Add QUtil::FileCloser to the public API

ChangeLog

@@ -1,3 +1,8 @@
+2022-05-18  Jay Berkenbilt  <ejb@ql.org>
+
+        * Add QUtil::FileCloser to the public API. This is a simple inline
+        class to help with automatic file closing.
+
 2022-05-17  Jay Berkenbilt  <ejb@ql.org>
 
         * Allow passing *uninitialized* (not null) objects to

include/qpdf/QUtil.hh

@@ -114,6 +114,33 @@ namespace QUtil
     QPDF_DLL
     FILE* fopen_wrapper(std::string const&, FILE*);
 
+    // This is a little class to help with automatic closing files.
+    // You can do something like
+    //
+    // QUtil::FileCloser fc(QUtil::safe_fopen(filename, "rb"));
+    //
+    // and then use fc.f to the file. Be sure to actually declare a
+    // variable of type FileCloser. Using it as a temporary won't work
+    // because it will close the file as soon as it goes out of scope.
+    class FileCloser
+    {
+      public:
+        FileCloser(FILE* f) :
+            f(f)
+        {
+        }
+
+        ~FileCloser()
+        {
+            if (f) {
+                fclose(f);
+                f = nullptr;
+            }
+        }
+
+        FILE* f;
+    };
+
     // Attempt to open the file read only and then close again
     QPDF_DLL
     bool file_can_be_opened(char const* filename);

libqpdf/QUtil.cc

@@ -305,26 +305,6 @@ static std::map<unsigned long, unsigned char> unicode_to_pdf_doc = {
     {0x20ac, 0xa0},
 };
 
-namespace
-{
-    class FileCloser
-    {
-      public:
-        FileCloser(FILE* f) :
-            f(f)
-        {
-        }
-
-        ~FileCloser()
-        {
-            fclose(f);
-        }
-
-      private:
-        FILE* f;
-    };
-} // namespace
-
 template <typename T>
 static std::string
 int_to_string_base_internal(T num, int base, int length)