feat: Add p/demo/avlhelpers. See the PR.

Signed-off-by: Jeff Thompson <[email protected]>

examples/gno.land/p/demo/avlhelpers/avlhelpers.gno

@@ -0,0 +1,32 @@
+package avlhelpers
+
+import (
+	"gno.land/p/demo/avl"
+)
+
+// Get a list of keys starting from the given prefix. Limit the
+// number of results to maxResults.
+func ListKeysByPrefix(tree avl.Tree, prefix string, maxResults int) []string {
+	end := ""
+	n := len(prefix)
+	// To make the end of the search, increment the final character ASCII by one.
+	for n > 0 {
+		if ascii := int(prefix[n-1]); ascii < 0xff {
+			end = prefix[0:n-1] + string(ascii+1)
+			break
+		}
+
+		// The last character is 0xff. Try the previous character.
+		n--
+	}
+
+	result := []string{}
+	tree.Iterate(prefix, end, func(key string, value interface{}) bool {
+		result = append(result, key)
+		if len(result) >= maxResults {
+			return true
+		}
+		return false
+	})
+	return result
+}

examples/gno.land/p/demo/avlhelpers/gno.mod

@@ -0,0 +1,3 @@
+module gno.land/p/demo/avlhelpers
+
+require gno.land/p/demo/avl v0.0.0-latest

examples/gno.land/p/demo/avlhelpers/z_0_filetest.gno

@@ -0,0 +1,94 @@
+// PKGPATH: gno.land/r/test
+package test
+
+import (
+	"encoding/hex"
+
+	"gno.land/p/demo/avl"
+	"gno.land/p/demo/avlhelpers"
+	"gno.land/p/demo/ufmt"
+)
+
+func init() {
+}
+
+func main() {
+	tree := avl.Tree{}
+
+	{
+		// Empty tree.
+		matches := avlhelpers.ListKeysByPrefix(tree, "", 10)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+	}
+
+	tree.Set("alice", "")
+	tree.Set("andy", "")
+	tree.Set("bob", "")
+
+	{
+		// Match only alice.
+		matches := avlhelpers.ListKeysByPrefix(tree, "al", 10)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+		println("match: " + matches[0])
+	}
+
+	{
+		// Match alice and andy.
+		matches := avlhelpers.ListKeysByPrefix(tree, "a", 10)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+		println("match: " + matches[0])
+		println("match: " + matches[1])
+	}
+
+	{
+		// Match alice and andy limited to 1.
+		matches := avlhelpers.ListKeysByPrefix(tree, "a", 1)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+		println("match: " + matches[0])
+	}
+
+	tree = avl.Tree{}
+	tree.Set("a\xff", "")
+	tree.Set("a\xff\xff", "")
+	tree.Set("b", "")
+	tree.Set("\xff\xff\x00", "")
+
+	{
+		// Match only "a\xff\xff".
+		matches := avlhelpers.ListKeysByPrefix(tree, "a\xff\xff", 10)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+		println(ufmt.Sprintf("match: %s", hex.EncodeToString([]byte(matches[0]))))
+	}
+
+	{
+		// Match "a\xff" and "a\xff\xff".
+		matches := avlhelpers.ListKeysByPrefix(tree, "a\xff", 10)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+		println(ufmt.Sprintf("match: %s", hex.EncodeToString([]byte(matches[0]))))
+		println(ufmt.Sprintf("match: %s", hex.EncodeToString([]byte(matches[1]))))
+	}
+
+	{
+		// Edge case: Match only "\xff\xff\x00".
+		matches := avlhelpers.ListKeysByPrefix(tree, "\xff\xff", 10)
+		println(ufmt.Sprintf("# matches: %d", len(matches)))
+		println(ufmt.Sprintf("match: %s", hex.EncodeToString([]byte(matches[0]))))
+	}
+}
+
+// Output:
+// # matches: 0
+// # matches: 1
+// match: alice
+// # matches: 2
+// match: alice
+// match: andy
+// # matches: 1
+// match: alice
+// # matches: 1
+// match: 61ffff
+// # matches: 2
+// match: 61ff
+// match: 61ffff
+// # matches: 1
+// match: ffff00