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</pre><pre class="rust">
<span class="doccomment">//! This modules provides an implementation of the Lempel–Ziv–Welch Compression Algorithm</span>
<span class="comment">// Note: This implementation borrows heavily from the work of Julius Pettersson</span>
<span class="comment">// See http://www.cplusplus.com/articles/iL18T05o/ for his extensive explanations</span>
<span class="comment">// and a C++ implementatation</span>
<span class="kw">use</span> <span class="ident">std::io</span>;
<span class="kw">use</span> <span class="ident">std::io</span>::{<span class="ident">Read</span>, <span class="ident">Write</span>};
<span class="kw">use</span> <span class="ident">bitstream</span>::{<span class="ident">Bits</span>, <span class="ident">BitReader</span>, <span class="ident">BitWriter</span>};
<span class="kw">const</span> <span class="ident">MAX_CODESIZE</span>: <span class="ident">u8</span> <span class="op">=</span> <span class="number">12</span>;
<span class="kw">const</span> <span class="ident">MAX_ENTRIES</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">MAX_CODESIZE</span> <span class="kw">as</span> <span class="ident">usize</span>;
<span class="doccomment">/// Alias for a LZW code point</span>
<span class="kw">type</span> <span class="ident">Code</span> <span class="op">=</span> <span class="ident">u16</span>;
<span class="doccomment">/// Decoding dictionary.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It is not generic due to current limitations of Rust</span>
<span class="doccomment">/// Inspired by http://www.cplusplus.com/articles/iL18T05o/</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">DecodingDict</span> {
<span class="ident">min_size</span>: <span class="ident">u8</span>,
<span class="ident">table</span>: <span class="ident">Vec</span><span class="op"><</span>(<span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>, <span class="ident">u8</span>)<span class="op">></span>,
<span class="ident">buffer</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span>,
}
<span class="kw">impl</span> <span class="ident">DecodingDict</span> {
<span class="doccomment">/// Creates a new dict</span>
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">min_size</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="ident">DecodingDict</span> {
<span class="ident">DecodingDict</span> {
<span class="ident">min_size</span>: <span class="ident">min_size</span>,
<span class="ident">table</span>: <span class="ident">Vec::with_capacity</span>(<span class="number">512</span>),
<span class="ident">buffer</span>: <span class="ident">Vec::with_capacity</span>((<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">MAX_CODESIZE</span> <span class="kw">as</span> <span class="ident">usize</span>) <span class="op">-</span> <span class="number">1</span>)
}
}
<span class="doccomment">/// Resets the dictionary</span>
<span class="kw">fn</span> <span class="ident">reset</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">clear</span>();
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..(<span class="number">1u16</span> <span class="op"><</span><span class="op"><</span> <span class="self">self</span>.<span class="ident">min_size</span> <span class="kw">as</span> <span class="ident">usize</span>) {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>((<span class="prelude-val">None</span>, <span class="ident">i</span> <span class="kw">as</span> <span class="ident">u8</span>));
}
}
<span class="doccomment">/// Inserts a value into the dict</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">push</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">key</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>, <span class="ident">value</span>: <span class="ident">u8</span>) {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>((<span class="ident">key</span>, <span class="ident">value</span>))
}
<span class="doccomment">/// Reconstructs the data for the corresponding code</span>
<span class="kw">fn</span> <span class="ident">reconstruct</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">code</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">io::Result</span><span class="op"><</span><span class="kw-2">&</span>[<span class="ident">u8</span>]<span class="op">></span> {
<span class="self">self</span>.<span class="ident">buffer</span>.<span class="ident">clear</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">code</span> <span class="op">=</span> <span class="ident">code</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cha</span>;
<span class="comment">// Check the first access more thoroughly since a bad code</span>
<span class="comment">// could occur if the data is malformed</span>
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">k</span>) <span class="op">=</span> <span class="ident">code</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">table</span>.<span class="ident">get</span>(<span class="ident">k</span> <span class="kw">as</span> <span class="ident">usize</span>) {
