src/lib/util/file_system.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COBALT_SRC_LIB_UTIL_FILE_SYSTEM_H_
#define COBALT_SRC_LIB_UTIL_FILE_SYSTEM_H_

#include <istream>
#include <memory>
#include <ostream>
#include <string>
#include <vector>

#include <google/protobuf/io/zero_copy_stream.h>

#include "src/public/lib/statusor/statusor.h"

namespace cobalt::util {

// FileSystem is an abstract class used for interacting with the file system
// in a platform independent way.
class FileSystem {
 public:
  // MakeDirectory creates a directory on the file system.
  //
  // |directory|. An absolute path to the directory to be created.
  //
  // Returns: True if the directory was created successfully.
  virtual bool MakeDirectory(const std::string &directory) = 0;

  // ListFiles lists the files in a given directory.
  //
  // |directory|. An absolute path to the directory to list.
  //
  // Returns: A StatusOr with a vector of filenames. An Ok status indicates that the list operation
  // succeeded, even if the vector is empty.
  //
  // Note: On unix like systems, the directories "." and ".." should not be returned.
  virtual lib::statusor::StatusOr<std::vector<std::string>> ListFiles(
      const std::string &directory) = 0;

  // Delete deletes a file or an empty directory.
  //
  // |file|. An absolute path to the file or directory to be deleted.
  //
  // Returns: True if the file was successfully deleted.
  virtual bool Delete(const std::string &file) = 0;

  // Deletes a directory and all children of that directory.
  //
  // |directory|. The starting directory of the delete.
  //
  // Returns: True if the directory was successfully deleted.
  //
  // Note: The default implementation is a wrapper around Delete(). A more efficient implementation
  // should be used if it exists on the target system.
  virtual bool DeleteRecursive(const std::string &directory);

  // FileSize returns the size of the |file| on disk.
  //
  // |file|. An absolute path to the file whose size is needed.
  //
  // Returns: A StatusOr containing the size of the file in bytes. An OK status indicates that the
  // FileSize operation succeeded, even if the size_t is 0.
  virtual lib::statusor::StatusOr<size_t> FileSize(const std::string &file) = 0;

  // FileExists returns true if the |file| exists.
  virtual bool FileExists(const std::string &file) = 0;

  // Rename renames a file.
  //
  // |from|. An absolute path to the file that is to be renamed.
  // |to|. An absolute path to the new name for the file.
  //
  // Returns: True if the file was renamed successfully.
  virtual bool Rename(const std::string &from, const std::string &to) = 0;

  using ProtoInputStreamPtr = std::unique_ptr<::google::protobuf::io::ZeroCopyInputStream>;
  using ProtoOutputStreamPtr = std::unique_ptr<::google::protobuf::io::ZeroCopyOutputStream>;

  // Open a file for reading.
  //
  // |file|. An absolute path to the file to be read.
  lib::statusor::StatusOr<ProtoInputStreamPtr> NewProtoInputStream(const std::string &file) {
    return NewProtoInputStream(file, -1);
  }

  // Open a file for reading.
  //
  // |file|. An absolute path to the file to be read.
  // |block_size|. The block size the underlying ZeroCopyStream should use.
  virtual lib::statusor::StatusOr<ProtoInputStreamPtr> NewProtoInputStream(const std::string &file,
                                                                           int block_size) = 0;

  // Open a file for writing.
  //
  // |file|. An absolute path to the file to be written.
  lib::statusor::StatusOr<ProtoOutputStreamPtr> NewProtoOutputStream(const std::string &file) {
    return NewProtoOutputStream(file, false, -1);
  }

  // Open a file for writing.
  //
  // |file|. An absolute path to the file to be written.
  // |append|. True if the file should be opened in append mode.
  lib::statusor::StatusOr<ProtoOutputStreamPtr> NewProtoOutputStream(const std::string &file,
                                                                     bool append) {
    return NewProtoOutputStream(file, append, -1);
  }

  // Open a file for writing.
  //
  // |file|. An absolute path to the file to be writing.
  // |append|. True if the file should be opened in append mode.
  // |block_size|. The block size the underlying ZeroCopyStream should use.
  virtual lib::statusor::StatusOr<ProtoOutputStreamPtr> NewProtoOutputStream(
      const std::string &file, bool append, int block_size) = 0;

  virtual ~FileSystem() = default;
};

}  // namespace cobalt::util

#endif  // COBALT_SRC_LIB_UTIL_FILE_SYSTEM_H_