New exception class QPDFSystemError (fixes #221)

3 files changed, 54 insertions, 16 deletions

diff --git a/libqpdf/QPDFSystemError.cc b/libqpdf/QPDFSystemError.cc
new file mode 100644
index 00000000..094341cd
--- /dev/null
+++ b/libqpdf/QPDFSystemError.cc
@@ -0,0 +1,51 @@
+#include <qpdf/QPDFSystemError.hh>
+#include <qpdf/QUtil.hh>
+#include <string.h>
+
+QPDFSystemError::QPDFSystemError(std::string const& description,
+                                 int system_errno) :
+    std::runtime_error(createWhat(description, system_errno)),
+    description(description),
+    system_errno(system_errno)
+{
+}
+
+QPDFSystemError::~QPDFSystemError() throw ()
+{
+}
+
+std::string
+QPDFSystemError::createWhat(std::string const& description,
+                            int system_errno)
+{
+    std::string message;
+#ifdef _MSC_VER
+    // "94" is mentioned in the MSVC docs, but it's still safe if the
+    // message is longer.  strerror_s is a templated function that
+    // knows the size of buf and truncates.
+    char buf[94];
+    if (strerror_s(buf, errno) != 0)
+    {
+        message = description + ": failed with an unknown error";
+    }
+    else
+    {
+        message = description + ": " + buf;
+    }
+#else
+    message = description + ": " + strerror(errno);
+#endif
+    return message;
+}
+
+std::string const&
+QPDFSystemError::getDescription() const
+{
+    return this->description;
+}
+
+int
+QPDFSystemError::getErrno() const
+{
+    return this->system_errno;
+}
diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index e2bc0bac..56bac386 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -7,6 +7,7 @@
 # include <qpdf/InsecureRandomDataProvider.hh>
 #endif
 #include <qpdf/SecureRandomDataProvider.hh>
+#include <qpdf/QPDFSystemError.hh>
 
 #include <cmath>
 #include <iomanip>
@@ -132,22 +133,7 @@ QUtil::unsigned_char_pointer(char const* str)
 void
 QUtil::throw_system_error(std::string const& description)
 {
-#ifdef _MSC_VER
-    // "94" is mentioned in the MSVC docs, but it's still safe if the
-    // message is longer.  strerror_s is a templated function that
-    // knows the size of buf and truncates.
-    char buf[94];
-    if (strerror_s(buf, errno) != 0)
-    {
-        throw std::runtime_error(description + ": failed with an unknown error");
-    }
-    else
-    {
-        throw std::runtime_error(description + ": " + buf);
-    }
-#else
-    throw std::runtime_error(description + ": " + strerror(errno));
-#endif
+    throw QPDFSystemError(description, errno);
 }
 
 int
diff --git a/libqpdf/build.mk b/libqpdf/build.mk
index 528456f8..61ea4b2d 100644
--- a/libqpdf/build.mk
+++ b/libqpdf/build.mk
@@ -45,6 +45,7 @@ SRCS_libqpdf = \
 	libqpdf/QPDFObjectHandle.cc \
 	libqpdf/QPDFPageDocumentHelper.cc \
 	libqpdf/QPDFPageObjectHelper.cc \
+	libqpdf/QPDFSystemError.cc \
 	libqpdf/QPDFTokenizer.cc \
 	libqpdf/QPDFWriter.cc \
 	libqpdf/QPDFXRefEntry.cc \