pydablooms: add error handling and reporting

 * add default values for named parameters
 * add simple parameter checking
 * add new exception type to be used when reporting errors
 * add check for existing filter in dealloc

from bitly#60

pydablooms/pydablooms.c

@@ -4,14 +4,17 @@
 
 int Py_ModuleVersion = 1;
 
+static PyObject *DabloomsError;
+
 typedef struct {
     PyObject_HEAD
     scaling_bloom_t *filter;    /* Type-specific fields go here. */
 } Dablooms;
 
 static void Dablooms_dealloc(Dablooms *self)
 {
-    free_scaling_bloom(self->filter);
+	if(self->filter)
+        free_scaling_bloom(self->filter);
     self->ob_type->tp_free((PyObject *)self);
 }
 
@@ -24,21 +27,33 @@ static PyObject *Dablooms_new(PyTypeObject *type, PyObject *args, PyObject *kwds
     }
 
     self->filter = NULL;
-
     return (PyObject *) self;
 }
 
 static int Dablooms_init(Dablooms *self, PyObject *args, PyObject *kwds)
 {
-    double error_rate;
-    const char *filepath;
-    unsigned int capacity;
+    double error_rate = 0.1;
+    const char *filepath = "/tmp/bloom.bin";
+    int capacity = 1;  // dropped the unsigned modifier to avoid implicit conversion from negative
     static char *kwlist[] = {"capacity", "error_rate", "filepath", NULL};
 
     if (! PyArg_ParseTupleAndKeywords(args, kwds, "|ids", kwlist,
                                       &capacity, &error_rate, &filepath)) {
         return -1;
     }
+
+    if (capacity < 1){
+        PyErr_SetString(DabloomsError, "Bloom creation failed: capacity must be greater than zero");
+    	return -1;
+    }
+    if (error_rate > 1 || error_rate < 0){
+    	PyErr_SetString(DabloomsError, "Bloom creation failed: error_rate must be between 0 and 1");
+    	return -1;
+    }
+    if(!(filepath && strlen(filepath))){
+    	PyErr_SetString(DabloomsError, "Bloom creation failed: filepath required");
+    	return -1;
+    }
 
     self->filter = new_scaling_bloom(capacity, error_rate, filepath);
 
@@ -181,18 +196,36 @@ static PyTypeObject DabloomsType = {
 static PyObject *load_dabloom(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
     Dablooms *self = (Dablooms *)PyObject_New(Dablooms, &DabloomsType);
-    double error_rate;
-    const char *filepath;
-    unsigned int capacity;
+    double error_rate = 0.1;
+    const char *filepath = "/tmp/bloom.bin";
+    int capacity = 1;  // dropped the unsigned modifier to avoid implicit conversion from negative
+    int result = 0;
     static char *kwlist[] = {"capacity", "error_rate", "filepath", NULL};
-    
+
     if (! PyArg_ParseTupleAndKeywords(args, kwds, "|ids", kwlist,
                                       &capacity, &error_rate, &filepath)) {
         return NULL;
     }
-
-    self->filter = new_scaling_bloom_from_file(capacity, error_rate, filepath);
-    return (PyObject *) self;
+
+    if (capacity < 1){
+        PyErr_SetString(DabloomsError, "Bloom creation failed: capacity must be greater than zero");
+    	result = -1;
+    }
+    else if (error_rate > 1 || error_rate < 0){
+    	PyErr_SetString(DabloomsError, "Bloom creation failed: error_rate must be between 0 and 1");
+    	result = -1;
+    }
+    else if(!(filepath && strlen(filepath))){
+    	PyErr_SetString(DabloomsError, "Bloom creation failed: filepath required");
+    	result = -1;
+    }
+
+    if (!result){
+        self->filter = new_scaling_bloom_from_file(capacity, error_rate, filepath);
+        return (PyObject *) self;
+    }
+    Dablooms_dealloc(self);
+    return NULL;
 }
 
 static PyMethodDef pydablooms_methods[] = {
@@ -222,4 +255,8 @@ PyMODINIT_FUNC initpydablooms(void)
 
     Py_INCREF(&DabloomsType);
     PyModule_AddObject(m, "Dablooms", (PyObject *)&DabloomsType);
+
+    DabloomsError = PyErr_NewException("Dablooms.Error", NULL, NULL);
+    Py_INCREF(DabloomsError);
+    PyModule_AddObject(m, "error", DabloomsError);
 }