--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/tesseract/src/lstm/reversed.cpp	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,86 @@
+///////////////////////////////////////////////////////////////////////
+// File:        reversed.cpp
+// Description: Runs a single network on time-reversed input, reversing output.
+// Author:      Ray Smith
+//
+// (C) Copyright 2013, Google Inc.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+///////////////////////////////////////////////////////////////////////
+
+#include "reversed.h"
+
+#include <cstdio>
+
+#include "networkscratch.h"
+
+namespace tesseract {
+
+Reversed::Reversed(const std::string &name, NetworkType type) : Plumbing(name) {
+  type_ = type;
+}
+
+// Returns the shape output from the network given an input shape (which may
+// be partially unknown ie zero).
+StaticShape Reversed::OutputShape(const StaticShape &input_shape) const {
+  if (type_ == NT_XYTRANSPOSE) {
+    StaticShape x_shape(input_shape);
+    x_shape.set_width(input_shape.height());
+    x_shape.set_height(input_shape.width());
+    x_shape = stack_[0]->OutputShape(x_shape);
+    x_shape.SetShape(x_shape.batch(), x_shape.width(), x_shape.height(), x_shape.depth());
+    return x_shape;
+  }
+  return stack_[0]->OutputShape(input_shape);
+}
+
+// Takes ownership of the given network to make it the reversed one.
+void Reversed::SetNetwork(Network *network) {
+  stack_.clear();
+  AddToStack(network);
+}
+
+// Runs forward propagation of activations on the input line.
+// See NetworkCpp for a detailed discussion of the arguments.
+void Reversed::Forward(bool debug, const NetworkIO &input, const TransposedArray *input_transpose,
+                       NetworkScratch *scratch, NetworkIO *output) {
+  NetworkScratch::IO rev_input(input, scratch);
+  ReverseData(input, rev_input);
+  NetworkScratch::IO rev_output(input, scratch);
+  stack_[0]->Forward(debug, *rev_input, nullptr, scratch, rev_output);
+  ReverseData(*rev_output, output);
+}
+
+// Runs backward propagation of errors on the deltas line.
+// See NetworkCpp for a detailed discussion of the arguments.
+bool Reversed::Backward(bool debug, const NetworkIO &fwd_deltas, NetworkScratch *scratch,
+                        NetworkIO *back_deltas) {
+  NetworkScratch::IO rev_input(fwd_deltas, scratch);
+  ReverseData(fwd_deltas, rev_input);
+  NetworkScratch::IO rev_output(fwd_deltas, scratch);
+  if (stack_[0]->Backward(debug, *rev_input, scratch, rev_output)) {
+    ReverseData(*rev_output, back_deltas);
+    return true;
+  }
+  return false;
+}
+
+// Copies src to *dest with the reversal according to type_.
+void Reversed::ReverseData(const NetworkIO &src, NetworkIO *dest) const {
+  if (type_ == NT_XREVERSED) {
+    dest->CopyWithXReversal(src);
+  } else if (type_ == NT_YREVERSED) {
+    dest->CopyWithYReversal(src);
+  } else {
+    dest->CopyWithXYTranspose(src);
+  }
+}
+
+} // namespace tesseract.