[Boost-commit] svn:boost r63098 - trunk/boost/spirit/home/support/iterators/detail

Subject: [Boost-commit] svn:boost r63098 - trunk/boost/spirit/home/support/iterators/detail
From: hartmut.kaiser_at_[hidden]
Date: 2010-06-19 08:54:05

Author: hkaiser
Date: 2010-06-19 08:54:04 EDT (Sat, 19 Jun 2010)
New Revision: 63098
URL: http://svn.boost.org/trac/boost/changeset/63098

Log:
Spirit: fixing problem in multi_pass
Text files modified: 
   trunk/boost/spirit/home/support/iterators/detail/istream_policy.hpp |    24 ++++++++++++++++++++----                
   1 files changed, 20 insertions(+), 4 deletions(-)

Modified: trunk/boost/spirit/home/support/iterators/detail/istream_policy.hpp
==============================================================================
--- trunk/boost/spirit/home/support/iterators/detail/istream_policy.hpp	(original)
+++ trunk/boost/spirit/home/support/iterators/detail/istream_policy.hpp	2010-06-19 08:54:04 EDT (Sat, 19 Jun 2010)
@@ -48,14 +48,19 @@
             static typename MultiPass::reference get_input(MultiPass& mp)
             {
                 if (!mp.shared()->initialized_)
-                    advance_input(mp);
+                    mp.shared()->read_one();
                 return mp.shared()->curtok_;
             }
 
             template <typename MultiPass>
             static void advance_input(MultiPass& mp)
             {
-                mp.shared()->read_one();
+                // We invalidate the currently cached input character to avoid
+                // reading more input from the underlying iterator than 
+                // required. Without this we would always read ahead one 
+                // character, even if this character never gets consumed by the 
+                // client.
+                mp.shared()->peek_one();
             }
 
             // test, whether we reached the end of the underlying stream
@@ -89,9 +94,20 @@
 
             void read_one()
             {
-                if (!(input_ >> curtok_))
+                if (!(input_ >> curtok_)) {
+                    initialized_ = false;
                     eof_reached_ = true;
-                initialized_ = true;
+                }
+                else {
+                    initialized_ = true;
+                }
+            }
+
+            void peek_one()
+            {
+                input_.peek();    // try for eof
+                initialized_ = false;
+                eof_reached_ = input_.eof();
             }
 
             T& input_;