OdbBackend: implement subclassed read_header

src/odb_backend.c

@@ -41,7 +41,8 @@ struct py_odb_backend
     git_odb_backend backend;
     PyObject *self;
     PyObject *read_callable,
-             *read_prefix_callable;
+             *read_prefix_callable,
+             *read_header_callable;
 };
 
 static int
@@ -65,7 +66,7 @@ py_odb_backend_read(void **ptr, size_t *sz,
         return GIT_EUSER;
 
     const char *bytes;
-    if (!PyArg_ParseTuple(result, "iy#", type, &bytes, sz) || !bytes)
+    if (!PyArg_ParseTuple(result, "ny#", type, &bytes, sz) || !bytes)
         return GIT_EUSER;
 
     /* XXX: This assumes the default libgit2 allocator is in use and will
@@ -100,7 +101,7 @@ py_odb_backend_read_prefix(git_oid *oid_out, void **ptr, size_t *sz,
         return GIT_EUSER;
 
     const char *bytes;
-    if (!PyArg_ParseTuple(result, "Oiy#",
+    if (!PyArg_ParseTuple(result, "Ony#",
                 &py_oid_out, type, &bytes, sz) || !bytes)
         return GIT_EUSER;
 
@@ -115,10 +116,36 @@ py_odb_backend_read_prefix(git_oid *oid_out, void **ptr, size_t *sz,
     return 0;
 }
 
+static int
+py_odb_backend_read_header(size_t *len, git_object_t *type,
+        git_odb_backend *_be, const git_oid *oid)
+{
+    int err;
+    PyObject *args, *py_oid, *result;
+    struct py_odb_backend *be = (struct py_odb_backend *)_be;
+
+    py_oid = git_oid_to_python(oid);
+    args = Py_BuildValue("(O)", py_oid);
+    result = PyObject_CallObject(be->read_header_callable, args);
+    Py_DECREF(py_oid);
+
+    if ((err = git_error_for_exc()) != 0) {
+        return err;
+    }
+
+    if (result == NULL)
+        return GIT_EUSER;
+
+    if (!PyArg_ParseTuple(result, "nn", type, len))
+        return GIT_EUSER;
+
+    return 0;
+}
+
 int
 OdbBackend_init(OdbBackend *self, PyObject *args, PyObject *kwds)
 {
-    if (kwds && PyTuple_Size(args) > 0) {
+    if (args && PyTuple_Size(args) > 0) {
         PyErr_SetString(PyExc_TypeError,
                         "OdbBackend takes no arguments");
         return -1;
@@ -135,18 +162,48 @@ OdbBackend_init(OdbBackend *self, PyObject *args, PyObject *kwds)
     be->self = (PyObject *)self;
 
     be->read_callable = PyObject_GetAttrString((PyObject *)self, "read");
-    if (be->read_callable)
+    if (be->read_callable) {
         be->backend.read = py_odb_backend_read;
+        Py_INCREF(be->read_callable);
+    }
 
     be->read_prefix_callable = PyObject_GetAttrString(
             (PyObject *)self, "read_prefix");
-    if (be->read_prefix_callable)
+    if (be->read_prefix_callable) {
         be->backend.read_prefix = py_odb_backend_read_prefix;
+        Py_INCREF(be->read_prefix_callable);
+    }
+
+    be->read_header_callable = PyObject_GetAttrString(
+            (PyObject *)self, "read_header");
+    if (be->read_header_callable) {
+        be->backend.read_header = py_odb_backend_read_header;
+        Py_INCREF(be->read_header_callable);
+    }
 
-    self->odb_backend = &be->backend;
+    self->odb_backend = (git_odb_backend *)be;
     return 0;
 }
 
+void
+OdbBackend_dealloc(OdbBackend *self)
+{
+    if (self->odb_backend && self->odb_backend->read == py_odb_backend_read) {
+        struct py_odb_backend *be = (struct py_odb_backend *)self->odb_backend;
+
+        if (be->read_callable)
+            Py_DECREF(be->read_callable);
+        if (be->read_prefix_callable)
+            Py_DECREF(be->read_prefix_callable);
+        if (be->read_header_callable)
+            Py_DECREF(be->read_header_callable);
+
+        free(be);
+    }
+
+    Py_TYPE(self)->tp_free((PyObject *) self);
+}
+
 static int
 OdbBackend_build_as_iter(const git_oid *oid, void *accum)
 {
@@ -267,9 +324,41 @@ OdbBackend_read_prefix(OdbBackend *self, PyObject *py_hex)
     return tuple;
 }
 
+PyDoc_STRVAR(OdbBackend_read_header__doc__,
+    "read_header(oid) -> (type, len)\n"
+    "\n"
+    "Read raw object header from this odb backend.\n");
+
+PyObject *
+OdbBackend_read_header(OdbBackend *self, PyObject *py_hex)
+{
+    int err;
+    size_t len;
+    git_object_t type;
+    git_oid oid;
+
+    if (self->odb_backend->read_header == NULL) {
+        Py_INCREF(Py_NotImplemented);
+        return Py_NotImplemented;
+    }
+
+    len = py_oid_to_git_oid(py_hex, &oid);
+    if (len == 0)
+        return NULL;
+
+    err = self->odb_backend->read_header(&len, &type, self->odb_backend, &oid);
+    if (err != 0) {
+        Error_set_oid(err, &oid, len);
+        return NULL;
+    }
+
+    return Py_BuildValue("(ni)", type, len);
+}
+
 PyMethodDef OdbBackend_methods[] = {
     METHOD(OdbBackend, read, METH_O),
     METHOD(OdbBackend, read_prefix, METH_O),
+    METHOD(OdbBackend, read_header, METH_O),
     {NULL}
 };
 
@@ -280,7 +369,7 @@ PyTypeObject OdbBackendType = {
     "_pygit2.OdbBackend",                      /* tp_name           */
     sizeof(OdbBackend),                        /* tp_basicsize      */
     0,                                         /* tp_itemsize       */
-    0,                                         /* tp_dealloc        */
+    (destructor)OdbBackend_dealloc,            /* tp_dealloc        */
     0,                                         /* tp_print          */
     0,                                         /* tp_getattr        */
     0,                                         /* tp_setattr        */