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</pre><pre class='rust '>
<span class='comment'>// Copyright 2014 The Rust Project Developers. See the COPYRIGHT</span>
<span class='comment'>// file at the top-level directory of this distribution and at</span>
<span class='comment'>// http://rust-lang.org/COPYRIGHT.</span>
<span class='comment'>//</span>
<span class='comment'>// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class='comment'>// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class='comment'>// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class='comment'>// option. This file may not be copied, modified, or distributed</span>
<span class='comment'>// except according to those terms.</span>
<span class='doccomment'>//! The ChaCha random number generator.</span>
<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>num</span>::<span class='ident'>Wrapping</span> <span class='kw'>as</span> <span class='ident'>w</span>;
<span class='kw'>use</span> {<span class='ident'>Rng</span>, <span class='ident'>SeedableRng</span>, <span class='ident'>Rand</span>, <span class='ident'>w32</span>};
<span class='kw'>const</span> <span class='ident'>KEY_WORDS</span> : <span class='ident'>usize</span> <span class='op'>=</span> <span class='number'>8</span>; <span class='comment'>// 8 words for the 256-bit key</span>
<span class='kw'>const</span> <span class='ident'>STATE_WORDS</span> : <span class='ident'>usize</span> <span class='op'>=</span> <span class='number'>16</span>;
<span class='kw'>const</span> <span class='ident'>CHACHA_ROUNDS</span>: <span class='ident'>u32</span> <span class='op'>=</span> <span class='number'>20</span>; <span class='comment'>// Cryptographically secure from 8 upwards as of this writing</span>
<span class='doccomment'>/// A random number generator that uses the ChaCha20 algorithm [1].</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// The ChaCha algorithm is widely accepted as suitable for</span>
<span class='doccomment'>/// cryptographic purposes, but this implementation has not been</span>
<span class='doccomment'>/// verified as such. Prefer a generator like `OsRng` that defers to</span>
<span class='doccomment'>/// the operating system for cases that need high security.</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// [1]: D. J. Bernstein, [*ChaCha, a variant of</span>
<span class='doccomment'>/// Salsa20*](http://cr.yp.to/chacha.html)</span>
<span class='attribute'>#[<span class='ident'>derive</span>(<span class='ident'>Copy</span>, <span class='ident'>Clone</span>)]</span>
<span class='kw'>pub</span> <span class='kw'>struct</span> <span class='ident'>ChaChaRng</span> {
<span class='ident'>buffer</span>: [<span class='ident'>w32</span>; <span class='ident'>STATE_WORDS</span>], <span class='comment'>// Internal buffer of output</span>
<span class='ident'>state</span>: [<span class='ident'>w32</span>; <span class='ident'>STATE_WORDS</span>], <span class='comment'>// Initial state</span>
<span class='ident'>index</span>: <span class='ident'>usize</span>, <span class='comment'>// Index into state</span>
}
<span class='kw'>static</span> <span class='ident'>EMPTY</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>ChaChaRng</span> {
<span class='ident'>buffer</span>: [<span class='ident'>w</span>(<span class='number'>0</span>); <span class='ident'>STATE_WORDS</span>],
<span class='ident'>state</span>: [<span class='ident'>w</span>(<span class='number'>0</span>); <span class='ident'>STATE_WORDS</span>],
<span class='ident'>index</span>: <span class='ident'>STATE_WORDS</span>
};
<span class='macro'>macro_rules</span><span class='macro'>!</span> <span class='ident'>quarter_round</span>{
(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span>: <span class='ident'>expr</span>, <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span>: <span class='ident'>expr</span>, <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span>: <span class='ident'>expr</span>, <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span>: <span class='ident'>expr</span>) <span class='op'>=></span> {{
<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span> <span class='op'>+</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span> <span class='op'>^</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span> <span class='op'>=</span> <span class='ident'>w</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span>.<span class='number'>0</span>.<span class='ident'>rotate_left</span>(<span class='number'>16</span>));
<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span> <span class='op'>+</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span> <span class='op'>^</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span> <span class='op'>=</span> <span class='ident'>w</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span>.<span class='number'>0</span>.<span class='ident'>rotate_left</span>(<span class='number'>12</span>));
