Empty objects start with a constant hash.

josephburnett · Feb 28, 2022 · 5048bb6 · 5048bb6
1 parent 2caa226
commit 5048bb6
Show file tree

Hide file tree

Showing 3 changed files with 16 additions and 3 deletions.
diff --git a/lib/common_test.go b/lib/common_test.go
@@ -202,6 +202,7 @@ func fuzz(t *testing.T, aStr, bStr string) {
 	}, {
 		"patch", "list",
 	}} {
+		a, _ = ReadJsonString(aStr) // Fresh parsed copy.
 		var metadata []Metadata
 		switch format[0] {
 		case "jd":

diff --git a/lib/fuzz_backport_test.go b/lib/fuzz_backport_test.go
@@ -9,9 +9,17 @@ import "testing"
 // To run fuzzing use `go1.18beta2 test -tags=test_fuzz ./lib/ -fuzz=FuzzJd`
 func TestFuzzBackport(t *testing.T) {
 	for _, backport := range [][2]string{{
-		"[]", "0", // FuzzJd/e193f6c4bfd5b8d3c12e1ac42162b2ccd7a31f9aafd466066c1ec7a95da48e1e
+		// FuzzJd/e193f6c4bfd5b8d3c12e1ac42162b2ccd7a31f9aafd466066c1ec7a95da48e1e
+		"[]",
+		"0",
 	}, {
-		"{}", " ", // FuzzJd/868060b2021521d32933f40415c6f95b38fda5f5c6bdb7fa6664d046c637c03c
+		// FuzzJd/868060b2021521d32933f40415c6f95b38fda5f5c6bdb7fa6664d046c637c03c
+		"{}",
+		" ",
+	}, {
+		// FuzzJd/61c145c6c646c53946229fb0125821ff47c91b63e87da5709002b4fee8b96ca4
+		"[{},[]]",
+		"[{},[{},[]]]",
 	}} {
 		fuzz(t, backport[0], backport[1])
 	}

diff --git a/lib/object.go b/lib/object.go
@@ -78,7 +78,11 @@ func (o jsonObject) ident(metadata []Metadata) [8]byte {
 	if len(keys) == 0 {
 		return o.hashCode(metadata)
 	}
-	hashes := make(hashCodes, 0)
+	hashes := hashCodes{
+		// We start with a constant hash to distinguish between
+		// an empty object and an empty array.
+		[8]byte{0x4B, 0x08, 0xD2, 0x0F, 0xBD, 0xC8, 0xDE, 0x9A}, // random bytes
+	}
 	for key := range keys {
 		v, ok := o.properties[key]
 		if ok {