Added truncate command.

c_src/bdberl_drv.c

@@ -29,6 +29,7 @@ static void do_async_put(void* arg);
 static void do_async_get(void* arg);
 static void do_async_txnop(void* arg);
 static void do_async_cursor_get(void* arg);
+static void do_async_truncate(void* arg);
 
 static int add_dbref(PortData* data, int dbref);
 static int del_dbref(PortData* data, int dbref);
@@ -606,6 +607,42 @@ static int bdberl_drv_control(ErlDrvData handle, unsigned int cmd,
         int rc = delete_database(dbname);
         RETURN_INT(rc, outbuf);
     }
+    case CMD_TRUNCATE:
+    {
+        FAIL_IF_ASYNC_PENDING(d, outbuf);
+
+        // Fail if a cursor is open
+        if (d->cursor)
+        {
+            RETURN_INT(ERROR_CURSOR_OPEN, outbuf);
+        }
+
+        // Inbuf is: <<DbRef:32>>
+        int dbref = UNPACK_INT(inbuf, 0);
+
+        DBG("Truncating...\n");
+
+        // Make sure this port currently has dbref open -- if it doesn't, error out. Of note,
+        // if it's in our list, we don't need to grab the RWLOCK, as we don't have to worry about
+        // the underlying handle disappearing since we have a reference.
+        if (has_dbref(d, dbref))
+        {
+            DBG("Doing truncate....");
+            // Mark the port as busy and then schedule the appropriate async operation
+            d->async_op = cmd;
+            d->async_pool = G_TPOOL_GENERAL;
+            d->async_job = bdberl_tpool_run(G_TPOOL_GENERAL, &do_async_truncate, d, 0);
+
+            // Let caller know that the operation is in progress
+            // Outbuf is: <<0:32>>
+            RETURN_INT(0, outbuf);
+        }
+        else
+        {
+            // Invalid dbref
+            RETURN_INT(ERROR_INVALID_DBREF, outbuf);
+        }
+    }
     }
     *outbuf = 0;
     return 0;
@@ -1104,6 +1141,48 @@ static void do_async_cursor_get(void* arg)
     }
 }
 
+static void do_async_truncate(void* arg)
+{
+    // Payload is: <<DbRef:32>>
+    PortData* d = (PortData*)arg;
+
+    // Get the database reference and flags from the payload
+    int dbref = UNPACK_INT(d->work_buffer, 0);
+    DB* db = G_DATABASES[dbref].db;
+
+    DBG("Truncating dbref %i\n", dbref);
+
+    u_int32_t count = 0;
+    int rc = db->truncate(db, d->txn, &count, 0);
+
+    // If any error occurs while we have a txn action, abort it
+    if (d->txn && rc)
+    {
+        d->txn->abort(d->txn);
+        d->txn = 0;
+    }
+
+    // Save the port and pid references -- we need copies independent from the PortData
+    // structure. Once we release the port_lock after clearing the cmd, it's possible that
+    // the port could go away without waiting on us to finish. This is acceptable, but we need
+    // to be certain that there is no overlap of data between the two threads. driver_send_term
+    // is safe to use from a thread, even if the port you're sending from has already expired.
+    ErlDrvPort port = d->port;
+    ErlDrvTermData port_owner = d->port_owner;
+
+    // Release the port for another operation
+    d->async_pool = 0;
+    d->async_job  = 0;
+    d->work_buffer_offset = 0;
+    erl_drv_mutex_lock(d->port_lock);
+    d->async_op = CMD_NONE;
+    erl_drv_mutex_unlock(d->port_lock);
+
+    // TODO: May need to tag the messages a bit more explicitly so that if another async
+    // job runs to completion before the message gets delivered we don't mis-interpret this
+    // response code.
+    send_ok_or_error(port, port_owner, rc);
+}
 
 
 static void* zalloc(unsigned int size)

c_src/bdberl_drv.h

@@ -44,6 +44,7 @@ static int bdberl_drv_control(ErlDrvData handle, unsigned int cmd,
 #define CMD_CURSOR_CLOSE    13
 #define CMD_PUT_COMMIT      14
 #define CMD_REMOVE_DB       15
+#define CMD_TRUNCATE        16
 
 
 /**

include/bdberl.hrl

@@ -21,6 +21,7 @@
 -define(CMD_CURSOR_CLOSE, 13).
 -define(CMD_PUT_COMMIT,   14).
 -define(CMD_REMOVE_DB,    15).
+-define(CMD_TRUNCATE,     16).
 
 -define(DB_TYPE_BTREE, 1).
 -define(DB_TYPE_HASH,  2).

src/bdberl.erl

@@ -20,6 +20,7 @@
          get/2, get/3,
          get_r/2, get_r/3,
          update/3, update/4,
+         truncate/1,
          delete_database/1,
          cursor_open/1, cursor_next/0, cursor_prev/0, cursor_current/0, cursor_close/0]).
 
@@ -209,6 +210,20 @@ update(Db, Key, Fun, Args) ->
         end,
     transaction(F).
 
+truncate(Db) ->
+    Cmd = <<Db:32/native>>,
+    <<Result:32/native-signed>> = erlang:port_control(get_port(), ?CMD_TRUNCATE, Cmd),
+    case decode_rc(Result) of
+        ok ->
+            receive
+                ok -> ok;
+                {error, Reason} -> {error, {truncate, decode_rc(Reason)}}
+            end;
+
+        Error ->
+            {error, {truncate, decode_rc(Error)}}
+    end.
+
 cursor_open(Db) ->
     Cmd = <<Db:32/native, 0:32/native>>,
     <<Rc:32/native-signed>> = erlang:port_control(get_port(), ?CMD_CURSOR_OPEN, Cmd),

test/bdberl_SUITE.erl

@@ -28,7 +28,8 @@ all() ->
      put_commit_should_end_txn,
      data_dir_should_be_priv_dir,
      delete_should_remove_file, 
-     delete_should_fail_if_db_inuse].
+     delete_should_fail_if_db_inuse,
+     truncate_should_empty_database].
 
 
 dbconfig(Config) ->
@@ -212,3 +213,9 @@ delete_should_fail_if_db_inuse(Config) ->
     true = filelib:is_file(Fname),
     {error, _} = bdberl:delete_database(Fname),
     true = filelib:is_file(Fname).
+
+truncate_should_empty_database(Config) ->
+    Db = ?config(db, Config),
+    ok = bdberl:put(Db, mykey, avalue),
+    ok = bdberl:truncate(Db),
+    not_found = bdberl:get(Db, mykey).