, &mut buffer, &mut writer);
            assert_eq!(
                buffer.get_buffer().len(),
                (WINDOW_SIZE * 2) + super::MAX_MATCH
            );
            assert_eq!(status, LZ77Status::EndBlock);
            let buf_len = buffer.get_buffer().len();
            assert!(buffer.get_buffer()[..] == data[..buf_len]);

            writer.clear();
            let (_, status) = lz77_compress_block_finish(
                &data[bytes_consumed..],
                &mut state,
                &mut buffer,
                &mut writer,
            );
            assert_eq!(status, LZ77Status::EndBlock);

        }

        #[test]
        fn multiple_inputs() {
            let data = b"Badger badger bababa test data 25 asfgestghresjkgh";
            let comp1 = lz77_compress(data).unwrap();
            let comp2 = {
                const SPLIT: usize = 25;
                let first_part = &data[..SPLIT];
                let second_part = &data[SPLIT..];
                let mut state = TestStruct::new();
                let (bytes_written, status, _) = state.compress_block(first_part, false);
                assert_eq!(bytes_written, first_part.len());
                assert_eq!(status, LZ77Status::NeedInput);
                let (bytes_written, status, _) = state.compress_block(second_part, true);
                assert_eq!(bytes_written, second_part.len());
                assert_eq!(status, LZ77Status::Finished);
                Vec::from(state.writer.get_buffer())
            };
            assert!(comp1 == comp2);
        }

        #[test]
        /// Test that the exit from process_chunk when buffer is full is working correctly.
        fn buffer_fill() {
            let data = get_test_data();
            // The comments above these calls refers the positions with the
            // corersponding comments in process_chunk_{greedy/lazy}.
            // POS BETTER OR NO MATCH
            buffer_test_literals(&data);
            // POS END
            // POS NO MATCH
            buffer_test_last_bytes(MatchingType::Greedy, &data);
            // POS ADD
            // POS AFTER ADD
            buffer_test_last_bytes(MatchingType::Lazy, &data);

            // POS MATCH
            buffer_test_match(MatchingType::Greedy);
            // POS MATCH(lazy)
            buffer_test_match(MatchingType::Lazy);

            // POS END
            buffer_test_add_end(&data);
        }

        /// Test buffer fill when a byte is added due to no match being found.
        fn buffer_test_literals(data: &[u8]) {
            let mut state = TestStruct::with_config(0, NO_RLE, MatchingType::Lazy);
            let (bytes_consumed, status, position) = state.compress_block(&data, false);

            // There should be enough data for the block to have ended.
            assert_eq!(status, LZ77Status::EndBlock);
            assert!(bytes_consumed <= (WINDOW_SIZE * 2) + MAX_MATCH);

            // The buffer should be full.
            assert_eq!(state.writer.get_buffer().len(), MAX_BUFFER_LENGTH);
            assert_eq!(position, state.writer.get_buffer().len());
            // Since all literals have been input, the block should have the exact number of litlens
            // as there were input bytes.
            assert_eq!(
                state.state.current_block_input_bytes() as usize,
                MAX_BUFFER_LENGTH
            );
            state.state.reset_input_bytes();

            let mut out = decompress_lz77(state.writer.get_buffer());

            state.writer.clear();
            // The buffer should now be cleared.
            assert_eq!(state.writer.get_buffer().len(), 0);

            assert!(data[..out.len()] == out[..]);

            let _ = state.compress_block(&data[bytes_consumed..], false);
            // We should have some new data in the buffer at this point.
            assert!(state.writer.get_buffer().len() > 0);
            assert_eq!(
                state.state.current_block_input_bytes() as usize,
                MAX_BUFFER_LENGTH
            );

            out.extend_from_slice(&decompress_lz77(state.writer.get_buffer()));
            assert!(data[..out.len()] == out[..]);
        }

        /// Test buffer fill at the last two bytes that are not hashed.
        fn buffer_test_last_bytes(matching_type: MatchingType, data: &[u8]) {
            const BYTES_USED: usize = MAX_BUFFER_LENGTH;
            assert!(
                &data[..BYTES_USED] ==
                    &decompress_lz77(&lz77_compress_conf(
                        &data[..BYTES_USED],
                        0,
                        NO_RLE,
                        matching_type,
                    ).unwrap())
                        [..]
            );
            assert!(
                &data[..BYTES_USED + 1] ==
                    &decompress_lz77(&lz77_compress_conf(
                        &data[..BYTES_USED + 1],
                        0,
                        NO_RLE,
                        matching_type,
                    ).unwrap())
                        [..]
            );
        }

        /// Test buffer fill when buffer is full at a match.
        fn buffer_test_match(matching_type: MatchingType) {
            // TODO: Also test this for the second block to make sure
            // buffer is slid.
            let mut state = TestStruct::with_config(1, 0, matching_type);
            for _ in 0..MAX_BUFFER_LENGTH - 4 {
                assert!(state.writer.write_literal(0) == BufferStatus::NotFull);
            }
            state.compress_block(&[1, 2, 3, 1, 2, 3, 4], true);
            assert!(*state.writer.get_buffer().last().unwrap() == LZValue::length_distance(3, 3));

        }

        /// Test buffer fill for the lazy match algorithm when adding a pending byte at the end.
        fn buffer_test_add_end(_data: &[u8]) {
            // This is disabled while the buffer size has not been stabilized.
            /*
            let mut state = TestStruct::with_config(DEFAULT_MAX_HASH_CHECKS,
                                                    DEFAULT_LAZY_IF_LESS_THAN,
                                                    MatchingType::Lazy);
            // For the test file, this is how much data needs to be added to get the buffer
            // full at the right spot to test that this buffer full exit is workong correctly.
            for i in 0..31743 {
                assert!(state.writer.write_literal(0) == BufferStatus::NotFull, "Buffer pos: {}", i);
            }

            let dec = decompress_lz77(&state.writer.get_buffer()[pos..]);
            assert!(dec.len() > 0);
            assert!(dec[..] == data[..dec.len()]);
             */
        }

        /// Check that decompressing lz77-data that refers to the back-buffer works.
        #[test]
        fn test_decompress_with_backbuffer() {
            let bb = vec![5; WINDOW_SIZE];
            let lz_compressed = [lit(2), lit(4), ld(4, 20), lit(1), lit(1), ld(5, 10)];
            let dec = decompress_lz77_with_backbuffer(&lz_compressed, &bb);

            // ------------l2 l4  <-ld4,20-> l1 l1  <---ld5,10-->
            assert!(dec == [2, 4, 5, 5, 5, 5, 1, 1, 5, 5, 2, 4, 5]);
        }

    }

    #[cfg(all(test, feature = "benchmarks"))]
    mod bench {
        use test_std::Bencher;
        use test_utils::get_test_data;
        use super::lz77_compress;
        #[bench]
        fn test_file_zlib_lz77_only(b: &mut Bencher) {
            let test_data = get_test_data();
            b.iter(|| lz77_compress(&test_data));
        }
    }

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