From 1f529bd61016de07501ef7819c51141fe40b8d8a Mon Sep 17 00:00:00 2001
From: David Capello <david@igara.com>
Date: Thu, 23 May 2024 12:26:25 -0300
Subject: [PATCH] Fix a couple of bugs restoring backup sessions

With https://community.aseprite.org/t/layers-become-empty-when-autosaving/22141
we found a couple of bugs where only 2 backed up versions of stored
objects were added in ObjVersions::add().

Also as ObjVersions has a limited space for 3 versions, it's a good
idea to ignore invalid binary files (files without the magic number
"FINE" as header). So now we only add valid versions to ObjVersions,
previously we could lead to a situation where 3 invalid binary
versions of the same object were added to the ObjVersions and a 4th
valid version were ignored.

Related to: https://github.com/aseprite/aseprite/issues/4481
---
 src/app/crash/internals.h       |  5 +++--
 src/app/crash/read_document.cpp | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/app/crash/internals.h b/src/app/crash/internals.h
index 77f3f029f..8ca8176a3 100644
--- a/src/app/crash/internals.h
+++ b/src/app/crash/internals.h
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2024  Igara Studio S.A.
 // Copyright (C) 2001-2015  David Capello
 //
 // This program is distributed under the terms of
@@ -43,10 +44,10 @@ namespace crash {
 
     // Adds a version (we don't know if the version if the latest one)
     void add(doc::ObjectVersion ver) {
-      auto minver = std::min_element(m_vers, m_vers+2);
+      auto* minver = std::min_element(m_vers, m_vers+size());
       if (*minver < ver) {
         *minver = ver;
-        std::sort(m_vers, m_vers+2, std::greater<doc::ObjectVersion>());
+        std::sort(m_vers, m_vers+size(), std::greater<doc::ObjectVersion>());
       }
     }
 
diff --git a/src/app/crash/read_document.cpp b/src/app/crash/read_document.cpp
index ec2ce2d4b..73a79e637 100644
--- a/src/app/crash/read_document.cpp
+++ b/src/app/crash/read_document.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2023  Igara Studio S.A.
+// Copyright (C) 2018-2024  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -58,6 +58,14 @@ using namespace doc;
 
 namespace {
 
+// Returns true if the file was saved correctly (has the "FINE" magic
+// number), so we can ignore broken versions of objects directly.
+bool check_magic_number(const std::string& fn)
+{
+  std::ifstream s(FSTREAM_PATH(fn), std::ifstream::binary);
+  return (read32(s) == MAGIC_NUMBER);
+}
+
 class Reader : public SubObjectsIO {
 public:
   Reader(const std::string& dir,
@@ -83,6 +91,11 @@ public:
       if (!id || !ver)
         continue;               // Error converting strings to ID/ver
 
+      if (!check_magic_number(base::join_path(m_dir, fn))) {
+        RECO_TRACE("RECO: Ignoring invalid file %s (no magic number)\n", fn.c_str());
+        continue;
+      }
+
       ObjVersions& versions = m_objVersions[id];
       versions.add(ver);