wxWidgets/interface/wx/file.h

458 lines
15 KiB
Objective-C

/////////////////////////////////////////////////////////////////////////////
// Name: file.h
// Purpose: interface of wxTempFile, wxFile
// Author: wxWidgets team
// RCS-ID: $Id$
// Licence: wxWindows license
/////////////////////////////////////////////////////////////////////////////
/**
We redefine these constants here because S_IREAD &c are _not_ standard
however, we do assume that the values correspond to the Unix umask bits.
*/
enum wxPosixPermissions
{
/// standard Posix names for these permission flags
//@{
wxS_IRUSR = 00400,
wxS_IWUSR = 00200,
wxS_IXUSR = 00100,
wxS_IRGRP = 00040,
wxS_IWGRP = 00020,
wxS_IXGRP = 00010,
wxS_IROTH = 00004,
wxS_IWOTH = 00002,
wxS_IXOTH = 00001,
//@}
/// longer but more readable synonims for the constants above
//@{
wxPOSIX_USER_READ = wxS_IRUSR,
wxPOSIX_USER_WRITE = wxS_IWUSR,
wxPOSIX_USER_EXECUTE = wxS_IXUSR,
wxPOSIX_GROUP_READ = wxS_IRGRP,
wxPOSIX_GROUP_WRITE = wxS_IWGRP,
wxPOSIX_GROUP_EXECUTE = wxS_IXGRP,
wxPOSIX_OTHERS_READ = wxS_IROTH,
wxPOSIX_OTHERS_WRITE = wxS_IWOTH,
wxPOSIX_OTHERS_EXECUTE = wxS_IXOTH,
//@}
/// Default mode for the new files: allow reading/writing them to everybody but
/// the effective file mode will be set after anding this value with umask and
/// so won't include wxS_IW{GRP,OTH} for the default 022 umask value
wxS_DEFAULT = (wxPOSIX_USER_READ | wxPOSIX_USER_WRITE | \
wxPOSIX_GROUP_READ | wxPOSIX_GROUP_WRITE | \
wxPOSIX_OTHERS_READ | wxPOSIX_OTHERS_WRITE),
/// Default mode for the new directories (see wxFileName::Mkdir): allow
/// reading/writing/executing them to everybody, but just like wxS_DEFAULT
/// the effective directory mode will be set after anding this value with umask
wxS_DIR_DEFAULT = (wxPOSIX_USER_READ | wxPOSIX_USER_WRITE | wxPOSIX_USER_EXECUTE | \
wxPOSIX_GROUP_READ | wxPOSIX_GROUP_WRITE | wxPOSIX_GROUP_EXECUTE | \
wxPOSIX_OTHERS_READ | wxPOSIX_OTHERS_WRITE | wxPOSIX_OTHERS_EXECUTE)
};
/**
@class wxTempFile
wxTempFile provides a relatively safe way to replace the contents of the
existing file. The name is explained by the fact that it may be also used as
just a temporary file if you don't replace the old file contents.
Usually, when a program replaces the contents of some file it first opens it for
writing, thus losing all of the old data and then starts recreating it.
This approach is not very safe because during the regeneration of the file bad
things may happen: the program may find that there is an internal error preventing
it from completing file generation, the user may interrupt it (especially if file
generation takes long time) and, finally, any other external interrupts (power
supply failure or a disk error) will leave you without either the original file
or the new one.
wxTempFile addresses this problem by creating a temporary file which is meant to
replace the original file - but only after it is fully written. So, if the user
interrupts the program during the file generation, the old file won't be lost.
Also, if the program discovers itself that it doesn't want to replace the old
file there is no problem - in fact, wxTempFile will @b not replace the old
file by default, you should explicitly call wxTempFile::Commit() to do it.
Calling wxTempFile::Discard() explicitly discards any modifications: it
closes and deletes the temporary file and leaves the original file unchanged.
If you don't call neither of Commit() and Discard(), the destructor will
call Discard() automatically.
To summarize: if you want to replace another file, create an instance of
wxTempFile passing the name of the file to be replaced to the constructor
(you may also use default constructor and pass the file name to wxTempFile::Open).
Then you can write to wxTempFile using wxFile-like functions and later call
wxTempFile::Commit() to replace the old file (and close this one) or call
wxTempFile::Discard() to cancel the modifications.
@library{wxbase}
@category{file}
*/
class wxTempFile
{
public:
/**
Associates wxTempFile with the file to be replaced and opens it.
