blob: 7ab5ca5859485a146fa5084f8b304503d1f19d5a [file] [log] [blame]
// Copyright (c) 2012 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.
#include <stdint.h>
#include <string>
#include "base/base_export.h"
#include "base/files/file_path.h"
#include "base/files/file_tracing.h"
#include "base/files/scoped_file.h"
#include "base/move.h"
#include "base/time/time.h"
#include "build/build_config.h"
#if defined(OS_WIN)
#include <windows.h>
#include "base/win/scoped_handle.h"
#if defined(OS_POSIX)
#include <sys/stat.h>
namespace base {
#if defined(OS_WIN)
typedef HANDLE PlatformFile;
#elif defined(OS_POSIX)
typedef int PlatformFile;
#if defined(OS_BSD) || defined(OS_MACOSX) || defined(OS_NACL)
typedef struct stat stat_wrapper_t;
typedef struct stat64 stat_wrapper_t;
#endif // defined(OS_POSIX)
// Thin wrapper around an OS-level file.
// Note that this class does not provide any support for asynchronous IO, other
// than the ability to create asynchronous handles on Windows.
// Note about const: this class does not attempt to determine if the underlying
// file system object is affected by a particular method in order to consider
// that method const or not. Only methods that deal with member variables in an
// obvious non-modifying way are marked as const. Any method that forward calls
// to the OS is not considered const, even if there is no apparent change to
// member variables.
class BASE_EXPORT File {
// FLAG_(OPEN|CREATE).* are mutually exclusive. You should specify exactly one
// of the five (possibly combining with other flags) when opening or creating
// a file.
// FLAG_(WRITE|APPEND) are mutually exclusive. This is so that APPEND behavior
// will be consistent with O_APPEND on POSIX.
// FLAG_EXCLUSIVE_(READ|WRITE) only grant exclusive access to the file on
// creation on POSIX; for existing files, consider using Lock().
enum Flags {
FLAG_OPEN = 1 << 0, // Opens a file, only if it exists.
FLAG_CREATE = 1 << 1, // Creates a new file, only if it does not
// already exist.
FLAG_OPEN_ALWAYS = 1 << 2, // May create a new file.
FLAG_CREATE_ALWAYS = 1 << 3, // May overwrite an old file.
FLAG_OPEN_TRUNCATED = 1 << 4, // Opens a file and truncates it, only if it
// exists.
FLAG_READ = 1 << 5,
FLAG_WRITE = 1 << 6,
FLAG_APPEND = 1 << 7,
FLAG_EXCLUSIVE_READ = 1 << 8, // EXCLUSIVE is opposite of Windows SHARE.
FLAG_ASYNC = 1 << 10,
FLAG_TEMPORARY = 1 << 11, // Used on Windows only.
FLAG_HIDDEN = 1 << 12, // Used on Windows only.
FLAG_WRITE_ATTRIBUTES = 1 << 14, // Used on Windows only.
FLAG_SHARE_DELETE = 1 << 15, // Used on Windows only.
FLAG_TERMINAL_DEVICE = 1 << 16, // Serial port flags.
FLAG_BACKUP_SEMANTICS = 1 << 17, // Used on Windows only.
FLAG_EXECUTE = 1 << 18, // Used on Windows only.
FLAG_SEQUENTIAL_SCAN = 1 << 19, // Used on Windows only.
// This enum has been recorded in multiple histograms. If the order of the
// fields needs to change, please ensure that those histograms are obsolete or
// have been moved to a different enum.
// FILE_ERROR_ACCESS_DENIED is returned when a call fails because of a
// filesystem restriction. FILE_ERROR_SECURITY is returned when a browser
// policy doesn't allow the operation to be executed.
enum Error {
FILE_OK = 0,
// Put new entries here and increment FILE_ERROR_MAX.
// This explicit mapping matches both FILE_ on Windows and SEEK_ on Linux.
enum Whence {
// 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::File::Info> implementation in
// ipc/
struct BASE_EXPORT Info {
#if defined(OS_POSIX)
// Fills this struct with values from |stat_info|.
void FromStat(const stat_wrapper_t& stat_info);
// The size of the file in bytes. Undefined when is_directory is true.
int64_t size;
// True if the file corresponds to a directory.
bool is_directory;
// True if the file corresponds to a symbolic link. For Windows currently
// not supported and thus always false.
bool is_symbolic_link;
// The last modified time of a file.
Time last_modified;
// The last accessed time of a file.
Time last_accessed;
// The creation time of a file.
Time creation_time;
// Creates or opens the given file. This will fail with 'access denied' if the
// |path| contains path traversal ('..') components.