<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span> <span class='op'>+</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span> <span class='op'>^</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>a</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span> <span class='op'>=</span> <span class='ident'>w</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span>.<span class='number'>0</span>.<span class='ident'>rotate_left</span>( <span class='number'>8</span>));
<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span> <span class='op'>+</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>d</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span> <span class='op'>^</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>c</span>; <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span> <span class='op'>=</span> <span class='ident'>w</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>b</span>.<span class='number'>0</span>.<span class='ident'>rotate_left</span>( <span class='number'>7</span>));
}}
}
<span class='macro'>macro_rules</span><span class='macro'>!</span> <span class='ident'>double_round</span>{
(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>: <span class='ident'>expr</span>) <span class='op'>=></span> {{
<span class='comment'>// Column round</span>
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>0</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>4</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>8</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>12</span>]);
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>1</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>5</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>9</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>13</span>]);
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>2</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>6</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>10</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>14</span>]);
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>3</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>7</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>11</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>15</span>]);
<span class='comment'>// Diagonal round</span>
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>0</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>5</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>10</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>15</span>]);
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>1</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>6</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>11</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>12</span>]);
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>2</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>7</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>8</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>13</span>]);
<span class='macro'>quarter_round</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>3</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>4</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[ <span class='number'>9</span>], <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>x</span>[<span class='number'>14</span>]);
}}
}
<span class='attribute'>#[<span class='ident'>inline</span>]</span>
<span class='kw'>fn</span> <span class='ident'>core</span>(<span class='ident'>output</span>: <span class='kw-2'>&</span><span class='kw-2'>mut</span> [<span class='ident'>w32</span>; <span class='ident'>STATE_WORDS</span>], <span class='ident'>input</span>: <span class='kw-2'>&</span>[<span class='ident'>w32</span>; <span class='ident'>STATE_WORDS</span>]) {
<span class='kw-2'>*</span><span class='ident'>output</span> <span class='op'>=</span> <span class='kw-2'>*</span><span class='ident'>input</span>;
<span class='kw'>for</span> _ <span class='kw'>in</span> <span class='number'>0</span>..<span class='ident'>CHACHA_ROUNDS</span> <span class='op'>/</span> <span class='number'>2</span> {
<span class='macro'>double_round</span><span class='macro'>!</span>(<span class='ident'>output</span>);
}
<span class='kw'>for</span> <span class='ident'>i</span> <span class='kw'>in</span> <span class='number'>0</span>..<span class='ident'>STATE_WORDS</span> {
<span class='ident'>output</span>[<span class='ident'>i</span>] <span class='op'>=</span> <span class='ident'>output</span>[<span class='ident'>i</span>] <span class='op'>+</span> <span class='ident'>input</span>[<span class='ident'>i</span>];
}
}
<span class='kw'>impl</span> <span class='ident'>ChaChaRng</span> {
<span class='doccomment'>/// Create an ChaCha random number generator using the default</span>
<span class='doccomment'>/// fixed key of 8 zero words.</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// # Examples</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// ```rust</span>
