Add Generate method in merkletree

A method is added to generate a merkle tree for data, and store the
generated tree in the output.

PiperOrigin-RevId: 315966571

1 files changed, 60 insertions, 0 deletions

diff --git a/pkg/merkletree/merkletree_test.go b/pkg/merkletree/merkletree_test.go
index 6221eec07..7344db0b6 100644
--- a/pkg/merkletree/merkletree_test.go
+++ b/pkg/merkletree/merkletree_test.go
@@ -15,6 +15,7 @@
 package merkletree
 
 import (
+	"bytes"
 	"fmt"
 	"testing"
 
@@ -60,3 +61,62 @@ func TestSize(t *testing.T) {
 		})
 	}
 }
+
+func TestGenerate(t *testing.T) {
+	// The input data has size dataSize. It starts with the data in startWith,
+	// and all other bytes are zeroes.
+	testCases := []struct {
+		dataSize     int
+		startWith    []byte
+		expectedRoot []byte
+	}{
+		{
+			dataSize:     usermem.PageSize,
+			startWith:    nil,
+			expectedRoot: []byte{173, 127, 172, 178, 88, 111, 198, 233, 102, 192, 4, 215, 209, 209, 107, 2, 79, 88, 5, 255, 124, 180, 124, 122, 133, 218, 189, 139, 72, 137, 44, 167},
+		},
+		{
+			dataSize:     128*usermem.PageSize + 1,
+			startWith:    nil,
+			expectedRoot: []byte{62, 93, 40, 92, 161, 241, 30, 223, 202, 99, 39, 2, 132, 113, 240, 139, 117, 99, 79, 243, 54, 18, 100, 184, 141, 121, 238, 46, 149, 202, 203, 132},
+		},
+		{
+			dataSize:     1,
+			startWith:    []byte{'a'},
+			expectedRoot: []byte{52, 75, 204, 142, 172, 129, 37, 14, 145, 137, 103, 203, 11, 162, 209, 205, 30, 169, 213, 72, 20, 28, 243, 24, 242, 2, 92, 43, 169, 59, 110, 210},
+		},
+		{
+			dataSize:     1,
+			startWith:    []byte{'1'},
+			expectedRoot: []byte{74, 35, 103, 179, 176, 149, 254, 112, 42, 65, 104, 66, 119, 56, 133, 124, 228, 15, 65, 161, 150, 0, 117, 174, 242, 34, 115, 115, 218, 37, 3, 105},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(fmt.Sprintf("%d", tc.dataSize), func(t *testing.T) {
+			var (
+				data bytes.Buffer
+				tree bytes.Buffer
+			)
+
+			startSize := len(tc.startWith)
+			_, err := data.Write(tc.startWith)
+			if err != nil {
+				t.Fatalf("Failed to write to data: %v", err)
+			}
+			_, err = data.Write(make([]byte, tc.dataSize-startSize))
+			if err != nil {
+				t.Fatalf("Failed to write to data: %v", err)
+			}
+
+			root, err := Generate(&data, int64(tc.dataSize), &tree, &tree)
+			if err != nil {
+				t.Fatalf("Generate failed: %v", err)
+			}
+
+			if !bytes.Equal(root, tc.expectedRoot) {
+				t.Errorf("Unexpected root")
+			}
+		})
+	}
+}