Move json util code to common

So that it can be shared by CE CDM extraction tool later.

Test: m wv_factory_extraction_tool
Bug: 414642286
Change-Id: I6dba70227ce2789dd3686ebbf6ed3a0dbf68dc00

libwvdrmengine/tools/factory_upload_tool/common/include/json_utils.h

@@ -0,0 +1,19 @@
+// Copyright 2025 Google LLC. All Rights Reserved. This file and proprietary
+// source code may only be used and distributed under the Widevine License
+// Agreement.
+
+#ifndef WIDEVINE_JSON_UTILS_H_
+#define WIDEVINE_JSON_UTILS_H_
+
+#include <map>
+#include <string>
+
+namespace widevine {
+
+std::string EscapeJson(const std::string& input);
+std::string StringMapToJson(
+    const std::map<std::string, std::string>& string_map);
+
+}  // namespace widevine
+
+#endif  // WIDEVINE_JSON_UTILS_H_

libwvdrmengine/tools/factory_upload_tool/common/src/json_utils.cpp

@@ -0,0 +1,63 @@
+// Copyright 2025 Google LLC. All Rights Reserved. This file and proprietary
+// source code may only be used and distributed under the Widevine License
+// Agreement.
+
+#include "json_utils.h"
+
+#include <sstream>
+
+namespace widevine {
+
+std::string EscapeJson(const std::string& input) {
+  std::string result;
+  for (const char& c : input) {
+    switch (c) {
+      case '\"':
+        result += "\\\"";
+        break;
+      case '\\':
+        result += "\\\\";
+        break;
+      case '\b':
+        result += "\\b";
+        break;
+      case '\f':
+        result += "\\f";
+        break;
+      case '\n':
+        result += "\\n";
+        break;
+      case '\r':
+        result += "\\r";
+        break;
+      case '\t':
+        result += "\\t";
+        break;
+      default:
+        result += c;
+        break;
+    }
+  }
+  return result;
+}
+
+std::string StringMapToJson(
+    const std::map<std::string, std::string>& string_map) {
+  if (string_map.empty()) {
+    return "{}";
+  }
+  std::ostringstream json_stream;
+  json_stream << "{";
+  bool is_first_element = true;
+  for (const auto& pair : string_map) {
+    if (!is_first_element) {
+      json_stream << ",";
+    }
+    json_stream << "\"" << pair.first << "\": \"" << pair.second << "\"";
+    is_first_element = false;
+  }
+  json_stream << "}";
+  return json_stream.str();
+}
+
+}  // namespace widevine