file.h

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// Copyright 2010-2025 Google LLC
// 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.
 
// emulates g3/file/base/file.h
#ifndef ORTOOLS_BASE_FILE_H_
#define ORTOOLS_BASE_FILE_H_
 
#include <cstddef>
#include <cstdint>
#include <string>
 
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "google/protobuf/message.h"
#include "ortools/base/status_macros.h"
 
// This file defines some IO interfaces for compatibility with Google
// IO specifications.
class File {
 public:
#ifndef SWIG  // no overloading
  // Opens file "name" with flags specified by "mode".
  // Flags are defined by fopen(), that is "r", "r+", "w", "w+". "a", and "a+".
  // The caller should call Close() to free the File after closing it.
  static File* Open(absl::string_view file_name, absl::string_view mode);
 
  // Opens file "name" with flags specified by "mode".
  // If open failed, program will exit.
  // The caller should call Close() to free the File after closing it.
  static File* OpenOrDie(absl::string_view file_name, absl::string_view mode);
#endif  // SWIG
 
  explicit File(absl::string_view name);
  virtual ~File() = default;
 
  // Reads "size" bytes to buf from file, buff should be pre-allocated.
  virtual size_t Read(void* buf, size_t size) = 0;
 
  // Writes "size" bytes of buf to file, buff should be pre-allocated.
  virtual size_t Write(const void* buf, size_t size) = 0;
 
  // Closes the file and delete the underlying FILE* descriptor.
  virtual absl::Status Close(int flags) = 0;
 
  // Flushes buffer.
  virtual bool Flush() = 0;
 
  // Returns file size.
  virtual size_t Size() = 0;
 
  // Returns whether the file is currently open.
  virtual bool Open() const = 0;
 
  // Reads the whole file to a string, with a maximum length of 'max_length'.
  // Returns the number of bytes read.
  int64_t ReadToString(std::string* line, uint64_t max_length);
 
  // Writes a string to file.
  size_t WriteString(absl::string_view str);
 
  // Inits internal data structures.
  static void Init();
 
  // Returns the file name.
  absl::string_view filename() const;
 
 protected:
  std::string name_;
};
 
namespace file {
 
using Options = int;
 
inline Options Defaults() { return 0xBABA; }
 
// As of 2016-01, these methods can only be used with flags = file::Defaults().
 
// ---- File API ----
 
// The caller should free the File after closing it by passing *f to delete.
absl::Status Open(absl::string_view file_name, absl::string_view mode, File** f,
                  Options options);
// The caller should free the File after closing it by passing the returned
// pointer to delete.
File* OpenOrDie(absl::string_view file_name, absl::string_view mode,
                Options options);
 
absl::Status Delete(absl::string_view path, Options options);
absl::Status Exists(absl::string_view path, Options options);
 
// ---- Content API ----
 
absl::StatusOr<std::string> GetContents(absl::string_view path,
                                        Options options);
 
absl::Status GetContents(absl::string_view file_name, std::string* output,
                         Options options);
 
absl::Status SetContents(absl::string_view file_name,
                         absl::string_view contents, Options options);
 
absl::Status WriteString(File* file, absl::string_view contents,
                         Options options);
 
// ---- Protobuf API ----
 
absl::Status GetTextProto(absl::string_view file_name,
                          google::protobuf::Message* proto, Options options);
 
template <typename T>
absl::StatusOr<T> GetTextProto(absl::string_view file_name, Options options) {
  T proto;
  RETURN_IF_ERROR(GetTextProto(file_name, &proto, options));
  return proto;
}
 
absl::Status SetTextProto(absl::string_view file_name,
                          const google::protobuf::Message& proto,
                          Options options);
 
absl::Status GetBinaryProto(absl::string_view file_name,
                            google::protobuf::Message* proto, Options options);
template <typename T>
 
absl::StatusOr<T> GetBinaryProto(absl::string_view file_name, Options options) {
  T proto;
  RETURN_IF_ERROR(GetBinaryProto(file_name, &proto, options));
  return proto;
}
 
absl::Status SetBinaryProto(absl::string_view file_name,
                            const google::protobuf::Message& proto,
                            Options options);
 
}  // namespace file
 
#endif  // ORTOOLS_BASE_FILE_H_