Add support for filtering during manifest parsing and serialization

6 files changed, 92 insertions, 20 deletions

diff --git a/libbutl/manifest-parser.cxx b/libbutl/manifest-parser.cxx
index 20932e3..9aa35b7 100644
--- a/libbutl/manifest-parser.cxx
+++ b/libbutl/manifest-parser.cxx
@@ -41,13 +41,17 @@ namespace butl
   using parsing = manifest_parsing;
   using name_value = manifest_name_value;
 
-  name_value manifest_parser::
-  next ()
+  void manifest_parser::
+  parse_next (name_value& r)
   {
     if (s_ == end)
-      return name_value {
+    {
+      r = name_value {
         "", "", line, column, line, column, position, position, position};
 
+      return;
+    }
+
     auto clp (skip_spaces ());
     xchar c (clp.first);
     uint64_t start_pos (clp.second);
@@ -67,15 +71,18 @@ namespace butl
     {
       s_ = start;
 
-      return name_value {"", "",
-                         c.line, c.column, c.line, c.column,
-                         start_pos, c.position, c.position};
+      r = name_value {"", "",
+                      c.line, c.column, c.line, c.column,
+                      start_pos, c.position, c.position};
+      return;
     }
 
+    r.name.clear ();
+    r.value.clear ();
+
     // Regardless of the state, what should come next is a name,
     // potentially the special empty one.
     //
-    name_value r;
     r.start_pos = start_pos;
 
     parse_name (r);
@@ -98,7 +105,7 @@ namespace butl
       r.value_column = r.name_column;
       r.colon_pos = r.start_pos;
       r.end_pos = r.start_pos;
-      return r;
+      return;
     }
 
     if (c != ':')
@@ -162,8 +169,6 @@ namespace butl
       //
       assert (!r.name.empty ());
     }
-
-    return r;
   }
 
   pair<string, string> manifest_parser::
diff --git a/libbutl/manifest-parser.ixx b/libbutl/manifest-parser.ixx
new file mode 100644
index 0000000..b308264
--- /dev/null
+++ b/libbutl/manifest-parser.ixx
@@ -0,0 +1,14 @@
+// file      : libbutl/manifest-parser.ixx -*- C++ -*-
+// copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+namespace butl
+{
+  inline manifest_name_value manifest_parser::
+  next ()
+  {
+    manifest_name_value r;
+    do { parse_next (r); } while (filter_ && !filter_ (r));
+    return r;
+  }
+}
diff --git a/libbutl/manifest-parser.mxx b/libbutl/manifest-parser.mxx
index 7fc4ee3..0289d6f 100644
--- a/libbutl/manifest-parser.mxx
+++ b/libbutl/manifest-parser.mxx
@@ -11,9 +11,10 @@
 #ifndef __cpp_lib_modules
 #include <string>
 #include <iosfwd>
-#include <cstdint>   // uint64_t
-#include <utility>   // pair
-#include <stdexcept> // runtime_error
+#include <cstdint>    // uint64_t
+#include <utility>    // pair, move()
+#include <stdexcept>  // runtime_error
+#include <functional>
 #endif
 
 // Other includes.
@@ -52,8 +53,19 @@ LIBBUTL_MODEXPORT namespace butl
   class LIBBUTL_SYMEXPORT manifest_parser: protected butl::char_scanner
   {
   public:
-    manifest_parser (std::istream& is, const std::string& name)
-        : char_scanner (is), name_ (name) {}
+    // The filter, if specified, is called by next() prior to returning the
+    // pair to the caller. If the filter returns false, then the pair is
+    // discarded.
+    //
+    // Note that the filter should handle the end-of-manifest pairs (see
+    // below) carefully, so next() doesn't end up with an infinite cycle.
+    //
+    using filter_function = bool (manifest_name_value&);
+
+    manifest_parser (std::istream& is,
+                     const std::string& name,
+                     std::function<filter_function> filter = {})
+      : char_scanner (is), name_ (name), filter_ (std::move (filter)) {}
 
