Initial project import

tools/v/vlib/hash/crc64/crc64.v

@@ -0,0 +1,80 @@
+// 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.
+
+// This is a pure V implementation of CRC64, providing one standard variant:
+// CRC-64-ECMA-182 (poly 0x42F0E1EBA9EA3693, init 0, refin false, refout false, xorout 0).
+module crc64
+
+// Polynomial constants for CRC-64
+pub const ecma = u64(0x42F0E1EBA9EA3693)
+
+struct Crc64 {
+mut:
+	table []u64
+}
+
+// generate_table populates a 256-word MSB-first lookup table for `poly`.
+@[direct_array_access]
+fn (mut c Crc64) generate_table(poly u64) {
+	c.table = []u64{len: 256}
+	for i in 0 .. 256 {
+		mut crc := u64(i) << 56
+		for _ in 0 .. 8 {
+			if crc & (u64(1) << 63) != 0 {
+				crc = (crc << 1) ^ poly
+			} else {
+				crc <<= 1
+			}
+		}
+		c.table[i] = crc
+	}
+}
+
+@[direct_array_access]
+fn (c &Crc64) update64(crc u64, b []u8) u64 {
+	mut next := crc
+	for i in 0 .. b.len {
+		next = c.table[u8(next >> 56) ^ b[i]] ^ (next << 8)
+	}
+	return next
+}
+
+// update_state updates an internal CRC state with the bytes in `b`.
+// For CRC-64-ECMA-182, use state 0 for a new stream.
+pub fn (c &Crc64) update_state(state u64, b []u8) u64 {
+	return c.update64(state, b)
+}
+
+// checksum returns the CRC-64 checksum of data `b` by using the polynomial represented by `c`'s table.
+pub fn (c &Crc64) checksum(b []u8) u64 {
+	return c.update_state(u64(0), b)
+}
+
+// update returns the updated CRC-64 checksum for `b`, starting from `crc`.
+// Use `crc = 0` for a fresh checksum, or pass a previous result to continue streaming.
+pub fn (c &Crc64) update(crc u64, b []u8) u64 {
+	return c.update_state(crc, b)
+}
+
+// new creates a `Crc64` polynomial.
+pub fn new(poly u64) &Crc64 {
+	mut c := &Crc64{}
+	c.generate_table(poly)
+	return c
+}
+
+// sum_with_poly calculates the CRC-64 checksum of `b` for the provided polynomial.
+pub fn sum_with_poly(poly u64, b []u8) u64 {
+	return match poly {
+		ecma { ecma_poly.checksum(b) }
+		else { new(poly).checksum(b) }
+	}
+}
+
+const ecma_poly = new(ecma)
+
+// sum calculates the CRC-64 checksum of `b` by using the ECMA polynomial.
+pub fn sum(b []u8) u64 {
+	return ecma_poly.checksum(b)
+}