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013efaf139
std.crypto.random * cross platform, even freestanding * can't fail. on initialization for some systems requires calling os.getrandom(), in which case there are rare but theoretically possible errors. The code panics in these cases, however the application may choose to override the default seed function and then handle the failure another way. * thread-safe * supports the full Random interface * cryptographically secure * no syscall required to initialize on Linux (AT_RANDOM) * calls arc4random on systems that support it `std.crypto.randomBytes` is removed in favor of `std.crypto.random.bytes`. I moved some of the Random implementations into their own files in the interest of organization. stage2 no longer requires passing a RNG; instead it uses this API. Closes #6704
109 lines
2.6 KiB
Zig
109 lines
2.6 KiB
Zig
// SPDX-License-Identifier: MIT
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// Copyright (c) 2015-2020 Zig Contributors
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// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
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// The MIT license requires this copyright notice to be included in all copies
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// and substantial portions of the software.
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//! Sfc64 pseudo-random number generator from Practically Random.
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//! Fastest engine of pracrand and smallest footprint.
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//! See http://pracrand.sourceforge.net/
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const std = @import("std");
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const Random = std.rand.Random;
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const math = std.math;
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const Sfc64 = @This();
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random: Random,
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a: u64 = undefined,
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b: u64 = undefined,
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c: u64 = undefined,
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counter: u64 = undefined,
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const Rotation = 24;
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const RightShift = 11;
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const LeftShift = 3;
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pub fn init(init_s: u64) Sfc64 {
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var x = Sfc64{
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.random = Random{ .fillFn = fill },
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};
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x.seed(init_s);
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return x;
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}
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fn next(self: *Sfc64) u64 {
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const tmp = self.a +% self.b +% self.counter;
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self.counter += 1;
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self.a = self.b ^ (self.b >> RightShift);
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self.b = self.c +% (self.c << LeftShift);
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self.c = math.rotl(u64, self.c, Rotation) +% tmp;
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return tmp;
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}
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fn seed(self: *Sfc64, init_s: u64) void {
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self.a = init_s;
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self.b = init_s;
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self.c = init_s;
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self.counter = 1;
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var i: u32 = 0;
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while (i < 12) : (i += 1) {
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_ = self.next();
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}
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}
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fn fill(r: *Random, buf: []u8) void {
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const self = @fieldParentPtr(Sfc64, "random", r);
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var i: usize = 0;
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const aligned_len = buf.len - (buf.len & 7);
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// Complete 8 byte segments.
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while (i < aligned_len) : (i += 8) {
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var n = self.next();
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comptime var j: usize = 0;
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inline while (j < 8) : (j += 1) {
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buf[i + j] = @truncate(u8, n);
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n >>= 8;
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}
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}
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// Remaining. (cuts the stream)
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if (i != buf.len) {
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var n = self.next();
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while (i < buf.len) : (i += 1) {
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buf[i] = @truncate(u8, n);
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n >>= 8;
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}
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}
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}
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test "Sfc64 sequence" {
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// Unfortunately there does not seem to be an official test sequence.
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var r = Sfc64.init(0);
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const seq = [_]u64{
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0x3acfa029e3cc6041,
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0xf5b6515bf2ee419c,
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0x1259635894a29b61,
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0xb6ae75395f8ebd6,
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0x225622285ce302e2,
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0x520d28611395cb21,
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0xdb909c818901599d,
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0x8ffd195365216f57,
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0xe8c4ad5e258ac04a,
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0x8f8ef2c89fdb63ca,
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0xf9865b01d98d8e2f,
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0x46555871a65d08ba,
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0x66868677c6298fcd,
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0x2ce15a7e6329f57d,
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0xb2f1833ca91ca79,
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0x4b0890ac9bf453ca,
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};
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for (seq) |s| {
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std.testing.expectEqual(s, r.next());
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}
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}
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