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<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">use</span> <span class="ident">std::mem</span>;
<span class="kw">use</span> <span class="ident">huffman_table::HuffmanTable</span>;
<span class="kw">use</span> <span class="ident">bitstream::LsbWriter</span>;
<span class="kw">use</span> <span class="ident">lzvalue::LZType</span>;
<span class="comment">// The first bits of each block, which describe the type of the block</span>
<span class="comment">// `-TTF` - TT = type, 00 = stored, 01 = fixed, 10 = dynamic, 11 = reserved, F - 1 if final block</span>
<span class="comment">// `0000`;</span>
<span class="kw">const</span> <span class="ident">FIXED_FIRST_BYTE</span>: <span class="ident">u16</span> <span class="op">=</span> <span class="number">0b010</span>;
<span class="kw">const</span> <span class="ident">FIXED_FIRST_BYTE_FINAL</span>: <span class="ident">u16</span> <span class="op">=</span> <span class="number">0b011</span>;
<span class="kw">const</span> <span class="ident">DYNAMIC_FIRST_BYTE</span>: <span class="ident">u16</span> <span class="op">=</span> <span class="number">0b100</span>;
<span class="kw">const</span> <span class="ident">DYNAMIC_FIRST_BYTE_FINAL</span>: <span class="ident">u16</span> <span class="op">=</span> <span class="number">0b101</span>;
<span class="attribute">#[<span class="ident">allow</span>(<span class="ident">dead_code</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">BType</span> {
<span class="ident">NoCompression</span> <span class="op">=</span> <span class="number">0b00</span>,
<span class="ident">FixedHuffman</span> <span class="op">=</span> <span class="number">0b01</span>,
<span class="ident">DynamicHuffman</span> <span class="op">=</span> <span class="number">0b10</span>, <span class="comment">// Reserved = 0b11, //Error</span>
}
<span class="doccomment">/// A struct wrapping a writer that writes data compressed using the provided huffman table</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">EncoderState</span> {
<span class="kw">pub</span> <span class="ident">huffman_table</span>: <span class="ident">HuffmanTable</span>,
<span class="kw">pub</span> <span class="ident">writer</span>: <span class="ident">LsbWriter</span>,
}
<span class="kw">impl</span> <span class="ident">EncoderState</span> {
<span class="doccomment">/// Creates a new encoder state using the provided huffman table and writer</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">writer</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">EncoderState</span> {
<span class="ident">EncoderState</span> {
<span class="ident">huffman_table</span>: <span class="ident">HuffmanTable::empty</span>(),
<span class="ident">writer</span>: <span class="ident">LsbWriter::new</span>(<span class="ident">writer</span>),
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="doccomment">/// Creates a new encoder state using the fixed huffman table</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">fixed</span>(<span class="ident">writer</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">EncoderState</span> {
<span class="ident">EncoderState</span> {
<span class="ident">huffman_table</span>: <span class="ident">HuffmanTable::fixed_table</span>(),
<span class="ident">writer</span>: <span class="ident">LsbWriter::new</span>(<span class="ident">writer</span>),
}
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">inner_vec</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-2">&</span><span class="kw-2">mut</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> {
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">w</span>
}
<span class="doccomment">/// Encodes a literal value to the writer</span>
<span class="kw">fn</span> <span class="ident">write_literal</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">value</span>: <span class="ident">u8</span>) {
<span class="kw">let</span> <span class="ident">code</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">huffman_table</span>.<span class="ident">get_literal</span>(<span class="ident">value</span>);
<span class="macro">debug_assert!</span>(<span class="ident">code</span>.<span class="ident">length</span> <span class="op">></span> <span class="number">0</span>);
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>.<span class="ident">code</span>, <span class="ident">code</span>.<span class="ident">length</span>);
}
<span class="doccomment">/// Write a LZvalue to the contained writer, returning Err if the write operation fails</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">write_lzvalue</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">value</span>: <span class="ident">LZType</span>) {
<span class="kw">match</span> <span class="ident">value</span> {
<span class="ident">LZType::Literal</span>(<span class="ident">l</span>) <span class="op">=</span><span class="op">></span> <span class="self">self</span>.<span class="ident">write_literal</span>(<span class="ident">l</span>),
<span class="ident">LZType::StoredLengthDistance</span>(<span class="ident">l</span>, <span class="ident">d</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">let</span> (<span class="ident">code</span>, <span class="ident">extra_bits_code</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">huffman_table</span>.<span class="ident">get_length_huffman</span>(<span class="ident">l</span>);
