"""New I/O library. This is an early prototype; eventually some of this will be reimplemented in C and the rest may be turned into a package. See PEP 3116. XXX need to default buffer size to 1 if isatty() XXX need to support 1 meaning line-buffered XXX change behavior of blocking I/O XXX don't use assert to validate input requirements """ __author__ = ("Guido van Rossum <guido@python.org>, " "Mike Verdone <mike.verdone@gmail.com>, " "Mark Russell <mark.russell@zen.co.uk>") __all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO", "SocketIO", "BytesIO", "StringIO", "BufferedIOBase", "BufferedReader", "BufferedWriter", "BufferedRWPair", "BufferedRandom", "TextIOBase", "TextIOWrapper"] import os import sys import codecs import _fileio import warnings DEFAULT_BUFFER_SIZE = 8 * 1024 # bytes class BlockingIOError(IOError): """Exception raised when I/O would block on a non-blocking I/O stream.""" def __init__(self, errno, strerror, characters_written=0): IOError.__init__(self, errno, strerror) self.characters_written = characters_written def open(file, mode="r", buffering=None, *, encoding=None): """Replacement for the built-in open function. Args: file: string giving the name of the file to be opened; or integer file descriptor of the file to be wrapped (*) mode: optional mode string; see below buffering: optional int >= 0 giving the buffer size; values can be: 0 = unbuffered, 1 = line buffered, larger = fully buffered encoding: optional string giving the text encoding (*must* be given as a keyword argument) (*) If a file descriptor is given, it is closed when the returned I/O object is closed. If you don't want this to happen, use os.dup() to create a duplicate file descriptor. Mode strings characters: 'r': open for reading (default) 'w': open for writing, truncating the file first 'a': open for writing, appending to the end if the file exists 'b': binary mode 't': text mode (default) '+': open a disk file for updating (implies reading and writing) 'U': universal newline mode (for backwards compatibility) Constraints: - encoding must not be given when a binary mode is given - buffering must not be zero when a text mode is given Returns: Depending on the mode and buffering arguments, either a raw binary stream, a buffered binary stream, or a buffered text stream, open for reading and/or writing. """ assert isinstance(file, (basestring, int)), repr(file) assert isinstance(mode, basestring), repr(mode) assert buffering is None or isinstance(buffering, int), repr(buffering) assert encoding is None or isinstance(encoding, basestring), repr(encoding) modes = set(mode) if modes - set("arwb+tU") or len(mode) > len(modes): raise ValueError("invalid mode: %r" % mode) reading = "r" in modes writing = "w" in modes appending = "a" in modes updating = "+" in modes text = "t" in modes binary = "b" in modes if "U" in modes and not (reading or writing or appending): reading = True if text and binary: raise ValueError("can't have text and binary mode at once") if reading + writing + appending > 1: raise ValueError("can't have read/write/append mode at once") if not (reading or writing or appending): raise ValueError("must have exactly one of read/write/append mode") if binary and encoding is not None: raise ValueError("binary mode doesn't take an encoding") raw = FileIO(file, (reading and "r" or "") + (writing and "w" or "") + (appending and "a" or "") + (updating and "+" or "")) if buffering is None: buffering = DEFAULT_BUFFER_SIZE # XXX Should default to line buffering if os.isatty(raw.fileno()) try: bs = os.fstat(raw.fileno()).st_blksize except (os.error, AttributeError): pass else: if bs > 1: buffering = bs if buffering < 0: raise ValueError("invalid buffering size") if buffering == 0: if binary: return raw raise ValueError("can't have unbuffered text I/O") if updating: buffer = BufferedRandom(raw, buffering) elif writing or appending: buffer = BufferedWriter(raw, buffering) else: assert reading buffer = BufferedReader(raw, buffering) if binary: return buffer # XXX What about newline conventions? textio = TextIOWrapper(buffer, encoding) return textio class IOBase: """Base class for all I/O classes. This class provides dummy implementations for many methods that derived classes can override selectively; the default implementations represent a file that cannot be read, written or seeked. This does not define read(), readinto() and write(), nor readline() and friends, since their signatures vary per layer. """ ### Internal ### def _unsupported(self, name: str) -> IOError: """Internal: raise an exception for unsupported operations.""" raise IOError("%s.%s() not supported" % (self.__class__.