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</pre><pre class="rust">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">byteorder</span>;
<span class="kw">use</span> <span class="ident">std</span>::{<span class="ident">fmt</span>, <span class="ident">error</span>, <span class="ident">str</span>};
<span class="kw">use</span> <span class="ident">byteorder</span>::{<span class="ident">BigEndian</span>, <span class="ident">ByteOrder</span>};
<span class="kw">mod</span> <span class="ident">tables</span>;
<span class="kw">mod</span> <span class="ident">line_wrap</span>;
<span class="kw">use</span> <span class="ident">line_wrap</span>::{<span class="ident">line_wrap_parameters</span>, <span class="ident">line_wrap</span>};
<span class="doccomment">/// Available encoding character sets</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">CharacterSet</span> {
<span class="doccomment">/// The standard character set (uses `+` and `/`)</span>
<span class="ident">Standard</span>,
<span class="doccomment">/// The URL safe character set (uses `-` and `_`)</span>
<span class="ident">UrlSafe</span>
}
<span class="kw">impl</span> <span class="ident">CharacterSet</span> {
<span class="kw">fn</span> <span class="ident">encode_table</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="lifetime">'static</span> [<span class="ident">u8</span>; <span class="number">64</span>] {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="ident">CharacterSet::Standard</span> <span class="op">=</span><span class="op">></span> <span class="ident">tables::STANDARD_ENCODE</span>,
<span class="ident">CharacterSet::UrlSafe</span> <span class="op">=</span><span class="op">></span> <span class="ident">tables::URL_SAFE_ENCODE</span>
}
}
<span class="kw">fn</span> <span class="ident">decode_table</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="lifetime">'static</span> [<span class="ident">u8</span>; <span class="number">256</span>] {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="ident">CharacterSet::Standard</span> <span class="op">=</span><span class="op">></span> <span class="ident">tables::STANDARD_DECODE</span>,
<span class="ident">CharacterSet::UrlSafe</span> <span class="op">=</span><span class="op">></span> <span class="ident">tables::URL_SAFE_DECODE</span>
}
}
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">LineEnding</span> {
<span class="ident">LF</span>,
<span class="ident">CRLF</span>,
}
<span class="kw">impl</span> <span class="ident">LineEnding</span> {
<span class="kw">fn</span> <span class="ident">len</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="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="ident">LineEnding::LF</span> <span class="op">=</span><span class="op">></span> <span class="number">1</span>,
<span class="ident">LineEnding::CRLF</span> <span class="op">=</span><span class="op">></span> <span class="number">2</span>
}
}
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">LineWrap</span> {
<span class="ident">NoWrap</span>,
<span class="comment">// wrap length is always > 0</span>
<span class="ident">Wrap</span>(<span class="ident">usize</span>, <span class="ident">LineEnding</span>)
}
<span class="doccomment">/// Contains configuration parameters for base64 encoding</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Config</span> {
<span class="doccomment">/// Character set to use</span>
<span class="ident">char_set</span>: <span class="ident">CharacterSet</span>,
<span class="doccomment">/// True to pad output with `=` characters</span>
<span class="ident">pad</span>: <span class="ident">bool</span>,
<span class="doccomment">/// Remove whitespace before decoding, at the cost of an allocation</span>
<span class="ident">strip_whitespace</span>: <span class="ident">bool</span>,
<span class="doccomment">/// ADT signifying whether to linewrap output, and if so by how many characters and with what ending</span>
<span class="ident">line_wrap</span>: <span class="ident">LineWrap</span>,
}
<span class="kw">impl</span> <span class="ident">Config</span> {
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">char_set</span>: <span class="ident">CharacterSet</span>,
<span class="ident">pad</span>: <span class="ident">bool</span>,
<span class="ident">strip_whitespace</span>: <span class="ident">bool</span>,
<span class="ident">input_line_wrap</span>: <span class="ident">LineWrap</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Config</span> {
<span class="kw">let</span> <span class="ident">line_wrap</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">input_line_wrap</span> {
<span class="ident">LineWrap::Wrap</span>(<span class="number">0</span>, <span class="kw">_</span>) <span class="op">=</span><span class="op">></span> <span class="ident">LineWrap::NoWrap</span>,
<span class="kw">_</span> <span class="op">=</span><span class="op">></span> <span class="ident">input_line_wrap</span>,
};
<span class="ident">Config</span> {
<span class="ident">char_set</span>: <span class="ident">char_set</span>,
<span class="ident">pad</span>: <span class="ident">pad</span>,
<span class="ident">strip_whitespace</span>: <span class="ident">strip_whitespace</span>,
<span class="ident">line_wrap</span>: <span class="ident">line_wrap</span>,
}
}
}
<span class="kw">pub</span> <span class="kw">static</span> <span class="ident">STANDARD</span>: <span class="ident">Config</span> <span class="op">=</span> <span class="ident">Config</span> {
<span class="ident">char_set</span>: <span class="ident">CharacterSet::Standard</span>,
<span class="ident">pad</span>: <span class="bool-val">true</span>,
<span class="ident">strip_whitespace</span>: <span class="bool-val">false</span>,
<span class="ident">line_wrap</span>: <span class="ident">LineWrap::NoWrap</span>,
};
<span class="kw">pub</span> <span class="kw">static</span> <span class="ident">MIME</span>: <span class="ident">Config</span> <span class="op">=</span> <span class="ident">Config</span> {
<span class="ident">char_set</span>: <span class="ident">CharacterSet::Standard</span>,
<span class="ident">pad</span>: <span class="bool-val">true</span>,
<span class="ident">strip_whitespace</span>: <span class="bool-val">true</span>,
<span class="ident">line_wrap</span>: <span class="ident">LineWrap::Wrap</span>(<span class="number">76</span>, <span class="ident">LineEnding::CRLF</span>),
};
<span class="kw">pub</span> <span class="kw">static</span> <span class="ident">URL_SAFE</span>: <span class="ident">Config</span> <span class="op">=</span> <span class="ident">Config</span> {
<span class="ident">char_set</span>: <span class="ident">CharacterSet::UrlSafe</span>,
<span class="ident">pad</span>: <span class="bool-val">true</span>,
<span class="ident">strip_whitespace</span>: <span class="bool-val">false</span>,
<span class="ident">line_wrap</span>: <span class="ident">LineWrap::NoWrap</span>,
};
<span class="kw">pub</span> <span class="kw">static</span> <span class="ident">URL_SAFE_NO_PAD</span>: <span class="ident">Config</span> <span class="op">=</span> <span class="ident">Config</span> {
<span class="ident">char_set</span>: <span class="ident">CharacterSet::UrlSafe</span>,
<span class="ident">pad</span>: <span class="bool-val">false</span>,
<span class="ident">strip_whitespace</span>: <span class="bool-val">false</span>,
