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d29871977f
We already have a LICENSE file that covers the Zig Standard Library. We no longer need to remind everyone that the license is MIT in every single file. Previously this was introduced to clarify the situation for a fork of Zig that made Zig's LICENSE file harder to find, and replaced it with their own license that required annual payments to their company. However that fork now appears to be dead. So there is no need to reinforce the copyright notice in every single file.
135 lines
3.2 KiB
Zig
135 lines
3.2 KiB
Zig
//! 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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try std.testing.expectEqual(s, r.next());
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}
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}
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test "Sfc64 fill" {
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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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var buf0: [8]u8 = undefined;
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var buf1: [7]u8 = undefined;
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std.mem.writeIntLittle(u64, &buf0, s);
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Sfc64.fill(&r.random, &buf1);
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try std.testing.expect(std.mem.eql(u8, buf0[0..7], buf1[0..]));
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}
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}
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