Manually add a Model for TMatrixTSym<double>. (#484)

* Manually add a Model for TMatrixTSym<double>.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Add test and fix Cursor index, for use in collections.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/uproot/__init__.py

@@ -144,6 +144,8 @@
 import uproot.models.RNTuple
 import uproot.models.TH
 import uproot.models.TGraph
+import uproot.models.TMatrixT
+
 from uproot.models.TTree import num_entries
 
 from uproot.containers import STLVector

src/uproot/model.py

@@ -102,6 +102,7 @@ def reset_classes():
     reload(uproot.models.RNTuple)
     reload(uproot.models.TH)
     reload(uproot.models.TGraph)
+    reload(uproot.models.TMatrixT)
 
 
 _classname_regularize = re.compile(r"\s*(<|>|::)\s*")

src/uproot/models/TMatrixT.py

@@ -0,0 +1,88 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot4/blob/main/LICENSE
+
+"""
+This module defines versioned models for ``TLeaf`` and its subclasses.
+"""
+
+
+import struct
+
+import numpy
+
+import uproot
+import uproot._util
+import uproot.model
+
+
+class Model_TMatrixTSym_3c_double_3e__v5(uproot.model.VersionedModel):
+    """
+    A :doc:`uproot.model.VersionedModel` for ``TMatrixTSym<double>`` version 2,
+    which shows up as version 5 because it's reading the ``TMatrixTBase<double>``
+    header.
+    """
+
+    def read_members(self, chunk, cursor, context, file):
+        if self.is_memberwise:
+            raise NotImplementedError(
+                "memberwise serialization of {}\nin file {}".format(
+                    type(self).__name__, self.file.file_path
+                )
+            )
+        self._bases.append(
+            file.class_named("TObject", 1).read(
+                chunk,
+                cursor,
+                context,
+                file,
+                self._file,
+                self._parent,
+                concrete=self.concrete,
+            )
+        )
+        (
+            self._members["fNrows"],
+            self._members["fNcols"],
+            self._members["fRowLwb"],
+            self._members["fColLwb"],
+            self._members["fNelems"],
+            self._members["fNrowIndex"],
+            self._members["fTol"],
+        ) = cursor.fields(chunk, self._format0, context)
+
+        num_elements = self.member("fNrows") * (self.member("fNcols") + 1) // 2
+        self._members["fElements"] = cursor.array(
+            chunk, num_elements, self._dtype0, context
+        )
+        self._num_bytes += self._members["fElements"].nbytes
+
+    _format0 = struct.Struct(">iiiiiid")
+    _format_memberwise0 = struct.Struct(">i")
+    _format_memberwise1 = struct.Struct(">i")
+    _format_memberwise2 = struct.Struct(">i")
+    _format_memberwise3 = struct.Struct(">i")
+    _format_memberwise4 = struct.Struct(">i")
+    _format_memberwise5 = struct.Struct(">i")
+    _format_memberwise6 = struct.Struct(">d")
+    _dtype0 = numpy.dtype(">f8")
+    base_names_versions = [("TObject", 1)]
+    member_names = [
+        "fNrows",
+        "fNcols",
+        "fRowLwb",
+        "fColLwb",
+        "fNelems",
+        "fNrowIndex",
+        "fTol",
+    ]
+    class_flags = {}
+
+
+class Model_TMatrixTSym_3c_double_3e_(uproot.model.DispatchByVersion):
+    """
+    A :doc:`uproot.model.DispatchByVersion` for ``TMatrixTSym<double>``.
+    """
+
+    known_versions = {5: Model_TMatrixTSym_3c_double_3e__v5}
+
+
+uproot.classes["TMatrixTSym<double>"] = Model_TMatrixTSym_3c_double_3e_

tests/test_0484-manually-add-model-for-TMatrixTSym_double_.py

@@ -0,0 +1,18 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot4/blob/main/LICENSE
+
+
+import io
+import os
+
+import numpy as np
+import pytest
+import skhep_testdata
+
+import uproot
+
+
+def test():
+    with uproot.open(skhep_testdata.data_path("uproot-issue-359.root")) as file:
+        matrix = file["covmatrixOCratio"]
+        num_elements = matrix.member("fNrows") * (matrix.member("fNcols") + 1) // 2
+        assert len(matrix.member("fElements")) == num_elements