objectstore{,/loose}: Document contracts more clearly

1 files changed, 39 insertions, 0 deletions

diff --git a/objectstore/loose/helpers_test.go b/objectstore/loose/helpers_test.go
index 6cc50163..f4c8dbb3 100644
--- a/objectstore/loose/helpers_test.go
+++ b/objectstore/loose/helpers_test.go
@@ -2,6 +2,7 @@ package loose_test
 
 import (
 	"io"
+	"os"
 	"testing"
 
 	"codeberg.org/lindenii/furgit/internal/testgit"
@@ -65,3 +66,41 @@ func expectedRawObject(t *testing.T, testRepo *testgit.TestRepo, id objectid.Obj
 
 	return ty, body, raw
 }
+
+func corruptLooseObjectTrailer(t *testing.T, testRepo *testgit.TestRepo, id objectid.ObjectID) {
+	t.Helper()
+
+	root := testRepo.OpenObjectsRoot(t)
+
+	hex := id.String()
+	relPath := hex[:2] + "/" + hex[2:]
+
+	file, err := root.OpenFile(relPath, os.O_RDWR, 0)
+	if err != nil {
+		t.Fatalf("OpenFile(%q): %v", relPath, err)
+	}
+
+	defer func() { _ = file.Close() }()
+
+	info, err := file.Stat()
+	if err != nil {
+		t.Fatalf("Stat(%q): %v", relPath, err)
+	}
+
+	if info.Size() == 0 {
+		t.Fatalf("corrupt trailer on empty file %q", relPath)
+	}
+
+	last := make([]byte, 1)
+	_, err = file.ReadAt(last, info.Size()-1)
+	if err != nil {
+		t.Fatalf("ReadAt(%q): %v", relPath, err)
+	}
+
+	last[0] ^= 0xff
+
+	_, err = file.WriteAt(last, info.Size()-1)
+	if err != nil {
+		t.Fatalf("WriteAt(%q): %v", relPath, err)
+	}
+}