Implement cstring type

Author: atpalmer

src/cstring.c

@@ -1,7 +1,43 @@
 #include <Python.h>
 
 struct cstring {
-    PyObject_HEAD
+    PyObject_VAR_HEAD
+    char value[];
+};
+
+#define CSTRING_VALUE(self) (((struct cstring *)self)->value)
+
+static PyObject *cstring_new(PyTypeObject *type, PyObject *args, PyObject **kwargs) {
+    char *value = NULL;
+
+    if(!PyArg_ParseTuple(args, "s", &value))
+        return NULL;
+
+    int size = strlen(value) + 1;
+
+    struct cstring *new = type->tp_alloc(type, size);
+    memcpy(new->value, value, size);
+    return (PyObject *)new;
+}
+
+static void cstring_dealloc(PyObject *self) {
+    Py_TYPE(self)->tp_free(self);
+}
+
+static PyObject *cstring_str(PyObject *self) {
+    return PyUnicode_FromString(CSTRING_VALUE(self));
+}
+
+static PyTypeObject cstring_type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "cstring",
+    .tp_doc = "",
+    .tp_basicsize = sizeof(struct cstring),
+    .tp_itemsize = sizeof(char),
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+    .tp_new = cstring_new,
+    .tp_dealloc = cstring_dealloc,
+    .tp_str = cstring_str,
 };
 
 static struct PyModuleDef module = {
@@ -13,5 +49,10 @@ static struct PyModuleDef module = {
 };
 
 PyMODINIT_FUNC PyInit_cstring(void) {
-    return PyModule_Create(&module);
+    if(PyType_Ready(&cstring_type) < 0)
+        return NULL;
+    Py_INCREF(&cstring_type);
+    PyObject *m = PyModule_Create(&module);
+    PyModule_AddObject(m, "cstring", (PyObject *)&cstring_type);
+    return m;
 }

test/test_cstring.py

@@ -1,6 +1,7 @@
-import cstring
+from cstring import cstring
 
 
-def test_cstring():
-    pass
+def test_str():
+    result = cstring('hello, world')
+    assert str(result) == 'hello, world'