sgx_rand/src/isaac.rs - incubator-teaclave-sgx-sdk - Git at Google

 // Copyright (c) 2017 Baidu, Inc. All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 //  * Redistributions of source code must retain the above copyright
 //    notice, this list of conditions and the following disclaimer.
 //  * Redistributions in binary form must reproduce the above copyright
 //    notice, this list of conditions and the following disclaimer in
 //    the documentation and/or other materials provided with the
 //    distribution.
 //  * Neither the name of Baidu, Inc., nor the names of its
 //    contributors may be used to endorse or promote products derived
 //    from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 //! The ISAAC random number generator.

 #![allow(non_camel_case_types)]

 use std::slice;
 use std::iter::repeat;
 use std::num::Wrapping as w;
 use std::fmt;

 use {Rng, SeedableRng, Rand, w32, w64};

 const RAND_SIZE_LEN: usize = 8;
 const RAND_SIZE: u32 = 1 << RAND_SIZE_LEN;
 const RAND_SIZE_USIZE: usize = 1 << RAND_SIZE_LEN;

 /// A random number generator that uses the ISAAC algorithm[1].
 ///
 /// The ISAAC algorithm is generally accepted as suitable for
 /// cryptographic purposes, but this implementation has not be
 /// verified as such. Prefer a generator like `OsRng` that defers to
 /// the operating system for cases that need high security.
 ///
 /// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
 /// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
 #[derive(Copy)]
 pub struct IsaacRng {
     cnt: u32,
     rsl: [w32; RAND_SIZE_USIZE],
     mem: [w32; RAND_SIZE_USIZE],
     a: w32,
     b: w32,
     c: w32,
 }

 static EMPTY: IsaacRng = IsaacRng {
     cnt: 0,
     rsl: [w(0); RAND_SIZE_USIZE],
     mem: [w(0); RAND_SIZE_USIZE],
     a: w(0), b: w(0), c: w(0),
 };

 impl IsaacRng {

     /// Create an ISAAC random number generator using the default
     /// fixed seed.
     pub fn new_unseeded() -> IsaacRng {
         let mut rng = EMPTY;
         rng.init(false);
         rng
     }

     /// Initialises `self`. If `use_rsl` is true, then use the current value
     /// of `rsl` as a seed, otherwise construct one algorithmically (not
     /// randomly).
     fn init(&mut self, use_rsl: bool) {
         let mut a = w(0x9e3779b9);
         let mut b = a;
         let mut c = a;
         let mut d = a;
         let mut e = a;
         let mut f = a;
         let mut g = a;
         let mut h = a;

         macro_rules! mix {
             () => {{
                 a=a^(b<<11); d=d+a; b=b+c;
                 b=b^(c>>2);  e=e+b; c=c+d;
                 c=c^(d<<8);  f=f+c; d=d+e;
                 d=d^(e>>16); g=g+d; e=e+f;
                 e=e^(f<<10); h=h+e; f=f+g;
                 f=f^(g>>4);  a=a+f; g=g+h;
                 g=g^(h<<8);  b=b+g; h=h+a;
                 h=h^(a>>9);  c=c+h; a=a+b;
             }}
         }

         for _ in 0..4 {
             mix!();
         }

         if use_rsl {
             macro_rules! memloop {
                 ($arr:expr) => {{
                     for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
                         a=a+$arr[i  ]; b=b+$arr[i+1];
                         c=c+$arr[i+2]; d=d+$arr[i+3];
                         e=e+$arr[i+4]; f=f+$arr[i+5];
                         g=g+$arr[i+6]; h=h+$arr[i+7];
                         mix!();
                         self.mem[i  ]=a; self.mem[i+1]=b;
                         self.mem[i+2]=c; self.mem[i+3]=d;
                         self.mem[i+4]=e; self.mem[i+5]=f;
                         self.mem[i+6]=g; self.mem[i+7]=h;
                     }
                 }}
             }

             memloop!(self.rsl);
             memloop!(self.mem);
         } else {
             for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
                 mix!();
                 self.mem[i  ]=a; self.mem[i+1]=b;
                 self.mem[i+2]=c; self.mem[i+3]=d;
                 self.mem[i+4]=e; self.mem[i+5]=f;
                 self.mem[i+6]=g; self.mem[i+7]=h;
             }
         }