<span class="ident">line_wrap</span>: <span class="ident">LineWrap::NoWrap</span>,
};
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">DecodeError</span> {
<span class="ident">InvalidByte</span>(<span class="ident">usize</span>, <span class="ident">u8</span>),
<span class="ident">InvalidLength</span>,
}
<span class="kw">impl</span> <span class="ident">fmt::Display</span> <span class="kw">for</span> <span class="ident">DecodeError</span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt::Formatter</span>) <span class="op">-</span><span class="op">></span> <span class="ident">fmt::Result</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index</span>, <span class="ident">byte</span>) <span class="op">=</span><span class="op">></span>
<span class="macro">write!</span>(<span class="ident">f</span>, <span class="string">"Invalid byte {}, offset {}."</span>, <span class="ident">byte</span>, <span class="ident">index</span>),
<span class="ident">DecodeError::InvalidLength</span> <span class="op">=</span><span class="op">></span>
<span class="macro">write!</span>(<span class="ident">f</span>, <span class="string">"Encoded text cannot have a 6-bit remainder."</span>)
}
}
}
<span class="kw">impl</span> <span class="ident">error::Error</span> <span class="kw">for</span> <span class="ident">DecodeError</span> {
<span class="kw">fn</span> <span class="ident">description</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">str</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="ident">DecodeError::InvalidByte</span>(<span class="kw">_</span>, <span class="kw">_</span>) <span class="op">=</span><span class="op">></span> <span class="string">"invalid byte"</span>,
<span class="ident">DecodeError::InvalidLength</span> <span class="op">=</span><span class="op">></span> <span class="string">"invalid length"</span>
}
}
<span class="kw">fn</span> <span class="ident">cause</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">error::Error</span><span class="op">></span> {
<span class="prelude-val">None</span>
}
}
<span class="doccomment">///Encode arbitrary octets as base64.</span>
<span class="doccomment">///Returns a String.</span>
<span class="doccomment">///Convenience for `encode_config(input, base64::STANDARD);`.</span>
<span class="doccomment">///</span>
<span class="doccomment">///# Example</span>
<span class="doccomment">///</span>
<span class="doccomment">///```rust</span>
<span class="doccomment">///extern crate base64;</span>
<span class="doccomment">///</span>
<span class="doccomment">///fn main() {</span>
<span class="doccomment">/// let b64 = base64::encode(b"hello world");</span>
<span class="doccomment">/// println!("{}", b64);</span>
<span class="doccomment">///}</span>
<span class="doccomment">///```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">encode</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span><span class="op">></span>(<span class="ident">input</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-</span><span class="op">></span> <span class="ident">String</span> {
<span class="ident">encode_config</span>(<span class="ident">input</span>, <span class="ident">STANDARD</span>)
}
<span class="doccomment">///Decode from string reference as octets.</span>
<span class="doccomment">///Returns a Result containing a Vec<u8>.</span>
<span class="doccomment">///Convenience `decode_config(input, base64::STANDARD);`.</span>
<span class="doccomment">///</span>
<span class="doccomment">///# Example</span>
<span class="doccomment">///</span>
<span class="doccomment">///```rust</span>
<span class="doccomment">///extern crate base64;</span>
<span class="doccomment">///</span>
<span class="doccomment">///fn main() {</span>
<span class="doccomment">/// let bytes = base64::decode("aGVsbG8gd29ybGQ=").unwrap();</span>
<span class="doccomment">/// println!("{:?}", bytes);</span>
<span class="doccomment">///}</span>
<span class="doccomment">///```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">decode</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span><span class="op">></span>(<span class="ident">input</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</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="ident">DecodeError</span><span class="op">></span> {
<span class="ident">decode_config</span>(<span class="ident">input</span>, <span class="ident">STANDARD</span>)
}
<span class="doccomment">///Encode arbitrary octets as base64.</span>
<span class="doccomment">///Returns a String.</span>
<span class="doccomment">///</span>
<span class="doccomment">///# Example</span>
<span class="doccomment">///</span>
<span class="doccomment">///```rust</span>
<span class="doccomment">///extern crate base64;</span>
<span class="doccomment">///</span>
<span class="doccomment">///fn main() {</span>
<span class="doccomment">/// let b64 = base64::encode_config(b"hello world~", base64::STANDARD);</span>
<span class="doccomment">/// println!("{}", b64);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let b64_url = base64::encode_config(b"hello internet~", base64::URL_SAFE);</span>
<span class="doccomment">/// println!("{}", b64_url);</span>
<span class="doccomment">///}</span>
<span class="doccomment">///```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">encode_config</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span><span class="op">></span>(<span class="ident">input</span>: <span class="kw-2">&</span><span class="ident">T</span>, <span class="ident">config</span>: <span class="ident">Config</span>) <span class="op">-</span><span class="op">></span> <span class="ident">String</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">encoded_size</span>(<span class="ident">input</span>.<span class="ident">as_ref</span>().<span class="ident">len</span>(), <span class="kw-2">&</span><span class="ident">config</span>) {
<span class="prelude-val">Some</span>(<span class="ident">n</span>) <span class="op">=</span><span class="op">></span> <span class="ident">String::with_capacity</span>(<span class="ident">n</span>),
<span class="prelude-val">None</span> <span class="op">=</span><span class="op">></span> <span class="macro">panic!</span>(<span class="string">"integer overflow when calculating buffer size"</span>)
};
<span class="ident">encode_config_buf</span>(<span class="ident">input</span>, <span class="ident">config</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buf</span>);
<span class="ident">buf</span>
}
<span class="doccomment">/// calculate the base64 encoded string size, including padding</span>
<span class="kw">fn</span> <span class="ident">encoded_size</span>(<span class="ident">bytes_len</span>: <span class="ident">usize</span>, <span class="ident">config</span>: <span class="kw-2">&</span><span class="ident">Config</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">rem</span> <span class="op">=</span> <span class="ident">bytes_len</span> <span class="op">%</span> <span class="number">3</span>;
<span class="kw">let</span> <span class="ident">complete_input_chunks</span> <span class="op">=</span> <span class="ident">bytes_len</span> <span class="op">/</span> <span class="number">3</span>;
