From 3950be71c13cc3ff82854264d793337df0984fd8 Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Sun, 12 May 2024 01:35:22 +0100
Subject: [PATCH] HPolyC example.

---
 vfs/adiantum/example_test.go | 52 ++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 vfs/adiantum/example_test.go

diff --git a/vfs/adiantum/example_test.go b/vfs/adiantum/example_test.go
new file mode 100644
index 0000000..e7d0eae
--- /dev/null
+++ b/vfs/adiantum/example_test.go
@@ -0,0 +1,52 @@
+//go:build (linux || darwin || windows || freebsd || illumos) && !sqlite3_nosys
+
+package adiantum_test
+
+import (
+	"crypto/rand"
+	"log"
+	"os"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/vfs"
+	"github.com/ncruces/go-sqlite3/vfs/adiantum"
+	"golang.org/x/crypto/argon2"
+	"lukechampine.com/adiantum/hbsh"
+	"lukechampine.com/adiantum/hpolyc"
+)
+
+func ExampleRegister_hpolyc() {
+	adiantum.Register("hpolyc", vfs.Find(""), hpolycCreator{})
+
+	db, err := sqlite3.Open("file:demo.db?vfs=hpolyc" +
+		"&textkey=correct+horse+battery+staple")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.Remove("./demo.db")
+	defer db.Close()
+	// Output:
+}
+
+type hpolycCreator struct{}
+
+// HBSH creates an HBSH cipher given a key.
+func (hpolycCreator) HBSH(key []byte) *hbsh.HBSH {
+	if len(key) != 32 {
+		// Key is not appropriate, return nil.
+		return nil
+	}
+	return hpolyc.New(key)
+}
+
+// KDF gets a key from a secret.
+func (hpolycCreator) KDF(secret string) []byte {
+	if secret == "" {
+		// No secret is given, generate a random key.
+		key := make([]byte, 32)
+		n, _ := rand.Read(key)
+		return key[:n]
+	}
+	// Hash the secret with a KDF.
+	return argon2.IDKey([]byte(secret), []byte("hpolyc"), 3, 64*1024, 4, 32)
+}