         self.isaac();
     }

     /// Refills the output buffer (`self.rsl`)
     #[inline]
     fn isaac(&mut self) {
         self.c = self.c + w(1);
         // abbreviations
         let mut a = self.a;
         let mut b = self.b + self.c;

         const MIDPOINT: usize = RAND_SIZE_USIZE / 2;

         macro_rules! ind {
             ($x:expr) => ( self.mem[($x >> 2usize).0 as usize & (RAND_SIZE_USIZE - 1)] )
         }

         let r = [(0, MIDPOINT), (MIDPOINT, 0)];
         for &(mr_offset, m2_offset) in r.iter() {

             macro_rules! rngstepp {
                 ($j:expr, $shift:expr) => {{
                     let base = $j;
                     let mix = a << $shift;

                     let x = self.mem[base  + mr_offset];
                     a = (a ^ mix) + self.mem[base + m2_offset];
                     let y = ind!(x) + a + b;
                     self.mem[base + mr_offset] = y;

                     b = ind!(y >> RAND_SIZE_LEN) + x;
                     self.rsl[base + mr_offset] = b;
                 }}
             }

             macro_rules! rngstepn {
                 ($j:expr, $shift:expr) => {{
                     let base = $j;
                     let mix = a >> $shift;

                     let x = self.mem[base  + mr_offset];
                     a = (a ^ mix) + self.mem[base + m2_offset];
                     let y = ind!(x) + a + b;
                     self.mem[base + mr_offset] = y;

                     b = ind!(y >> RAND_SIZE_LEN) + x;
                     self.rsl[base + mr_offset] = b;
                 }}
             }

             for i in (0..MIDPOINT/4).map(|i| i * 4) {
                 rngstepp!(i + 0, 13);
                 rngstepn!(i + 1, 6);
                 rngstepp!(i + 2, 2);
                 rngstepn!(i + 3, 16);
             }
         }

         self.a = a;
         self.b = b;
         self.cnt = RAND_SIZE;
     }
 }

 // Cannot be derived because [u32; 256] does not implement Clone
 impl Clone for IsaacRng {
     fn clone(&self) -> IsaacRng {
         *self
     }
 }

 impl Rng for IsaacRng {
     #[inline]
     fn next_u32(&mut self) -> u32 {
         if self.cnt == 0 {
             // make some more numbers
             self.isaac();
         }
         self.cnt -= 1;

         // self.cnt is at most RAND_SIZE, but that is before the
         // subtraction above. We want to index without bounds
         // checking, but this could lead to incorrect code if someone
         // misrefactors, so we check, sometimes.
         //
         // (Changes here should be reflected in Isaac64Rng.next_u64.)
         debug_assert!(self.cnt < RAND_SIZE);

         // (the % is cheaply telling the optimiser that we're always
         // in bounds, without unsafe. NB. this is a power of two, so
         // it optimises to a bitwise mask).
         self.rsl[(self.cnt % RAND_SIZE) as usize].0
     }
 }

 impl<'a> SeedableRng<&'a [u32]> for IsaacRng {
     fn reseed(&mut self, seed: &'a [u32]) {
         // make the seed into [seed[0], seed[1], ..., seed[seed.len()
         // - 1], 0, 0, ...], to fill rng.rsl.
         let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u32));

         for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
             *rsl_elem = w(seed_elem);
         }
         self.cnt = 0;
         self.a = w(0);
         self.b = w(0);
         self.c = w(0);

         self.init(true);
     }

     /// Create an ISAAC random number generator with a seed. This can
     /// be any length, although the maximum number of elements used is
     /// 256 and any more will be silently ignored. A generator
     /// constructed with a given seed will generate the same sequence
     /// of values as all other generators constructed with that seed.
     fn from_seed(seed: &'a [u32]) -> IsaacRng {
         let mut rng = EMPTY;
         rng.reseed(seed);
         rng
     }
 }

 impl Rand for IsaacRng {
     fn rand<R: Rng>(other: &mut R) -> IsaacRng {
         let mut ret = EMPTY;
         unsafe {
             let ptr = ret.rsl.as_mut_ptr() as *mut u8;

             let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_USIZE * 4);
             other.fill_bytes(slice);
         }
         ret.cnt = 0;
         ret.a = w(0);
         ret.b = w(0);
         ret.c = w(0);

         ret.init(true);
         return ret;
     }
 }

 impl fmt::Debug for IsaacRng {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "IsaacRng {{}}")
     }
 }

 const RAND_SIZE_64_LEN: usize = 8;
 const RAND_SIZE_64: usize = 1 << RAND_SIZE_64_LEN;