<span class='doccomment'>/// use rand::{Rng, ChaChaRng};</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// let mut ra = ChaChaRng::new_unseeded();</span>
<span class='doccomment'>/// println!("{:?}", ra.next_u32());</span>
<span class='doccomment'>/// println!("{:?}", ra.next_u32());</span>
<span class='doccomment'>/// ```</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// Since this equivalent to a RNG with a fixed seed, repeated executions</span>
<span class='doccomment'>/// of an unseeded RNG will produce the same result. This code sample will</span>
<span class='doccomment'>/// consistently produce:</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// - 2917185654</span>
<span class='doccomment'>/// - 2419978656</span>
<span class='kw'>pub</span> <span class='kw'>fn</span> <span class='ident'>new_unseeded</span>() <span class='op'>-></span> <span class='ident'>ChaChaRng</span> {
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>rng</span> <span class='op'>=</span> <span class='ident'>EMPTY</span>;
<span class='ident'>rng</span>.<span class='ident'>init</span>(<span class='kw-2'>&</span>[<span class='number'>0</span>; <span class='ident'>KEY_WORDS</span>]);
<span class='ident'>rng</span>
}
<span class='doccomment'>/// Sets the internal 128-bit ChaCha counter to</span>
<span class='doccomment'>/// a user-provided value. This permits jumping</span>
<span class='doccomment'>/// arbitrarily ahead (or backwards) in the pseudorandom stream.</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// Since the nonce words are used to extend the counter to 128 bits,</span>
<span class='doccomment'>/// users wishing to obtain the conventional ChaCha pseudorandom stream</span>
<span class='doccomment'>/// associated with a particular nonce can call this function with</span>
<span class='doccomment'>/// arguments `0, desired_nonce`.</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// # Examples</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// ```rust</span>
<span class='doccomment'>/// use rand::{Rng, ChaChaRng};</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// let mut ra = ChaChaRng::new_unseeded();</span>
<span class='doccomment'>/// ra.set_counter(0u64, 1234567890u64);</span>
<span class='doccomment'>/// println!("{:?}", ra.next_u32());</span>
<span class='doccomment'>/// println!("{:?}", ra.next_u32());</span>
<span class='doccomment'>/// ```</span>
<span class='kw'>pub</span> <span class='kw'>fn</span> <span class='ident'>set_counter</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>, <span class='ident'>counter_low</span>: <span class='ident'>u64</span>, <span class='ident'>counter_high</span>: <span class='ident'>u64</span>) {
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>12</span>] <span class='op'>=</span> <span class='ident'>w</span>((<span class='ident'>counter_low</span> <span class='op'>>></span> <span class='number'>0</span>) <span class='kw'>as</span> <span class='ident'>u32</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>13</span>] <span class='op'>=</span> <span class='ident'>w</span>((<span class='ident'>counter_low</span> <span class='op'>>></span> <span class='number'>32</span>) <span class='kw'>as</span> <span class='ident'>u32</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>14</span>] <span class='op'>=</span> <span class='ident'>w</span>((<span class='ident'>counter_high</span> <span class='op'>>></span> <span class='number'>0</span>) <span class='kw'>as</span> <span class='ident'>u32</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>15</span>] <span class='op'>=</span> <span class='ident'>w</span>((<span class='ident'>counter_high</span> <span class='op'>>></span> <span class='number'>32</span>) <span class='kw'>as</span> <span class='ident'>u32</span>);
<span class='self'>self</span>.<span class='ident'>index</span> <span class='op'>=</span> <span class='ident'>STATE_WORDS</span>; <span class='comment'>// force recomputation</span>
}
<span class='doccomment'>/// Initializes `self.state` with the appropriate key and constants</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// We deviate slightly from the ChaCha specification regarding</span>
<span class='doccomment'>/// the nonce, which is used to extend the counter to 128 bits.</span>
<span class='doccomment'>/// This is provably as strong as the original cipher, though,</span>
<span class='doccomment'>/// since any distinguishing attack on our variant also works</span>
<span class='doccomment'>/// against ChaCha with a chosen-nonce. See the XSalsa20 [1]</span>
<span class='doccomment'>/// security proof for a more involved example of this.</span>
<span class='doccomment'>///</span>
<span class='doccomment'>/// The modified word layout is:</span>
<span class='doccomment'>/// ```text</span>
<span class='doccomment'>/// constant constant constant constant</span>