<span class="prelude-val">Some</span>(<span class="kw-2">&</span>(<span class="ident">code_</span>, <span class="ident">cha_</span>)) <span class="op">=</span><span class="op">></span> {
<span class="ident">code</span> <span class="op">=</span> <span class="ident">code_</span>;
<span class="ident">cha</span> <span class="op">=</span> <span class="ident">cha_</span>;
}
<span class="prelude-val">None</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">io::Error::new</span>(
<span class="ident">io::ErrorKind::InvalidInput</span>,
<span class="kw-2">&</span><span class="kw-2">*</span><span class="macro">format!</span>(<span class="string">"Invalid code {:X}, expected code <= {:X}"</span>, <span class="ident">k</span>, <span class="self">self</span>.<span class="ident">table</span>.<span class="ident">len</span>())
))
}
<span class="self">self</span>.<span class="ident">buffer</span>.<span class="ident">push</span>(<span class="ident">cha</span>);
}
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">k</span>) <span class="op">=</span> <span class="ident">code</span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">buffer</span>.<span class="ident">len</span>() <span class="op">></span><span class="op">=</span> <span class="ident">MAX_ENTRIES</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">io::Error::new</span>(
<span class="ident">io::ErrorKind::InvalidInput</span>,
<span class="string">"Invalid code sequence. Cycle in decoding table."</span>
))
}
<span class="comment">//(code, cha) = self.table[k as usize];</span>
<span class="comment">// Note: This could possibly be replaced with an unchecked array access if</span>
<span class="comment">// - value is asserted to be < self.next_code() in push</span>
<span class="comment">// - min_size is asserted to be < MAX_CODESIZE </span>
<span class="kw">let</span> <span class="ident">entry</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">table</span>[<span class="ident">k</span> <span class="kw">as</span> <span class="ident">usize</span>]; <span class="ident">code</span> <span class="op">=</span> <span class="ident">entry</span>.<span class="number">0</span>; <span class="ident">cha</span> <span class="op">=</span> <span class="ident">entry</span>.<span class="number">1</span>;
<span class="self">self</span>.<span class="ident">buffer</span>.<span class="ident">push</span>(<span class="ident">cha</span>);
}
<span class="self">self</span>.<span class="ident">buffer</span>.<span class="ident">reverse</span>();
<span class="prelude-val">Ok</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">buffer</span>)
}
<span class="doccomment">/// Returns the buffer constructed by the last reconstruction</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">buffer</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="kw-2">&</span>[<span class="ident">u8</span>] {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">buffer</span>
}
<span class="doccomment">/// Number of entries in the dictionary</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">next_code</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">u16</span> {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">len</span>() <span class="kw">as</span> <span class="ident">u16</span>
}
}
<span class="macro">macro_rules!</span> <span class="ident">define_decoder_struct</span> {
{$(
<span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span>:<span class="ident">ident</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">offset</span>:<span class="ident">expr</span>, <span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">doc</span>:<span class="ident">meta</span>]</span>;
)<span class="kw-2">*</span>} <span class="op">=</span><span class="op">></span> {
$( <span class="comment">// START struct definition</span>
<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">doc</span>]</span>
<span class="doccomment">/// </span>
<span class="doccomment">/// The maximum supported code size is 16 bits. The decoder assumes two</span>
<span class="doccomment">/// special code word to be present in the stream:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * `CLEAR_CODE == 1 << min_code_size`</span>
<span class="doccomment">/// * `END_CODE == CLEAR_CODE + 1`</span>
<span class="doccomment">///</span>
<span class="doccomment">///Furthermore the decoder expects the stream to start with a `CLEAR_CODE`. This</span>
<span class="doccomment">/// corresponds to the implementation needed for en- and decoding GIF and TIFF files.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">BitReader</span><span class="op">></span> {
<span class="ident">r</span>: <span class="ident">R</span>,
<span class="ident">prev</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>,
<span class="ident">table</span>: <span class="ident">DecodingDict</span>,
<span class="ident">buf</span>: [<span class="ident">u8</span>; <span class="number">1</span>],