<span class="kw">let</span> <span class="ident">complete_chunk_output</span> <span class="op">=</span> <span class="ident">complete_input_chunks</span>.<span class="ident">checked_mul</span>(<span class="number">4</span>);
<span class="kw">let</span> <span class="ident">encoded_len_no_wrap</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">rem</span> <span class="op">></span> <span class="number">0</span> {
<span class="kw">if</span> <span class="ident">config</span>.<span class="ident">pad</span> {
<span class="ident">complete_chunk_output</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">c</span><span class="op">|</span> <span class="ident">c</span>.<span class="ident">checked_add</span>(<span class="number">4</span>))
} <span class="kw">else</span> {
<span class="kw">let</span> <span class="ident">encoded_rem</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">rem</span> {
<span class="number">1</span> <span class="op">=</span><span class="op">></span> <span class="number">2</span>,
<span class="number">2</span> <span class="op">=</span><span class="op">></span> <span class="number">3</span>,
<span class="kw">_</span> <span class="op">=</span><span class="op">></span> <span class="macro">panic!</span>(<span class="string">"Impossible remainder"</span>)
};
<span class="ident">complete_chunk_output</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">c</span><span class="op">|</span> <span class="ident">c</span>.<span class="ident">checked_add</span>(<span class="ident">encoded_rem</span>))
}
} <span class="kw">else</span> {
<span class="ident">complete_chunk_output</span>
};
<span class="ident">encoded_len_no_wrap</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">e</span><span class="op">|</span> {
<span class="kw">match</span> <span class="ident">config</span>.<span class="ident">line_wrap</span> {
<span class="ident">LineWrap::NoWrap</span> <span class="op">=</span><span class="op">></span> <span class="ident">e</span>,
<span class="ident">LineWrap::Wrap</span>(<span class="ident">line_len</span>, <span class="ident">line_ending</span>) <span class="op">=</span><span class="op">></span> {
<span class="ident">line_wrap_parameters</span>(<span class="ident">e</span>, <span class="ident">line_len</span>, <span class="ident">line_ending</span>).<span class="ident">total_len</span>
}
}
})
}
<span class="doccomment">///Encode arbitrary octets as base64.</span>
<span class="doccomment">///Writes into the supplied buffer to avoid allocations.</span>
<span class="doccomment">///</span>
<span class="doccomment">///# Example</span>
<span class="doccomment">///</span>
<span class="doccomment">///```rust</span>
<span class="doccomment">///extern crate base64;</span>
<span class="doccomment">///</span>
<span class="doccomment">///fn main() {</span>
<span class="doccomment">/// let mut buf = String::new();</span>
<span class="doccomment">/// base64::encode_config_buf(b"hello world~", base64::STANDARD, &mut buf);</span>
<span class="doccomment">/// println!("{}", buf);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// buf.clear();</span>
<span class="doccomment">/// base64::encode_config_buf(b"hello internet~", base64::URL_SAFE, &mut buf);</span>
<span class="doccomment">/// println!("{}", buf);</span>
<span class="doccomment">///}</span>
<span class="doccomment">///```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">encode_config_buf</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span><span class="op">></span>(<span class="ident">input</span>: <span class="kw-2">&</span><span class="ident">T</span>, <span class="ident">config</span>: <span class="ident">Config</span>, <span class="ident">buf</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">String</span>) {
<span class="kw">let</span> <span class="ident">input_bytes</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">as_ref</span>();
<span class="kw">let</span> <span class="ident">encoded_size</span> <span class="op">=</span> <span class="ident">encoded_size</span>(<span class="ident">input_bytes</span>.<span class="ident">len</span>(), <span class="kw-2">&</span><span class="ident">config</span>)
.<span class="ident">expect</span>(<span class="string">"usize overflow when calculating buffer size"</span>);
<span class="kw">let</span> <span class="ident">orig_buf_len</span> <span class="op">=</span> <span class="ident">buf</span>.<span class="ident">len</span>();
<span class="comment">// we're only going to insert valid utf8</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf_bytes</span>;
<span class="kw">unsafe</span> {
<span class="ident">buf_bytes</span> <span class="op">=</span> <span class="ident">buf</span>.<span class="ident">as_mut_vec</span>();
}
<span class="ident">buf_bytes</span>.<span class="ident">resize</span>(<span class="ident">orig_buf_len</span>.<span class="ident">checked_add</span>(<span class="ident">encoded_size</span>)
.<span class="ident">expect</span>(<span class="string">"usize overflow when calculating expanded buffer size"</span>), <span class="number">0</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">b64_output</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buf_bytes</span>[<span class="ident">orig_buf_len</span>..];
<span class="kw">let</span> <span class="ident">encoded_bytes</span> <span class="op">=</span> <span class="ident">encode_with_padding</span>(<span class="ident">input_bytes</span>, <span class="ident">b64_output</span>, <span class="ident">config</span>.<span class="ident">char_set</span>.<span class="ident">encode_table</span>(),
<span class="ident">config</span>.<span class="ident">pad</span>);
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">LineWrap::Wrap</span>(<span class="ident">line_len</span>, <span class="ident">line_end</span>) <span class="op">=</span> <span class="ident">config</span>.<span class="ident">line_wrap</span> {
<span class="ident">line_wrap</span>(<span class="ident">b64_output</span>, <span class="ident">encoded_bytes</span>, <span class="ident">line_len</span>, <span class="ident">line_end</span>);
}
}
<span class="doccomment">/// Encode input bytes and pad if configured.</span>
<span class="doccomment">/// `output` must be long enough to hold the encoded `input` with padding.</span>
<span class="doccomment">/// Returns the number of bytes written.</span>
<span class="kw">fn</span> <span class="ident">encode_with_padding</span>(<span class="ident">input</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">output</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>], <span class="ident">encode_table</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>; <span class="number">64</span>], <span class="ident">pad</span>: <span class="ident">bool</span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">let</span> <span class="ident">b64_bytes_written</span> <span class="op">=</span> <span class="ident">encode_to_slice</span>(<span class="ident">input</span>, <span class="ident">output</span>, <span class="ident">encode_table</span>);
<span class="kw">let</span> <span class="ident">padding_bytes</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">pad</span> {
<span class="ident">add_padding</span>(<span class="ident">input</span>.<span class="ident">len</span>(), <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output</span>[<span class="ident">b64_bytes_written</span>..])
