find_library: Centralize functionality here

Signed-off-by: Eric Cousineau <eric.cousineau@tri.global>

CMakeLists.txt

@@ -21,6 +21,14 @@ include_directories(include)
 
 ament_export_include_directories(include)
 
+add_library(${PROJECT_NAME} SHARED
+  src/find_library.cpp)
+target_include_directories(${PROJECT_NAME}
+  PUBLIC
+  include
+)
+ament_export_libraries(${PROJECT_NAME})
+
 if(BUILD_TESTING)
   find_package(ament_cmake_gtest REQUIRED)
   find_package(ament_lint_auto REQUIRED)
@@ -32,10 +40,22 @@ if(BUILD_TESTING)
   ament_lint_auto_find_test_dependencies()
 
   ament_add_gtest(test_basic test/test_basic.cpp)
+
+  add_library(toy_test_library SHARED test/toy_test_library.cpp)
+  ament_add_gtest(test_find_library test/test_find_library.cpp)
+  target_link_libraries(test_find_library ${PROJECT_NAME} toy_test_library)
+  set_tests_properties(test_find_library PROPERTIES
+      ENVIRONMENT
+        "_TOY_TEST_LIBRARY_DIR=$<TARGET_FILE_DIR:toy_test_library>;_TOY_TEST_LIBRARY=$<TARGET_FILE:toy_test_library>")
 endif()
 
 ament_package()
 
 install(
   DIRECTORY include/
   DESTINATION include)
+install(
+  TARGETS ${PROJECT_NAME}
+  ARCHIVE DESTINATION lib
+  LIBRARY DESTINATION lib
+)

include/rcpputils/find_library.hpp

@@ -0,0 +1,32 @@
+// Copyright 2019 Open Source Robotics Foundation, 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.
+
+#ifndef RCPPUTILS__FIND_LIBRARY_H_
+#define RCPPUTILS__FIND_LIBRARY_H_
+
+#include <string>
+
+namespace rcpputils {
+
+/// Finds a library (using the appropriate shared-library environment variable,
+/// e.g. `LD_LIBRARY_PATH` on Linux), and returns the absolute filesystem path
+/// (including the appropriate prefix and suffix).
+/**
+ * \param[in] library_name Name of the library to find.
+ */
+std::string find_library_path(const std::string & library_name);
+
+}  // namespace rcpputils
+
+#endif  // RCPPUTILS__FIND_LIBRARY_H_

src/find_library.cpp

@@ -0,0 +1,106 @@
+// Copyright 2019 Open Source Robotics Foundation, 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 "rcpputils/find_library.hpp"
+
+#include <cstddef>
+
+#include <list>
+#include <fstream>
+#include <sstream>
+
+namespace rcpputils {
+
+namespace {
+
+std::string get_env_var(const char * env_var)
+{
+  char * value = nullptr;
+#ifndef _WIN32
+  value = getenv(env_var);
+#else
+  size_t value_size;
+  _dupenv_s(&value, &value_size, env_var);
+#endif
+  std::string value_str = "";
+  if (value) {
+    value_str = value;
+#ifdef _WIN32
+    free(value);
+#endif
+  }
+  // printf("get_env_var(%s) = %s\n", env_var, value_str.c_str());
+  return value_str;
+}
+
+std::list<std::string> split(const std::string & value, const char delimiter)
+{
+  std::list<std::string> list;
+  std::istringstream ss(value);
+  std::string s;
+  while (std::getline(ss, s, delimiter)) {
+    list.push_back(s);
+  }
+  // printf("split(%s) = %zu\n", value.c_str(), list.size());
+  return list;
+}
+
+bool is_file_exist(const char * filename)
+{
+  std::ifstream h(filename);
+  // printf("is_file_exist(%s) = %s\n", filename, h.good() ? "true" : "false");
+  return h.good();
+}
+
+}  // namespace
+
+std::string find_library_path(const std::string & library_name)
+{
+  // TODO(eric.cousineau): Does Poco provide this functionality?
+  const char * env_var;
+  char separator;
+  const char * filename_prefix;
+  const char * filename_extension;
+#ifdef _WIN32
+  env_var = "PATH";
+  separator = ';';
+  filename_prefix = "";
+  filename_extension = ".dll";
+#elif __APPLE__
+  env_var = "DYLD_LIBRARY_PATH";
+  separator = ':';
+  filename_prefix = "lib";
+  filename_extension = ".dylib";
+#else
+  env_var = "LD_LIBRARY_PATH";
+  separator = ':';
+  filename_prefix = "lib";
+  filename_extension = ".so";
+#endif
+  std::string search_path = get_env_var(env_var);
+  std::list<std::string> search_paths = split(search_path, separator);
+
+  std::string filename = filename_prefix;
+  filename += library_name + filename_extension;
+
+  for (auto it : search_paths) {
+    std::string path = it + "/" + filename;
+    if (is_file_exist(path.c_str())) {
+      return path;
+    }
+  }
+  return "";
+}
+
+}  // namespace rcpputils

test/test_find_library.cpp

@@ -0,0 +1,53 @@
+// Copyright 2019 Open Source Robotics Foundation, 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 "gtest/gtest.h"
+
+#include "rcpputils/find_library.hpp"
+
+namespace rcpputils {
+namespace {
+
+TEST(test_find_library, find_library) {
+  // Get ground-truth values from CTest properties.
+  const char * toy_lib_expected = getenv("_TOY_TEST_LIBRARY");
+  EXPECT_NE(toy_lib_expected, nullptr);
+  const char * toy_lib_dir = getenv("_TOY_TEST_LIBRARY_DIR");
+  EXPECT_NE(toy_lib_dir, nullptr);
+
+  // Set our relevant path variable.
+  const char * env_var{};
+#ifdef _WIN32
+  env_var = "PATH";
+#elif __APPLE__
+  env_var = "DYLD_LIBRARY_PATH";
+#else
+  env_var = "LD_LIBRARY_PATH";
+#endif
+  const int override = 1;
+  setenv(env_var, toy_lib_dir, override);
+
+  // Positive test.
+  const std::string toy_lib_actual = find_library_path("toy_test_library");
+  EXPECT_EQ(toy_lib_actual, toy_lib_expected);
+
+  // (Hopefully) Negative test.
+  const std::string bad_path = find_library_path(
+      "this_is_a_junk_libray_name_please_dont_define_this_if_you_do_then_"
+      "you_are_really_naughty");
+  EXPECT_EQ(bad_path, "");
+}
+
+}  // namespace
+}  // namespace rcpputils

test/toy_test_library.cpp

@@ -0,0 +1,22 @@
+// Copyright 2019 Open Source Robotics Foundation, 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.
+
+/// @file
+/// Trivial library to ensure we have some linking present.
+
+namespace toy_test_library {
+
+int add_one(int x) { return x + 1; }
+
+}  // namespace toy_test_library