Initial project import

tools/v/vlib/rand/wyrand/wyrand.v

@@ -0,0 +1,87 @@
+// Copyright (c) 2019-2024 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module wyrand
+
+import rand.buffer
+import rand.seed
+
+// Redefinition of some constants that we will need for pseudorandom number generation.
+const wyp0 = u64(0x2d358dccaa6c78a5)
+const wyp1 = u64(0x8bb84b93962eacc9)
+
+pub const seed_len = 2
+
+// WyRandRNG is a RNG based on the WyHash hashing algorithm.
+pub struct WyRandRNG {
+	buffer.PRNGBuffer
+mut:
+	state      u64 = seed.time_seed_64()
+	bytes_left int
+	buffer     u64
+}
+
+// seed sets the seed, needs only two `u32`s in little-endian format as [lower, higher].
+pub fn (mut rng WyRandRNG) seed(seed_data []u32) {
+	if seed_data.len != 2 {
+		eprintln('WyRandRNG needs 2 32-bit unsigned integers as the seed.')
+		exit(1)
+	}
+	rng.state = seed_data[0] | (u64(seed_data[1]) << 32)
+	rng.bytes_left = 0
+	rng.buffer = 0
+}
+
+// byte returns a uniformly distributed pseudorandom 8-bit unsigned positive `byte`.
+@[inline]
+pub fn (mut rng WyRandRNG) u8() u8 {
+	// Can we extract a value from the buffer?
+	if rng.bytes_left >= 1 {
+		rng.bytes_left -= 1
+		value := u8(rng.buffer)
+		rng.buffer >>= 8
+		return value
+	}
+	// Add a new value to the buffer
+	rng.buffer = rng.u64()
+	rng.bytes_left = 7
+	value := u8(rng.buffer)
+	rng.buffer >>= 8
+	return value
+}
+
+// u16 returns a pseudorandom 16bit int in range `[0, 2¹⁶)`.
+@[inline]
+pub fn (mut rng WyRandRNG) u16() u16 {
+	if rng.bytes_left >= 2 {
+		rng.bytes_left -= 2
+		value := u16(rng.buffer)
+		rng.buffer >>= 16
+		return value
+	}
+	ans := rng.u64()
+	rng.buffer = ans >> 16
+	rng.bytes_left = 6
+	return u16(ans)
+}
+
+// u32 returns a pseudorandom 32bit int in range `[0, 2³²)`.
+@[inline]
+pub fn (mut rng WyRandRNG) u32() u32 {
+	if rng.bytes_left >= 4 {
+		rng.bytes_left -= 4
+		value := u32(rng.buffer)
+		rng.buffer >>= 32
+		return value
+	}
+	ans := rng.u64()
+	rng.buffer = ans >> 32
+	rng.bytes_left = 4
+	return u32(ans)
+}
+
+// block_size returns the number of bits that the RNG can produce in a single iteration.
+@[inline]
+pub fn (mut rng WyRandRNG) block_size() int {
+	return 64
+}