diff --git a/include/qpdf/InputSource.hh b/include/qpdf/InputSource.hh
index 7a5e8ec8..94817155 100644
--- a/include/qpdf/InputSource.hh
+++ b/include/qpdf/InputSource.hh
@@ -78,7 +78,7 @@ class QPDF_DLL_CLASS InputSource
     // semantically equivalent to seek(-1, SEEK_CUR) but is much more efficient.
     virtual void unreadCh(char ch) = 0;
 
-    // The following methods are for use by QPDFTokenizer
+    // The following methods are for internal use by qpdf only.
     inline qpdf_offset_t fastTell();
     inline bool fastRead(char&);
     inline void fastUnread(bool);
@@ -111,57 +111,4 @@ class QPDF_DLL_CLASS InputSource
     qpdf_offset_t buf_start = 0;
 };
 
-inline void
-InputSource::loadBuffer()
-{
-    this->buf_idx = 0;
-    this->buf_len = qpdf_offset_t(read(this->buffer, this->buf_size));
-    // NB read sets last_offset
-    this->buf_start = this->last_offset;
-}
-
-inline qpdf_offset_t
-InputSource::fastTell()
-{
-    if (this->buf_len == 0) {
-        loadBuffer();
-    } else {
-        auto curr = tell();
-        if (curr < this->buf_start || curr >= (this->buf_start + this->buf_len)) {
-            loadBuffer();
-        } else {
-            this->last_offset = curr;
-            this->buf_idx = curr - this->buf_start;
-        }
-    }
-    return this->last_offset;
-}
-
-inline bool
-InputSource::fastRead(char& ch)
-{
-    // Before calling fastRead, fastTell must be called to prepare the buffer. Once reading is
-    // complete, fastUnread must be called to set the correct file position.
-    if (this->buf_idx < this->buf_len) {
-        ch = this->buffer[this->buf_idx];
-        ++(this->buf_idx);
-        ++(this->last_offset);
-        return true;
-
-    } else if (this->buf_len == 0) {
-        return false;
-    } else {
-        seek(this->buf_start + this->buf_len, SEEK_SET);
-        fastTell();
-        return fastRead(ch);
-    }
-}
-
-inline void
-InputSource::fastUnread(bool back)
-{
-    this->last_offset -= back ? 1 : 0;
-    seek(this->last_offset, SEEK_SET);
-}
-
 #endif // QPDF_INPUTSOURCE_HH
diff --git a/libqpdf/InputSource.cc b/libqpdf/InputSource.cc
index 9389c2f5..12778522 100644
--- a/libqpdf/InputSource.cc
+++ b/libqpdf/InputSource.cc
@@ -1,4 +1,4 @@
-#include <qpdf/InputSource.hh>
+#include <qpdf/InputSource_private.hh>
 
 #include <qpdf/QIntC.hh>
 #include <qpdf/QTC.hh>
diff --git a/libqpdf/QPDFTokenizer.cc b/libqpdf/QPDFTokenizer.cc
index 7f7c6d9e..9eba21bd 100644
--- a/libqpdf/QPDFTokenizer.cc
+++ b/libqpdf/QPDFTokenizer.cc
@@ -3,6 +3,7 @@
 // DO NOT USE ctype -- it is locale dependent for some things, and it's not worth the risk of
 // including it in case it may accidentally be used.
 
+#include <qpdf/InputSource_private.hh>
 #include <qpdf/QIntC.hh>
 #include <qpdf/QPDFExc.hh>
 #include <qpdf/QPDFObjectHandle.hh>
diff --git a/libqpdf/qpdf/InputSource_private.hh b/libqpdf/qpdf/InputSource_private.hh
new file mode 100644
index 00000000..a81efe40
--- /dev/null
+++ b/libqpdf/qpdf/InputSource_private.hh
@@ -0,0 +1,59 @@
+#ifndef QPDF_INPUTSOURCE_PRIVATE_HH
+#define QPDF_INPUTSOURCE_PRIVATE_HH
+
+#include <qpdf/InputSource.hh>
+
+inline void
+InputSource::loadBuffer()
+{
+    buf_idx = 0;
+    buf_len = qpdf_offset_t(read(buffer, buf_size));
+    // NB read sets last_offset
+    buf_start = last_offset;
+}
+
+inline qpdf_offset_t
+InputSource::fastTell()
+{
+    if (buf_len == 0) {
+        loadBuffer();
+    } else {
+        auto curr = tell();
+        if (curr < buf_start || curr >= (buf_start + buf_len)) {
+            loadBuffer();
+        } else {
+            last_offset = curr;
+            buf_idx = curr - buf_start;
+        }
+    }
+    return last_offset;
+}
+
+inline bool
+InputSource::fastRead(char& ch)
+{
+    // Before calling fastRead, fastTell must be called to prepare the buffer. Once reading is
+    // complete, fastUnread must be called to set the correct file position.
+    if (buf_idx < buf_len) {
+        ch = buffer[buf_idx];
+        ++(buf_idx);
+        ++(last_offset);
+        return true;
+
+    } else if (buf_len == 0) {
+        return false;
+    } else {
+        seek(buf_start + buf_len, SEEK_SET);
+        fastTell();
+        return fastRead(ch);
+    }
+}
+
+inline void
+InputSource::fastUnread(bool back)
+{
+    last_offset -= back ? 1 : 0;
+    seek(last_offset, SEEK_SET);
+}
+
+#endif // QPDF_INPUTSOURCE_PRIVATE_HH