started a new database-backed runtime from scratch

src/runtime/c/pgf.cxx

@@ -0,0 +1,51 @@
+#include "data.h"
+#include "reader.h"
+
+PGF_API
+PgfPGF *pgf_read(const char* fpath, PgfExn* err)
+{
+    PgfPGF *pgf = NULL;
+
+    try {
+        std::string fpath_n = fpath;
+        size_t len = fpath_n.length();
+        if (len > 4 && fpath_n.substr(len-4) == ".pgf")
+            fpath_n[len-3] = 'n';
+        else if (!(len > 4 && fpath_n.substr(len-4) == ".ngf"))
+            fpath_n += ".ngf";
+
+        pgf = new PgfPGF(fpath_n.c_str());
+
+        if (pgf->db.get_root<PgfPGFRoot>() == 0) {
+            std::ifstream in(fpath, std::ios::binary);
+            if (in.fail()) {
+                throw std::system_error(errno, std::generic_category());
+            }
+
+            PgfReader rdr(&in);
+            rdr.read_pgf(pgf);
+
+            pgf->set_root();
+        }
+
+        return pgf;
+    } catch (std::system_error& e) {
+        err->type = "system_error";
+        err->msg  = NULL;
+    } catch (pgf_error& e) {
+        err->type = "pgf_error";
+        err->msg  = e.what();
+    }
+
+    if (pgf != NULL)
+        delete pgf;
+
+    return NULL;
+}
+
+void PgfPGF::set_root() {
+    ref<PgfPGFRoot> root = db.malloc<PgfPGFRoot>();
+    root->major_version = major_version;
+    root->minor_version = minor_version;
+    db.set_root(root);
+}