File(const FilePath& path, uint32_t flags);
// Takes ownership of |platform_file|.
explicit File(PlatformFile platform_file);
// Creates an object with a specific error_details code.
explicit File(Error error_details);
File(File&& other);
// Takes ownership of |platform_file|.
static File CreateForAsyncHandle(PlatformFile platform_file);
File& operator=(File&& other);
// Creates or opens the given file.
void Initialize(const FilePath& path, uint32_t flags);
// Returns |true| if the handle / fd wrapped by this object is valid. This
// method doesn't interact with the file system (and is safe to be called from
// ThreadRestrictions::SetIOAllowed(false) threads).
bool IsValid() const;
// Returns true if a new file was created (or an old one truncated to zero
// length to simulate a new file, which can happen with
// FLAG_CREATE_ALWAYS), and false otherwise.
bool created() const { return created_; }
// Returns the OS result of opening this file. Note that the way to verify
// the success of the operation is to use IsValid(), not this method:
// File file(path, flags);
// if (!file.IsValid())
// return;
Error error_details() const { return error_details_; }
PlatformFile GetPlatformFile() const;
PlatformFile TakePlatformFile();
// Destroying this object closes the file automatically.
void Close();
// Changes current position in the file to an |offset| relative to an origin
// defined by |whence|. Returns the resultant current position in the file
// (relative to the start) or -1 in case of error.
int64_t Seek(Whence whence, int64_t offset);
// 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. Note that
// this function makes a best effort to read all data on all platforms, so it
// is not intended for stream oriented files but instead for cases when the
// normal expectation is that actually |size| bytes are read unless there is
// an error.
int Read(int64_t offset, char* data, int size);
// Same as above but without seek.
int ReadAtCurrentPos(char* data, int size);
// Reads the given number of bytes (or until EOF is reached) starting with the
// given offset, but does not make any effort to read all data on all
// platforms. Returns the number of bytes read, or -1 on error.
int ReadNoBestEffort(int64_t offset, char* data, int size);
// Same as above but without seek.
int ReadAtCurrentPosNoBestEffort(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. Note that this function makes a best effort to write all data on
// all platforms.
// Ignores the offset and writes to the end of the file if the file was opened
// with FLAG_APPEND.
int Write(int64_t offset, const char* data, int size);
// Save as above but without seek.
int WriteAtCurrentPos(const char* data, int size);
// Save as above but does not make any effort to write all data on all
// platforms. Returns the number of bytes written, or -1 on error.
int WriteAtCurrentPosNoBestEffort(const char* data, int size);
// Returns the current size of this file, or a negative number on failure.
int64_t GetLength();
// Truncates the 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.
bool SetLength(int64_t length);
// Instructs the filesystem to flush the file to disk. (POSIX: fsync, Windows:
// FlushFileBuffers).
bool Flush();
// Updates the file times.
bool SetTimes(Time last_access_time, Time last_modified_time);
// Returns some basic information for the given file.
bool GetInfo(Info* info);
// Attempts to take an exclusive write lock on the file. Returns immediately
// (i.e. does not wait for another process to unlock the file). If the lock
// was obtained, the result will be FILE_OK. A lock only guarantees
// that other processes may not also take a lock on the same file with the
// same API - it may still be opened, renamed, unlinked, etc.
// Common semantics:
// * Locks are held by processes, but not inherited by child processes.
// * Locks are released by the OS on file close or process termination.
// * Locks are reliable only on local filesystems.
// * Duplicated file handles may also write to locked files.
// Windows-specific semantics:
// * Locks are mandatory for read/write APIs, advisory for mapping APIs.
// * Within a process, locking the same file (by the same or new handle)
// will fail.
// POSIX-specific semantics:
// * Locks are advisory only.
// * Within a process, locking the same file (by the same or new handle)
// will succeed.
// * Closing any descriptor on a given file releases the lock.
Error Lock();
// Unlock a file previously locked.
Error Unlock();
// Returns a new object referencing this file for use within the current
// process. Handling of FLAG_DELETE_ON_CLOSE varies by OS. On POSIX, the File
// object that was created or initialized with this flag will have unlinked
// the underlying file when it was created or opened. On Windows, the
// underlying file is deleted when the last handle to it is closed.
File Duplicate();
bool async() const { return async_; }
#if defined(OS_WIN)
static Error OSErrorToFileError(DWORD last_error);
#elif defined(OS_POSIX)
static Error OSErrorToFileError(int saved_errno);
// Converts an error value to a human-readable form. Used for logging.
static std::string ErrorToString(Error error);
friend class FileTracing::ScopedTrace;
// Creates or opens the given file. Only called if |path| has no
// traversal ('..') components.
void DoInitialize(const FilePath& path, uint32_t flags);
// TODO(tnagel): Reintegrate into Flush() once histogram isn't needed anymore,
// cf. issue 473337.
bool DoFlush();
void SetPlatformFile(PlatformFile file);
#if defined(OS_WIN)
win::ScopedHandle file_;
#elif defined(OS_POSIX)
ScopedFD file_;
// A path to use for tracing purposes. Set if file tracing is enabled during
// |Initialize()|.
FilePath tracing_path_;
// Object tied to the lifetime of |this| that enables/disables tracing.
FileTracing::ScopedEnabler trace_enabler_;
Error error_details_;
bool created_;
bool async_;
} // namespace base
#endif // BASE_FILES_FILE_H_