     const std::string&
     name () const {return name_;}
@@ -83,6 +95,9 @@ LIBBUTL_MODEXPORT namespace butl
 
   private:
     void
+    parse_next (manifest_name_value&);
+
+    void
     parse_name (manifest_name_value&);
 
     void
@@ -98,8 +113,11 @@ LIBBUTL_MODEXPORT namespace butl
 
   private:
     const std::string name_;
+    const std::function<filter_function> filter_;
 
     enum {start, body, end} s_ = start;
     std::string version_; // Current format version.
   };
 }
+
+#include <libbutl/manifest-parser.ixx>
diff --git a/libbutl/manifest-serializer.cxx b/libbutl/manifest-serializer.cxx
index 2d2e722..dfbd9e1 100644
--- a/libbutl/manifest-serializer.cxx
+++ b/libbutl/manifest-serializer.cxx
@@ -39,7 +39,7 @@ namespace butl
   using serialization = manifest_serialization;
 
   void manifest_serializer::
-  next (const string& n, const string& v)
+  write_next (const string& n, const string& v)
   {
     switch (s_)
     {
diff --git a/libbutl/manifest-serializer.ixx b/libbutl/manifest-serializer.ixx
new file mode 100644
index 0000000..1108ba1
--- /dev/null
+++ b/libbutl/manifest-serializer.ixx
@@ -0,0 +1,13 @@
+// file      : libbutl/manifest-serializer.ixx -*- C++ -*-
+// copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+namespace butl
+{
+  inline void manifest_serializer::
+  next (const std::string& n, const std::string& v)
+  {
+    if (!filter_ || filter_ (n, v))
+      write_next (n, v);
+  }
+}
diff --git a/libbutl/manifest-serializer.mxx b/libbutl/manifest-serializer.mxx
index 66ca398..6a87656 100644
--- a/libbutl/manifest-serializer.mxx
+++ b/libbutl/manifest-serializer.mxx
@@ -11,8 +11,9 @@
 #ifndef __cpp_lib_modules
 #include <string>
 #include <iosfwd>
-#include <cstddef>   // size_t
-#include <stdexcept> // runtime_error
+#include <cstddef>    // size_t
+#include <stdexcept>  // runtime_error
+#include <functional>
 #endif
 
 // Other includes.
@@ -42,8 +43,23 @@ LIBBUTL_MODEXPORT namespace butl
   class LIBBUTL_SYMEXPORT manifest_serializer
   {
   public:
-    manifest_serializer (std::ostream& os, const std::string& name)
-        : os_ (os), name_ (name) {}
+    // The filter, if specified, is called by next() prior to serializing the
+    // pair into the stream. If the filter returns false, then the pair is
+    // discarded.
+    //
+    // Note that currently there is no way for the filter to modify the name
+    // or value. If we ever need this functionality, then we can add an
+    // "extended" filter alternative with two "receiving" arguments:
+    //
+    // bool (..., optional<string>& n, optional<string>& v);
+    //
+    using filter_function = bool (const std::string& name,
+                                  const std::string& value);
+
+    manifest_serializer (std::ostream& os,
+                         const std::string& name,
+                         std::function<filter_function> filter = {})
+        : os_ (os), name_ (name), filter_ (std::move (filter)) {}
 
     const std::string&
     name () const {return name_;}
@@ -77,6 +93,9 @@ LIBBUTL_MODEXPORT namespace butl
   private:
     friend class manifest_rewriter;
 
+    void
+    write_next (const std::string& name, const std::string& value);
+
     // Validate and write a name.
     //
     void
@@ -105,5 +124,8 @@ LIBBUTL_MODEXPORT namespace butl
   private:
     std::ostream& os_;
     const std::string name_;
+    const std::function<filter_function> filter_;
   };
 }
+
+#include <libbutl/manifest-serializer.ixx>