Truncate file if it became smaller in all cases

CMakeLists.txt

@@ -53,6 +53,7 @@ use_cpp_utilities(VISIBILITY PUBLIC)
 include(3rdParty)
 use_zlib()
 use_crypto()
+use_standard_filesystem()
 
 # include modules to apply configuration
 include(BasicConfig)

io/passwordfile.cpp

@@ -17,6 +17,7 @@
 #include <zlib.h>
 
 #include <cstring>
+#include <filesystem>
 #include <functional>
 #include <limits>
 #include <memory>
@@ -400,7 +401,9 @@ void PasswordFile::save(PasswordFileSaveFlags options)
     }
 
     // use already opened and writable file; otherwise re-open the file
+    auto fileSize = std::size_t();
     if (m_file.good() && m_file.is_open() && !(m_openOptions & PasswordFileOpenFlags::ReadOnly)) {
+        fileSize = size();
         m_file.seekp(0);
     } else {
         m_file.clear();
@@ -418,8 +421,16 @@ void PasswordFile::save(PasswordFileSaveFlags options)
         }
     }
 
+    // write entries
     write(options);
     m_file.flush();
+
+    // truncate file if it became smaller
+    const auto newSize = static_cast<std::size_t>(m_file.tellp());
+    if (fileSize && newSize < fileSize) {
+        m_file.close();
+        std::filesystem::resize_file(m_path, newSize);
+    }
 }
 
 /*!

tests/passwordfiletests.cpp

@@ -208,7 +208,7 @@ void PasswordFileTests::testExtendedWriting()
     CPPUNIT_ASSERT_EQUAL(""s, file.extendedHeader());
     CPPUNIT_ASSERT_EQUAL(""s, file.encryptedExtendedHeader());
     file.rootEntry()->setLabel("testfile2 - modified");
-    new AccountEntry("newAccount", file.rootEntry());
+    auto *const newAccount = new AccountEntry("newAccount", file.rootEntry());
     file.setPassword("654321");
     file.extendedHeader() = "foo";
     file.encryptedExtendedHeader() = "bar";
@@ -220,4 +220,18 @@ void PasswordFileTests::testExtendedWriting()
 
     // check backup files
     testReading("extended writing", testfile1 + ".backup", "123456", testfile2 + ".backup", string(), false, false);
+
+    // remove newAccount again to check what happens if the file size decreases
+    const auto fileSize = file.size();
+    delete newAccount;
+    file.save(PasswordFileSaveFlags::Encryption | PasswordFileSaveFlags::PasswordHashing);
+    file.close();
+    file.clearEntries();
+    file.open();
+    CPPUNIT_ASSERT_LESS(fileSize, file.size());
+    file.load();
+
+    auto path = std::list<std::string>{"newAccount"};
+    CPPUNIT_ASSERT(file.rootEntry());
+    CPPUNIT_ASSERT(!file.rootEntry()->entryByPath(path));
 }