 /// A random number generator that uses ISAAC-64[1], the 64-bit
 /// variant of the ISAAC algorithm.
 ///
 /// The ISAAC algorithm is generally accepted as suitable for
 /// cryptographic purposes, but this implementation has not be
 /// verified as such. Prefer a generator like `OsRng` that defers to
 /// the operating system for cases that need high security.
 ///
 /// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
 /// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
 #[derive(Copy)]
 pub struct Isaac64Rng {
     cnt: usize,
     rsl: [w64; RAND_SIZE_64],
     mem: [w64; RAND_SIZE_64],
     a: w64,
     b: w64,
     c: w64,
 }

 static EMPTY_64: Isaac64Rng = Isaac64Rng {
     cnt: 0,
     rsl: [w(0); RAND_SIZE_64],
     mem: [w(0); RAND_SIZE_64],
     a: w(0), b: w(0), c: w(0),
 };

 impl Isaac64Rng {
     /// Create a 64-bit ISAAC random number generator using the
     /// default fixed seed.
     pub fn new_unseeded() -> Isaac64Rng {
         let mut rng = EMPTY_64;
         rng.init(false);
         rng
     }

     /// Initialises `self`. If `use_rsl` is true, then use the current value
     /// of `rsl` as a seed, otherwise construct one algorithmically (not
     /// randomly).
     fn init(&mut self, use_rsl: bool) {
         macro_rules! init {
             ($var:ident) => (
                 let mut $var = w(0x9e3779b97f4a7c13);
             )
         }
         init!(a); init!(b); init!(c); init!(d);
         init!(e); init!(f); init!(g); init!(h);

         macro_rules! mix {
             () => {{
                 a=a-e; f=f^(h>>9);  h=h+a;
                 b=b-f; g=g^(a<<9);  a=a+b;
                 c=c-g; h=h^(b>>23); b=b+c;
                 d=d-h; a=a^(c<<15); c=c+d;
                 e=e-a; b=b^(d>>14); d=d+e;
                 f=f-b; c=c^(e<<20); e=e+f;
                 g=g-c; d=d^(f>>17); f=f+g;
                 h=h-d; e=e^(g<<14); g=g+h;
             }}
         }

         for _ in 0..4 {
             mix!();
         }

         if use_rsl {
             macro_rules! memloop {
                 ($arr:expr) => {{
                     for i in (0..RAND_SIZE_64 / 8).map(|i| i * 8) {
                         a=a+$arr[i  ]; b=b+$arr[i+1];
                         c=c+$arr[i+2]; d=d+$arr[i+3];
                         e=e+$arr[i+4]; f=f+$arr[i+5];
                         g=g+$arr[i+6]; h=h+$arr[i+7];
                         mix!();
                         self.mem[i  ]=a; self.mem[i+1]=b;
                         self.mem[i+2]=c; self.mem[i+3]=d;
                         self.mem[i+4]=e; self.mem[i+5]=f;
                         self.mem[i+6]=g; self.mem[i+7]=h;
                     }
                 }}
             }

             memloop!(self.rsl);
             memloop!(self.mem);
         } else {
             for i in (0..RAND_SIZE_64 / 8).map(|i| i * 8) {
                 mix!();
                 self.mem[i  ]=a; self.mem[i+1]=b;
                 self.mem[i+2]=c; self.mem[i+3]=d;
                 self.mem[i+4]=e; self.mem[i+5]=f;
                 self.mem[i+6]=g; self.mem[i+7]=h;
             }
         }

         self.isaac64();
     }

     /// Refills the output buffer (`self.rsl`)
     fn isaac64(&mut self) {
         self.c = self.c + w(1);
         // abbreviations
         let mut a = self.a;
         let mut b = self.b + self.c;
         const MIDPOINT: usize =  RAND_SIZE_64 / 2;
         const MP_VEC: [(usize, usize); 2] = [(0,MIDPOINT), (MIDPOINT, 0)];
         macro_rules! ind {
             ($x:expr) => {
                 *self.mem.get_unchecked((($x >> 3usize).0 as usize) & (RAND_SIZE_64 - 1))
             }
         }

         for &(mr_offset, m2_offset) in MP_VEC.iter() {
             for base in (0..MIDPOINT / 4).map(|i| i * 4) {

                 macro_rules! rngstepp {
                     ($j:expr, $shift:expr) => {{
                         let base = base + $j;
                         let mix = a ^ (a << $shift);
                         let mix = if $j == 0 {!mix} else {mix};

