New exception class QPDFSystemError (fixes #221)

2 files changed, 65 insertions, 2 deletions

diff --git a/include/qpdf/QPDFSystemError.hh b/include/qpdf/QPDFSystemError.hh
new file mode 100644
index 00000000..037bbe0a
--- /dev/null
+++ b/include/qpdf/QPDFSystemError.hh
@@ -0,0 +1,58 @@
+// Copyright (c) 2005-2018 Jay Berkenbilt
+//
+// This file is part of qpdf.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Versions of qpdf prior to version 7 were released under the terms
+// of version 2.0 of the Artistic License. At your option, you may
+// continue to consider qpdf to be licensed under those terms. Please
+// see the manual for additional information.
+
+#ifndef QPDFSYSTEMERROR_HH
+#define QPDFSYSTEMERROR_HH
+
+#include <qpdf/DLL.h>
+#include <qpdf/Types.h>
+
+#include <qpdf/Constants.h>
+#include <string>
+#include <stdexcept>
+
+class QPDFSystemError: public std::runtime_error
+{
+  public:
+    QPDF_DLL
+    QPDFSystemError(std::string const& description,
+                    int system_errno);
+    QPDF_DLL
+    virtual ~QPDFSystemError() throw ();
+
+    // To get a complete error string, call what(), provided by
+    // std::exception.  The accessors below return the original values
+    // used to create the exception.
+
+    QPDF_DLL
+    std::string const& getDescription() const;
+    QPDF_DLL
+    int getErrno() const;
+
+  private:
+    static std::string createWhat(std::string const& description,
+				  int system_errno);
+
+    std::string description;
+    int system_errno;
+};
+
+#endif // QPDFSYSTEMERROR_HH
diff --git a/include/qpdf/QUtil.hh b/include/qpdf/QUtil.hh
index 68e64370..bcedd4d3 100644
--- a/include/qpdf/QUtil.hh
+++ b/include/qpdf/QUtil.hh
@@ -61,9 +61,14 @@ namespace QUtil
     QPDF_DLL
     unsigned char* unsigned_char_pointer(char const* str);
 
-    // Throw std::runtime_error with a string formed by appending to
+    // Throw QPDFSystemError, which is derived from
+    // std::runtime_error, with a string formed by appending to
     // "description: " the standard string corresponding to the
-    // current value of errno.
+    // current value of errno. You can retrieve the value of errno by
+    // calling getErrno() on the QPDFSystemError. Prior to qpdf 8.2.0,
+    // this method threw system::runtime_error directly, but since
+    // QPDFSystemError is derived from system::runtime_error, old code
+    // that specifically catches std::runtime_error will still work.
     QPDF_DLL
     void throw_system_error(std::string const& description);