Fix GetEnteringArcs declaration...

Author: danpovey

k2/csrc/fsa.h

@@ -112,17 +112,6 @@ struct DenseFsa {
   DenseFsa(Weight *data, int32_t T, int32_t num_symbols, int32_t stride);
 };
 
-/*
-  this general-purpose structure conceptually the same as
-  std::vector<std::vector>; elements of `ranges` are (begin, end) indexes into
-  `values`.
-
-
- */
-struct VecOfVec {
-  std::vector<std::pair<int32, int32> > elems;
-};
-
 struct Fst {
   Fsa core;
   std::vector<int32_t> aux_label;

k2/csrc/fsa_util.h

@@ -15,10 +15,23 @@ namespace k2 {
   Computes lists of arcs entering each state (needed for algorithms that
   traverse the Fsa in reverse order).
 
-  Requires that `fsa` be valid and top-sorted, i.e.
-  CheckProperties(fsa, KTopSorted) == true.
+  Requires that `fsa` be valid and top-sorted, i.e.  CheckProperties(fsa,
+  KTopSorted) == true.
+
+    @param [out] arc_index   A list of arc indexes.
+                             For states 0 < s < fsa.NumStates(),
+                             the elements arc_index[i] for end_index[s-1] <= i < end_index[s]
+                             contain the arc-indexes in fsa.arcs for arcs that
+                             enter state s.
+    @param [out] end_index   For each state, the `end` index in `arc_index`
+                             where we can find arcs entering this state, i.e.
+                             one past the index of the last element in `arc_index`
+                             that points to an arc entering this state.
 */
-void GetEnteringArcs(const Fsa &fsa, VecOfVec *entering_arcs);
+void GetEnteringArcs(const Fsa &fsa,
+                     std::vector<int32_t> *arc_index,
+                     std::vector<int32_t> *end_index);
+
 
 }  // namespace k2