3 files changed, 188 insertions, 2 deletions
diff --git a/utils/merkletrie/noder/noder_test.go b/utils/merkletrie/noder/noder_test.go
index 14bef4a..5e014fe 100644
--- a/utils/merkletrie/noder/noder_test.go
+++ b/utils/merkletrie/noder/noder_test.go
@@ -1,6 +1,12 @@
 package noder
 
-import . "gopkg.in/check.v1"
+import (
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
 
 type NoderSuite struct{}
 
diff --git a/utils/merkletrie/noder/path.go b/utils/merkletrie/noder/path.go
index c992f7e..85742db 100644
--- a/utils/merkletrie/noder/path.go
+++ b/utils/merkletrie/noder/path.go
@@ -1,6 +1,9 @@
 package noder
 
-import "bytes"
+import (
+	"bytes"
+	"strings"
+)
 
 // Path values represent a noder and its ancestors.  The root goes first
 // and the actual final noder the path is refering to will be the last.
@@ -57,3 +60,29 @@ func (p Path) Children() ([]Noder, error) {
 func (p Path) NumChildren() (int, error) {
 	return p.Last().NumChildren()
 }
+
+// Compare returns -1, 0 or 1 if the path p is smaller, equal or bigger
+// than other, in "directory order"; for example:
+//
+// "a" < "b"
+// "a/b/c/d/z" < "b"
+// "a/b/a" > "a/b"
+func (p Path) Compare(other Path) int {
+	i := 0
+	for {
+		switch {
+		case len(other) == len(p) && i == len(p):
+			return 0
+		case i == len(other):
+			return 1
+		case i == len(p):
+			return -1
+		default:
+			cmp := strings.Compare(p[i].Name(), other[i].Name())
+			if cmp != 0 {
+				return cmp
+			}
+		}
+		i++
+	}
+}
diff --git a/utils/merkletrie/noder/path_test.go b/utils/merkletrie/noder/path_test.go
new file mode 100644
index 0000000..44e3c3c
--- /dev/null
+++ b/utils/merkletrie/noder/path_test.go
@@ -0,0 +1,151 @@
+package noder
+
+import . "gopkg.in/check.v1"
+
+type PathSuite struct{}
+
+var _ = Suite(&PathSuite{})
+
+func (s *PathSuite) TestShortFile(c *C) {
+	f := &noderMock{
+		name:  "1",
+		isDir: false,
+	}
+	p := Path([]Noder{f})
+	c.Assert(p.String(), Equals, "1")
+}
+
+func (s *PathSuite) TestShortDir(c *C) {
+	d := &noderMock{
+		name:     "1",
+		isDir:    true,
+		children: NoChildren,
+	}
+	p := Path([]Noder{d})
+	c.Assert(p.String(), Equals, "1")
+}
+
+func (s *PathSuite) TestLongFile(c *C) {
+	n3 := &noderMock{
+		name:  "3",
+		isDir: false,
+	}
+	n2 := &noderMock{
+		name:     "2",
+		isDir:    true,
+		children: []Noder{n3},
+	}
+	n1 := &noderMock{
+		name:     "1",
+		isDir:    true,
+		children: []Noder{n2},
+	}
+	p := Path([]Noder{n1, n2, n3})
+	c.Assert(p.String(), Equals, "1/2/3")
+}
+
+func (s *PathSuite) TestLongDir(c *C) {
+	n3 := &noderMock{
+		name:     "3",
+		isDir:    true,
+		children: NoChildren,
+	}
+	n2 := &noderMock{
+		name:     "2",
+		isDir:    true,
+		children: []Noder{n3},
+	}
+	n1 := &noderMock{
+		name:     "1",
+		isDir:    true,
+		children: []Noder{n2},
+	}
+	p := Path([]Noder{n1, n2, n3})
+	c.Assert(p.String(), Equals, "1/2/3")
+}
+
+func (s *PathSuite) TestCompareDepth1(c *C) {
+	p1 := Path([]Noder{&noderMock{name: "a"}})
+	p2 := Path([]Noder{&noderMock{name: "b"}})
+	c.Assert(p1.Compare(p2), Equals, -1)
+	c.Assert(p2.Compare(p1), Equals, 1)
+
+	p1 = Path([]Noder{&noderMock{name: "a"}})
+	p2 = Path([]Noder{&noderMock{name: "a"}})
+	c.Assert(p1.Compare(p2), Equals, 0)
+	c.Assert(p2.Compare(p1), Equals, 0)
+
+	p1 = Path([]Noder{&noderMock{name: "a.go"}})
+	p2 = Path([]Noder{&noderMock{name: "a"}})
+	c.Assert(p1.Compare(p2), Equals, 1)
+	c.Assert(p2.Compare(p1), Equals, -1)
+}
+
+func (s *PathSuite) TestCompareDepth2(c *C) {
+	p1 := Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "b"},
+	})
+	p2 := Path([]Noder{
+		&noderMock{name: "b"},
+		&noderMock{name: "a"},
+	})
+	c.Assert(p1.Compare(p2), Equals, -1)
+	c.Assert(p2.Compare(p1), Equals, 1)
+
+	p1 = Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "b"},
+	})
+	p2 = Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "b"},
+	})
+	c.Assert(p1.Compare(p2), Equals, 0)
+	c.Assert(p2.Compare(p1), Equals, 0)
+
+	p1 = Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "b"},
+	})
+	p2 = Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "a"},
+	})
+	c.Assert(p1.Compare(p2), Equals, 1)
+	c.Assert(p2.Compare(p1), Equals, -1)
+}
+
+func (s *PathSuite) TestCompareMixedDepths(c *C) {
+	p1 := Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "b"},
+	})
+	p2 := Path([]Noder{&noderMock{name: "b"}})
+	c.Assert(p1.Compare(p2), Equals, -1)
+	c.Assert(p2.Compare(p1), Equals, 1)
+
+	p1 = Path([]Noder{
+		&noderMock{name: "b"},
+		&noderMock{name: "b"},
+	})
+	p2 = Path([]Noder{&noderMock{name: "b"}})
+	c.Assert(p1.Compare(p2), Equals, 1)
+	c.Assert(p2.Compare(p1), Equals, -1)
+
+	p1 = Path([]Noder{&noderMock{name: "a.go"}})
+	p2 = Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "a.go"},
+	})
+	c.Assert(p1.Compare(p2), Equals, 1)
+	c.Assert(p2.Compare(p1), Equals, -1)
+
+	p1 = Path([]Noder{&noderMock{name: "b.go"}})
+	p2 = Path([]Noder{
+		&noderMock{name: "a"},
+		&noderMock{name: "a.go"},
+	})
+	c.Assert(p1.Compare(p2), Equals, 1)
+	c.Assert(p2.Compare(p1), Equals, -1)
+}