                         unsafe {
                             let x = *self.mem.get_unchecked(base + mr_offset);
                             a = mix + *self.mem.get_unchecked(base + m2_offset);
                             let y = ind!(x) + a + b;
                             *self.mem.get_unchecked_mut(base + mr_offset) = y;

                             b = ind!(y >> RAND_SIZE_64_LEN) + x;
                             *self.rsl.get_unchecked_mut(base + mr_offset) = b;
                         }
                     }}
                 }

                 macro_rules! rngstepn {
                     ($j:expr, $shift:expr) => {{
                         let base = base + $j;
                         let mix = a ^ (a >> $shift);
                         let mix = if $j == 0 {!mix} else {mix};

                         unsafe {
                             let x = *self.mem.get_unchecked(base + mr_offset);
                             a = mix + *self.mem.get_unchecked(base + m2_offset);
                             let y = ind!(x) + a + b;
                             *self.mem.get_unchecked_mut(base + mr_offset) = y;

                             b = ind!(y >> RAND_SIZE_64_LEN) + x;
                             *self.rsl.get_unchecked_mut(base + mr_offset) = b;
                         }
                     }}
                 }

                 rngstepp!(0, 21);
                 rngstepn!(1, 5);
                 rngstepp!(2, 12);
                 rngstepn!(3, 33);
             }
         }

         self.a = a;
         self.b = b;
         self.cnt = RAND_SIZE_64;
     }
 }

 // Cannot be derived because [u32; 256] does not implement Clone
 impl Clone for Isaac64Rng {
     fn clone(&self) -> Isaac64Rng {
         *self
     }
 }

 impl Rng for Isaac64Rng {
     // FIXME #7771: having next_u32 like this should be unnecessary
     #[inline]
     fn next_u32(&mut self) -> u32 {
         self.next_u64() as u32
     }

     #[inline]
     fn next_u64(&mut self) -> u64 {
         if self.cnt == 0 {
             // make some more numbers
             self.isaac64();
         }
         self.cnt -= 1;

         // See corresponding location in IsaacRng.next_u32 for
         // explanation.
         debug_assert!(self.cnt < RAND_SIZE_64);
         self.rsl[(self.cnt % RAND_SIZE_64) as usize].0
     }
 }

 impl<'a> SeedableRng<&'a [u64]> for Isaac64Rng {
     fn reseed(&mut self, seed: &'a [u64]) {
         // make the seed into [seed[0], seed[1], ..., seed[seed.len()
         // - 1], 0, 0, ...], to fill rng.rsl.
         let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u64));

         for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
             *rsl_elem = w(seed_elem);
         }
         self.cnt = 0;
         self.a = w(0);
         self.b = w(0);
         self.c = w(0);

         self.init(true);
     }

     /// Create an ISAAC random number generator with a seed. This can
     /// be any length, although the maximum number of elements used is
     /// 256 and any more will be silently ignored. A generator
     /// constructed with a given seed will generate the same sequence
     /// of values as all other generators constructed with that seed.
     fn from_seed(seed: &'a [u64]) -> Isaac64Rng {
         let mut rng = EMPTY_64;
         rng.reseed(seed);
         rng
     }
 }

 impl Rand for Isaac64Rng {
     fn rand<R: Rng>(other: &mut R) -> Isaac64Rng {
         let mut ret = EMPTY_64;
         unsafe {
             let ptr = ret.rsl.as_mut_ptr() as *mut u8;

             let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_64 * 8);
             other.fill_bytes(slice);
         }
         ret.cnt = 0;
         ret.a = w(0);
         ret.b = w(0);
         ret.c = w(0);

         ret.init(true);
         return ret;
     }
 }

 impl fmt::Debug for Isaac64Rng {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "Isaac64Rng {{}}")
     }
 }
	// Copyright (c) 2017 Baidu, Inc. All Rights Reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions
	// are met:
	//
	// * Redistributions of source code must retain the above copyright
	// notice, this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above copyright
	// notice, this list of conditions and the following disclaimer in
	// the documentation and/or other materials provided with the
	// distribution.
	// * Neither the name of Baidu, Inc., nor the names of its
	// contributors may be used to endorse or promote products derived
	// from this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	//! The ISAAC random number generator.

