find_library: Centralize functionality here

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

CMakeLists.txt

@@ -3,6 +3,7 @@ cmake_minimum_required(VERSION 3.5)
 project(rcpputils)
 
 find_package(ament_cmake REQUIRED)
+find_package(ament_cmake_ros REQUIRED)
 
 # Default to C11
 if(NOT CMAKE_C_STANDARD)
@@ -21,6 +22,14 @@ include_directories(include)
 
 ament_export_include_directories(include)
 
+add_library(${PROJECT_NAME}
+  src/find_library.cpp)
+target_include_directories(${PROJECT_NAME}
+  PUBLIC
+  include
+)
+ament_export_libraries(${PROJECT_NAME})
+
 if(BUILD_TESTING)
   find_package(ament_cmake_gtest REQUIRED)
   find_package(ament_lint_auto REQUIRED)
@@ -36,10 +45,23 @@ if(BUILD_TESTING)
   ament_add_gtest(test_split test/test_split.cpp)
 
   ament_add_gtest(test_filesystem_helper test/test_filesystem_helper.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
+  RUNTIME DESTINATION bin
+)

README.md

@@ -2,14 +2,23 @@
 
 `rcpputils` is a C++ API consisting of macros, functions, and data structures intended for use throughout the ROS 2 codebase
 
-This package currently contains:
-*   Clang thread safety annotation macros
+See below sections for what this package currently contains.
 
 ## Clang Thread Safety Annotation Macros
-the `rcpputils/thread_safety_annotations.hpp` header provides macros for Clang's [Thread Safety Analysis](https://clang.llvm.org/docs/ThreadSafetyAnalysis.html) feature.
+
+The `rcpputils/thread_safety_annotations.hpp` header provides macros for Clang's [Thread Safety Analysis](https://clang.llvm.org/docs/ThreadSafetyAnalysis.html) feature.
 
 The macros allow you to annotate your code, but expand to nothing when using a non-clang compiler, so they are safe for cross-platform use.
 
 To use thread safety annotation in your package (in a Clang+libcxx build), enable the `-Wthread-safety` compiler flag.
 
 For example usage, see [the documentation of this feature](https://clang.llvm.org/docs/ThreadSafetyAnalysis.html) and the tests in `test/test_basic.cpp`
+
+## Library Discovery
+
+In `rcpputils/find_library.hpp`:
+
+*   `find_library(library_name)`: Namely used for dynamically loading RMW
+implementations.
+    *   For dynamically loading user-defind plugins in C++, please use
+[`pluginlib`](https://github.com/ros/pluginlib) instead.

include/rcpputils/find_library.hpp

@@ -0,0 +1,42 @@
+// 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_HPP_
+#define RCPPUTILS__FIND_LIBRARY_HPP_
+
+#include <string>
+
+#include "rcpputils/visibility_control.hpp"
+
+namespace rcpputils
+{
+
+/// Finds a library located in the OS's specified environment variable for
+/// library paths and returns the absolute filesystem path, including the
+/// appropriate prefix and extension.
+/**
+ * The environment variable and file format per platform:
+ *  * Linux: `${LD_LIBRARY_PATH}`, `lib{}.so`
+ *  * Apple: `${DYLD_LIBRARY_PATH}`, `lib{}.dyld`
+ *  * Windows: `%PATH%`, `{}.dll`
+ *
+ * \param[in] library_name Name of the library to find.
+ * \return Absolute path of library.
+ */
+RCPPUTILS_PUBLIC
+std::string find_library_path(const std::string & library_name);
+
+}  // namespace rcpputils
+
+#endif  // RCPPUTILS__FIND_LIBRARY_HPP_