<span class="ident">code_size</span>: <span class="ident">u8</span>,
<span class="ident">min_code_size</span>: <span class="ident">u8</span>,
<span class="ident">clear_code</span>: <span class="ident">Code</span>,
<span class="ident">end_code</span>: <span class="ident">Code</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> <span class="kw">where</span> <span class="ident">R</span>: <span class="ident">BitReader</span> {
<span class="doccomment">/// Creates a new LZW decoder. </span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">reader</span>: <span class="ident">R</span>, <span class="ident">min_code_size</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> {
<span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span> {
<span class="ident">r</span>: <span class="ident">reader</span>,
<span class="ident">prev</span>: <span class="prelude-val">None</span>,
<span class="ident">table</span>: <span class="ident">DecodingDict::new</span>(<span class="ident">min_code_size</span>),
<span class="ident">buf</span>: [<span class="number">0</span>; <span class="number">1</span>],
<span class="ident">code_size</span>: <span class="ident">min_code_size</span> <span class="op">+</span> <span class="number">1</span>,
<span class="ident">min_code_size</span>: <span class="ident">min_code_size</span>,
<span class="ident">clear_code</span>: <span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">min_code_size</span>,
<span class="ident">end_code</span>: (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">min_code_size</span>) <span class="op">+</span> <span class="number">1</span>,
}
}
<span class="doccomment">/// Tries to obtain and decode a code word from `bytes`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns the number of bytes that have been consumed from `bytes`. An empty</span>
<span class="doccomment">/// slice does not indicate `EOF`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">decode_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">bytes</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>]) <span class="op">-</span><span class="op">></span> <span class="ident">io::Result</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="kw-2">&</span>[<span class="ident">u8</span>])<span class="op">></span> {
<span class="prelude-val">Ok</span>(<span class="kw">match</span> <span class="self">self</span>.<span class="ident">r</span>.<span class="ident">read_bits</span>(<span class="ident">bytes</span>, <span class="self">self</span>.<span class="ident">code_size</span>) {
<span class="ident">Bits::Some</span>(<span class="ident">consumed</span>, <span class="ident">code</span>) <span class="op">=</span><span class="op">></span> {
(<span class="ident">consumed</span>, <span class="kw">if</span> <span class="ident">code</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">clear_code</span> {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">reset</span>();
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>(<span class="prelude-val">None</span>, <span class="number">0</span>); <span class="comment">// clear code</span>
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>(<span class="prelude-val">None</span>, <span class="number">0</span>); <span class="comment">// end code</span>
<span class="self">self</span>.<span class="ident">code_size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">min_code_size</span> <span class="op">+</span> <span class="number">1</span>;
<span class="self">self</span>.<span class="ident">prev</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw-2">&</span>[]
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">code</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">end_code</span> {
<span class="kw-2">&</span>[]
} <span class="kw">else</span> {
<span class="kw">let</span> <span class="ident">next_code</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">table</span>.<span class="ident">next_code</span>();
<span class="kw">if</span> <span class="ident">code</span> <span class="op">></span> <span class="ident">next_code</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">io::Error::new</span>(
<span class="ident">io::ErrorKind::InvalidInput</span>,
<span class="kw-2">&</span><span class="kw-2">*</span><span class="macro">format!</span>(<span class="string">"Invalid code {:X}, expected code <= {:X}"</span>,
<span class="ident">code</span>,
<span class="ident">next_code</span>
)
))
}
<span class="kw">let</span> <span class="ident">prev</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">prev</span>;
<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">prev</span>.<span class="ident">is_none</span>() {
<span class="self">self</span>.<span class="ident">buf</span> <span class="op">=</span> [<span class="ident">code</span> <span class="kw">as</span> <span class="ident">u8</span>];
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">buf</span>[..]
