Mojo: Add logging macros (and supporting code) for use in mojo/public/cpp.

mojo/public/cpp/environment/lib/logging.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/public/cpp/environment/logging.h"
+
+#include "mojo/public/cpp/environment/environment.h"
+
+namespace mojo {
+namespace internal {
+
+namespace {
+
+// Gets a pointer to the filename portion of |s|. Assumes that the filename
+// follows the last slash or backslash in |s|, or is |s| if no slash or
+// backslash is present.
+//
+// E.g., a pointer to "foo.cc" is returned for the following inputs: "foo.cc",
+// "./foo.cc", ".\foo.cc", "/absolute/path/to/foo.cc",
+// "relative/path/to/foo.cc", "C:\absolute\path\to\foo.cc", etc.
+const char* GetFilename(const char* s) {
+  const char* rv = s;
+  while (*s) {
+    if (*s == '/' || *s == '\\')
+      rv = s + 1;
+    s++;
+  }
+  return rv;
+}
+
+}  // namespace
+
+LogMessage::LogMessage(const char* file, int line, MojoLogLevel log_level)
+    : log_level_(log_level) {
+  // Note: Don't include the log level in the message, since that's passed on.
+  stream_ << GetFilename(file) << '(' << line << "): ";
+}
+
+LogMessage::~LogMessage() {
+  Environment::GetDefaultLogger()->LogMessage(log_level_,
+                                              stream_.str().c_str());
+}
+
+}  // namespace internal
+}  // namespace mojo