base/platform_file.h

// Copyright (c) 2011 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.

#ifndef BASE_PLATFORM_FILE_H_
#define BASE_PLATFORM_FILE_H_
#pragma once

#include "build/build_config.h"
#if defined(OS_WIN)
#include <windows.h>
#endif

#include <string>

#include "base/base_api.h"
#include "base/basictypes.h"
#include "base/file_path.h"
#include "base/time.h"

namespace base {

#if defined(OS_WIN)
typedef HANDLE PlatformFile;
const PlatformFile kInvalidPlatformFileValue = INVALID_HANDLE_VALUE;
#elif defined(OS_POSIX)
typedef int PlatformFile;
const PlatformFile kInvalidPlatformFileValue = -1;
#endif

// PLATFORM_FILE_(OPEN|CREATE).* are mutually exclusive. You should specify
// exactly one of the five (possibly combining with other flags) when opening
// or creating a file.
enum PlatformFileFlags {
  PLATFORM_FILE_OPEN = 1,             // Opens a file, only if it exists.
  PLATFORM_FILE_CREATE = 2,           // Creates a new file, only if it does not
                                      // already exist.
  PLATFORM_FILE_OPEN_ALWAYS = 4,      // May create a new file.
  PLATFORM_FILE_CREATE_ALWAYS = 8,    // May overwrite an old file.
  PLATFORM_FILE_OPEN_TRUNCATED = 16,  // Opens a file and truncates it, only if
                                      // it exists.
  PLATFORM_FILE_READ = 32,
  PLATFORM_FILE_WRITE = 64,
  PLATFORM_FILE_EXCLUSIVE_READ = 128,  // EXCLUSIVE is opposite of Windows SHARE
  PLATFORM_FILE_EXCLUSIVE_WRITE = 256,
  PLATFORM_FILE_ASYNC = 512,
  PLATFORM_FILE_TEMPORARY = 1024,       // Used on Windows only
  PLATFORM_FILE_HIDDEN = 2048,          // Used on Windows only
  PLATFORM_FILE_DELETE_ON_CLOSE = 4096,

  PLATFORM_FILE_WRITE_ATTRIBUTES = 8192,  // Used on Windows only
  PLATFORM_FILE_ENUMERATE = 16384,  // May enumerate directory

  PLATFORM_FILE_SHARE_DELETE = 32768,  // Used on Windows only
};

// PLATFORM_FILE_ERROR_ACCESS_DENIED is returned when a call fails because of
// a filesystem restriction. PLATFORM_FILE_ERROR_SECURITY is returned when a
// browser policy doesn't allow the operation to be executed.
enum PlatformFileError {
  PLATFORM_FILE_OK = 0,
  PLATFORM_FILE_ERROR_FAILED = -1,
  PLATFORM_FILE_ERROR_IN_USE = -2,
  PLATFORM_FILE_ERROR_EXISTS = -3,
  PLATFORM_FILE_ERROR_NOT_FOUND = -4,
  PLATFORM_FILE_ERROR_ACCESS_DENIED = -5,
  PLATFORM_FILE_ERROR_TOO_MANY_OPENED = -6,
  PLATFORM_FILE_ERROR_NO_MEMORY = -7,
  PLATFORM_FILE_ERROR_NO_SPACE = -8,
  PLATFORM_FILE_ERROR_NOT_A_DIRECTORY = -9,
  PLATFORM_FILE_ERROR_INVALID_OPERATION = -10,
  PLATFORM_FILE_ERROR_SECURITY = -11,
  PLATFORM_FILE_ERROR_ABORT = -12,
  PLATFORM_FILE_ERROR_NOT_A_FILE = -13,
  PLATFORM_FILE_ERROR_NOT_EMPTY = -14,
  PLATFORM_FILE_ERROR_INVALID_URL = -15,
};

// Used to hold information about a given file.
// If you add more fields to this structure (platform-specific fields are OK),
// make sure to update all functions that use it in file_util_{win|posix}.cc
// too, and the ParamTraits<base::PlatformFileInfo> implementation in
// chrome/common/common_param_traits.cc.
struct BASE_API PlatformFileInfo {
  PlatformFileInfo();
  ~PlatformFileInfo();

  // The size of the file in bytes.  Undefined when is_directory is true.
  int64 size;

  // True if the file corresponds to a directory.
  bool is_directory;

  // True if the file corresponds to a symbolic link.
  bool is_symbolic_link;

  // The last modified time of a file.
  base::Time last_modified;

  // The last accessed time of a file.
  base::Time last_accessed;

  // The creation time of a file.
  base::Time creation_time;
};

// Creates or opens the given file. If |created| is provided, it will be set to
// true if a new file was created [or an old one truncated to zero length to
// simulate a new file, which can happen with PLATFORM_FILE_CREATE_ALWAYS], and
// false otherwise.  |error_code| can be NULL.
BASE_API PlatformFile CreatePlatformFile(const FilePath& name,
                                         int flags,
                                         bool* created,
                                         PlatformFileError* error_code);

// Closes a file handle. Returns |true| on success and |false| otherwise.
BASE_API bool ClosePlatformFile(PlatformFile file);

// Reads the given number of bytes (or until EOF is reached) starting with the
// given offset. Returns the number of bytes read, or -1 on error.
BASE_API int ReadPlatformFile(PlatformFile file, int64 offset,
                              char* data, int size);

// Writes the given buffer into the file at the given offset, overwritting any
// data that was previously there. Returns the number of bytes written, or -1
// on error.
BASE_API int WritePlatformFile(PlatformFile file, int64 offset,
                               const char* data, int size);

// Truncates the given file to the given length. If |length| is greater than
// the current size of the file, the file is extended with zeros. If the file
// doesn't exist, |false| is returned.
BASE_API bool TruncatePlatformFile(PlatformFile file, int64 length);

// Flushes the buffers of the given file.
BASE_API bool FlushPlatformFile(PlatformFile file);

// Touches the given file.
BASE_API bool TouchPlatformFile(PlatformFile file, const Time& last_access_time,
                                const Time& last_modified_time);

// Returns some information for the given file.
BASE_API bool GetPlatformFileInfo(PlatformFile file, PlatformFileInfo* info);

// Use this class to pass ownership of a PlatformFile to a receiver that may or
// may not want to accept it.  This class does not own the storage for the
// PlatformFile.
//
// EXAMPLE:
//
//  void MaybeProcessFile(PassPlatformFile pass_file) {
//    if (...) {
//      PlatformFile file = pass_file.ReleaseValue();
//      // Now, we are responsible for closing |file|.
//    }
//  }
//
//  void OpenAndMaybeProcessFile(const FilePath& path) {
//    PlatformFile file = CreatePlatformFile(path, ...);
//    MaybeProcessFile(PassPlatformFile(&file));
//    if (file != kInvalidPlatformFileValue)
//      ClosePlatformFile(file);
//  }
//
class BASE_API PassPlatformFile {
 public:
  explicit PassPlatformFile(PlatformFile* value) : value_(value) {
  }

  // Called to retrieve the PlatformFile stored in this object.  The caller
  // gains ownership of the PlatformFile and is now responsible for closing it.
  // Any subsequent calls to this method will return an invalid PlatformFile.
  PlatformFile ReleaseValue() {
    PlatformFile temp = *value_;
    *value_ = kInvalidPlatformFileValue;
    return temp;
  }

 private:
  PlatformFile* value_;
};

}  // namespace base

#endif  // BASE_PLATFORM_FILE_H_