} <span class="kw">else</span> {
<span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">code</span> <span class="op">=</span><span class="op">=</span> <span class="ident">next_code</span> {
<span class="kw">let</span> <span class="ident">cha</span> <span class="op">=</span> <span class="macro">try!</span>(<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">reconstruct</span>(<span class="ident">prev</span>))[<span class="number">0</span>];
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>(<span class="ident">prev</span>, <span class="ident">cha</span>);
<span class="macro">try!</span>(<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">reconstruct</span>(<span class="prelude-val">Some</span>(<span class="ident">code</span>)))
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">code</span> <span class="op"><</span> <span class="ident">next_code</span> {
<span class="kw">let</span> <span class="ident">cha</span> <span class="op">=</span> <span class="macro">try!</span>(<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">reconstruct</span>(<span class="prelude-val">Some</span>(<span class="ident">code</span>)))[<span class="number">0</span>];
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>(<span class="ident">prev</span>, <span class="ident">cha</span>);
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">buffer</span>()
} <span class="kw">else</span> {
<span class="comment">// code > next_code is already tested a few lines earlier</span>
<span class="macro">unreachable!</span>()
};
<span class="ident">data</span>
};
<span class="kw">if</span> <span class="ident">next_code</span> <span class="op">=</span><span class="op">=</span> (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="self">self</span>.<span class="ident">code_size</span> <span class="kw">as</span> <span class="ident">usize</span>) <span class="op">-</span> <span class="number">1</span> <span class="op">-</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">offset</span>
<span class="op">&&</span> <span class="self">self</span>.<span class="ident">code_size</span> <span class="op"><</span> <span class="ident">MAX_CODESIZE</span> {
<span class="self">self</span>.<span class="ident">code_size</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
}
<span class="self">self</span>.<span class="ident">prev</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">code</span>);
<span class="ident">result</span>
})
},
<span class="ident">Bits::None</span>(<span class="ident">consumed</span>) <span class="op">=</span><span class="op">></span> {
(<span class="ident">consumed</span>, <span class="kw-2">&</span>[])
}
})
}
}
)<span class="op">*</span> <span class="comment">// END struct definition</span>
}
}
<span class="macro">define_decoder_struct!</span>{
<span class="ident">Decoder</span>, <span class="number">0</span>, <span class="attribute">#[<span class="ident">doc</span> <span class="op">=</span> <span class="string">"Decoder for a LZW compressed stream (this algorithm is used for GIF files)."</span>]</span>;
<span class="ident">DecoderEarlyChange</span>, <span class="number">1</span>, <span class="attribute">#[<span class="ident">doc</span> <span class="op">=</span> <span class="string">"Decoder for a LZW compressed stream using an “early change” algorithm (used in TIFF files)."</span>]</span>;
}
<span class="kw">struct</span> <span class="ident">Node</span> {
<span class="ident">prefix</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>,
<span class="ident">c</span>: <span class="ident">u8</span>,
<span class="ident">left</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>,
<span class="ident">right</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>,
}
<span class="kw">impl</span> <span class="ident">Node</span> {
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">c</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Node</span> {
<span class="ident">Node</span> {
<span class="ident">prefix</span>: <span class="prelude-val">None</span>,
<span class="ident">c</span>: <span class="ident">c</span>,
<span class="ident">left</span>: <span class="prelude-val">None</span>,
<span class="ident">right</span>: <span class="prelude-val">None</span>
}
}
}
<span class="kw">struct</span> <span class="ident">EncodingDict</span> {
<span class="ident">table</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">Node</span><span class="op">></span>,
<span class="ident">min_size</span>: <span class="ident">u8</span>,
}
<span class="doccomment">/// Encoding dictionary based on a binary tree</span>
<span class="kw">impl</span> <span class="ident">EncodingDict</span> {
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">min_size</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="ident">EncodingDict</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">this</span> <span class="op">=</span> <span class="ident">EncodingDict</span> {
<span class="ident">table</span>: <span class="ident">Vec::with_capacity</span>(<span class="ident">MAX_ENTRIES</span>),
<span class="ident">min_size</span>: <span class="ident">min_size</span>
};
<span class="ident">this</span>.<span class="ident">reset</span>();
<span class="ident">this</span>