} <span class="kw">else</span> {
<span class="number">0</span>
};
<span class="ident">b64_bytes_written</span>.<span class="ident">checked_add</span>(<span class="ident">padding_bytes</span>)
.<span class="ident">expect</span>(<span class="string">"usize overflow when calculating b64 length"</span>)
}
<span class="doccomment">/// Encode input bytes to utf8 base64 bytes. Does not pad or line wrap.</span>
<span class="doccomment">/// `output` must be long enough to hold the encoded `input` without padding or line wrapping.</span>
<span class="doccomment">/// Returns the number of bytes written.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">encode_to_slice</span>(<span class="ident">input</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">output</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>], <span class="ident">encode_table</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>; <span class="number">64</span>]) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">input_index</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">const</span> <span class="ident">BLOCKS_PER_FAST_LOOP</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">4</span>;
<span class="kw">const</span> <span class="ident">LOW_SIX_BITS</span>: <span class="ident">u64</span> <span class="op">=</span> <span class="number">0x3F</span>;
<span class="comment">// we read 8 bytes at a time (u64) but only actually consume 6 of those bytes. Thus, we need</span>
<span class="comment">// 2 trailing bytes to be available to read..</span>
<span class="kw">let</span> <span class="ident">last_fast_index</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">len</span>().<span class="ident">saturating_sub</span>(<span class="ident">BLOCKS_PER_FAST_LOOP</span> <span class="op">*</span> <span class="number">6</span> <span class="op">+</span> <span class="number">2</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">output_index</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">if</span> <span class="ident">last_fast_index</span> <span class="op">></span> <span class="number">0</span> {
<span class="kw">while</span> <span class="ident">input_index</span> <span class="op"><</span><span class="op">=</span> <span class="ident">last_fast_index</span> {
<span class="comment">// Major performance wins from letting the optimizer do the bounds check once, mostly</span>
<span class="comment">// on the output side</span>
<span class="kw">let</span> <span class="ident">input_chunk</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">input</span>[<span class="ident">input_index</span>..(<span class="ident">input_index</span> <span class="op">+</span> (<span class="ident">BLOCKS_PER_FAST_LOOP</span> <span class="op">*</span> <span class="number">6</span> <span class="op">+</span> <span class="number">2</span>))];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">output_chunk</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output</span>[<span class="ident">output_index</span>..(<span class="ident">output_index</span> <span class="op">+</span> <span class="ident">BLOCKS_PER_FAST_LOOP</span> <span class="op">*</span> <span class="number">8</span>)];
<span class="comment">// Hand-unrolling for 32 vs 16 or 8 bytes produces yields performance about equivalent</span>
<span class="comment">// to unsafe pointer code on a Xeon E5-1650v3. 64 byte unrolling was slightly better for</span>
<span class="comment">// large inputs but significantly worse for 50-byte input, unsurprisingly. I suspect</span>
<span class="comment">// that it's a not uncommon use case to encode smallish chunks of data (e.g. a 64-byte</span>
<span class="comment">// SHA-512 digest), so it would be nice if that fit in the unrolled loop at least once.</span>
<span class="comment">// Plus, single-digit percentage performance differences might well be quite different</span>
<span class="comment">// on different hardware.</span>
<span class="kw">let</span> <span class="ident">input_u64</span> <span class="op">=</span> <span class="ident">BigEndian::read_u64</span>(<span class="kw-2">&</span><span class="ident">input_chunk</span>[<span class="number">0</span>..]);
<span class="ident">output_chunk</span>[<span class="number">0</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">58</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">1</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">52</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">2</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">46</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">3</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">40</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">4</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">34</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">5</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">28</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">6</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">22</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">7</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">16</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">let</span> <span class="ident">input_u64</span> <span class="op">=</span> <span class="ident">BigEndian::read_u64</span>(<span class="kw-2">&</span><span class="ident">input_chunk</span>[<span class="number">6</span>..]);
<span class="ident">output_chunk</span>[<span class="number">8</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">58</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">9</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">52</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">10</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">46</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">11</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">40</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">12</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">34</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">13</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">28</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">14</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">22</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">15</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">16</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">let</span> <span class="ident">input_u64</span> <span class="op">=</span> <span class="ident">BigEndian::read_u64</span>(<span class="kw-2">&</span><span class="ident">input_chunk</span>[<span class="number">12</span>..]);
<span class="ident">output_chunk</span>[<span class="number">16</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">58</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">17</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">52</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">18</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">46</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">19</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">40</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">20</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">34</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">21</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">28</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">22</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">22</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">23</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">16</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">let</span> <span class="ident">input_u64</span> <span class="op">=</span> <span class="ident">BigEndian::read_u64</span>(<span class="kw-2">&</span><span class="ident">input_chunk</span>[<span class="number">18</span>..]);
