From d970c5ae7716ba90d53100e8c97705416bf520ed Mon Sep 17 00:00:00 2001
From: David Wendt <45795991+davidwendt@users.noreply.github.com>
Date: Wed, 23 Nov 2022 09:44:14 -0500
Subject: [PATCH] Add cudf::strings:udf::replace function (#12210)

Add udf function for replacing all occurrences of a target string within a source string with a replacement string.
This is to support #12207

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Bradley Dice (https://github.com/bdice)
  - https://github.com/brandon-b-miller

URL: https://github.com/rapidsai/cudf/pull/12210
---
 .../cpp/include/cudf/strings/udf/replace.cuh  | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 python/strings_udf/cpp/include/cudf/strings/udf/replace.cuh

diff --git a/python/strings_udf/cpp/include/cudf/strings/udf/replace.cuh b/python/strings_udf/cpp/include/cudf/strings/udf/replace.cuh
new file mode 100644
index 00000000000..c1f0cdc94c5
--- /dev/null
+++ b/python/strings_udf/cpp/include/cudf/strings/udf/replace.cuh
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2022, NVIDIA CORPORATION.
+ *
+ * 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.
+ */
+#pragma once
+
+#include <cudf/strings/string_view.cuh>
+#include <cudf/strings/udf/udf_string.cuh>
+
+namespace cudf {
+namespace strings {
+namespace udf {
+
+/**
+ * @brief Returns new string replacing all occurrences of target with replacement
+ *
+ * If target is empty then replacement is inserted between every character.
+ *
+ * @param source Source string to search
+ * @param target String to match within source
+ * @param replacement String to replace the target within the source
+ * @return Resulting string
+ */
+__device__ inline udf_string replace(string_view source,
+                                     string_view target,
+                                     string_view replacement)
+{
+  udf_string result;
+  auto const tgt_length   = target.length();
+  auto const src_length   = source.length();
+  size_type last_position = 0;
+  size_type position      = 0;
+  while (position != string_view::npos) {
+    position = source.find(target, last_position);
+    if (position != string_view::npos) {
+      result.append(source.substr(last_position, position - last_position));
+      result.append(replacement);
+      last_position = position + tgt_length;
+      if ((tgt_length == 0) && (++last_position <= src_length)) {
+        result.append(source.substr(position, 1));
+      }
+    }
+  }
+  if (last_position < src_length) {
+    result.append(source.substr(last_position, src_length - last_position));
+  }
+
+  return result;
+}
+
+}  // namespace udf
+}  // namespace strings
+}  // namespace cudf