internal/testutil: Add test utility package

internal/testutil/testutil.go

@@ -0,0 +1,86 @@
+package testutil
+
+import "fmt"
+import "slices"
+import "strings"
+
+// Snake lets you compare blocks of data where the ordering of certain parts may
+// be swapped every which way. It is designed for comparing the encoding of
+// maps where the ordering of individual elements is inconsistent.
+//
+// The snake is divided into sectors, which hold a number of variations. For a
+// sector to be satisfied by some data, some ordering of it must match the data
+// exactly. for the snake to be satisfied by some data, its sectors must match
+// the data in order, but the internal ordering of each sector doesn't matter.
+type Snake []    []     []byte
+//         snake sector variation
+
+// S returns a new snake.
+func S(data ...byte) Snake {
+	return (Snake { }).Add(data...)
+}
+
+// AddVar returns a new snake with the given sector added on to it. Successive
+// calls of this method can be chained together to create a big ass snake.
+func (sn Snake) AddVar(sector ...[]byte) Snake {
+	slice := make(Snake, len(sn) + 1)
+	copy(slice, sn)
+	slice[len(slice) - 1] = sector
+	return slice
+}
+
+// Add is like AddVar, but adds a sector with only one variation, which means it
+// does not vary, hence why the method is called that.
+func (sn Snake) Add(data ...byte) Snake {
+	return sn.AddVar(data)
+}
+
+// Check determines if the data satisfies the snake.
+func (sn Snake) Check(data []byte) (ok bool, n int) {
+	left := data
+	variations := map[int] []byte { }
+	for _, sector := range sn {
+		clear(variations)
+		for key, variation := range sector {
+			variations[key] = variation
+		}
+		for len(variations) > 0 {
+			found := false
+			for key, variation := range variations {
+				if len(left) < len(variation) { continue }
+				if !slices.Equal(left[:len(variation)], variation) { continue }
+				n += len(variation)
+				left = data[n:]
+				delete(variations, key)
+				found = true
+			}
+			if !found { return false, n }
+		}
+	}
+	return true, n
+}
+
+func (sn Snake) String() string {
+	out := strings.Builder { }
+	for index, sector := range sn {
+		if index > 0 { out.WriteString(" : ") }
+		out.WriteRune('[')
+		for index, variation := range sector {
+			if index > 0 { out.WriteString(" / ") }
+			for _, byt := range variation {
+				fmt.Fprintf(&out, "%02x", byt)
+			}
+		}
+		out.WriteRune(']')
+	}
+	return out.String()
+}
+
+// HexBytes formats bytes into a hexadecimal string.
+func HexBytes(data []byte) string {
+	out := strings.Builder { }
+	for _, byt := range data {
+		fmt.Fprintf(&out, "%02x", byt)
+	}
+	return out.String()
+}

internal/testutil/testutil_test.go

@@ -0,0 +1,64 @@
+package testutil
+
+import "testing"
+
+func TestSnakeA(test *testing.T) {
+	snake := S(1, 6).AddVar(
+		[]byte { 1 },
+		[]byte { 2 },
+		[]byte { 3 },
+		[]byte { 4 },
+		[]byte { 5 },
+	).Add(9)
+
+	test.Log(snake)
+
+	ok, n := snake.Check([]byte { 1, 6, 1, 2, 3, 4, 5, 9 })
+	if !ok { test.Fatal("false negative:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 5, 4, 3, 2, 1, 9 })
+	if !ok { test.Fatal("false negative:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 3, 1, 4, 2, 5, 9 })
+	if !ok { test.Fatal("false negative:", n) }
+	
+	ok, n = snake.Check([]byte { 1, 6, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 1, 2, 3, 4, 5, 6, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 0, 2, 3, 4, 5, 6, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 7, 1, 4, 2, 5, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 7, 3, 1, 4, 2, 5, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 7, 3, 1, 4, 2, 5, 9 })
+	if ok { test.Fatal("false positive:", n) }
+}
+
+func TestSnakeB(test *testing.T) {
+	snake := S(1, 6).AddVar(
+		[]byte { 1 },
+		[]byte { 2 },
+	).Add(9).AddVar(
+		[]byte { 3, 2 },
+		[]byte { 0 },
+		[]byte { 1, 1, 2, 3 },
+	)
+
+	test.Log(snake)
+
+	ok, n := snake.Check([]byte { 1, 6, 1, 2, 9, 3, 2, 0, 1, 1, 2, 3})
+	if !ok { test.Fatal("false negative:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 2, 1, 9, 0, 1, 1, 2, 3, 3, 2})
+	if !ok { test.Fatal("false negative:", n) }
+	
+	ok, n = snake.Check([]byte { 1, 6, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 1, 2, 9 })
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 9, 3, 2, 0, 1, 1, 2, 3})
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 2, 9, 0, 1, 1, 2, 3, 3, 2})
+	if ok { test.Fatal("false positive:", n) }
+	ok, n = snake.Check([]byte { 1, 6, 1, 2, 9, 3, 2, 1, 1, 2, 3})
+	if ok { test.Fatal("false positive:", n) }
+}