chore: move from tools/dsa (#1)

Moved the implementation of this hash table from `tools/dsa` #1.

Reviewed-on: #1
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

hash_example_test.go

@@ -0,0 +1,34 @@
+package cuckoo_test
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"git.maximhutz.com/tools/go-cuckoo"
+)
+
+func NewStringHash(seed uint64) cuckoo.Hash[string] {
+	key := binary.LittleEndian.AppendUint64(nil, seed)
+	hash := hmac.New(sha256.New, key)
+
+	return func(key string) uint64 {
+		hash.Reset()
+		// This will never return an error, as part of the [hash.Hash] contract. We
+		// can safely ignore it.
+		(io.WriteString(hash, key))
+		return binary.LittleEndian.Uint64(hash.Sum(nil))
+	}
+}
+
+func ExampleHash_stringHash() {
+	hash := NewStringHash(1)
+	fmt.Printf("Digest 'Hello, world!': %x\n", hash("Hello, world!"))
+	fmt.Printf("Digest 'Hello, world?': %x\n", hash("Hello, world?"))
+
+	// Output:
+	// Digest 'Hello, world!': dc6602d6edcdf549
+	// Digest 'Hello, world?': 432c2ddc1ae9f14b
+}