}
<span class="kw">fn</span> <span class="ident">reset</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">clear</span>();
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span> .. (<span class="number">1u16</span> <span class="op"><</span><span class="op"><</span> <span class="self">self</span>.<span class="ident">min_size</span> <span class="kw">as</span> <span class="ident">usize</span>) {
<span class="self">self</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="ident">i</span> <span class="kw">as</span> <span class="ident">u8</span>));
}
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">push_node</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">node</span>: <span class="ident">Node</span>) {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>(<span class="ident">node</span>)
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">clear_code</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Code</span> {
<span class="number">1u16</span> <span class="op"><</span><span class="op"><</span> <span class="self">self</span>.<span class="ident">min_size</span>
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">end_code</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Code</span> {
<span class="self">self</span>.<span class="ident">clear_code</span>() <span class="op">+</span> <span class="number">1</span>
}
<span class="comment">// Searches for a new prefix</span>
<span class="kw">fn</span> <span class="ident">search_and_insert</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">i</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>, <span class="ident">c</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span> {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">i</span>) <span class="op">=</span> <span class="ident">i</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span> <span class="kw">as</span> <span class="ident">usize</span>) {
<span class="kw">let</span> <span class="ident">table_size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">table</span>.<span class="ident">len</span>() <span class="kw">as</span> <span class="ident">Code</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="kw-2">mut</span> <span class="ident">j</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">table</span>[<span class="ident">i</span>].<span class="ident">prefix</span> {
<span class="kw">loop</span> {
<span class="kw">let</span> <span class="ident">entry</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">table</span>[<span class="ident">j</span> <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">c</span> <span class="op"><</span> <span class="ident">entry</span>.<span class="ident">c</span> {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">k</span>) <span class="op">=</span> <span class="ident">entry</span>.<span class="ident">left</span> {
<span class="ident">j</span> <span class="op">=</span> <span class="ident">k</span>
} <span class="kw">else</span> {
<span class="ident">entry</span>.<span class="ident">left</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">table_size</span>);
<span class="kw">break</span>
}
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">c</span> <span class="op">></span> <span class="ident">entry</span>.<span class="ident">c</span> {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">k</span>) <span class="op">=</span> <span class="ident">entry</span>.<span class="ident">right</span> {
<span class="ident">j</span> <span class="op">=</span> <span class="ident">k</span>
} <span class="kw">else</span> {
<span class="ident">entry</span>.<span class="ident">right</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">table_size</span>);
<span class="kw">break</span>
}
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="prelude-val">Some</span>(<span class="ident">j</span>)
}
}
} <span class="kw">else</span> {
<span class="self">self</span>.<span class="ident">table</span>[<span class="ident">i</span>].<span class="ident">prefix</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">table_size</span>);
}
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">push</span>(<span class="ident">Node::new</span>(<span class="ident">c</span>));
<span class="prelude-val">None</span>
} <span class="kw">else</span> {
<span class="prelude-val">Some</span>(<span class="self">self</span>.<span class="ident">search_initials</span>(<span class="ident">c</span> <span class="kw">as</span> <span class="ident">Code</span>))
}
}
<span class="kw">fn</span> <span class="ident">next_code</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="self">self</span>.<span class="ident">table</span>.<span class="ident">len</span>()
}
<span class="kw">fn</span> <span class="ident">search_initials</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">i</span>: <span class="ident">Code</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Code</span> {
<span class="self">self</span>.<span class="ident">table</span>[<span class="ident">i</span> <span class="kw">as</span> <span class="ident">usize</span>].<span class="ident">c</span> <span class="kw">as</span> <span class="ident">Code</span>
}
}
