From 7f4a4df919f0b305ba7d3b63ed722ab38e3eb2d5 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Thu, 22 Oct 2020 05:44:48 -0400
Subject: [PATCH] Add range_check method to QIntC

---
 include/qpdf/BufferInputSource.hh |  2 --
 include/qpdf/QIntC.hh             | 14 ++++++++++++++
 libqpdf/BufferInputSource.cc      | 19 ++-----------------
 3 files changed, 16 insertions(+), 19 deletions(-)

diff --git a/include/qpdf/BufferInputSource.hh b/include/qpdf/BufferInputSource.hh
index 65206d50..561018f6 100644
--- a/include/qpdf/BufferInputSource.hh
+++ b/include/qpdf/BufferInputSource.hh
@@ -54,8 +54,6 @@ class BufferInputSource: public InputSource
     virtual void unreadCh(char ch);
 
   private:
-    static void range_check(qpdf_offset_t cur, qpdf_offset_t delta);
-
     class Members
     {
         friend class BufferInputSource;
diff --git a/include/qpdf/QIntC.hh b/include/qpdf/QIntC.hh
index 6f1f4b63..5f7f21bb 100644
--- a/include/qpdf/QIntC.hh
+++ b/include/qpdf/QIntC.hh
@@ -222,6 +222,20 @@ namespace QIntC // QIntC = qpdf Integer Conversion
     {
         return IntConverter<T, unsigned long long>::convert(i);
     }
+
+    template <typename T>
+    void range_check(T const& cur, T const& delta)
+    {
+        if ((delta > 0) &&
+            ((std::numeric_limits<T>::max() - cur) < delta))
+        {
+            std::ostringstream msg;
+            msg.imbue(std::locale::classic());
+            msg << "adding " << delta << " to " << cur
+                << " would cause an integer overflow";
+            throw std::range_error(msg.str());
+        }
+    }
 };
 
 #endif // QINTC_HH
diff --git a/libqpdf/BufferInputSource.cc b/libqpdf/BufferInputSource.cc
index fb4010ef..9e9b4c17 100644
--- a/libqpdf/BufferInputSource.cc
+++ b/libqpdf/BufferInputSource.cc
@@ -101,21 +101,6 @@ BufferInputSource::tell()
     return this->m->cur_offset;
 }
 
-void
-BufferInputSource::range_check(qpdf_offset_t cur, qpdf_offset_t delta)
-{
-    if ((delta > 0) &&
-        ((std::numeric_limits<qpdf_offset_t>::max() - cur) < delta))
-    {
-        std::ostringstream msg;
-        msg.imbue(std::locale::classic());
-        msg << "seeking forward from " << cur
-            << " by " << delta
-            << " would cause an overflow of the offset type";
-        throw std::range_error(msg.str());
-    }
-}
-
 void
 BufferInputSource::seek(qpdf_offset_t offset, int whence)
 {
@@ -126,12 +111,12 @@ BufferInputSource::seek(qpdf_offset_t offset, int whence)
 	break;
 
       case SEEK_END:
-        range_check(this->m->max_offset, offset);
+        QIntC::range_check(this->m->max_offset, offset);
 	this->m->cur_offset = this->m->max_offset + offset;
 	break;
 
       case SEEK_CUR:
-        range_check(this->m->cur_offset, offset);
+        QIntC::range_check(this->m->cur_offset, offset);
 	this->m->cur_offset += offset;
 	break;