<span class="ident">output_chunk</span>[<span class="number">24</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">58</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">25</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">52</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">26</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">46</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">27</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">40</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">28</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">34</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">29</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">28</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">30</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">22</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">31</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_u64</span> <span class="op">></span><span class="op">></span> <span class="number">16</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_index</span> <span class="op">+</span><span class="op">=</span> <span class="ident">BLOCKS_PER_FAST_LOOP</span> <span class="op">*</span> <span class="number">8</span>;
<span class="ident">input_index</span> <span class="op">+</span><span class="op">=</span> <span class="ident">BLOCKS_PER_FAST_LOOP</span> <span class="op">*</span> <span class="number">6</span>;
}
}
<span class="comment">// Encode what's left after the fast loop.</span>
<span class="kw">const</span> <span class="ident">LOW_SIX_BITS_U8</span>: <span class="ident">u8</span> <span class="op">=</span> <span class="number">0x3F</span>;
<span class="kw">let</span> <span class="ident">rem</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">len</span>() <span class="op">%</span> <span class="number">3</span>;
<span class="kw">let</span> <span class="ident">start_of_rem</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="ident">rem</span>;
<span class="comment">// start at the first index not handled by fast loop, which may be 0.</span>
<span class="kw">while</span> <span class="ident">input_index</span> <span class="op"><</span> <span class="ident">start_of_rem</span> {
<span class="kw">let</span> <span class="ident">input_chunk</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">input</span>[<span class="ident">input_index</span>..(<span class="ident">input_index</span> <span class="op">+</span> <span class="number">3</span>)];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">output_chunk</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output</span>[<span class="ident">output_index</span>..(<span class="ident">output_index</span> <span class="op">+</span> <span class="number">4</span>)];
<span class="ident">output_chunk</span>[<span class="number">0</span>] <span class="op">=</span> <span class="ident">encode_table</span>[(<span class="ident">input_chunk</span>[<span class="number">0</span>] <span class="op">></span><span class="op">></span> <span class="number">2</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">1</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_chunk</span>[<span class="number">0</span>] <span class="op"><</span><span class="op"><</span> <span class="number">4</span> <span class="op">|</span> <span class="ident">input_chunk</span>[<span class="number">1</span>] <span class="op">></span><span class="op">></span> <span class="number">4</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS_U8</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">2</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input_chunk</span>[<span class="number">1</span>] <span class="op"><</span><span class="op"><</span> <span class="number">2</span> <span class="op">|</span> <span class="ident">input_chunk</span>[<span class="number">2</span>] <span class="op">></span><span class="op">></span> <span class="number">6</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS_U8</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_chunk</span>[<span class="number">3</span>] <span class="op">=</span> <span class="ident">encode_table</span>[(<span class="ident">input_chunk</span>[<span class="number">2</span>] <span class="op">&</span> <span class="ident">LOW_SIX_BITS_U8</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">input_index</span> <span class="op">+</span><span class="op">=</span> <span class="number">3</span>;
<span class="ident">output_index</span> <span class="op">+</span><span class="op">=</span> <span class="number">4</span>;
}
<span class="kw">if</span> <span class="ident">rem</span> <span class="op">=</span><span class="op">=</span> <span class="number">2</span> {
<span class="ident">output</span>[<span class="ident">output_index</span>] <span class="op">=</span> <span class="ident">encode_table</span>[(<span class="ident">input</span>[<span class="ident">start_of_rem</span>] <span class="op">></span><span class="op">></span> <span class="number">2</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output</span>[<span class="ident">output_index</span> <span class="op">+</span> <span class="number">1</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input</span>[<span class="ident">start_of_rem</span>] <span class="op"><</span><span class="op"><</span> <span class="number">4</span> <span class="op">|</span> <span class="ident">input</span>[<span class="ident">start_of_rem</span> <span class="op">+</span> <span class="number">1</span>] <span class="op">></span><span class="op">></span> <span class="number">4</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS_U8</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output</span>[<span class="ident">output_index</span> <span class="op">+</span> <span class="number">2</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input</span>[<span class="ident">start_of_rem</span> <span class="op">+</span> <span class="number">1</span>] <span class="op"><</span><span class="op"><</span> <span class="number">2</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS_U8</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_index</span> <span class="op">+</span><span class="op">=</span> <span class="number">3</span>;
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">rem</span> <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
<span class="ident">output</span>[<span class="ident">output_index</span>] <span class="op">=</span> <span class="ident">encode_table</span>[(<span class="ident">input</span>[<span class="ident">start_of_rem</span>] <span class="op">></span><span class="op">></span> <span class="number">2</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output</span>[<span class="ident">output_index</span> <span class="op">+</span> <span class="number">1</span>] <span class="op">=</span> <span class="ident">encode_table</span>[((<span class="ident">input</span>[<span class="ident">start_of_rem</span>] <span class="op"><</span><span class="op"><</span> <span class="number">4</span>) <span class="op">&</span> <span class="ident">LOW_SIX_BITS_U8</span>) <span class="kw">as</span> <span class="ident">usize</span>];
<span class="ident">output_index</span> <span class="op">+</span><span class="op">=</span> <span class="number">2</span>;
}
<span class="ident">output_index</span>
}
<span class="doccomment">/// Write padding characters.</span>
<span class="doccomment">/// `output` is the slice where padding should be written, of length at least 2.</span>
<span class="kw">fn</span> <span class="ident">add_padding</span>(<span class="ident">input_len</span>: <span class="ident">usize</span>, <span class="ident">output</span>: <span class="kw-2">&</span><span class="kw-2">mut</span>[<span class="ident">u8</span>]) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="kw">let</span> <span class="ident">rem</span> <span class="op">=</span> <span class="ident">input_len</span> <span class="op">%</span> <span class="number">3</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bytes_written</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..((<span class="number">3</span> <span class="op">-</span> <span class="ident">rem</span>) <span class="op">%</span> <span class="number">3</span>) {
<span class="ident">output</span>[<span class="ident">bytes_written</span>] <span class="op">=</span> <span class="string">b'='</span>;
<span class="ident">bytes_written</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
}
<span class="ident">bytes_written</span>
}
<span class="doccomment">///Decode from string reference as octets.</span>
<span class="doccomment">///Returns a Result containing a Vec<u8>.</span>
<span class="doccomment">///</span>
