fast word completion for functions names in the shell

src/runtime/c/pgf/namespace.h

@@ -627,6 +627,32 @@ void namespace_iter(Namespace<V> map, PgfItor* itor, PgfExn *err)
         return;
 }
 
+template <class V>
+void namespace_iter_prefix(Namespace<V> map, PgfText *prefix, PgfItor* itor, PgfExn *err)
+{
+    if (map == 0)
+        return;
+
+    int cmp = textcmp_prefix(prefix,&map->value->name);
+    if (cmp < 0)
+        namespace_iter_prefix(map->left, prefix, itor, err);
+    else if (cmp > 0)
+        namespace_iter_prefix(map->right, prefix, itor, err);
+    else {
+        namespace_iter_prefix(map->left, prefix, itor, err);
+        if (err->type != PGF_EXN_NONE)
+            return;
+
+        itor->fn(itor, &map->value->name, map->value.as_object(), err);
+        if (err->type != PGF_EXN_NONE)
+            return;
+
+        namespace_iter_prefix(map->right, prefix, itor, err);
+        if (err->type != PGF_EXN_NONE)
+            return;
+    }
+}
+
 template <class V>
 Namespace<V> namespace_map(Namespace<V> map, std::function<ref<V>(ref<V>)> f)
 {

src/runtime/c/pgf/pgf.cxx

@@ -487,6 +487,19 @@ void pgf_iter_functions(PgfDB *db, PgfRevision revision,
     } PGF_API_END
 }
 
+PGF_API
+void pgf_iter_functions_by_prefix(PgfDB *db, PgfRevision revision,
+                                  PgfText *prefix, PgfItor *itor, PgfExn *err)
+{
+    PGF_API_BEGIN {
+        DB_scope scope(db, READER_SCOPE);
+        ref<PgfPGF> pgf = db->revision2pgf(revision);
+
+        pgf_exn_clear(err);
+        namespace_iter_prefix(pgf->abstract.funs, prefix, itor, err);
+    } PGF_API_END
+}
+
 PGF_API
 void pgf_iter_functions_by_cat(PgfDB *db, PgfRevision revision,
                                PgfText *cat, PgfItor *itor, PgfExn *err)

src/runtime/c/pgf/pgf.h

@@ -336,6 +336,10 @@ PGF_API_DECL
 void pgf_iter_functions(PgfDB *db, PgfRevision revision,
                         PgfItor *itor, PgfExn *err);
 
+PGF_API_DECL
+void pgf_iter_functions_by_prefix(PgfDB *db, PgfRevision revision,
+                                  PgfText *prefix, PgfItor *itor, PgfExn *err);
+
 PGF_API_DECL
 void pgf_iter_functions_by_cat(PgfDB *db, PgfRevision revision,
                                PgfText *cat, PgfItor *itor, PgfExn *err);

src/runtime/c/pgf/text.cxx

@@ -16,6 +16,22 @@ int textcmp(PgfText *t1, PgfText *t2)
     }
 }
 
+PGF_INTERNAL
+int textcmp_prefix(PgfText *t1, PgfText *t2)
+{
+    for (size_t i = 0; ; i++) {
+        if (i >= t1->size)
+            return 0;
+        if (i >= t2->size)
+            return 1;
+
+        if (t1->text[i] > t2->text[i])
+            return 1;
+        else if (t1->text[i] < t2->text[i])
+            return -1;
+    }
+}
+
 PGF_INTERNAL
 void texticmp(PgfText *t1, PgfText *t2, int res[2])
 {

src/runtime/c/pgf/text.h

@@ -5,6 +5,10 @@
 PGF_INTERNAL_DECL
 int textcmp(PgfText *t1, PgfText *t2);
 
+/* The same as textcmp but returns 0 if t1 is a prefix of t2. */
+PGF_INTERNAL_DECL
+int textcmp_prefix(PgfText *t1, PgfText *t2);
+
 /* Performs both case-insensitive and case-sensitive comparison. 
  * The first element in res contains the result from
  * the case-insensitive comparison. The second the result