<span class="macro">debug_assert!</span>(
<span class="ident">code</span>.<span class="ident">length</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span>,
<span class="macro">format!</span>(<span class="string">"Code: {:?}, Value: {:?}"</span>, <span class="ident">code</span>, <span class="ident">value</span>)
);
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>.<span class="ident">code</span>, <span class="ident">code</span>.<span class="ident">length</span>);
<span class="self">self</span>.<span class="ident">writer</span>
.<span class="ident">write_bits</span>(<span class="ident">extra_bits_code</span>.<span class="ident">code</span>, <span class="ident">extra_bits_code</span>.<span class="ident">length</span>);
<span class="kw">let</span> (<span class="ident">code</span>, <span class="ident">extra_bits_code</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">huffman_table</span>.<span class="ident">get_distance_huffman</span>(<span class="ident">d</span>);
<span class="macro">debug_assert!</span>(
<span class="ident">code</span>.<span class="ident">length</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span>,
<span class="macro">format!</span>(<span class="string">"Code: {:?}, Value: {:?}"</span>, <span class="ident">code</span>, <span class="ident">value</span>)
);
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>.<span class="ident">code</span>, <span class="ident">code</span>.<span class="ident">length</span>);
<span class="self">self</span>.<span class="ident">writer</span>
.<span class="ident">write_bits</span>(<span class="ident">extra_bits_code</span>.<span class="ident">code</span>, <span class="ident">extra_bits_code</span>.<span class="ident">length</span>)
}
};
}
<span class="doccomment">/// Write the start of a block, returning Err if the write operation fails.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">write_start_of_block</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">fixed</span>: <span class="ident">bool</span>, <span class="ident">final_block</span>: <span class="ident">bool</span>) {
<span class="kw">if</span> <span class="ident">final_block</span> {
<span class="comment">// The final block has one bit flipped to indicate it's</span>
<span class="comment">// the final one</span>
<span class="kw">if</span> <span class="ident">fixed</span> {
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">FIXED_FIRST_BYTE_FINAL</span>, <span class="number">3</span>)
} <span class="kw">else</span> {
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">DYNAMIC_FIRST_BYTE_FINAL</span>, <span class="number">3</span>)
}
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">fixed</span> {
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">FIXED_FIRST_BYTE</span>, <span class="number">3</span>)
} <span class="kw">else</span> {
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">DYNAMIC_FIRST_BYTE</span>, <span class="number">3</span>)
}
}
<span class="doccomment">/// Write the end of block code</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">write_end_of_block</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">code</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">huffman_table</span>.<span class="ident">get_end_of_block</span>();
<span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">write_bits</span>(<span class="ident">code</span>.<span class="ident">code</span>, <span class="ident">code</span>.<span class="ident">length</span>)
}
<span class="doccomment">/// Flush the contained writer and it's bitstream wrapper.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">flush</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">writer</span>.<span class="ident">flush_raw</span>()
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">set_huffman_to_fixed</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">huffman_table</span>.<span class="ident">set_to_fixed</span>()
}
<span class="doccomment">/// Reset the encoder state with a new writer, returning the old one if flushing</span>
<span class="doccomment">/// succeeds.</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">pub</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="ident">writer</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> {
<span class="comment">// Make sure the writer is flushed</span>
<span class="comment">// Ideally this should be done before this function is called, but we</span>
<span class="comment">// do it here just in case.</span>
<span class="self">self</span>.<span class="ident">flush</span>();
<span class="comment">// Reset the huffman table</span>
<span class="comment">// This probably isn't needed, but again, we do it just in case to avoid leaking any data</span>
<span class="comment">// If this turns out to be a performance issue, it can probably be ignored later.</span>
<span class="self">self</span>.<span class="ident">huffman_table</span> <span class="op">=</span> <span class="ident">HuffmanTable::empty</span>();
<span class="ident">mem::replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">writer</span>.<span class="ident">w</span>, <span class="ident">writer</span>)
}
}
</pre></div>
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