<span class="doccomment">///# Example</span>
<span class="doccomment">///</span>
<span class="doccomment">///```rust</span>
<span class="doccomment">///extern crate base64;</span>
<span class="doccomment">///</span>
<span class="doccomment">///fn main() {</span>
<span class="doccomment">/// let bytes = base64::decode_config("aGVsbG8gd29ybGR+Cg==", base64::STANDARD).unwrap();</span>
<span class="doccomment">/// println!("{:?}", bytes);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let bytes_url = base64::decode_config("aGVsbG8gaW50ZXJuZXR-Cg==", base64::URL_SAFE).unwrap();</span>
<span class="doccomment">/// println!("{:?}", bytes_url);</span>
<span class="doccomment">///}</span>
<span class="doccomment">///```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">decode_config</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span><span class="op">></span>(<span class="ident">input</span>: <span class="kw-2">&</span><span class="ident">T</span>, <span class="ident">config</span>: <span class="ident">Config</span>) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</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="ident">DecodeError</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buffer</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="ident">::with_capacity</span>(<span class="ident">input</span>.<span class="ident">as_ref</span>().<span class="ident">len</span>() <span class="op">*</span> <span class="number">4</span> <span class="op">/</span> <span class="number">3</span>);
<span class="ident">decode_config_buf</span>(<span class="ident">input</span>, <span class="ident">config</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buffer</span>).<span class="ident">map</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">buffer</span>)
}
<span class="doccomment">///Decode from string reference as octets.</span>
<span class="doccomment">///Writes into the supplied buffer to avoid allocation.</span>
<span class="doccomment">///Returns a Result containing an empty tuple, aka ().</span>
<span class="doccomment">///</span>
<span class="doccomment">///# Example</span>
<span class="doccomment">///</span>
<span class="doccomment">///```rust</span>
<span class="doccomment">///extern crate base64;</span>
<span class="doccomment">///</span>
<span class="doccomment">///fn main() {</span>
<span class="doccomment">/// let mut buffer = Vec::<u8>::new();</span>
<span class="doccomment">/// base64::decode_config_buf("aGVsbG8gd29ybGR+Cg==", base64::STANDARD, &mut buffer).unwrap();</span>
<span class="doccomment">/// println!("{:?}", buffer);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// buffer.clear();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// base64::decode_config_buf("aGVsbG8gaW50ZXJuZXR-Cg==", base64::URL_SAFE, &mut buffer).unwrap();</span>
<span class="doccomment">/// println!("{:?}", buffer);</span>
<span class="doccomment">///}</span>
<span class="doccomment">///```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">decode_config_buf</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span><span class="op">></span>(<span class="ident">input</span>: <span class="kw-2">&</span><span class="ident">T</span>,
<span class="ident">config</span>: <span class="ident">Config</span>,
<span class="ident">buffer</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="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">DecodeError</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">input_copy</span>;
<span class="kw">let</span> <span class="ident">input_bytes</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">config</span>.<span class="ident">strip_whitespace</span> {
<span class="ident">input_copy</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="ident">::with_capacity</span>(<span class="ident">input</span>.<span class="ident">as_ref</span>().<span class="ident">len</span>());
<span class="ident">input_copy</span>.<span class="ident">extend</span>(<span class="ident">input</span>.<span class="ident">as_ref</span>().<span class="ident">iter</span>().<span class="ident">filter</span>(<span class="op">|</span><span class="ident">b</span><span class="op">|</span> <span class="op">!</span><span class="string">b" \n\t\r\x0b\x0c"</span>.<span class="ident">contains</span>(<span class="ident">b</span>)));
<span class="ident">input_copy</span>.<span class="ident">as_ref</span>()
} <span class="kw">else</span> {
<span class="ident">input</span>.<span class="ident">as_ref</span>()
};
<span class="kw">let</span> <span class="ident">decode_table</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">config</span>.<span class="ident">char_set</span>.<span class="ident">decode_table</span>();
<span class="comment">// decode logic operates on chunks of 8 input bytes without padding</span>
<span class="kw">const</span> <span class="ident">INPUT_CHUNK_LEN</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">8</span>;
<span class="kw">const</span> <span class="ident">DECODED_CHUNK_LEN</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">6</span>;
<span class="comment">// we read a u64 and write a u64, but a u64 of input only yields 6 bytes of output, so the last</span>
<span class="comment">// 2 bytes of any output u64 should not be counted as written to (but must be available in a</span>
<span class="comment">// slice).</span>
<span class="kw">const</span> <span class="ident">DECODED_CHUNK_SUFFIX</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">2</span>;
<span class="kw">let</span> <span class="ident">remainder_len</span> <span class="op">=</span> <span class="ident">input_bytes</span>.<span class="ident">len</span>() <span class="op">%</span> <span class="ident">INPUT_CHUNK_LEN</span>;
<span class="kw">let</span> <span class="ident">trailing_bytes_to_skip</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">remainder_len</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="comment">// if input is a multiple of the chunk size, ignore the last chunk as it may have padding,</span>
<span class="comment">// and the fast decode logic cannot handle padding</span>
<span class="ident">INPUT_CHUNK_LEN</span>
} <span class="kw">else</span> {
<span class="ident">remainder_len</span>
};
<span class="kw">let</span> <span class="ident">length_of_full_chunks</span> <span class="op">=</span> <span class="ident">input_bytes</span>.<span class="ident">len</span>().<span class="ident">saturating_sub</span>(<span class="ident">trailing_bytes_to_skip</span>);
<span class="kw">let</span> <span class="ident">starting_output_index</span> <span class="op">=</span> <span class="ident">buffer</span>.<span class="ident">len</span>();
<span class="comment">// Resize to hold decoded output from fast loop. Need the extra two bytes because</span>
<span class="comment">// we write a full 8 bytes for the last 6-byte decoded chunk and then truncate off the last two.</span>
<span class="kw">let</span> <span class="ident">new_size</span> <span class="op">=</span> <span class="ident">starting_output_index</span>
.<span class="ident">checked_add</span>(<span class="ident">length_of_full_chunks</span> <span class="op">/</span> <span class="ident">INPUT_CHUNK_LEN</span> <span class="op">*</span> <span class="ident">DECODED_CHUNK_LEN</span>)
.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">l</span>.<span class="ident">checked_add</span>(<span class="ident">DECODED_CHUNK_SUFFIX</span>))
.<span class="ident">expect</span>(<span class="string">"Overflow when calculating output buffer length"</span>);
<span class="ident">buffer</span>.<span class="ident">resize</span>(<span class="ident">new_size</span>, <span class="number">0</span>);
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">output_index</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">input_index</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="ident">buffer_slice</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buffer</span>.<span class="ident">as_mut_slice</span>()[<span class="ident">starting_output_index</span>..];
<span class="comment">// how many u64's of input to handle at a time</span>
<span class="kw">const</span> <span class="ident">CHUNKS_PER_FAST_LOOP_BLOCK</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">4</span>;