<span class='doccomment'>/// key key key key</span>
<span class='doccomment'>/// key key key key</span>
<span class='doccomment'>/// counter counter counter counter</span>
<span class='doccomment'>/// ```</span>
<span class='doccomment'>/// [1]: Daniel J. Bernstein. [*Extending the Salsa20</span>
<span class='doccomment'>/// nonce.*](http://cr.yp.to/papers.html#xsalsa)</span>
<span class='kw'>fn</span> <span class='ident'>init</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>, <span class='ident'>key</span>: <span class='kw-2'>&</span>[<span class='ident'>u32</span>; <span class='ident'>KEY_WORDS</span>]) {
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>0</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0x61707865</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>1</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0x3320646E</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>2</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0x79622D32</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>3</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0x6B206574</span>);
<span class='kw'>for</span> <span class='ident'>i</span> <span class='kw'>in</span> <span class='number'>0</span>..<span class='ident'>KEY_WORDS</span> {
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>4</span><span class='op'>+</span><span class='ident'>i</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='ident'>key</span>[<span class='ident'>i</span>]);
}
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>12</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>13</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>14</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0</span>);
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>15</span>] <span class='op'>=</span> <span class='ident'>w</span>(<span class='number'>0</span>);
<span class='self'>self</span>.<span class='ident'>index</span> <span class='op'>=</span> <span class='ident'>STATE_WORDS</span>;
}
<span class='doccomment'>/// Refill the internal output buffer (`self.buffer`)</span>
<span class='kw'>fn</span> <span class='ident'>update</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>) {
<span class='ident'>core</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>.<span class='ident'>buffer</span>, <span class='kw-2'>&</span><span class='self'>self</span>.<span class='ident'>state</span>);
<span class='self'>self</span>.<span class='ident'>index</span> <span class='op'>=</span> <span class='number'>0</span>;
<span class='comment'>// update 128-bit counter</span>
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>12</span>] <span class='op'>=</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>12</span>] <span class='op'>+</span> <span class='ident'>w</span>(<span class='number'>1</span>);
<span class='kw'>if</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>12</span>] <span class='op'>!=</span> <span class='ident'>w</span>(<span class='number'>0</span>) { <span class='kw'>return</span> };
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>13</span>] <span class='op'>=</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>13</span>] <span class='op'>+</span> <span class='ident'>w</span>(<span class='number'>1</span>);
<span class='kw'>if</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>13</span>] <span class='op'>!=</span> <span class='ident'>w</span>(<span class='number'>0</span>) { <span class='kw'>return</span> };
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>14</span>] <span class='op'>=</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>14</span>] <span class='op'>+</span> <span class='ident'>w</span>(<span class='number'>1</span>);
<span class='kw'>if</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>14</span>] <span class='op'>!=</span> <span class='ident'>w</span>(<span class='number'>0</span>) { <span class='kw'>return</span> };
<span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>15</span>] <span class='op'>=</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>15</span>] <span class='op'>+</span> <span class='ident'>w</span>(<span class='number'>1</span>);
}
}
<span class='kw'>impl</span> <span class='ident'>Rng</span> <span class='kw'>for</span> <span class='ident'>ChaChaRng</span> {
<span class='attribute'>#[<span class='ident'>inline</span>]</span>
<span class='kw'>fn</span> <span class='ident'>next_u32</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>) <span class='op'>-></span> <span class='ident'>u32</span> {
<span class='kw'>if</span> <span class='self'>self</span>.<span class='ident'>index</span> <span class='op'>==</span> <span class='ident'>STATE_WORDS</span> {
<span class='self'>self</span>.<span class='ident'>update</span>();
}
<span class='kw'>let</span> <span class='ident'>value</span> <span class='op'>=</span> <span class='self'>self</span>.<span class='ident'>buffer</span>[<span class='self'>self</span>.<span class='ident'>index</span> <span class='op'>%</span> <span class='ident'>STATE_WORDS</span>];