<span class="doccomment">/// Convenience function that reads and compresses all bytes from `R`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">encode</span><span class="op"><</span><span class="ident">R</span>, <span class="ident">W</span><span class="op">></span>(<span class="ident">r</span>: <span class="ident">R</span>, <span class="kw-2">mut</span> <span class="ident">w</span>: <span class="ident">W</span>, <span class="ident">min_code_size</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="ident">io::Result</span><span class="op"><</span>()<span class="op">></span>
<span class="kw">where</span> <span class="ident">R</span>: <span class="ident">Read</span>, <span class="ident">W</span>: <span class="ident">BitWriter</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dict</span> <span class="op">=</span> <span class="ident">EncodingDict::new</span>(<span class="ident">min_code_size</span>);
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// clear code</span>
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// end code</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">code_size</span> <span class="op">=</span> <span class="ident">min_code_size</span> <span class="op">+</span> <span class="number">1</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">i</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="comment">// gif spec: first clear code</span>
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">dict</span>.<span class="ident">clear_code</span>(), <span class="ident">code_size</span>));
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">r</span>.<span class="ident">bytes</span>();
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(<span class="ident">c</span>)) <span class="op">=</span> <span class="ident">r</span>.<span class="ident">next</span>() {
<span class="kw">let</span> <span class="ident">prev</span> <span class="op">=</span> <span class="ident">i</span>;
<span class="ident">i</span> <span class="op">=</span> <span class="ident">dict</span>.<span class="ident">search_and_insert</span>(<span class="ident">prev</span>, <span class="ident">c</span>);
<span class="kw">if</span> <span class="ident">i</span>.<span class="ident">is_none</span>() {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">code</span>) <span class="op">=</span> <span class="ident">prev</span> {
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>, <span class="ident">code_size</span>));
}
<span class="ident">i</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">dict</span>.<span class="ident">search_initials</span>(<span class="ident">c</span> <span class="kw">as</span> <span class="ident">Code</span>))
}
<span class="comment">// There is a hit: do not write out code but continue</span>
<span class="kw">let</span> <span class="ident">next_code</span> <span class="op">=</span> <span class="ident">dict</span>.<span class="ident">next_code</span>();
<span class="kw">if</span> <span class="ident">next_code</span> <span class="op">></span> (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">code_size</span> <span class="kw">as</span> <span class="ident">usize</span>)
<span class="op">&&</span> <span class="ident">code_size</span> <span class="op"><</span> <span class="ident">MAX_CODESIZE</span> {
<span class="ident">code_size</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
}
<span class="kw">if</span> <span class="ident">next_code</span> <span class="op">></span> <span class="ident">MAX_ENTRIES</span> {
<span class="ident">dict</span>.<span class="ident">reset</span>();
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// clear code</span>
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// end code</span>
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">dict</span>.<span class="ident">clear_code</span>(), <span class="ident">code_size</span>));
<span class="ident">code_size</span> <span class="op">=</span> <span class="ident">min_code_size</span> <span class="op">+</span> <span class="number">1</span>;
}
}
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">code</span>) <span class="op">=</span> <span class="ident">i</span> {
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>, <span class="ident">code_size</span>));
}
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">dict</span>.<span class="ident">end_code</span>(), <span class="ident">code_size</span>));
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">flush</span>());
<span class="prelude-val">Ok</span>(())
}
<span class="doccomment">/// LZW encoder using the algorithm of GIF files.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Encoder</span><span class="op"><</span><span class="ident">W</span>: <span class="ident">BitWriter</span><span class="op">></span> {
<span class="ident">w</span>: <span class="ident">W</span>,
<span class="ident">dict</span>: <span class="ident">EncodingDict</span>,
<span class="ident">min_code_size</span>: <span class="ident">u8</span>,
<span class="ident">code_size</span>: <span class="ident">u8</span>,
<span class="ident">i</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Code</span><span class="op">></span>
