1 files changed, 91 insertions, 0 deletions
diff --git a/libbutl/char-scanner.cxx b/libbutl/char-scanner.cxx
new file mode 100644
index 0000000..cbc2503
--- /dev/null
+++ b/libbutl/char-scanner.cxx
@@ -0,0 +1,91 @@
+// file      : libbutl/char-scanner.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbutl/char-scanner.hxx>
+
+#include <istream>
+
+using namespace std;
+
+namespace butl
+{
+  auto char_scanner::
+  peek () -> xchar
+  {
+    if (unget_)
+      return buf_;
+    else
+    {
+      if (eos_)
+        return xchar (xchar::traits_type::eof (), line, column);
+      else
+      {
+        xchar::int_type v (is_.peek ());
+
+        if (v == xchar::traits_type::eof ())
+          eos_ = true;
+        else if (crlf_ && v == 0x0D)
+        {
+          is_.get ();
+          xchar::int_type v1 (is_.peek ());
+
+          if (v1 != '\n')
+          {
+            unget_ = true;
+            buf_ = '\n';
+          }
+
+          v = '\n';
+        }
+
+        return xchar (v, line, column);
+      }
+    }
+  }
+
+  auto char_scanner::
+  get () -> xchar
+  {
+    if (unget_)
+    {
+      unget_ = false;
+      return buf_;
+    }
+    else
+    {
+      // When is_.get () returns eof, the failbit is also set (stupid,
+      // isn't?) which may trigger an exception. To work around this
+      // we will call peek() first and only call get() if it is not
+      // eof. But we can only call peek() on eof once; any subsequent
+      // calls will spoil the failbit (even more stupid).
+      //
+      xchar c (peek ());
+
+      if (!eos (c))
+      {
+        is_.get ();
+
+        if (c == '\n')
+        {
+          line++;
+          column = 1;
+        }
+        else
+          column++;
+      }
+
+      return c;
+    }
+  }
+
+  void char_scanner::
+  unget (const xchar& c)
+  {
+    // Because iostream::unget cannot work once eos is reached,
+    // we have to provide our own implementation.
+    //
+    buf_ = c;
+    unget_ = true;
+  }
+}