add support for dlopen'd feature functions

5 files changed, 87 insertions, 0 deletions

diff --git a/decoder/Makefile.am b/decoder/Makefile.am
index 4a98a4f1..28863dbe 100644
--- a/decoder/Makefile.am
+++ b/decoder/Makefile.am
@@ -33,6 +33,7 @@ libcdec_a_SOURCES = \
   cfg.cc \
   dwarf.cc \
   ff_dwarf.cc \
+  ff_external.cc \
   rule_lexer.cc \
   fst_translator.cc \
   csplit.cc \
diff --git a/decoder/cdec_ff.cc b/decoder/cdec_ff.cc
index b516c386..54f6e12b 100644
--- a/decoder/cdec_ff.cc
+++ b/decoder/cdec_ff.cc
@@ -18,6 +18,7 @@
 #include "ff_charset.h"
 #include "ff_wordset.h"
 #include "ff_dwarf.h"
+#include "ff_external.h"
 
 #ifdef HAVE_GLC
 #include <cdec/ff_glc.h>
@@ -69,6 +70,7 @@ void register_feature_functions() {
   ff_registry.Register("WordPairFeatures", new FFFactory<WordPairFeatures>);
   ff_registry.Register("WordSet", new FFFactory<WordSet>);
   ff_registry.Register("Dwarf", new FFFactory<Dwarf>);
+  ff_registry.Register("External", new FFFactory<ExternalFeature>);
 #ifdef HAVE_GLC
   ff_registry.Register("ContextCRF", new FFFactory<Model1Features>);
 #endif
diff --git a/decoder/ff.h b/decoder/ff.h
index 6c22d39f..227787ca 100644
--- a/decoder/ff.h
+++ b/decoder/ff.h
@@ -27,6 +27,7 @@ typedef std::vector<WordID> Features; // set of features ids
 // depends on context, you may also need to implement
 // FinalTraversalFeatures(...)
 class FeatureFunction {
+  friend class ExternalFeature;
  public:
   std::string name_; // set by FF factory using usage()
   bool debug_; // also set by FF factory checking param for immediate initial "debug"
diff --git a/decoder/ff_external.cc b/decoder/ff_external.cc
new file mode 100644
index 00000000..520e98b1
--- /dev/null
+++ b/decoder/ff_external.cc
@@ -0,0 +1,57 @@
+#include "ff_external.h"
+#include "stringlib.h"
+
+#include <dlfcn.h>
+
+using namespace std;
+
+ExternalFeature::ExternalFeature(const string& param) {
+  size_t pos = param.find(' ');
+  string nparam;
+  string file = param;
+  if (pos < param.size()) {
+    nparam = Trim(param.substr(pos + 1));
+    file = param.substr(0, pos);
+  }
+  if (file.size() < 1) {
+    cerr << "External requires a path to a dynamic library!\n";
+    abort();
+  }
+  lib_handle = dlopen(file.c_str(), RTLD_LAZY);
+  if (!lib_handle) {
+    cerr << "dlopen reports: " << dlerror() << endl;
+    cerr << "Did you provide a full path to the dynamic library?\n";
+    abort();
+  }
+  FeatureFunction* (*fn)(const string&) =
+    (FeatureFunction* (*)(const string&))(dlsym(lib_handle, "create_ff"));
+  if (!fn) {
+    cerr << "dlsym reports: " << dlerror() << endl;
+    abort();
+  }
+  ff_ext = (*fn)(nparam);
+}
+
+ExternalFeature::~ExternalFeature() {
+  delete ff_ext;
+  dlclose(lib_handle);
+}
+
+void ExternalFeature::PrepareForInput(const SentenceMetadata& smeta) {
+  ff_ext->PrepareForInput(smeta);
+}
+
+void ExternalFeature::FinalTraversalFeatures(const void* context,
+                                             SparseVector<double>* features) const {
+  ff_ext->FinalTraversalFeatures(context, features);
+}
+
+void ExternalFeature::TraversalFeaturesImpl(const SentenceMetadata& smeta,
+                                     const Hypergraph::Edge& edge,
+                                     const std::vector<const void*>& ant_contexts,
+                                     FeatureVector* features,
+                                     FeatureVector* estimated_features,
+                                     void* context) const {
+  ff_ext->TraversalFeaturesImpl(smeta, edge, ant_contexts, features, estimated_features, context);
+}
+
diff --git a/decoder/ff_external.h b/decoder/ff_external.h
new file mode 100644
index 00000000..283e58e8
--- /dev/null
+++ b/decoder/ff_external.h
@@ -0,0 +1,26 @@
+#ifndef _FFEXTERNAL_H_
+#define _FFEXTERNAL_H_
+
+#include "ff.h"
+
+// dynamically loaded feature function
+class ExternalFeature : public FeatureFunction {
+ public:
+  ExternalFeature(const std::string& param);
+  ~ExternalFeature();
+  virtual void PrepareForInput(const SentenceMetadata& smeta);
+  virtual void FinalTraversalFeatures(const void* context,
+                                      SparseVector<double>* features) const;
+ protected:
+  virtual void TraversalFeaturesImpl(const SentenceMetadata& smeta,
+                                     const Hypergraph::Edge& edge,
+                                     const std::vector<const void*>& ant_contexts,
+                                     FeatureVector* features,
+                                     FeatureVector* estimated_features,
+                                     void* context) const;
+ private:
+  void* lib_handle;
+  FeatureFunction* ff_ext;
+};
+
+#endif