You should use IsOpened() to verify if the constructor succeeded.
*/
wxTempFile(const wxString& strName);
/**
Destructor calls Discard() if temporary file is still opened.
*/
~wxTempFile();
/**
Validate changes: deletes the old file of name m_strName and renames the new
file to the old name. Returns @true if both actions succeeded.
If @false is returned it may unfortunately mean two quite different things:
either that either the old file couldn't be deleted or that the new file
couldn't be renamed to the old name.
*/
bool Commit();
/**
Discard changes: the old file contents is not changed, temporary file is
deleted.
*/
void Discard();
/**
Returns @true if the file was successfully opened.
*/
bool IsOpened() const;
/**
Returns the length of the file.
This method may return wxInvalidOffset if the length couldn't be
determined or also 0 even for non-empty files if the file is not
seekable.
In general, the only way to determine if the file for which this function
returns 0 is really empty or not is to try reading from it.
*/
wxFileOffset Length() const;
/**
Open the temporary file, returns @true on success, @false if an error
occurred.
@a strName is the name of file to be replaced. The temporary file is always
created in the directory where @a strName is. In particular, if @a strName
doesn't include the path, it is created in the current directory and the
program should have write access to it for the function to succeed.
*/
bool Open(const wxString& strName);
/**
Seeks to the specified position.
*/
wxFileOffset Seek(wxFileOffset ofs,
wxSeekMode mode = wxFromStart);
/**
Returns the current position or wxInvalidOffset if file is not opened or
if another error occurred.
*/
wxFileOffset Tell() const;
/**
Write to the file, return @true on success, @false on failure.
The second argument is only meaningful in Unicode build of wxWidgets when
@a conv is used to convert @a str to multibyte representation.
*/
bool Write(const wxString& str,
const wxMBConv& conv = wxConvUTF8);
};
/**
@class wxFile
A wxFile performs raw file I/O.
This is a very small class designed to minimize the overhead of using it - in fact,
there is hardly any overhead at all, but using it brings you automatic error
checking and hides differences between platforms and compilers.
wxFile also automatically closes the file in its destructor making it unnecessary
to worry about forgetting to do it.
A wxFile performs raw file I/O. This is a very small class designed to
minimize the overhead of using it - in fact, there is hardly any overhead at
all, but using it brings you automatic error checking and hides differences
between platforms and compilers. wxFile also automatically closes the file in
its destructor making it unnecessary to worry about forgetting to do it.
wxFile is a wrapper around @c file descriptor. - see also wxFFile for a
wrapper around @c FILE structure.
::wxFileOffset is used by the wxFile functions which require offsets as
parameter or return them. If the platform supports it, wxFileOffset is a
typedef for a native 64 bit integer, otherwise a 32 bit integer is used for
::wxFileOffset.
@library{wxbase}
@category{file}
*/
class wxFile
{
public:
/**
The OpenMode enumeration defines the different modes for opening a file with wxFile.
It is also used with wxFile::Access function.
*/
enum OpenMode {
/** Open file for reading or test if it can be opened for reading with Access() */
read,
/** Open file for writing deleting the contents of the file if it already exists
or test if it can be opened for writing with Access(). */
write,
/** Open file for reading and writing; can not be used with Access() */
read_write,
/** Open file for appending: the file is opened for writing, but the old contents
of the file is not erased and the file pointer is initially placed at the end
of the file; can not be used with Access().
This is the same as OpenMode::write if the file doesn't exist.
*/
write_append,
/**
Open the file securely for writing (Uses O_EXCL | O_CREAT).
Will fail if the file already exists, else create and open it atomically.
Useful for opening temporary files without being vulnerable to race exploits.
*/
write_excl
};
/**
Standard file descriptors
*/
enum { fd_invalid = -1, fd_stdin, fd_stdout, fd_stderr };
/**
Default constructor.
*/
wxFile();
/**
Opens a file with a filename.
@param filename
The filename.
@param mode
The mode in which to open the file.
*/
wxFile(const wxString& filename,
wxFile::OpenMode mode = wxFile::read);
/**
Associates the file with the given file descriptor, which has already been
opened. See Attach() for the list of predefined descriptors.
@param fd
An existing file descriptor.
*/
wxFile(int fd);
/**
Destructor will close the file.
@note it is not virtual so you should not use wxFile polymorphically.