<span class='self'>self</span>.<span class='ident'>index</span> <span class='op'>+=</span> <span class='number'>1</span>;
<span class='ident'>value</span>.<span class='number'>0</span>
}
}
<span class='kw'>impl</span><span class='op'><</span><span class='lifetime'>'a</span><span class='op'>></span> <span class='ident'>SeedableRng</span><span class='op'><</span><span class='kw-2'>&</span><span class='lifetime'>'a</span> [<span class='ident'>u32</span>]<span class='op'>></span> <span class='kw'>for</span> <span class='ident'>ChaChaRng</span> {
<span class='kw'>fn</span> <span class='ident'>reseed</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>, <span class='ident'>seed</span>: <span class='kw-2'>&</span><span class='lifetime'>'a</span> [<span class='ident'>u32</span>]) {
<span class='comment'>// reset state</span>
<span class='self'>self</span>.<span class='ident'>init</span>(<span class='kw-2'>&</span>[<span class='number'>0u32</span>; <span class='ident'>KEY_WORDS</span>]);
<span class='comment'>// set key in place</span>
<span class='kw'>let</span> <span class='ident'>key</span> <span class='op'>=</span> <span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='self'>self</span>.<span class='ident'>state</span>[<span class='number'>4</span> .. <span class='number'>4</span><span class='op'>+</span><span class='ident'>KEY_WORDS</span>];
<span class='kw'>for</span> (<span class='ident'>k</span>, <span class='ident'>s</span>) <span class='kw'>in</span> <span class='ident'>key</span>.<span class='ident'>iter_mut</span>().<span class='ident'>zip</span>(<span class='ident'>seed</span>.<span class='ident'>iter</span>()) {
<span class='kw-2'>*</span><span class='ident'>k</span> <span class='op'>=</span> <span class='ident'>w</span>(<span class='kw-2'>*</span><span class='ident'>s</span>);
}
}
<span class='doccomment'>/// Create a ChaCha generator from a seed,</span>
<span class='doccomment'>/// obtained from a variable-length u32 array.</span>
<span class='doccomment'>/// Only up to 8 words are used; if less than 8</span>
<span class='doccomment'>/// words are used, the remaining are set to zero.</span>
<span class='kw'>fn</span> <span class='ident'>from_seed</span>(<span class='ident'>seed</span>: <span class='kw-2'>&</span><span class='lifetime'>'a</span> [<span class='ident'>u32</span>]) <span class='op'>-></span> <span class='ident'>ChaChaRng</span> {
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>rng</span> <span class='op'>=</span> <span class='ident'>EMPTY</span>;
<span class='ident'>rng</span>.<span class='ident'>reseed</span>(<span class='ident'>seed</span>);
<span class='ident'>rng</span>
}
}
<span class='kw'>impl</span> <span class='ident'>Rand</span> <span class='kw'>for</span> <span class='ident'>ChaChaRng</span> {
<span class='kw'>fn</span> <span class='ident'>rand</span><span class='op'><</span><span class='ident'>R</span>: <span class='ident'>Rng</span><span class='op'>></span>(<span class='ident'>other</span>: <span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='ident'>R</span>) <span class='op'>-></span> <span class='ident'>ChaChaRng</span> {
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>key</span> : [<span class='ident'>u32</span>; <span class='ident'>KEY_WORDS</span>] <span class='op'>=</span> [<span class='number'>0</span>; <span class='ident'>KEY_WORDS</span>];
<span class='kw'>for</span> <span class='ident'>word</span> <span class='kw'>in</span> <span class='ident'>key</span>.<span class='ident'>iter_mut</span>() {
<span class='kw-2'>*</span><span class='ident'>word</span> <span class='op'>=</span> <span class='ident'>other</span>.<span class='ident'>gen</span>();
}
<span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='kw-2'>&</span><span class='ident'>key</span>[..])
}
}
<span class='attribute'>#[<span class='ident'>cfg</span>(<span class='ident'>test</span>)]</span>
<span class='kw'>mod</span> <span class='ident'>test</span> {
<span class='kw'>use</span> {<span class='ident'>Rng</span>, <span class='ident'>SeedableRng</span>};
<span class='kw'>use</span> <span class='kw'>super</span>::<span class='ident'>ChaChaRng</span>;
<span class='attribute'>#[<span class='ident'>test</span>]</span>
<span class='kw'>fn</span> <span class='ident'>test_rng_rand_seeded</span>() {
<span class='kw'>let</span> <span class='ident'>s</span> <span class='op'>=</span> ::<span class='ident'>test</span>::<span class='ident'>rng</span>().<span class='ident'>gen_iter</span>::<span class='op'><</span><span class='ident'>u32</span><span class='op'>></span>().<span class='ident'>take</span>(<span class='number'>8</span>).<span class='ident'>collect</span>::<span class='op'><</span><span class='ident'>Vec</span><span class='op'><</span><span class='ident'>u32</span><span class='op'>>></span>();