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">W</span>: <span class="ident">BitWriter</span><span class="op">></span> <span class="ident">Encoder</span><span class="op"><</span><span class="ident">W</span><span class="op">></span> {
<span class="doccomment">/// Creates a new LZW encoder.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// **Note**: If `min_code_size < 8` then `Self::encode_bytes` might panic when</span>
<span class="doccomment">/// the supplied data containts values that exceed `1 << min_code_size`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="kw-2">mut</span> <span class="ident">w</span>: <span class="ident">W</span>, <span class="ident">min_code_size</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="ident">io::Result</span><span class="op"><</span><span class="ident">Encoder</span><span class="op"><</span><span class="ident">W</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dict</span> <span class="op">=</span> <span class="ident">EncodingDict::new</span>(<span class="ident">min_code_size</span>);
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// clear code</span>
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// end code</span>
<span class="kw">let</span> <span class="ident">code_size</span> <span class="op">=</span> <span class="ident">min_code_size</span> <span class="op">+</span> <span class="number">1</span>;
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">dict</span>.<span class="ident">clear_code</span>(), <span class="ident">code_size</span>));
<span class="prelude-val">Ok</span>(<span class="ident">Encoder</span> {
<span class="ident">w</span>: <span class="ident">w</span>,
<span class="ident">dict</span>: <span class="ident">dict</span>,
<span class="ident">min_code_size</span>: <span class="ident">min_code_size</span>,
<span class="ident">code_size</span>: <span class="ident">code_size</span>,
<span class="ident">i</span>: <span class="prelude-val">None</span>
})
}
<span class="doccomment">/// Compresses `bytes` and writes the result into the writer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function might panic if any of the input bytes exceeds `1 << min_code_size`.</span>
<span class="doccomment">/// This cannot happen if `min_code_size >= 8`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">encode_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">bytes</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>]) <span class="op">-</span><span class="op">></span> <span class="ident">io::Result</span><span class="op"><</span>()<span class="op">></span> {
<span class="kw">let</span> <span class="ident">w</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">w</span>;
<span class="kw">let</span> <span class="ident">dict</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">dict</span>;
<span class="kw">let</span> <span class="ident">code_size</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">code_size</span>;
<span class="kw">let</span> <span class="ident">i</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">i</span>;
<span class="kw">for</span> <span class="kw-2">&</span><span class="ident">c</span> <span class="kw">in</span> <span class="ident">bytes</span> {
<span class="kw">let</span> <span class="ident">prev</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">i</span>;
<span class="kw-2">*</span><span class="ident">i</span> <span class="op">=</span> <span class="ident">dict</span>.<span class="ident">search_and_insert</span>(<span class="ident">prev</span>, <span class="ident">c</span>);
<span class="kw">if</span> <span class="ident">i</span>.<span class="ident">is_none</span>() {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">code</span>) <span class="op">=</span> <span class="ident">prev</span> {
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>, <span class="kw-2">*</span><span class="ident">code_size</span>));
}
<span class="kw-2">*</span><span class="ident">i</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">dict</span>.<span class="ident">search_initials</span>(<span class="ident">c</span> <span class="kw">as</span> <span class="ident">Code</span>))
}
<span class="comment">// There is a hit: do not write out code but continue</span>
<span class="kw">let</span> <span class="ident">next_code</span> <span class="op">=</span> <span class="ident">dict</span>.<span class="ident">next_code</span>();
<span class="kw">if</span> <span class="ident">next_code</span> <span class="op">></span> (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="kw-2">*</span><span class="ident">code_size</span> <span class="kw">as</span> <span class="ident">usize</span>)
<span class="op">&&</span> <span class="kw-2">*</span><span class="ident">code_size</span> <span class="op"><</span> <span class="ident">MAX_CODESIZE</span> {
<span class="kw-2">*</span><span class="ident">code_size</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
}
<span class="kw">if</span> <span class="ident">next_code</span> <span class="op">></span> <span class="ident">MAX_ENTRIES</span> {
<span class="ident">dict</span>.<span class="ident">reset</span>();
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// clear code</span>
<span class="ident">dict</span>.<span class="ident">push_node</span>(<span class="ident">Node::new</span>(<span class="number">0</span>)); <span class="comment">// end code</span>
