1 files changed, 72 insertions, 0 deletions
diff --git a/klm/util/exception.hh b/klm/util/exception.hh
new file mode 100644
index 00000000..124689cf
--- /dev/null
+++ b/klm/util/exception.hh
@@ -0,0 +1,72 @@
+#ifndef UTIL_EXCEPTION__
+#define UTIL_EXCEPTION__
+
+#include "util/string_piece.hh"
+
+#include <exception>
+#include <sstream>
+#include <string>
+
+namespace util {
+
+class Exception : public std::exception {
+  public:
+    Exception() throw();
+    virtual ~Exception() throw();
+
+    const char *what() const throw() { return what_.c_str(); }
+
+    // This helps restrict operator<< defined below.  
+    template <class T> struct ExceptionTag {
+      typedef T Identity;
+    };
+
+    std::string &Str() {
+      return what_;
+    }
+
+  protected:
+    std::string what_;
+};
+
+/* This implements the normal operator<< for Exception and all its children. 
+ * SNIFAE means it only applies to Exception.  Think of this as an ersatz
+ * boost::enable_if.  
+ */
+template <class Except, class Data> typename Except::template ExceptionTag<Except&>::Identity operator<<(Except &e, const Data &data) {
+  // Argh I had a stringstream in the exception, but the only way to get the string is by calling str().  But that's a temporary string, so virtual const char *what() const can't actually return it.  
+  std::stringstream stream;
+  stream << data;
+  e.Str() += stream.str();
+  return e;
+}
+template <class Except> typename Except::template ExceptionTag<Except&>::Identity operator<<(Except &e, const char *data) {
+  e.Str() += data;
+  return e;
+}
+template <class Except> typename Except::template ExceptionTag<Except&>::Identity operator<<(Except &e, const std::string &data) {
+  e.Str() += data;
+  return e;
+}
+template <class Except> typename Except::template ExceptionTag<Except&>::Identity operator<<(Except &e, const StringPiece &str) {
+  e.Str().append(str.data(), str.length());
+  return e;
+}
+
+#define UTIL_THROW(Exception, Modify) { Exception UTIL_e; {UTIL_e << Modify;} throw UTIL_e; }
+
+class ErrnoException : public Exception {
+  public:
+    ErrnoException() throw();
+
+    virtual ~ErrnoException() throw();
+
+    int Error() { return errno_; }
+
+  private:
+    int errno_;
+};
+
+} // namespace util
+
+#endif // UTIL_EXCEPTION__