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>ra</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='kw-2'>&</span><span class='ident'>s</span>[..]);
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>rb</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='kw-2'>&</span><span class='ident'>s</span>[..]);
<span class='macro'>assert</span><span class='macro'>!</span>(::<span class='ident'>test</span>::<span class='ident'>iter_eq</span>(<span class='ident'>ra</span>.<span class='ident'>gen_ascii_chars</span>().<span class='ident'>take</span>(<span class='number'>100</span>),
<span class='ident'>rb</span>.<span class='ident'>gen_ascii_chars</span>().<span class='ident'>take</span>(<span class='number'>100</span>)));
}
<span class='attribute'>#[<span class='ident'>test</span>]</span>
<span class='kw'>fn</span> <span class='ident'>test_rng_seeded</span>() {
<span class='kw'>let</span> <span class='ident'>seed</span> : <span class='kw-2'>&</span>[_] <span class='op'>=</span> <span class='kw-2'>&</span>[<span class='number'>0</span>,<span class='number'>1</span>,<span class='number'>2</span>,<span class='number'>3</span>,<span class='number'>4</span>,<span class='number'>5</span>,<span class='number'>6</span>,<span class='number'>7</span>];
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>ra</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='ident'>seed</span>);
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>rb</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='ident'>seed</span>);
<span class='macro'>assert</span><span class='macro'>!</span>(::<span class='ident'>test</span>::<span class='ident'>iter_eq</span>(<span class='ident'>ra</span>.<span class='ident'>gen_ascii_chars</span>().<span class='ident'>take</span>(<span class='number'>100</span>),
<span class='ident'>rb</span>.<span class='ident'>gen_ascii_chars</span>().<span class='ident'>take</span>(<span class='number'>100</span>)));
}
<span class='attribute'>#[<span class='ident'>test</span>]</span>
<span class='kw'>fn</span> <span class='ident'>test_rng_reseed</span>() {
<span class='kw'>let</span> <span class='ident'>s</span> <span class='op'>=</span> ::<span class='ident'>test</span>::<span class='ident'>rng</span>().<span class='ident'>gen_iter</span>::<span class='op'><</span><span class='ident'>u32</span><span class='op'>></span>().<span class='ident'>take</span>(<span class='number'>8</span>).<span class='ident'>collect</span>::<span class='op'><</span><span class='ident'>Vec</span><span class='op'><</span><span class='ident'>u32</span><span class='op'>>></span>();
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>r</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='kw-2'>&</span><span class='ident'>s</span>[..]);
<span class='kw'>let</span> <span class='ident'>string1</span>: <span class='ident'>String</span> <span class='op'>=</span> <span class='ident'>r</span>.<span class='ident'>gen_ascii_chars</span>().<span class='ident'>take</span>(<span class='number'>100</span>).<span class='ident'>collect</span>();
<span class='ident'>r</span>.<span class='ident'>reseed</span>(<span class='kw-2'>&</span><span class='ident'>s</span>);
<span class='kw'>let</span> <span class='ident'>string2</span>: <span class='ident'>String</span> <span class='op'>=</span> <span class='ident'>r</span>.<span class='ident'>gen_ascii_chars</span>().<span class='ident'>take</span>(<span class='number'>100</span>).<span class='ident'>collect</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>string1</span>, <span class='ident'>string2</span>);
}
<span class='attribute'>#[<span class='ident'>test</span>]</span>
<span class='kw'>fn</span> <span class='ident'>test_rng_true_values</span>() {
<span class='comment'>// Test vectors 1 and 2 from</span>
<span class='comment'>// http://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04</span>
<span class='kw'>let</span> <span class='ident'>seed</span> : <span class='kw-2'>&</span>[_] <span class='op'>=</span> <span class='kw-2'>&</span>[<span class='number'>0u32</span>; <span class='number'>8</span>];
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>ra</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='ident'>seed</span>);
<span class='kw'>let</span> <span class='ident'>v</span> <span class='op'>=</span> (<span class='number'>0</span>..<span class='number'>16</span>).<span class='ident'>map</span>(<span class='op'>|</span>_<span class='op'>|</span> <span class='ident'>ra</span>.<span class='ident'>next_u32</span>()).<span class='ident'>collect</span>::<span class='op'><</span><span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>>></span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>v</span>,
<span class='macro'>vec</span><span class='macro'>!</span>(<span class='number'>0xade0b876</span>, <span class='number'>0x903df1a0</span>, <span class='number'>0xe56a5d40</span>, <span class='number'>0x28bd8653</span>,
