runfiles,C++: implement runfiles lib foundations

Implement the foundation of the C++ runfiles
library, along with a directory-based Runfiles
implementation.

Subsequent commits will add more feataures:
- manifest-based runfiles handling
- creating list of envvars to pass to child
  processes
- automatic Runfiles creation based on argv[0] and
  the envvars of this process

See https://github.com/bazelbuild/bazel/issues/4460

Change-Id: Id5a38619a1ae874499f04523863081559360410c
PiperOrigin-RevId: 187031518

1 files changed, 101 insertions, 0 deletions

diff --git a/src/tools/runfiles/runfiles.cc b/src/tools/runfiles/runfiles.cc
new file mode 100644
index 0000000000..9ff1f3f4c5
--- /dev/null
+++ b/src/tools/runfiles/runfiles.cc
@@ -0,0 +1,101 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// 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 "tools/runfiles/runfiles.h"
+
+namespace bazel {
+namespace runfiles {
+
+using std::string;
+
+namespace {
+
+class RunfilesImpl : public Runfiles {
+ public:
+  // TODO(laszlocsomor): implement Create(
+  //   const string& argv0, function<string(const string&)> env_lookup, string*
+  //   error);
+
+  string Rlocation(const string& path) const override;
+
+  // Returns the runtime-location of a given runfile.
+  //
+  // This method assumes that the caller already validated the `path`. See
+  // Runfiles::Rlocation for requirements.
+  virtual string RlocationChecked(const string& path) const = 0;
+
+ protected:
+  RunfilesImpl() {}
+  virtual ~RunfilesImpl() {}
+};
+
+// TODO(laszlocsomor): derive a ManifestBased class from RunfilesImpl.
+
+// Runfiles implementation that appends runfiles paths to the runfiles root.
+class DirectoryBased : public RunfilesImpl {
+ public:
+  DirectoryBased(string runfiles_path)
+      : runfiles_path_(std::move(runfiles_path)) {}
+  string RlocationChecked(const string& path) const override;
+
+ private:
+  DirectoryBased(const DirectoryBased&) = delete;
+  DirectoryBased(DirectoryBased&&) = delete;
+  DirectoryBased& operator=(const DirectoryBased&) = delete;
+  DirectoryBased& operator=(DirectoryBased&&) = delete;
+
+  const string runfiles_path_;
+};
+
+bool IsAbsolute(const string& path) {
+  if (path.empty()) {
+    return false;
+  }
+  char c = path.front();
+  return (c == '/') || (path.size() >= 3 &&
+                        ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) &&
+                        path[1] == ':' && (path[2] == '\\' || path[2] == '/'));
+}
+
+string RunfilesImpl::Rlocation(const string& path) const {
+  if (path.empty() || path.find("..") != string::npos) {
+    return std::move(string());
+  }
+  if (IsAbsolute(path)) {
+    return path;
+  }
+  return RlocationChecked(path);
+}
+
+string DirectoryBased::RlocationChecked(const string& path) const {
+  return std::move(runfiles_path_ + "/" + path);
+}
+
+}  // namespace
+
+namespace testing {
+
+bool TestOnly_IsAbsolute(const string& path) { return IsAbsolute(path); }
+
+}  // namespace testing
+
+Runfiles* Runfiles::CreateDirectoryBased(const string& directory_path,
+                                         string* error) {
+  // Note: `error` is intentionally unused because we don't expect any errors
+  // here. We expect an `error` pointer so that we may use it in the future if
+  // need be, without having to change the API.
+  return new DirectoryBased(directory_path);
+}
+
+}  // namespace runfiles
+}  // namespace bazel