	#![allow(non_camel_case_types)]

	use std::slice;
	use std::iter::repeat;
	use std::num::Wrapping as w;
	use std::fmt;

	use {Rng, SeedableRng, Rand, w32, w64};

	const RAND_SIZE_LEN: usize = 8;
	const RAND_SIZE: u32 = 1 << RAND_SIZE_LEN;
	const RAND_SIZE_USIZE: usize = 1 << RAND_SIZE_LEN;

	/// A random number generator that uses the ISAAC algorithm[1].
	///
	/// The ISAAC algorithm is generally accepted as suitable for
	/// cryptographic purposes, but this implementation has not be
	/// verified as such. Prefer a generator like `OsRng` that defers to
	/// the operating system for cases that need high security.
	///
	/// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
	/// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
	#[derive(Copy)]
	pub struct IsaacRng {
	cnt: u32,
	rsl: [w32; RAND_SIZE_USIZE],
	mem: [w32; RAND_SIZE_USIZE],
	a: w32,
	b: w32,
	c: w32,
	}

	static EMPTY: IsaacRng = IsaacRng {
	cnt: 0,
	rsl: [w(0); RAND_SIZE_USIZE],
	mem: [w(0); RAND_SIZE_USIZE],
	a: w(0), b: w(0), c: w(0),
	};

	impl IsaacRng {

	/// Create an ISAAC random number generator using the default
	/// fixed seed.
	pub fn new_unseeded() -> IsaacRng {
	let mut rng = EMPTY;
	rng.init(false);
	rng
	}

	/// Initialises `self`. If `use_rsl` is true, then use the current value
	/// of `rsl` as a seed, otherwise construct one algorithmically (not
	/// randomly).
	fn init(&mut self, use_rsl: bool) {
	let mut a = w(0x9e3779b9);
	let mut b = a;
	let mut c = a;
	let mut d = a;
	let mut e = a;
	let mut f = a;
	let mut g = a;
	let mut h = a;

	macro_rules! mix {
	() => {{
	a=a^(b<<11); d=d+a; b=b+c;
	b=b^(c>>2); e=e+b; c=c+d;
	c=c^(d<<8); f=f+c; d=d+e;
	d=d^(e>>16); g=g+d; e=e+f;
	e=e^(f<<10); h=h+e; f=f+g;
	f=f^(g>>4); a=a+f; g=g+h;
	g=g^(h<<8); b=b+g; h=h+a;
	h=h^(a>>9); c=c+h; a=a+b;
	}}
	}

	for _ in 0..4 {
	mix!();
	}

	if use_rsl {
	macro_rules! memloop {
	($arr:expr) => {{
	for i in (0..RAND_SIZE_USIZE/8).map(\|i\| i * 8) {
	a=a+$arr[i ]; b=b+$arr[i+1];
	c=c+$arr[i+2]; d=d+$arr[i+3];
	e=e+$arr[i+4]; f=f+$arr[i+5];
	g=g+$arr[i+6]; h=h+$arr[i+7];
	mix!();
	self.mem[i ]=a; self.mem[i+1]=b;
	self.mem[i+2]=c; self.mem[i+3]=d;
	self.mem[i+4]=e; self.mem[i+5]=f;
	self.mem[i+6]=g; self.mem[i+7]=h;
	}
	}}
	}

	memloop!(self.rsl);
	memloop!(self.mem);
	} else {
	for i in (0..RAND_SIZE_USIZE/8).map(\|i\| i * 8) {
	mix!();
	self.mem[i ]=a; self.mem[i+1]=b;
	self.mem[i+2]=c; self.mem[i+3]=d;
	self.mem[i+4]=e; self.mem[i+5]=f;
	self.mem[i+6]=g; self.mem[i+7]=h;
	}
	}

