[WIP] OdbBackend: Python subclassing

src/error.c

@@ -135,3 +135,20 @@ Error_type_error(const char *format, PyObject *value)
     PyErr_Format(PyExc_TypeError, format, Py_TYPE(value)->tp_name);
     return NULL;
 }
+
+int
+git_error_for_exc()
+{
+    PyObject *err;
+    if ((err = PyErr_Occurred()) != NULL) {
+        if (PyErr_GivenExceptionMatches(err, PyExc_KeyError)) {
+            return GIT_ENOTFOUND;
+        }
+        if (PyErr_GivenExceptionMatches(err, PyExc_ValueError)) {
+            return GIT_EAMBIGUOUS;
+        }
+        /* TODO: others? */
+        return GIT_EUSER;
+    }
+    return 0;
+}

src/error.h

@@ -38,5 +38,6 @@ PyObject* Error_set_exc(PyObject* exception);
 PyObject* Error_set_str(int err, const char *str);
 PyObject* Error_set_oid(int err, const git_oid *oid, size_t len);
 PyObject* Error_type_error(const char *format, PyObject *value);
+int git_error_for_exc();
 
 #endif

src/odb.c

@@ -158,7 +158,7 @@ Odb_read_raw(git_odb *odb, const git_oid *oid, size_t len)
     int err;
 
     err = git_odb_read_prefix(&obj, odb, oid, (unsigned int)len);
-    if (err < 0) {
+    if (err < 0 && err != GIT_EUSER) {
         Error_set_oid(err, oid, len);
         return NULL;
     }
@@ -240,6 +240,31 @@ Odb_write(Odb *self, PyObject *args)
     return git_oid_to_python(&oid);
 }
 
+PyDoc_STRVAR(Odb_exists__doc__,
+    "exists(oid) -> bool\n"
+    "\n"
+    "Returns true if the given oid can be found in this odb.");
+
+PyObject *
+Odb_exists(Odb *self, PyObject *py_hex)
+{
+    git_oid oid;
+    size_t len;
+    int result;
+
+    len = py_oid_to_git_oid(py_hex, &oid);
+    if (len == 0)
+        return NULL;
+
+    result = git_odb_exists(self->odb, &oid);
+    if (result < 0)
+        return Error_set(result);
+    else if (result == 0)
+        Py_RETURN_FALSE;
+    else
+        Py_RETURN_TRUE;
+}
+
 
 PyDoc_STRVAR(Odb_add_backend__doc__,
     "add_backend(backend, priority)\n"
@@ -263,7 +288,7 @@ Odb_add_backend(Odb *self, PyObject *args)
     }
 
     err = git_odb_add_backend(self->odb, backend->odb_backend, priority);
-    if (err > 0)
+    if (err != 0)
         return Error_set(err);
 
     Py_RETURN_NONE;
@@ -274,6 +299,7 @@ PyMethodDef Odb_methods[] = {
     METHOD(Odb, add_disk_alternate, METH_O),
     METHOD(Odb, read, METH_O),
     METHOD(Odb, write, METH_VARARGS),
+    METHOD(Odb, exists, METH_O),
     METHOD(Odb, add_backend, METH_VARARGS),
     {NULL}
 };