include/rcpputils/visibility_control.hpp

@@ -0,0 +1,67 @@
+// Copyright (c) 2019, Open Source Robotics Foundation, Inc.
+// All rights reserved.
+//
+// Software License Agreement (BSD License 2.0)
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+//
+//  * Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//  * Redistributions in binary form must reproduce the above
+//    copyright notice, this list of conditions and the following
+//    disclaimer in the documentation and/or other materials provided
+//    with the distribution.
+//  * Neither the name of the copyright holders nor the names of its
+//    contributors may be used to endorse or promote products derived
+//    from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef RCPPUTILS__VISIBILITY_CONTROL_HPP_
+#define RCPPUTILS__VISIBILITY_CONTROL_HPP_
+
+// This logic was borrowed (then namespaced) from the examples on the gcc wiki:
+//     https://gcc.gnu.org/wiki/Visibility
+
+#if defined _WIN32 || defined __CYGWIN__
+  #ifdef __GNUC__
+    #define RCPPUTILS_EXPORT __attribute__ ((dllexport))
+    #define RCPPUTILS_IMPORT __attribute__ ((dllimport))
+  #else
+    #define RCPPUTILS_EXPORT __declspec(dllexport)
+    #define RCPPUTILS_IMPORT __declspec(dllimport)
+  #endif
+  #ifdef RCPPUTILS_BUILDING_LIBRARY
+    #define RCPPUTILS_PUBLIC RCPPUTILS_EXPORT
+  #else
+    #define RCPPUTILS_PUBLIC RCPPUTILS_IMPORT
+  #endif
+  #define RCPPUTILS_PUBLIC_TYPE RCPPUTILS_PUBLIC
+  #define RCPPUTILS_LOCAL
+#else
+  #define RCPPUTILS_EXPORT __attribute__ ((visibility("default")))
+  #define RCPPUTILS_IMPORT
+  #if __GNUC__ >= 4
+    #define RCPPUTILS_PUBLIC __attribute__ ((visibility("default")))
+    #define RCPPUTILS_LOCAL  __attribute__ ((visibility("hidden")))
+  #else
+    #define RCPPUTILS_PUBLIC
+    #define RCPPUTILS_LOCAL
+  #endif
+  #define RCPPUTILS_PUBLIC_TYPE
+#endif
+
+#endif  // RCPPUTILS__VISIBILITY_CONTROL_HPP_

package.xml

@@ -8,6 +8,7 @@
   <license>Apache License 2.0</license>
 
   <buildtool_depend>ament_cmake</buildtool_depend>
+  <buildtool_depend>ament_cmake_ros</buildtool_depend>
 
   <test_depend>ament_lint_common</test_depend>
   <test_depend>ament_lint_auto</test_depend>

src/find_library.cpp

@@ -0,0 +1,94 @@
+// 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 <cassert>
+#include <cstddef>
+
+#include <list>
+#include <fstream>
+#include <sstream>
+#include <string>
+
+namespace rcpputils
+{
+
+namespace
+{
+
+#ifdef _WIN32
+static constexpr char kPathVar[] = "PATH";
+static constexpr char kPathSeparator = ';';
+static constexpr char kSolibPrefix[] = "";
+static constexpr char kSolibExtension[] = ".dll";
+#elif __APPLE__
+static constexpr char kPathVar[] = "DYLD_LIBRARY_PATH";
+static constexpr char kPathSeparator = ':';
+static constexpr char kSolibPrefix[] = "lib";
+static constexpr char kSolibExtension[] = ".dylib";
+#else
+static constexpr char kPathVar[] = "LD_LIBRARY_PATH";
+static constexpr char kPathSeparator = ':';
+static constexpr char kSolibPrefix[] = "lib";
+static constexpr char kSolibExtension[] = ".so";
+#endif
+
+std::string get_env_var(const char * kPathVar)
+{
+  char * value = getenv(kPathVar);
+  return value ? value : "";
+}
+
+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);
+  }
+  return list;
+}
+
+bool is_file_exist(const char * filename)
+{
+  std::ifstream h(filename);
+  return h.good();
+}
+
+}  // namespace
+
+std::string find_library_path(const std::string & library_name)
+{
+  // TODO(eric.cousineau): Does Poco provide this functionality
+  // (ros2/rcpputils#7)?
+  // TODO(eric.cousineau): Have this return a library pointer instead
+  // (ros2/rcpputils#8).
+  std::string search_path = get_env_var(kPathVar);
+  std::list<std::string> search_paths = split(search_path, kPathSeparator);
+
+  std::string filename = kSolibPrefix;
+  filename += library_name + kSolibExtension;
+
+  for (const auto & search_path : search_paths) {
+    std::string path = search_path + "/" + filename;
+    if (is_file_exist(path.c_str())) {
+      return path;
+    }
+  }
+  return "";
+}
+
+}  // namespace rcpputils

test/test_find_library.cpp

@@ -0,0 +1,58 @@
+// 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 <string>
+
+#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 +1,26 @@
+// 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