Work in progress

c_src/esqlite_nif.c

@@ -5,6 +5,7 @@
 #include <stdio.h> /* for debugging */
 #include <erl_nif.h>
 
+#include "queue.h"
 #include "sqlite3.h"
 
 #define MAX_PATHNAME 512 /* unfortunately not in sqlite.h. */
@@ -14,65 +15,176 @@ static ErlNifResourceType *esqlite_sqlite3_type = NULL;
 static ERL_NIF_TERM _atom_ok;
 static ERL_NIF_TERM _atom_error;
 
+/* database connection context */
 typedef struct {
+  ErlNifTid tid;
+  ErlNifThreadOpts* opts;
+  
   sqlite3 *db;
-} esqlite_sqlite3;
+  queue *commands;
+
+  int alive;
+} esqlite_db;
+
+typedef enum {
+  cmd_unknown,
+  cmd_open,
+  cmd_exec,
+  cmd_close,
+  cmd_stop
+} command_type;
+
+typedef struct {
+  command_type type;
+
+  ErlNifEnv *env;
+  ERL_NIF_TERM ref; 
+  ErlNifPid pid;
+
+  /* Args */
+
+} esqlite_command;
+
+static void
+command_destroy(void *obj) 
+{
+  esqlite_command *cmd = (esqlite_command *) obj;
+
+  if(cmd->env != NULL) 
+    enif_free_env(cmd->env);
+  enif_free(cmd);
+}
+
+static esqlite_command *
+command_create() 
+{
+  esqlite_command *cmd = (esqlite_command *) enif_alloc(sizeof(esqlite_command));
+  if(cmd == NULL)
+    return NULL;
+
+  cmd->env = enif_alloc_env();
+  if(cmd->env == NULL) {
+    command_destroy(cmd);
+    return NULL;
+  }
+
+  cmd->type = cmd_unknown;
+  cmd->ref = 0;
+}
 
 /*
  */
-static void descruct_esqlite_sqlite3(ErlNifEnv *env, void *esqlite_db)
+static void 
+descruct_esqlite_db(ErlNifEnv *env, void *arg)
 {
-  /* The destructor should only be called after all the prepared statements are finalized... */
-  /* TODO keep references, so this is the case */
-  int rc;
-  
-  rc = sqlite3_close(((esqlite_sqlite3 *) esqlite_db)->db);
-  if(rc == SQLITE_BUSY) {
-    /* Can I raise exceptions here errors here? */
-    fprintf(stderr, "Close failed, still busy\n");
+  esqlite_db *db = (esqlite_db *) arg;
+  esqlite_command *cmd = command_create();
+
+  /* send the stop command */
+  cmd->type = cmd_stop;
+  queue_push(db->commands, cmd);
+  queue_send(db->commands, cmd);
+
+  /* wait for the thread to finish */
+  enif_thread_join(db->tid, NULL);
+  enif_thread_opts_destroy(db->opts);
+}
+
+static void *
+esqlite_db_run(void *arg)
+{
+  esqlite_db *db = (esqlite_db *) arg;
+  esqlite_command *cmd;
+
+  db->alive = 1;
+
+  /* Wait for incoming commands and execute them */
+  while(1) {
+    cmd = get_command(db);
+
+    /* We are stopping... */
+    if(cmd_stop == command->type) {
+      command_destroy(command);
+      break;
+    }
+
+    /* Evaluate the command */
+    switch(command->type) {
+    cmd_open:
+      /* do open */
+      break;
+    cmd_exec:
+      /* do exec */
+      break;
+    cmd_close:
+      /* do close */
+      break;
+    default:
+      assert(0 && "Invalid command");
+    }
+
+    enif_send(NULL, &(command->pid), command->env, _atom_ok);
+    command_destroy(command);
   }
+
+  db->alive = 0;
 }
 
 /*
  * Open database. Expects utf-8 input
-*/
-static ERL_NIF_TERM esqlite_open_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+ *
+ * Note the database is opened in a thread. New commands are send to
+ * the thread and when it finishes the result is send back. The reason
+ * for this is that we don't want to block the erlang scheduler of the
+ * calling function.
+ */
+static ERL_NIF_TERM 
+start_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
 {
-    char filename[MAX_PATHNAME];
-    sqlite3 *db;
-    esqlite_sqlite3 *esqldb;
-    ERL_NIF_TERM esqlite_db;
-   
-    /* TODO ignores the utf-8 stuff for now. nifs only encoding is latin1 */
-    if(!enif_get_string(env, argv[0], filename, MAX_PATHNAME, ERL_NIF_LATIN1))
-        return enif_make_badarg(env);   
+  esqlite_db *esqldb;
+  ERL_NIF_TERM esqlite_db;
 
-    if(sqlite3_open(filename, &db)) {
-      fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
-      sqlite3_close(db);
-      /* TODO maak een error tuple */
-      return enif_make_tuple2(env, _atom_error, _atom_error); /* todo add error message */
-    }
+  /* initialize the resource */
+  esqldb = enif_alloc_resource(esqlite_sqlite3_type, sizeof(esqlite_db));
+  esqldb->db = NULL;
+  esqldb->alive = 0;
 
