Implementing new ddio_GetTmpFileName()

New function uses std::filesystem::path and generates result faster than ddio_GetTempFileName() (benchmarked on Linux).

ddio/CMakeLists.txt

@@ -35,3 +35,7 @@ target_include_directories(ddio PUBLIC
   ${PROJECT_SOURCE_DIR}/ddio
   >
 )
+
+if(BUILD_TESTING)
+  add_subdirectory(tests)
+endif()

ddio/ddio.h

@@ -383,6 +383,15 @@ void ddio_DoForeachFile(const std::filesystem::path &search_path, const std::reg
 // Returns TRUE if successful, FALSE if an error
 bool ddio_GetTempFileName(const char *basedir, const char *prefix, char *filename);
 
+/**
+ * Generates a temporary filename based on the prefix in basedir. Function ensures that generated
+ * filename does not exists in basedir directory.
+ * @param basedir directory to put the files
+ * @param prefix prefix for the temp filename
+ * @return generated filename with ".tmp" extension in basedir directory or empty path on failure
+ */
+std::filesystem::path ddio_GetTmpFileName(const std::filesystem::path &basedir, const char *prefix);
+
 /**
  * Check process existence by PID
  * @param pid PID of requested process
@@ -412,4 +421,4 @@ bool ddio_CreateLockFile(const std::filesystem::path &dir);
  */
 bool ddio_DeleteLockFile(const std::filesystem::path &dir);
 
-#endif
+#endif

ddio/file.cpp

@@ -17,13 +17,16 @@
  */
 
 #include <array>
+#include <cstring>
 #include <filesystem>
 #include <fstream>
 #include <iterator>
 #include <regex>
 
 #include "IOOps.h"
+#include "chrono_timer.h"
 #include "ddio.h"
+#include "mem.h"
 #include "pserror.h"
 
 const std::array<char, 4> LOCK_TAG = {'L', 'O', 'C', 'K'};
@@ -156,3 +159,36 @@ void ddio_DoForeachFile(const std::filesystem::path &search_path, const std::reg
     }
   }
 }
+
+std::filesystem::path ddio_GetTmpFileName(const std::filesystem::path &basedir, const char *prefix) {
+  static const char alphanum[] =
+      "0123456789"
+      "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+      "abcdefghijklmnopqrstuvwxyz";
+  // size of random part
+  const int len = 10;
+  const char *ext = ".tmp";
+  std::filesystem::path result;
+  size_t len_result = strlen((basedir / prefix).u8string().c_str());
+  char *random_name = (char *)mem_malloc(len_result + len + strlen(ext) + 1);
+  strncpy(random_name, (basedir / prefix).u8string().c_str(), len_result);
+
+  srand(D3::ChronoTimer::GetTimeMS());
+
+  int tries = 20;
+  while (tries > 0) {
+    for (size_t i = len_result; i < len_result + len; i++) {
+      random_name[i] = alphanum[rand() % (sizeof(alphanum) - 1)];
+    }
+    random_name[len_result + len] = '\0';
+    strcat(random_name, ext);
+    if (!std::filesystem::exists(random_name)) {
+      // Found unique name, break the loop
+      result = random_name;
+      break;
+    }
+    tries--;
+  }
+  mem_free(random_name);
+  return result;
+}

ddio/tests/CMakeLists.txt

@@ -0,0 +1,10 @@
+set(CMAKE_FOLDER "tests")
+
+add_executable(ddio_tests
+  ddio_tests.cpp
+)
+target_link_libraries(ddio_tests PRIVATE
+  GTest::gtest_main
+  ddio
+)
+gtest_discover_tests(ddio_tests)

ddio/tests/ddio_tests.cpp

@@ -0,0 +1,30 @@
+/*
+ * Descent 3
+ * Copyright (C) 2024 Descent Developers
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <filesystem>
+#include <gtest/gtest.h>
+
+#include "ddio.h"
+
+TEST(D3, DDIO_GetTmpFileName) {
+  std::filesystem::path temp_dir = std::filesystem::temp_directory_path();
+  std::filesystem::path result = ddio_GetTmpFileName(temp_dir, "prefix_");
+  EXPECT_FALSE(result.empty());
+  EXPECT_EQ(result.extension(), ".tmp");
+  EXPECT_TRUE(canonical(result.parent_path()) == canonical(temp_dir));
+}