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">dict</span>.<span class="ident">clear_code</span>(), <span class="kw-2">*</span><span class="ident">code_size</span>));
<span class="kw-2">*</span><span class="ident">code_size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">min_code_size</span> <span class="op">+</span> <span class="number">1</span>;
}
}
<span class="prelude-val">Ok</span>(())
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">W</span>: <span class="ident">BitWriter</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Encoder</span><span class="op"><</span><span class="ident">W</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"raii_no_panic"</span>)]</span>
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">w</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">w</span>;
<span class="kw">let</span> <span class="ident">code_size</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">code_size</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">code</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">i</span> {
<span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>, <span class="kw-2">*</span><span class="ident">code_size</span>);
}
<span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="self">self</span>.<span class="ident">dict</span>.<span class="ident">end_code</span>(), <span class="kw-2">*</span><span class="ident">code_size</span>);
<span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="ident">w</span>.<span class="ident">flush</span>();
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"raii_no_panic"</span>))]</span>
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
(<span class="op">|</span><span class="op">|</span> {
<span class="kw">let</span> <span class="ident">w</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">w</span>;
<span class="kw">let</span> <span class="ident">code_size</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">code_size</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">code</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">i</span> {
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>, <span class="kw-2">*</span><span class="ident">code_size</span>));
}
<span class="macro">try!</span>(<span class="ident">w</span>.<span class="ident">write_bits</span>(<span class="self">self</span>.<span class="ident">dict</span>.<span class="ident">end_code</span>(), <span class="kw-2">*</span><span class="ident">code_size</span>));
<span class="ident">w</span>.<span class="ident">flush</span>()
})().<span class="ident">unwrap</span>()
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">round_trip</span>() {
<span class="kw">use</span> {<span class="ident">LsbWriter</span>, <span class="ident">LsbReader</span>};
<span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> <span class="number">8</span>;
<span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="string">b"TOBEORNOTTOBEORTOBEORNOT"</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">compressed</span> <span class="op">=</span> <span class="macro">vec!</span>[];
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">enc</span> <span class="op">=</span> <span class="ident">Encoder::new</span>(<span class="ident">LsbWriter::new</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">compressed</span>), <span class="ident">size</span>).<span class="ident">unwrap</span>();
<span class="ident">enc</span>.<span class="ident">encode_bytes</span>(<span class="ident">data</span>).<span class="ident">unwrap</span>();
}
<span class="macro">println!</span>(<span class="string">"{:?}"</span>, <span class="ident">compressed</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dec</span> <span class="op">=</span> <span class="ident">Decoder::new</span>(<span class="ident">LsbReader::new</span>(), <span class="ident">size</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">compressed</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">compressed</span>[..];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">data2</span> <span class="op">=</span> <span class="macro">vec!</span>[];
<span class="kw">while</span> <span class="ident">compressed</span>.<span class="ident">len</span>() <span class="op">></span> <span class="number">0</span> {
<span class="kw">let</span> (<span class="ident">start</span>, <span class="ident">bytes</span>) <span class="op">=</span> <span class="ident">dec</span>.<span class="ident">decode_bytes</span>(<span class="kw-2">&</span><span class="ident">compressed</span>).<span class="ident">unwrap</span>();
<span class="ident">compressed</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">compressed</span>[<span class="ident">start</span>..];
<span class="ident">data2</span>.<span class="ident">extend</span>(<span class="ident">bytes</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">&</span><span class="ident">i</span><span class="op">|</span> <span class="ident">i</span>));
}
<span class="macro">assert_eq!</span>(<span class="ident">data2</span>, <span class="ident">data</span>)
}</pre></div>
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