Refactor platform discovery function

Merge different implemetations of the discoverEnabledPlatforms()
functions. Use ur_getenv() util function as a common getter of the environment
variable for linux and Windows.

Author: PatKamin

source/loader/CMakeLists.txt

@@ -79,6 +79,7 @@ target_sources(loader
         ${CMAKE_CURRENT_SOURCE_DIR}/ur_libddi.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/ur_lib.hpp
         ${CMAKE_CURRENT_SOURCE_DIR}/ur_lib.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/platform_discovery.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/layers/validation/ur_valddi.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/layers/validation/ur_validation_layer.cpp
 )
@@ -95,14 +96,12 @@ if(WIN32)
     target_sources(loader
         PRIVATE
             ${CMAKE_CURRENT_SOURCE_DIR}/windows/lib_init.cpp
-            ${CMAKE_CURRENT_SOURCE_DIR}/windows/platform_discovery_win.cpp
             ${CMAKE_CURRENT_SOURCE_DIR}/windows/loader_init.cpp
     )
 else()
     target_sources(loader
         PRIVATE
             ${CMAKE_CURRENT_SOURCE_DIR}/linux/lib_init.cpp
-            ${CMAKE_CURRENT_SOURCE_DIR}/linux/platform_discovery_lin.cpp
             ${CMAKE_CURRENT_SOURCE_DIR}/linux/loader_init.cpp
     )
 endif()

source/loader/linux/platform_discovery_lin.cpp

@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright (C) 2022-2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+#include "platform_discovery.hpp"
+#include "ur_util.hpp"
+
+#include <array>
+
+namespace loader {
+
+static constexpr std::array<const char *, 1> knownPlatformNames{
+    MAKE_LIBRARY_NAME("ur_adapter_level_zero", "0")};
+
+static auto getKnownPlatforms() {
+    std::vector<PlatformLibraryPath> enabledPlatforms;
+
+    for (auto path : knownPlatformNames) {
+        enabledPlatforms.emplace_back(path);
+    }
+    return enabledPlatforms;
+}
+
+std::vector<PlatformLibraryPath> discoverEnabledPlatforms() {
+    std::optional<std::string> altPlatforms;
+
+    // UR_ADAPTERS_FORCE_LOAD  is for development/debug only
+    try {
+        altPlatforms = ur_getenv("UR_ADAPTERS_FORCE_LOAD");
+    } catch (const std::invalid_argument &e) {
+        std::cerr << e.what();
+        return getKnownPlatforms();
+    }
+    if (!altPlatforms) {
+        return getKnownPlatforms();
+    }
+
+    std::vector<PlatformLibraryPath> enabledPlatforms;
+    std::stringstream ss(*altPlatforms);
+    while (ss.good()) {
+        std::string substr;
+        getline(ss, substr, ',');
+        enabledPlatforms.emplace_back(substr);
+    }
+    return enabledPlatforms;
+}
+
+} // namespace loader