2 files changed, 77 insertions, 0 deletions
diff --git a/v_windows/v/vlib/hash/crc32/crc32.v b/v_windows/v/vlib/hash/crc32/crc32.v
new file mode 100644
index 0000000..d29aa12
--- /dev/null
+++ b/v_windows/v/vlib/hash/crc32/crc32.v
@@ -0,0 +1,63 @@
+// Copyright (c) 2019-2021 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 very basic crc32 implementation
+// at the moment with no architecture optimizations
+module crc32
+
+// polynomials
+pub const (
+	ieee       = u32(0xedb88320)
+	castagnoli = u32(0x82f63b78)
+	koopman    = u32(0xeb31d82e)
+)
+
+// The size of a CRC-32 checksum in bytes.
+const (
+	size = 4
+)
+
+struct Crc32 {
+mut:
+	table []u32
+}
+
+fn (mut c Crc32) generate_table(poly int) {
+	for i in 0 .. 256 {
+		mut crc := u32(i)
+		for _ in 0 .. 8 {
+			if crc & u32(1) == u32(1) {
+				crc = (crc >> 1) ^ u32(poly)
+			} else {
+				crc >>= u32(1)
+			}
+		}
+		c.table << crc
+	}
+}
+
+fn (c &Crc32) sum32(b []byte) u32 {
+	mut crc := ~u32(0)
+	for i in 0 .. b.len {
+		crc = c.table[byte(crc) ^ b[i]] ^ (crc >> 8)
+	}
+	return ~crc
+}
+
+pub fn (c &Crc32) checksum(b []byte) u32 {
+	return c.sum32(b)
+}
+
+// pass the polynomial to use
+pub fn new(poly int) &Crc32 {
+	mut c := &Crc32{}
+	c.generate_table(poly)
+	return c
+}
+
+// calculate crc32 using ieee
+pub fn sum(b []byte) u32 {
+	c := new(int(crc32.ieee))
+	return c.sum32(b)
+}
diff --git a/v_windows/v/vlib/hash/crc32/crc32_test.v b/v_windows/v/vlib/hash/crc32/crc32_test.v
new file mode 100644
index 0000000..7355179
--- /dev/null
+++ b/v_windows/v/vlib/hash/crc32/crc32_test.v
@@ -0,0 +1,14 @@
+import hash.crc32
+
+fn test_hash_crc32() {
+	b1 := 'testing crc32'.bytes()
+	sum1 := crc32.sum(b1)
+	assert sum1 == u32(1212124400)
+	assert sum1.hex() == '483f8cf0'
+
+	c := crc32.new(int(crc32.ieee))
+	b2 := 'testing crc32 again'.bytes()
+	sum2 := c.checksum(b2)
+	assert sum2 == u32(1420327025)
+	assert sum2.hex() == '54a87871'
+}