From 5c37c06b1356ab7c53dfdc1524470d5cd4df330b Mon Sep 17 00:00:00 2001
From: Justus Kuhlmann <justus@kuhl-mann.de>
Date: Thu, 9 Apr 2026 09:54:39 +0200
Subject: [PATCH] add an implementation to read the first ~200 bytes of the par
 file of openQCD's qcd2

---
 corrlib/input/openQCD.py | 56 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/corrlib/input/openQCD.py b/corrlib/input/openQCD.py
index a3bce6f..9c5fbbc 100644
--- a/corrlib/input/openQCD.py
+++ b/corrlib/input/openQCD.py
@@ -4,6 +4,7 @@ import os
 import fnmatch
 from typing import Any, Optional
 from pathlib import Path
+import struct
 
 
 def read_ms1_param(path: Path, project: str, file_in_project: str) -> dict[str, Any]:
@@ -304,3 +305,58 @@ def extract_t1(path: Path, project: str, dir_in_project: str, param: dict[str, A
     t1_dict[param["type"]] = {}
     t1_dict[param["type"]][pars] = t0
     return t1_dict
+
+
+def read_par_file(fname: str) -> dict[str, dict[str, Any]]:
+
+    def _qcd2_write_lat_parms() -> dict[str, Any]:
+        lat_pars = {}
+
+        t = fp.read(16)
+        lat_pars["N"] = list(struct.unpack('iiii', t)) # lattice extends
+        t = fp.read(8)
+        nk, isw = struct.unpack('ii', t)
+        lat_pars["nk"] = nk
+        lat_pars["isw"] = isw
+        t = fp.read(8)
+        lat_pars["beta"] = struct.unpack('d', t)[0]
+        t = fp.read(8)
+        lat_pars["c0"] = struct.unpack('d', t)[0]
+        t = fp.read(8)
+        lat_pars["c1"] = struct.unpack('d', t)[0]
+        t = fp.read(8)
+        lat_pars["csw"] = struct.unpack('d', t)[0]
+        kappas = []
+        m0s = []
+        for ik in range(nk):
+            t = fp.read(8)
+            kappas.append(struct.unpack('d', t)[0])
+            t = fp.read(8)
+            m0s.append(struct.unpack('d', t)[0])
+        lat_pars["kappas"] = kappas
+        lat_pars["m0s"] = m0s
+        return lat_pars
+
+    def _qcd2_write_bc_parms() -> dict[str, Any]:
+        bc_pars = {}
+        t = fp.read(4)
+        bc_pars["type"] = struct.unpack('i', t)[0]
+        t = fp.read(104)
+        bc_parms = struct.unpack('d'*13, t)
+        bc_pars["cG"] = list(bc_parms[:2])
+        bc_pars["cF"] = list(bc_parms[2:4])
+        phi = [[], []]
+        phi[0] = list(bc_parms[4:7])
+        phi[1] = list(bc_parms[7:10])
+        bc_pars["phi"] = phi
+        bc_pars["theta"] = list(bc_parms[10:])
+        return bc_pars
+
+    with open(fname, "rb") as fp:
+        lat_par_dict = _qcd2_write_lat_parms()
+        bc_par_dict = _qcd2_write_bc_parms()
+        fp.close()
+    par_dict = {}
+    par_dict["lat"] = lat_par_dict
+    par_dict["bc"] = bc_par_dict
+    return par_dict