	self.isaac();
	}

	/// Refills the output buffer (`self.rsl`)
	#[inline]
	fn isaac(&mut self) {
	self.c = self.c + w(1);
	// abbreviations
	let mut a = self.a;
	let mut b = self.b + self.c;

	const MIDPOINT: usize = RAND_SIZE_USIZE / 2;

	macro_rules! ind {
	($x:expr) => ( self.mem[($x >> 2usize).0 as usize & (RAND_SIZE_USIZE - 1)] )
	}

	let r = [(0, MIDPOINT), (MIDPOINT, 0)];
	for &(mr_offset, m2_offset) in r.iter() {

	macro_rules! rngstepp {
	($j:expr, $shift:expr) => {{
	let base = $j;
	let mix = a << $shift;

	let x = self.mem[base + mr_offset];
	a = (a ^ mix) + self.mem[base + m2_offset];
	let y = ind!(x) + a + b;
	self.mem[base + mr_offset] = y;

	b = ind!(y >> RAND_SIZE_LEN) + x;
	self.rsl[base + mr_offset] = b;
	}}
	}

	macro_rules! rngstepn {
	($j:expr, $shift:expr) => {{
	let base = $j;
	let mix = a >> $shift;

	let x = self.mem[base + mr_offset];
	a = (a ^ mix) + self.mem[base + m2_offset];
	let y = ind!(x) + a + b;
	self.mem[base + mr_offset] = y;

	b = ind!(y >> RAND_SIZE_LEN) + x;
	self.rsl[base + mr_offset] = b;
	}}
	}

	for i in (0..MIDPOINT/4).map(\|i\| i * 4) {
	rngstepp!(i + 0, 13);
	rngstepn!(i + 1, 6);
	rngstepp!(i + 2, 2);
	rngstepn!(i + 3, 16);
	}
	}

	self.a = a;
	self.b = b;
	self.cnt = RAND_SIZE;
	}
	}

	// Cannot be derived because [u32; 256] does not implement Clone
	impl Clone for IsaacRng {
	fn clone(&self) -> IsaacRng {
	*self
	}
	}

	impl Rng for IsaacRng {
	#[inline]
	fn next_u32(&mut self) -> u32 {
	if self.cnt == 0 {
	// make some more numbers
	self.isaac();
	}
	self.cnt -= 1;

	// self.cnt is at most RAND_SIZE, but that is before the
	// subtraction above. We want to index without bounds
	// checking, but this could lead to incorrect code if someone
	// misrefactors, so we check, sometimes.
	//
	// (Changes here should be reflected in Isaac64Rng.next_u64.)
	debug_assert!(self.cnt < RAND_SIZE);

	// (the % is cheaply telling the optimiser that we're always
	// in bounds, without unsafe. NB. this is a power of two, so
	// it optimises to a bitwise mask).
	self.rsl[(self.cnt % RAND_SIZE) as usize].0
	}
	}

	impl<'a> SeedableRng<&'a [u32]> for IsaacRng {
	fn reseed(&mut self, seed: &'a [u32]) {
	// make the seed into [seed[0], seed[1], ..., seed[seed.len()
	// - 1], 0, 0, ...], to fill rng.rsl.
	let seed_iter = seed.iter().map(\|&x\| x).chain(repeat(0u32));

	for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
	*rsl_elem = w(seed_elem);
	}
	self.cnt = 0;
	self.a = w(0);
	self.b = w(0);
	self.c = w(0);

	self.init(true);
	}

	/// Create an ISAAC random number generator with a seed. This can
	/// be any length, although the maximum number of elements used is
	/// 256 and any more will be silently ignored. A generator
	/// constructed with a given seed will generate the same sequence
	/// of values as all other generators constructed with that seed.
	fn from_seed(seed: &'a [u32]) -> IsaacRng {
	let mut rng = EMPTY;
	rng.reseed(seed);
	rng
	}
	}

	impl Rand for IsaacRng {
	fn rand<R: Rng>(other: &mut R) -> IsaacRng {
	let mut ret = EMPTY;
	unsafe {
	let ptr = ret.rsl.as_mut_ptr() as *mut u8;

	let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_USIZE * 4);
	other.fill_bytes(slice);
	}
	ret.cnt = 0;
	ret.a = w(0);
	ret.b = w(0);
	ret.c = w(0);

	ret.init(true);
	return ret;
	}
	}

	impl fmt::Debug for IsaacRng {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	write!(f, "IsaacRng {{}}")
	}
	}

	const RAND_SIZE_64_LEN: usize = 8;
	const RAND_SIZE_64: usize = 1 << RAND_SIZE_64_LEN;

