cpython/Include/cpython/bytearrayobject.h

#ifndef Py_CPYTHON_BYTEARRAYOBJECT_H
#  error "this header file must not be included directly"
#endif

/* Object layout */
PyByteArrayObject;

PyAPI_DATA(char) _PyByteArray_empty_string[];

/* Macros and static inline functions, trading safety for speed */
#define _PyByteArray_CAST(op) …

static inline char* PyByteArray_AS_STRING(PyObject *op)
{ … }
#define PyByteArray_AS_STRING(self) …

static inline Py_ssize_t PyByteArray_GET_SIZE(PyObject *op) { … }
#define PyByteArray_GET_SIZE(self) …