logging: add XLOG() and XLOGF() logging macros

[folly.git] / folly / experimental / logging / xlog.cpp

diff --git a/folly/experimental/logging/xlog.cpp b/folly/experimental/logging/xlog.cpp
new file mode 100644 (file)
index 0000000..92390a2
--- /dev/null
+++ b/folly/experimental/logging/xlog.cpp
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2004-present 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/experimental/logging/xlog.h>
+#include <folly/Synchronized.h>
+
+using folly::StringPiece;
+
+namespace folly {
+
+namespace {
+/**
+ * buck copies header files from their original location in the source tree
+ * and places them under buck-out/ with a path like
+ * buck-out/<rule-name-components>/<original-path>
+ *
+ * We want to strip off the buck-out/<rule-name-components> portion,
+ * so that the filename we use is just the original path in the source tree.
+ *
+ * The <rule-name-component> section should always end in a path component that
+ * includes a '#': it's format is <rule-name>#<parameters>, where <parameters>
+ * is a comma separated list that never includes '/'.
+ *
+ * Search for the first path component with a '#', and strip off everything up
+ * to this component.
+ */
+StringPiece stripBuckOutPrefix(StringPiece filename) {
+  size_t idx = 0;
+  while (true) {
+    auto end = filename.find('/', idx);
+    if (end == StringPiece::npos) {
+      // We were unable to find where the buck-out prefix should end.
+      return filename;
+    }
+
+    auto component = filename.subpiece(idx, end - idx);
+    if (component.find('#') != StringPiece::npos) {
+      return filename.subpiece(end + 1);
+    }
+    idx = end + 1;
+  }
+}
+} // unnamed namespace
+
+std::string getXlogCategoryNameForFile(StringPiece filename) {
+  // Buck mangles the directory layout for header files.  Rather than including
+  // them from their original location, it moves them into deep directories
+  // inside buck-out, and includes them from there.
+  //
+  // If this path looks like a buck header directory, try to strip off the
+  // buck-specific portion.
+  if (filename.startsWith("buck-out/")) {
+    filename = stripBuckOutPrefix(filename);
+  }
+
+  std::string categoryName = filename.str();
+
+  // Translate slashes to dots, to turn the directory layout into
+  // a category hierarchy.
+  size_t lastDot = std::string::npos;
+  for (size_t n = 0; n < categoryName.size(); ++n) {
+    if (categoryName[n] == '/') {
+      categoryName[n] = '.';
+      lastDot = std::string::npos;
+    } else if (categoryName[n] == '.') {
+      lastDot = n;
+    }
+  }
+
+  // Strip off the filename extension, if one was present.
+  if (lastDot != std::string::npos) {
+    categoryName.resize(lastDot);
+  }
+  return categoryName;
+}
+}