	/// A random number generator that uses ISAAC-64[1], the 64-bit
	/// variant of the ISAAC algorithm.
	///
	/// The ISAAC algorithm is generally accepted as suitable for
	/// cryptographic purposes, but this implementation has not be
	/// verified as such. Prefer a generator like `OsRng` that defers to
	/// the operating system for cases that need high security.
	///
	/// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
	/// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
	#[derive(Copy)]
	pub struct Isaac64Rng {
	cnt: usize,
	rsl: [w64; RAND_SIZE_64],
	mem: [w64; RAND_SIZE_64],
	a: w64,
	b: w64,
	c: w64,
	}

	static EMPTY_64: Isaac64Rng = Isaac64Rng {
	cnt: 0,
	rsl: [w(0); RAND_SIZE_64],
	mem: [w(0); RAND_SIZE_64],
	a: w(0), b: w(0), c: w(0),
	};

	impl Isaac64Rng {
	/// Create a 64-bit ISAAC random number generator using the
	/// default fixed seed.
	pub fn new_unseeded() -> Isaac64Rng {
	let mut rng = EMPTY_64;
	rng.init(false);
	rng
	}

	/// Initialises `self`. If `use_rsl` is true, then use the current value
	/// of `rsl` as a seed, otherwise construct one algorithmically (not
	/// randomly).
	fn init(&mut self, use_rsl: bool) {
	macro_rules! init {
	($var:ident) => (
	let mut $var = w(0x9e3779b97f4a7c13);
	)
	}
	init!(a); init!(b); init!(c); init!(d);
	init!(e); init!(f); init!(g); init!(h);

	macro_rules! mix {
	() => {{
	a=a-e; f=f^(h>>9); h=h+a;
	b=b-f; g=g^(a<<9); a=a+b;
	c=c-g; h=h^(b>>23); b=b+c;
	d=d-h; a=a^(c<<15); c=c+d;
	e=e-a; b=b^(d>>14); d=d+e;
	f=f-b; c=c^(e<<20); e=e+f;
	g=g-c; d=d^(f>>17); f=f+g;
	h=h-d; e=e^(g<<14); g=g+h;
	}}
	}

	for _ in 0..4 {
	mix!();
	}

	if use_rsl {
	macro_rules! memloop {
	($arr:expr) => {{
	for i in (0..RAND_SIZE_64 / 8).map(\|i\| i * 8) {
	a=a+$arr[i ]; b=b+$arr[i+1];
	c=c+$arr[i+2]; d=d+$arr[i+3];
	e=e+$arr[i+4]; f=f+$arr[i+5];
	g=g+$arr[i+6]; h=h+$arr[i+7];
	mix!();
	self.mem[i ]=a; self.mem[i+1]=b;
	self.mem[i+2]=c; self.mem[i+3]=d;
	self.mem[i+4]=e; self.mem[i+5]=f;
	self.mem[i+6]=g; self.mem[i+7]=h;
	}
	}}
	}

	memloop!(self.rsl);
	memloop!(self.mem);
	} else {
	for i in (0..RAND_SIZE_64 / 8).map(\|i\| i * 8) {
	mix!();
	self.mem[i ]=a; self.mem[i+1]=b;
	self.mem[i+2]=c; self.mem[i+3]=d;
	self.mem[i+4]=e; self.mem[i+5]=f;
	self.mem[i+6]=g; self.mem[i+7]=h;
	}
	}

	self.isaac64();
	}

	/// Refills the output buffer (`self.rsl`)
	fn isaac64(&mut self) {
	self.c = self.c + w(1);
	// abbreviations
	let mut a = self.a;
	let mut b = self.b + self.c;
	const MIDPOINT: usize = RAND_SIZE_64 / 2;
	const MP_VEC: [(usize, usize); 2] = [(0,MIDPOINT), (MIDPOINT, 0)];
	macro_rules! ind {
	($x:expr) => {
	*self.mem.get_unchecked((($x >> 3usize).0 as usize) & (RAND_SIZE_64 - 1))
	}
	}