<span class="kw">const</span> <span class="ident">INPUT_BLOCK_LEN</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="ident">CHUNKS_PER_FAST_LOOP_BLOCK</span> <span class="op">*</span> <span class="ident">INPUT_CHUNK_LEN</span>;
<span class="comment">// includes the trailing 2 bytes for the final u64 write</span>
<span class="kw">const</span> <span class="ident">DECODED_BLOCK_LEN</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="ident">CHUNKS_PER_FAST_LOOP_BLOCK</span> <span class="op">*</span> <span class="ident">DECODED_CHUNK_LEN</span> <span class="op">+</span>
<span class="ident">DECODED_CHUNK_SUFFIX</span>;
<span class="comment">// the start index of the last block of data that is big enough to use the unrolled loop</span>
<span class="kw">let</span> <span class="ident">last_block_start_index</span> <span class="op">=</span> <span class="ident">length_of_full_chunks</span>
.<span class="ident">saturating_sub</span>(<span class="ident">INPUT_CHUNK_LEN</span> <span class="op">*</span> <span class="ident">CHUNKS_PER_FAST_LOOP_BLOCK</span>);
<span class="comment">// manual unroll to CHUNKS_PER_FAST_LOOP_BLOCK of u64s to amortize slice bounds checks</span>
<span class="kw">if</span> <span class="ident">last_block_start_index</span> <span class="op">></span> <span class="number">0</span> {
<span class="kw">while</span> <span class="ident">input_index</span> <span class="op"><</span><span class="op">=</span> <span class="ident">last_block_start_index</span> {
<span class="kw">let</span> <span class="ident">input_slice</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">input_bytes</span>[<span class="ident">input_index</span>..(<span class="ident">input_index</span> <span class="op">+</span> <span class="ident">INPUT_BLOCK_LEN</span>)];
<span class="kw">let</span> <span class="ident">output_slice</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buffer_slice</span>[<span class="ident">output_index</span>..(<span class="ident">output_index</span> <span class="op">+</span> <span class="ident">DECODED_BLOCK_LEN</span>)];
<span class="ident">decode_chunk</span>(<span class="kw-2">&</span><span class="ident">input_slice</span>[<span class="number">0</span>..], <span class="ident">input_index</span>, <span class="ident">decode_table</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output_slice</span>[<span class="number">0</span>..])<span class="question-mark">?</span>;
<span class="ident">decode_chunk</span>(<span class="kw-2">&</span><span class="ident">input_slice</span>[<span class="number">8</span>..], <span class="ident">input_index</span> <span class="op">+</span> <span class="number">8</span>, <span class="ident">decode_table</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output_slice</span>[<span class="number">6</span>..])<span class="question-mark">?</span>;
<span class="ident">decode_chunk</span>(<span class="kw-2">&</span><span class="ident">input_slice</span>[<span class="number">16</span>..], <span class="ident">input_index</span> <span class="op">+</span> <span class="number">16</span>, <span class="ident">decode_table</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output_slice</span>[<span class="number">12</span>..])<span class="question-mark">?</span>;
<span class="ident">decode_chunk</span>(<span class="kw-2">&</span><span class="ident">input_slice</span>[<span class="number">24</span>..], <span class="ident">input_index</span> <span class="op">+</span> <span class="number">24</span>, <span class="ident">decode_table</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">output_slice</span>[<span class="number">18</span>..])<span class="question-mark">?</span>;
<span class="ident">input_index</span> <span class="op">+</span><span class="op">=</span> <span class="ident">INPUT_BLOCK_LEN</span>;
<span class="ident">output_index</span> <span class="op">+</span><span class="op">=</span> <span class="ident">DECODED_BLOCK_LEN</span> <span class="op">-</span> <span class="ident">DECODED_CHUNK_SUFFIX</span>;
}
}
<span class="comment">// still pretty fast loop: 8 bytes at a time for whatever we didn't do in the faster loop.</span>
<span class="kw">while</span> <span class="ident">input_index</span> <span class="op"><</span> <span class="ident">length_of_full_chunks</span> {
<span class="ident">decode_chunk</span>(<span class="kw-2">&</span><span class="ident">input_bytes</span>[<span class="ident">input_index</span>..(<span class="ident">input_index</span> <span class="op">+</span> <span class="number">8</span>)], <span class="ident">input_index</span>, <span class="ident">decode_table</span>,
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buffer_slice</span>[<span class="ident">output_index</span>..(<span class="ident">output_index</span> <span class="op">+</span> <span class="number">8</span>)])<span class="question-mark">?</span>;
<span class="ident">output_index</span> <span class="op">+</span><span class="op">=</span> <span class="ident">DECODED_CHUNK_LEN</span>;
<span class="ident">input_index</span> <span class="op">+</span><span class="op">=</span> <span class="ident">INPUT_CHUNK_LEN</span>;
}
}
<span class="comment">// Truncate off the last two bytes from writing the last u64.</span>
<span class="comment">// Unconditional because we added on the extra 2 bytes in the resize before the loop,</span>
<span class="comment">// so it will never underflow.</span>
<span class="kw">let</span> <span class="ident">new_len</span> <span class="op">=</span> <span class="ident">buffer</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="ident">DECODED_CHUNK_SUFFIX</span>;
<span class="ident">buffer</span>.<span class="ident">truncate</span>(<span class="ident">new_len</span>);
<span class="comment">// handle leftovers (at most 8 bytes, decoded to 6).</span>
<span class="comment">// Use a u64 as a stack-resident 8 byte buffer.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">leftover_bits</span>: <span class="ident">u64</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">morsels_in_leftover</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">padding_bytes</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">first_padding_index</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">for</span> (<span class="ident">i</span>, <span class="ident">b</span>) <span class="kw">in</span> <span class="ident">input_bytes</span>[<span class="ident">length_of_full_chunks</span>..].<span class="ident">iter</span>().<span class="ident">enumerate</span>() {
<span class="comment">// '=' padding</span>
<span class="kw">if</span> <span class="kw-2">*</span><span class="ident">b</span> <span class="op">=</span><span class="op">=</span> <span class="number">0x3D</span> {
<span class="comment">// There can be bad padding in a few ways:</span>
<span class="comment">// 1 - Padding with non-padding characters after it</span>
<span class="comment">// 2 - Padding after zero or one non-padding characters before it</span>
<span class="comment">// in the current quad.</span>
<span class="comment">// 3 - More than two characters of padding. If 3 or 4 padding chars</span>
<span class="comment">// are in the same quad, that implies it will be caught by #2.</span>
<span class="comment">// If it spreads from one quad to another, it will be caught by</span>
<span class="comment">// #2 in the second quad.</span>
<span class="kw">if</span> <span class="ident">i</span> <span class="op">%</span> <span class="number">4</span> <span class="op"><</span> <span class="number">2</span> {
<span class="comment">// Check for case #2.</span>
<span class="kw">let</span> <span class="ident">bad_padding_index</span> <span class="op">=</span> <span class="ident">length_of_full_chunks</span> <span class="op">+</span> <span class="kw">if</span> <span class="ident">padding_bytes</span> <span class="op">></span> <span class="number">0</span> {
<span class="comment">// If we've already seen padding, report the first padding index.</span>
<span class="comment">// This is to be consistent with the faster logic above: it will report an error</span>
<span class="comment">// on the first padding character (since it doesn't expect to see anything but</span>
<span class="comment">// actual encoded data).</span>
<span class="ident">first_padding_index</span>