<span class='number'>0xb819d2bd</span>, <span class='number'>0x1aed8da0</span>, <span class='number'>0xccef36a8</span>, <span class='number'>0xc70d778b</span>,
<span class='number'>0x7c5941da</span>, <span class='number'>0x8d485751</span>, <span class='number'>0x3fe02477</span>, <span class='number'>0x374ad8b8</span>,
<span class='number'>0xf4b8436a</span>, <span class='number'>0x1ca11815</span>, <span class='number'>0x69b687c3</span>, <span class='number'>0x8665eeb2</span>));
<span class='kw'>let</span> <span class='ident'>v</span> <span class='op'>=</span> (<span class='number'>0</span>..<span class='number'>16</span>).<span class='ident'>map</span>(<span class='op'>|</span>_<span class='op'>|</span> <span class='ident'>ra</span>.<span class='ident'>next_u32</span>()).<span class='ident'>collect</span>::<span class='op'><</span><span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>>></span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>v</span>,
<span class='macro'>vec</span><span class='macro'>!</span>(<span class='number'>0xbee7079f</span>, <span class='number'>0x7a385155</span>, <span class='number'>0x7c97ba98</span>, <span class='number'>0x0d082d73</span>,
<span class='number'>0xa0290fcb</span>, <span class='number'>0x6965e348</span>, <span class='number'>0x3e53c612</span>, <span class='number'>0xed7aee32</span>,
<span class='number'>0x7621b729</span>, <span class='number'>0x434ee69c</span>, <span class='number'>0xb03371d5</span>, <span class='number'>0xd539d874</span>,
<span class='number'>0x281fed31</span>, <span class='number'>0x45fb0a51</span>, <span class='number'>0x1f0ae1ac</span>, <span class='number'>0x6f4d794b</span>));
<span class='kw'>let</span> <span class='ident'>seed</span> : <span class='kw-2'>&</span>[_] <span class='op'>=</span> <span class='kw-2'>&</span>[<span class='number'>0</span>,<span class='number'>1</span>,<span class='number'>2</span>,<span class='number'>3</span>,<span class='number'>4</span>,<span class='number'>5</span>,<span class='number'>6</span>,<span class='number'>7</span>];
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>ra</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='ident'>seed</span>);
<span class='comment'>// Store the 17*i-th 32-bit word,</span>
<span class='comment'>// i.e., the i-th word of the i-th 16-word block</span>
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>v</span> : <span class='ident'>Vec</span><span class='op'><</span><span class='ident'>u32</span><span class='op'>></span> <span class='op'>=</span> <span class='ident'>Vec</span>::<span class='ident'>new</span>();
<span class='kw'>for</span> _ <span class='kw'>in</span> <span class='number'>0</span>..<span class='number'>16</span> {
<span class='ident'>v</span>.<span class='ident'>push</span>(<span class='ident'>ra</span>.<span class='ident'>next_u32</span>());
<span class='kw'>for</span> _ <span class='kw'>in</span> <span class='number'>0</span>..<span class='number'>16</span> {
<span class='ident'>ra</span>.<span class='ident'>next_u32</span>();
}
}
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>v</span>,
<span class='macro'>vec</span><span class='macro'>!</span>(<span class='number'>0xf225c81a</span>, <span class='number'>0x6ab1be57</span>, <span class='number'>0x04d42951</span>, <span class='number'>0x70858036</span>,
<span class='number'>0x49884684</span>, <span class='number'>0x64efec72</span>, <span class='number'>0x4be2d186</span>, <span class='number'>0x3615b384</span>,
<span class='number'>0x11cfa18e</span>, <span class='number'>0xd3c50049</span>, <span class='number'>0x75c775f6</span>, <span class='number'>0x434c6530</span>,
<span class='number'>0x2c5bad8f</span>, <span class='number'>0x898881dc</span>, <span class='number'>0x5f1c86d9</span>, <span class='number'>0xc1f8e7f4</span>));
}
<span class='attribute'>#[<span class='ident'>test</span>]</span>
<span class='kw'>fn</span> <span class='ident'>test_rng_clone</span>() {
<span class='kw'>let</span> <span class='ident'>seed</span> : <span class='kw-2'>&</span>[_] <span class='op'>=</span> <span class='kw-2'>&</span>[<span class='number'>0u32</span>; <span class='number'>8</span>];
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>rng</span>: <span class='ident'>ChaChaRng</span> <span class='op'>=</span> <span class='ident'>SeedableRng</span>::<span class='ident'>from_seed</span>(<span class='ident'>seed</span>);
<span class='kw'>let</span> <span class='kw-2'>mut</span> <span class='ident'>clone</span> <span class='op'>=</span> <span class='ident'>rng</span>.<span class='ident'>clone</span>();
<span class='kw'>for</span> _ <span class='kw'>in</span> <span class='number'>0</span>..<span class='number'>16</span> {
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>rng</span>.<span class='ident'>next_u64</span>(), <span class='ident'>clone</span>.<span class='ident'>next_u64</span>());
}
}
}
</pre>
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