-    esqldb = enif_alloc_resource(esqlite_sqlite3_type, sizeof(esqlite_sqlite3));
-    esqldb->db = db;
-    esqlite_db = enif_make_resource(env, esqldb);
-    enif_release_resource(esqldb);
+  /* Start the command processing thread */
+  esqldb->opts = enif_thread_opts_create("esqldb_thread_opts");
+  if(enif_thread_create("", &esqldb->tid, esqlite_db_run, esqldb, esqldb->opts) != 0) {
+    goto error;
+  }
 
-    return enif_make_tuple2(env, _atom_ok, esqlite_db);
+  /* */
+  esqlite_db = enif_make_resource(env, esqldb);
+  enif_release_resource(esqldb);
+
+  return enif_make_tuple2(env, _atom_ok, esqlite_db);
 }
 
-static ERL_NIF_TERM esqlite_prepare_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+static ERL_NIF_TERM
+esqlite_open_nif(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 {
-
-  return enif_make_tuple2(env, _atom_ok, _atom_ok);
+  return _atom_ok;
 }
 
+static ERL_NIF_TERM 
+esqlite_exec_nif(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+  return _atom_ok;
+}
 
-static int on_load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
+static ERL_NIF_TERM
+esqlite_close_nif(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+  return _atom_ok;
+}
+
+static int 
+on_load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
 {
   ErlNifResourceType *rt = enif_open_resource_type(env, "esqlite", "esqlite_sqlite3_type", 
-						   descruct_esqlite_sqlite3, ERL_NIF_RT_CREATE, NULL);
+						   descruct_esqlite_db, ERL_NIF_RT_CREATE, NULL);
   if(!rt) 
     return -1;
 
@@ -86,8 +198,10 @@ static int on_load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
 
 
 static ErlNifFunc nif_funcs[] = {
-  {"open", 1, esqlite_open_nif},
-  {"prepare", 2, esqlite_prepare_nif}
+  {"esqlite_start", 0, start_nif},
+  {"esqlite_open", 2, esqlite_open_nif},
+  {"esqlite_exec", 4, esqlite_exec_nif}, 
+  {"esqlite_close", 3, esqlite_close_nif}
 };
 
 ERL_NIF_INIT(esqlite, nif_funcs, on_load, NULL, NULL, NULL);

src/esqlite.erl

@@ -5,18 +5,79 @@
 -module(esqlite).
 -author("Maas-Maarten Zeeman <mmzeeman@xs4all.nl>").
 
--export([open/1, prepare/2]).
+-export([open/1, open/2, exec/2, exec/3, close/1, close/2]).
 
 -on_load(init/0).
 
+-define(DEFAULT_TIMEOUT, infinity).
+
 init() ->
     ok = erlang:load_nif(code:priv_dir(esqlite) ++ "/esqlite_nif", 0).
 
 %% @doc Open a new database connection
 %%
-open(_Filename) ->
+open(Filename) ->
+    open(Filename, ?DEFAULT_TIMEOUT).
+
+%% @doc Open a database connection
+%%
+open(Filename, Timeout) ->
+    Db = esqlite_start(),
+
+    Ref = make_ref(),
+    ok = esqlite_open(Db, Ref, Filename, self()),
+    case receive_answer(Ref, Timeout) of
+	ok ->
+	    {ok, Db};
+	Other ->
+	    {error, Other}
+    end.
+
+%% @doc Execute Sql statement
+%%
+exec(Sql, Db) ->
+    exec(Sql, Db, ?DEFAULT_TIMEOUT).
+
+exec(Sql, Db, Timeout) ->
+    Ref = make_ref(),
+    ok = esqlite_exec(Db, Ref, self(), Sql),
+    receive_answer(Ref, Timeout).
+
+%% @doc Close the database
+%%
+close(Db) ->
+    close(Db, ?DEFAULT_TIMEOUT).
+
+close(Db, Timeout) ->
+    Ref = make_ref(),
+    ok = esqlite_close(Db, Ref, self()),
+    receive_answer(Ref, Timeout).
+    
+
+%% ---- Internal ----
+esqlite_start() ->
     exit(nif_library_not_loaded).
 
-prepare(_Db, _Sql) ->
+esqlite_open(_Db, _Ref, _Dest, _Filename) ->
     exit(nif_library_not_loaded).
 
+esqlite_exec(_Db, _Ref, _Dest, _Sql) ->
+    exit(nif_library_not_loaded).
+
+esqlite_close(_Db, _Ref, _Dest) ->
+    exit(nif_library_not_loaded).
+
+receive_answer(Ref, Timeout) ->
+    receive 
+	{Ref, Resp} ->
+	    Resp;
+	Other ->
+	    throw(Other)
+    after Timeout ->
+	    throw({error, timeout, Ref})
+    end.
+
+    
+
+
+

test/esqlite_test.erl

@@ -6,5 +6,13 @@
 
 -include_lib("eunit/include/eunit.hrl").
 
-open_test() ->
-    {ok, C} = esqlite:open("test.db").
+open_single_database_test() ->
+    {ok, _C1} = esqlite:open("test.db"),
+    ok.
+
+open_multiple_databases_test() ->
+    {ok, _C1} = esqlite:open("test.db"),
+    {ok, _C2} = esqlite:open("test.db"),
+
+    ok.
+