} <span class="kw">else</span> {
<span class="comment">// haven't seen padding before, just use where we are now</span>
<span class="ident">i</span>
};
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">bad_padding_index</span>, <span class="kw-2">*</span><span class="ident">b</span>));
}
<span class="kw">if</span> <span class="ident">padding_bytes</span> <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="ident">first_padding_index</span> <span class="op">=</span> <span class="ident">i</span>;
}
<span class="ident">padding_bytes</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
<span class="kw">continue</span>;
}
<span class="comment">// Check for case #1.</span>
<span class="comment">// To make '=' handling consistent with the main loop, don't allow</span>
<span class="comment">// non-suffix '=' in trailing chunk either. Report error as first</span>
<span class="comment">// erroneous padding.</span>
<span class="kw">if</span> <span class="ident">padding_bytes</span> <span class="op">></span> <span class="number">0</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(
<span class="ident">length_of_full_chunks</span> <span class="op">+</span> <span class="ident">first_padding_index</span>, <span class="number">0x3D</span>));
}
<span class="comment">// can use up to 8 * 6 = 48 bits of the u64, if last chunk has no padding.</span>
<span class="comment">// To minimize shifts, pack the leftovers from left to right.</span>
<span class="kw">let</span> <span class="ident">shift</span> <span class="op">=</span> <span class="number">64</span> <span class="op">-</span> (<span class="ident">morsels_in_leftover</span> <span class="op">+</span> <span class="number">1</span>) <span class="op">*</span> <span class="number">6</span>;
<span class="comment">// tables are all 256 elements, lookup with a u8 index always succeeds</span>
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="kw-2">*</span><span class="ident">b</span> <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">length_of_full_chunks</span> <span class="op">+</span> <span class="ident">i</span>, <span class="kw-2">*</span><span class="ident">b</span>));
}
<span class="ident">leftover_bits</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="ident">shift</span>;
<span class="ident">morsels_in_leftover</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
}
<span class="kw">let</span> <span class="ident">leftover_bits_ready_to_append</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">morsels_in_leftover</span> {
<span class="number">0</span> <span class="op">=</span><span class="op">></span> <span class="number">0</span>,
<span class="number">1</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidLength</span>),
<span class="number">2</span> <span class="op">=</span><span class="op">></span> <span class="number">8</span>,
<span class="number">3</span> <span class="op">=</span><span class="op">></span> <span class="number">16</span>,
<span class="number">4</span> <span class="op">=</span><span class="op">></span> <span class="number">24</span>,
<span class="number">5</span> <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidLength</span>),
<span class="number">6</span> <span class="op">=</span><span class="op">></span> <span class="number">32</span>,
<span class="number">7</span> <span class="op">=</span><span class="op">></span> <span class="number">40</span>,
<span class="number">8</span> <span class="op">=</span><span class="op">></span> <span class="number">48</span>,
<span class="kw">_</span> <span class="op">=</span><span class="op">></span> <span class="macro">panic!</span>(<span class="string">"Impossible: must only have 0 to 4 input bytes in last quad"</span>)
};
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">leftover_bits_appended_to_buf</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">while</span> <span class="ident">leftover_bits_appended_to_buf</span> <span class="op"><</span> <span class="ident">leftover_bits_ready_to_append</span> {
<span class="comment">// `as` simply truncates the higher bits, which is what we want here</span>
<span class="kw">let</span> <span class="ident">selected_bits</span> <span class="op">=</span> (<span class="ident">leftover_bits</span> <span class="op">></span><span class="op">></span> (<span class="number">56</span> <span class="op">-</span> <span class="ident">leftover_bits_appended_to_buf</span>)) <span class="kw">as</span> <span class="ident">u8</span>;
<span class="ident">buffer</span>.<span class="ident">push</span>(<span class="ident">selected_bits</span>);
<span class="ident">leftover_bits_appended_to_buf</span> <span class="op">+</span><span class="op">=</span> <span class="number">8</span>;
};
<span class="prelude-val">Ok</span>(())
}
<span class="comment">// yes, really inline (worth 30-50% speedup)</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">decode_chunk</span>(<span class="ident">input</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">index_at_start_of_input</span>: <span class="ident">usize</span>, <span class="ident">decode_table</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>; <span class="number">256</span>],
<span class="ident">output</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">DecodeError</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">accum</span>: <span class="ident">u64</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">0</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span>, <span class="ident">input</span>[<span class="number">0</span>]));
}
<span class="ident">accum</span> <span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">58</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">1</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">1</span>, <span class="ident">input</span>[<span class="number">1</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">52</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">2</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">2</span>, <span class="ident">input</span>[<span class="number">2</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">46</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">3</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">3</span>, <span class="ident">input</span>[<span class="number">3</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">40</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">4</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">4</span>, <span class="ident">input</span>[<span class="number">4</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">34</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">5</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">5</span>, <span class="ident">input</span>[<span class="number">5</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">28</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">6</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">6</span>, <span class="ident">input</span>[<span class="number">6</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">22</span>;
<span class="kw">let</span> <span class="ident">morsel</span> <span class="op">=</span> <span class="ident">decode_table</span>[<span class="ident">input</span>[<span class="number">7</span>] <span class="kw">as</span> <span class="ident">usize</span>];
<span class="kw">if</span> <span class="ident">morsel</span> <span class="op">=</span><span class="op">=</span> <span class="ident">tables::INVALID_VALUE</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">DecodeError::InvalidByte</span>(<span class="ident">index_at_start_of_input</span> <span class="op">+</span> <span class="number">7</span>, <span class="ident">input</span>[<span class="number">7</span>]));
}
<span class="ident">accum</span> <span class="op">|</span><span class="op">=</span> (<span class="ident">morsel</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><</span><span class="op"><</span> <span class="number">16</span>;
<span class="ident">BigEndian::write_u64</span>(<span class="ident">output</span>, <span class="ident">accum</span>);
<span class="prelude-val">Ok</span>(())
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">tests</span>;
</pre></div>
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