Add portability header for libgen.h

Summary: The only thing that matters in it is dirname, and Windows doesn't have it.

Reviewed By: yfeldblum

Differential Revision: D2977655

fb-gh-sync-id: eb5703485089f5c66882fbc9cc142686214c1148
fbshipit-source-id: eb5703485089f5c66882fbc9cc142686214c1148

folly/Makefile.am

@@ -275,6 +275,7 @@ nobase_follyinclude_HEADERS = \
 	portability/Environment.h \
 	portability/GFlags.h \
 	portability/IOVec.h \
+	portability/Libgen.h \
 	portability/Malloc.h \
 	portability/Memory.h \
 	portability/PThread.h \
@@ -421,6 +422,7 @@ libfolly_la_SOURCES = \
 	MemoryMapping.cpp \
 	portability/Dirent.cpp \
 	portability/Environment.cpp \
+	portability/Libgen.cpp \
 	portability/Malloc.cpp \
 	portability/String.cpp \
 	portability/Strings.cpp \

folly/portability/Libgen.cpp

+/*
+ * Copyright 2016 Facebook, 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 <folly/portability/Libgen.h>
+
+#include <string.h>
+
+namespace folly {
+namespace portability {
+static char mutableDot[] = {'.', '\0'};
+char* internal_dirname(char* path) {
+  if (path == nullptr || !strcmp(path, "")) {
+    return mutableDot;
+  }
+  if (!strcmp(path, "/") || !strcmp(path, "\\")) {
+    return path;
+  }
+
+  size_t len = strlen(path);
+  if (path[len - 1] == '/' || path[len - 1] == '\\') {
+    path[len - 1] = '\0';
+  }
+
+  char* pos = strrchr(path, '/');
+  if (strrchr(path, '\\') > pos) {
+    pos = strrchr(path, '\\');
+  }
+  if (pos == nullptr) {
+    return mutableDot;
+  }
+
+  if (pos == path) {
+    *(pos + 1) = '\0';
+  } else {
+    *pos = '\0';
+  }
+  return path;
+}
+}
+}
+
+#ifdef _WIN32
+extern "C" char* dirname(char* path) {
+  return folly::portability::internal_dirname(path);
+}
+#endif

folly/portability/Libgen.h

+/*
+ * Copyright 2016 Facebook, 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.
+ */
+
+#pragma once
+
+namespace folly {
+namespace portability {
+char* internal_dirname(char* path);
+}
+}
+
+#ifndef _WIN32
+#include <libgen.h>
+#else
+extern "C" char* dirname(char* path);
+#endif

folly/portability/test/LibgenTest.cpp

+/*
+ * Copyright 2016 Facebook, 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 <folly/portability/Libgen.h>
+
+TEST(Libgen, dirname) {
+  auto doDirname = [](const char* str) -> std::string {
+    auto tmp = strdup(str); // we need a mutable string for dirname.
+    auto ret = std::string(folly::portability::internal_dirname(tmp));
+    free(tmp);
+    return ret;
+  };
+  EXPECT_EQ("/usr", doDirname("/usr/lib"));
+  EXPECT_EQ("/", doDirname("/usr/"));
+  EXPECT_EQ(".", doDirname("usr"));
+  EXPECT_EQ("/", doDirname("/"));
+  EXPECT_EQ(".", doDirname("."));
+  EXPECT_EQ(".", doDirname(".."));
+}