Adding code. Closes #0.

test/filesystem_for_testing.cc

@@ -0,0 +1,102 @@
+// Copyright 2017 Google 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 "filesystem_for_testing.h"
+
+#include <cassert>
+#include <climits>
+#include <cstdio>
+#include <cstring>
+#include <utility>
+
+namespace cpu_features {
+
+FakeFile::FakeFile(int file_descriptor, const char* content)
+    : file_descriptor_(file_descriptor), content_(content) {}
+
+FakeFile::~FakeFile() { assert(!opened_); }
+
+void FakeFile::Open() {
+  assert(!opened_);
+  opened_ = true;
+}
+
+void FakeFile::Close() {
+  assert(opened_);
+  opened_ = false;
+}
+
+int FakeFile::Read(int fd, void* buf, size_t count) {
+  assert(count < INT_MAX);
+  assert(fd == file_descriptor_);
+  const size_t remainder = content_.size() - head_index_;
+  const size_t read = count > remainder ? remainder : count;
+  memcpy(buf, content_.data() + head_index_, read);
+  head_index_ += read;
+  assert(read < INT_MAX);
+  return read;
+}
+
+void FakeFilesystem::Reset() { files_.clear(); }
+
+FakeFile* FakeFilesystem::CreateFile(const std::string& filename,
+                                     const char* content) {
+  auto& file = files_[filename];
+  file =
+      std::unique_ptr<FakeFile>(new FakeFile(next_file_descriptor_++, content));
+  return file.get();
+}
+
+FakeFile* FakeFilesystem::FindFileOrNull(const std::string& filename) const {
+  const auto itr = files_.find(filename);
+  return itr == files_.end() ? nullptr : itr->second.get();
+}
+
+FakeFile* FakeFilesystem::FindFileOrDie(const int file_descriptor) const {
+  for (const auto& filename_file_pair : files_) {
+    FakeFile* const file_ptr = filename_file_pair.second.get();
+    if (file_ptr->GetFileDescriptor() == file_descriptor) {
+      return file_ptr;
+    }
+  }
+  assert(false);
+  return nullptr;
+}
+
+static FakeFilesystem* kFilesystem = new FakeFilesystem();
+
+FakeFilesystem& GetEmptyFilesystem() {
+  kFilesystem->Reset();
+  return *kFilesystem;
+}
+
+extern "C" int OpenFile(const char* filename) {
+  auto* const file = kFilesystem->FindFileOrNull(filename);
+  if (file) {
+    file->Open();
+    return file->GetFileDescriptor();
+  }
+  return -1;
+}
+
+extern "C" void CloseFile(int file_descriptor) {
+  kFilesystem->FindFileOrDie(file_descriptor)->Close();
+}
+
+extern "C" int ReadFile(int file_descriptor, void* buf, size_t count) {
+  return kFilesystem->FindFileOrDie(file_descriptor)
+      ->Read(file_descriptor, buf, count);
+}
+
+}  // namespace cpu_features