*/
~wxFile();
/**
This function verifies if we may access the given file in specified mode.
Only values of @c wxFile::read or @c wxFile::write really make sense here.
*/
static bool Access(const wxString& name, wxFile::OpenMode mode);
/**
Attaches an existing file descriptor to the wxFile object.
Example of predefined file descriptors are 0, 1 and 2 which correspond to
stdin, stdout and stderr (and have symbolic names of @c wxFile::fd_stdin,
@c wxFile::fd_stdout and @c wxFile::fd_stderr).
The descriptor should be already opened and it will be closed by wxFile
object.
*/
void Attach(int fd);
/**
Closes the file.
*/
void Close();
/**
Creates a file for writing.
If the file already exists, setting @b overwrite to @true will ensure
it is overwritten.
@a access may be an OR combination of the ::wxPosixPermissions enumeration
values.
*/
bool Create(const wxString& filename,
bool overwrite = false,
int access = wxS_DEFAULT);
/**
Get back a file descriptor from wxFile object - the caller is responsible for
closing the file if this descriptor is opened.
IsOpened() will return @false after call to Detach().
*/
void Detach();
/**
Returns @true if the end of the file has been reached.
Note that the behaviour of the file pointer based class wxFFile is
different as wxFFile::Eof() will return @true here only if an
attempt has been made to read @b past the last byte of the file, while
wxFile::Eof() will return @true even before such attempt is made if the
file pointer is at the last position in the file.
Note also that this function doesn't work on unseekable file descriptors
(examples include pipes, terminals and sockets under Unix) and an attempt to
use it will result in an error message in such case.
So, to read the entire file into memory, you should write a loop which uses
Read() repeatedly and tests its return condition instead of using Eof()
as this will not work for special files under Unix.
*/
bool Eof() const;
/**
Returns @true if the given name specifies an existing regular file
(not a directory or a link)
*/
static bool Exists(const wxString& filename);
/**
Flushes the file descriptor.
Note that Flush() is not implemented on some Windows compilers due to a
missing fsync function, which reduces the usefulness of this function
(it can still be called but it will do nothing on unsupported compilers).
*/
bool Flush();
/**
Returns the type of the file.
*/
wxFileKind GetKind() const;
/**
Returns @true if the file has been opened.
*/
bool IsOpened() const;
/**
Returns the length of the file.
*/
wxFileOffset Length() const;
/**
Opens the file, returning @true if successful.
@param filename
The filename.
@param mode
The mode in which to open the file.
@param access
An OR-combination of wxPosixPermissions enumeration values.
*/
bool Open(const wxString& filename,
wxFile::OpenMode mode = wxFile::read,
int access = wxS_DEFAULT);
/**
Reads from the file into a memory buffer.
@param buffer
Buffer to write in
@param count
Bytes to read
@return The number of bytes read, or the symbol wxInvalidOffset.
*/
size_t Read(void* buffer, size_t count);
/**
Seeks to the specified position.
@param ofs
Offset to seek to.
@param mode
One of wxFromStart, wxFromEnd, wxFromCurrent.
@return The actual offset position achieved, or wxInvalidOffset on
failure.
*/
wxFileOffset Seek(wxFileOffset ofs,
wxSeekMode mode = wxFromStart);
/**
Moves the file pointer to the specified number of bytes relative to the
end of the file. For example, @c SeekEnd(-5) would position the pointer 5
bytes before the end.
@param ofs
Number of bytes before the end of the file.
@return The actual offset position achieved, or wxInvalidOffset on
failure.
*/
wxFileOffset SeekEnd(wxFileOffset ofs = 0);
/**
Returns the current position or wxInvalidOffset if file is not opened or
if another error occurred.
*/
wxFileOffset Tell() const;
/**
Write data to the file (descriptor).
@param buffer
Buffer from which to read data
@param count
Number of bytes to write
@return The number of bytes written.
*/
size_t Write(const void *buffer, size_t count);
/**
Writes the contents of the string to the file, returns @true on success.
The second argument is only meaningful in Unicode build of wxWidgets when
@a conv is used to convert @a s to a multibyte representation.
Note that this method only works with @c NUL-terminated strings, if you want
to write data with embedded @c NULs to the file you should use the other
Write() overload.
*/
bool Write(const wxString& s, const wxMBConv& conv = wxConvUTF8);
/**
Returns the file descriptor associated with the file.
*/
int fd() const;
};