remove hardcoded dependency on header size

Author: ari-kl

libqretprop/_build_qlcp.py

@@ -16,7 +16,10 @@
 _PROTOCOL_DIR = _ROOT / "libqretprop" / "_protocol"
 
 ffi = cffi.FFI()
-ffi.cdef((_LIB_DIR / "qlcp_lib_expanded.h").read_text())
+ffi.cdef(
+    (_LIB_DIR / "qlcp_lib_expanded.h").read_text()
+    + "\n#define QLCP_HEADER_SIZE ..." # Tells cffi to treat this #define as a constant pulled from the header
+)
 ffi.set_source(
     "_qlcp",  # flat name — no dots
     '#include "qlcp_lib.h"',

libqretprop/protocol.py

@@ -13,9 +13,7 @@
 _MAX_CONFIG   = 4096
 _ENCODE_BUF_SIZE = 4096
 
-# HEADER_SIZE cannot be sourced from the C header via cffi since it's a #define
-# This must be kept in sync with the actual header size in qlcp_lib.h
-HEADER_SIZE = 9
+HEADER_SIZE = _lib.QLCP_HEADER_SIZE
 
 # ============================================================================
 # UTILS