Add QUtil::file_can_be_opened

5 files changed, 29 insertions, 18 deletions

diff --git a/ChangeLog b/ChangeLog
index 33542286..546c5658 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2021-12-29  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add method QUtil::file_can_be_opened
+
 2021-12-21  Jay Berkenbilt  <ejb@ql.org>
 
 	* 10.5.0: release
diff --git a/include/qpdf/QUtil.hh b/include/qpdf/QUtil.hh
index dd42fe1c..5a064d5c 100644
--- a/include/qpdf/QUtil.hh
+++ b/include/qpdf/QUtil.hh
@@ -111,6 +111,10 @@ namespace QUtil
     QPDF_DLL
     FILE* fopen_wrapper(std::string const&, FILE*);
 
+    // Attempt to open the file read only and then close again
+    QPDF_DLL
+    bool file_can_be_opened(char const* filename);
+
     // Wrap around off_t versions of fseek and ftell if available
     QPDF_DLL
     int seek(FILE* stream, qpdf_offset_t offset, int whence);
diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index f45468a0..daa663a3 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -515,6 +515,21 @@ QUtil::fopen_wrapper(std::string const& description, FILE* f)
     return f;
 }
 
+bool
+QUtil::file_can_be_opened(char const* filename)
+{
+    try
+    {
+        fclose(safe_fopen(filename, "rb"));
+        return true;
+    }
+    catch (std::runtime_error&)
+    {
+        // can't open the file
+    }
+    return false;
+}
+
 int
 QUtil::seek(FILE* stream, qpdf_offset_t offset, int whence)
 {
diff --git a/libtests/qutil.cc b/libtests/qutil.cc
index f52ec2dc..46eb840c 100644
--- a/libtests/qutil.cc
+++ b/libtests/qutil.cc
@@ -203,6 +203,9 @@ void fopen_wrapper_test()
 	std::cout << "exception: " << s.what() << std::endl;
         assert(s.getErrno() != 0);
     }
+
+    assert(QUtil::file_can_be_opened("qutil.out"));
+    assert(! QUtil::file_can_be_opened("/does/not/exist"));
 }
 
 void getenv_test()
diff --git a/qpdf/qpdf.cc b/qpdf/qpdf.cc
index 77b7bdf1..aa1827d9 100644
--- a/qpdf/qpdf.cc
+++ b/qpdf/qpdf.cc
@@ -740,21 +740,6 @@ static void parse_object_id(std::string const& objspec,
     }
 }
 
-static bool file_exists(char const* filename)
-{
-    try
-    {
-        fclose(QUtil::safe_fopen(filename, "rb"));
-        return true;
-    }
-    catch (std::runtime_error&)
-    {
-        // can't open the file
-    }
-    return false;
-}
-
-
 // This is not a general-purpose argument parser. It is tightly
 // crafted to work with qpdf. qpdf's command-line syntax is very
 // complex because of its long history, and it doesn't really follow
@@ -2976,7 +2961,7 @@ ArgParser::handleArgFileArguments()
             argfile = 1 + argv[i];
             if (strcmp(argfile, "-") != 0)
             {
-                if (! file_exists(argfile))
+                if (! QUtil::file_can_be_opened(argfile))
                 {
                     // The file's not there; treating as regular option
                     argfile = nullptr;
@@ -3276,7 +3261,7 @@ ArgParser::parsePagesOptions()
         char const* file = argv[cur_arg++];
         char const* password = 0;
         char const* range = argv[cur_arg++];
-        if (! file_exists(file))
+        if (! QUtil::file_can_be_opened(file))
         {
             check_unclosed(file, 0);
         }
@@ -3315,7 +3300,7 @@ ArgParser::parsePagesOptions()
                     // "." means the input file.
                     QTC::TC("qpdf", "qpdf pages range omitted with .");
                 }
-                else if (file_exists(range))
+                else if (QUtil::file_can_be_opened(range))
                 {
                     QTC::TC("qpdf", "qpdf pages range omitted in middle");
                     // Yup, it's a file.