	for &(mr_offset, m2_offset) in MP_VEC.iter() {
	for base in (0..MIDPOINT / 4).map(\|i\| i * 4) {

	macro_rules! rngstepp {
	($j:expr, $shift:expr) => {{
	let base = base + $j;
	let mix = a ^ (a << $shift);
	let mix = if $j == 0 {!mix} else {mix};

	unsafe {
	let x = *self.mem.get_unchecked(base + mr_offset);
	a = mix + *self.mem.get_unchecked(base + m2_offset);
	let y = ind!(x) + a + b;
	*self.mem.get_unchecked_mut(base + mr_offset) = y;

	b = ind!(y >> RAND_SIZE_64_LEN) + x;
	*self.rsl.get_unchecked_mut(base + mr_offset) = b;
	}
	}}
	}

	macro_rules! rngstepn {
	($j:expr, $shift:expr) => {{
	let base = base + $j;
	let mix = a ^ (a >> $shift);
	let mix = if $j == 0 {!mix} else {mix};

	unsafe {
	let x = *self.mem.get_unchecked(base + mr_offset);
	a = mix + *self.mem.get_unchecked(base + m2_offset);
	let y = ind!(x) + a + b;
	*self.mem.get_unchecked_mut(base + mr_offset) = y;

	b = ind!(y >> RAND_SIZE_64_LEN) + x;
	*self.rsl.get_unchecked_mut(base + mr_offset) = b;
	}
	}}
	}

	rngstepp!(0, 21);
	rngstepn!(1, 5);
	rngstepp!(2, 12);
	rngstepn!(3, 33);
	}
	}

	self.a = a;
	self.b = b;
	self.cnt = RAND_SIZE_64;
	}
	}

	// Cannot be derived because [u32; 256] does not implement Clone
	impl Clone for Isaac64Rng {
	fn clone(&self) -> Isaac64Rng {
	*self
	}
	}

	impl Rng for Isaac64Rng {
	// FIXME #7771: having next_u32 like this should be unnecessary
	#[inline]
	fn next_u32(&mut self) -> u32 {
	self.next_u64() as u32
	}

	#[inline]
	fn next_u64(&mut self) -> u64 {
	if self.cnt == 0 {
	// make some more numbers
	self.isaac64();
	}
	self.cnt -= 1;

	// See corresponding location in IsaacRng.next_u32 for
	// explanation.
	debug_assert!(self.cnt < RAND_SIZE_64);
	self.rsl[(self.cnt % RAND_SIZE_64) as usize].0
	}
	}

	impl<'a> SeedableRng<&'a [u64]> for Isaac64Rng {
	fn reseed(&mut self, seed: &'a [u64]) {
	// make the seed into [seed[0], seed[1], ..., seed[seed.len()
	// - 1], 0, 0, ...], to fill rng.rsl.
	let seed_iter = seed.iter().map(\|&x\| x).chain(repeat(0u64));

	for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
	*rsl_elem = w(seed_elem);
	}
	self.cnt = 0;
	self.a = w(0);
	self.b = w(0);
	self.c = w(0);

	self.init(true);
	}

	/// Create an ISAAC random number generator with a seed. This can
	/// be any length, although the maximum number of elements used is
	/// 256 and any more will be silently ignored. A generator
	/// constructed with a given seed will generate the same sequence
	/// of values as all other generators constructed with that seed.
	fn from_seed(seed: &'a [u64]) -> Isaac64Rng {
	let mut rng = EMPTY_64;
	rng.reseed(seed);
	rng
	}
	}

	impl Rand for Isaac64Rng {
	fn rand<R: Rng>(other: &mut R) -> Isaac64Rng {
	let mut ret = EMPTY_64;
	unsafe {
	let ptr = ret.rsl.as_mut_ptr() as *mut u8;

	let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_64 * 8);
	other.fill_bytes(slice);
	}
	ret.cnt = 0;
	ret.a = w(0);
	ret.b = w(0);
	ret.c = w(0);

	ret.init(true);
	return ret;
	}
	}

	impl fmt::Debug for Isaac64Rng {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
	write!(f, "Isaac64Rng {{}}")
	}
	}