__name__, name)) ### Positioning ### def seek(self, pos: int, whence: int = 0) -> None: """seek(pos: int, whence: int = 0) -> None. Change stream position. Seek to byte offset pos relative to position indicated by whence: 0 Start of stream (the default). pos should be >= 0; 1 Current position - whence may be negative; 2 End of stream - whence usually negative. """ self._unsupported("seek") def tell(self) -> int: """tell() -> int. Return current stream position.""" self._unsupported("tell") def truncate(self, pos: int = None) -> None: """truncate(size: int = None) -> None. Truncate file to size bytes. Size defaults to the current IO position as reported by tell(). """ self._unsupported("truncate") ### Flush and close ### def flush(self) -> None: """flush() -> None. Flushes write buffers, if applicable. This is a no-op for read-only and non-blocking streams. """ __closed = False def close(self) -> None: """close() -> None. Flushes and closes the IO object. This must be idempotent. It should also set a flag for the 'closed' property (see below) to test. """ if not self.__closed: self.__closed = True self.flush() def __del__(self) -> None: """Destructor. Calls close().""" # The try/except block is in case this is called at program # exit time, when it's possible that globals have already been # deleted, and then the close() call might fail. Since # there's nothing we can do about such failures and they annoy # the end users, we suppress the traceback. try: self.close() except: pass ### Inquiries ### def seekable(self) -> bool: """seekable() -> bool. Return whether object supports random access. If False, seek(), tell() and truncate() will raise IOError. This method may need to do a test seek(). """ return False def readable(self) -> bool: """readable() -> bool. Return whether object was opened for reading. If False, read() will raise IOError. """ return False def writable(self) -> bool: """writable() -> bool. Return whether object was opened for writing. If False, write() and truncate() will raise IOError. """ return False @property def closed(self): """closed: bool. True iff the file has been closed. For backwards compatibility, this is a property, not a predicate. """ return self.__closed ### Context manager ### def __enter__(self) -> "IOBase": # That's a forward reference """Context management protocol. Returns self.""" return self def __exit__(self, *args) -> None: """Context management protocol. Calls close()""" self.close() ### Lower-level APIs ### # XXX Should these be present even if unimplemented? def fileno(self) -> int: """fileno() -> int. Returns underlying file descriptor if one exists. Raises IOError if the IO object does not use a file descriptor. """ self._unsupported("fileno") def isatty(self) -> bool: """isatty() -> int. Returns whether this is an 'interactive' stream. Returns False if we don't know. """ return False class RawIOBase(IOBase): """Base class for raw binary I/O. The read() method is implemented by calling readinto(); derived classes that want to support read() only need to implement readinto() as a primitive operation. In general, readinto() can be more efficient than read(). (It would be tempting to also provide an implementation of readinto() in terms of read(), in case the latter is a more suitable primitive operation, but that would lead to nasty recursion in case a subclass doesn't implement either.) """ def read(self, n: int) -> bytes: """read(n: int) -> bytes. Read and return up to n bytes. Returns an empty bytes array on EOF, or None if the object is set not to block and has no data to read. """ b = bytes(n.__index__()) n = self.readinto(b) del b[n:] return b def readinto(self, b: bytes) -> int: """readinto(b: bytes) -> int. Read up to len(b) bytes into b. Returns number of bytes read (0 for EOF), or None if the object is set not to block as has no data to read. """ self._unsupported("readinto") def write(self, b: bytes) -> int: """write(b: bytes) -> int. Write the given buffer to the IO stream. Returns the number of bytes written, which may be less than len(b). """ self._unsupported("write") class FileIO(_fileio._FileIO, RawIOBase): """Raw I/O implementation for OS files. This multiply inherits from _FileIO and RawIOBase to make isinstance(io.FileIO(), io.RawIOBase) return True without requiring that _fileio._FileIO inherits from io.RawIOBase (which would be hard to do since _fileio.c is written in C). """ class SocketIO(RawIOBase): """Raw I/O implementation for stream sockets.""" # XXX More docs # XXX Hook this up to socket.py def __init__(self, sock, mode): assert mode in ("r", "w", "rw") RawIOBase.__init__(self) self._sock = sock self._mode = mode def readinto(self, b): return self._sock.recv_into(b) def write(self, b): return self._sock.send(b) def close(self): if not self.closed: RawIOBase.close() self._sock.close() def readable(self): return "r" in self._mode def writable(self): return "w" in self._mode def fileno(self): return self._sock.fileno() class BufferedIOBase(IOBase): """Base class for buffered IO objects. The main difference with RawIOBase is that the read() method supports omitting the size argument, and does not have a default implementation that defers to readinto(). In addition, read(), readinto() and write() may raise BlockingIOError if the underlying raw stream is in non-blocking mode and not ready; unlike their raw counterparts, they will never return None. A typical implementation should not inherit from a RawIOBase implementation, but wrap one. """ def read(self, n: int = -1) -> bytes: """read(n: int = -1) -> bytes. Read and return up to n bytes. If the argument is omitted, or negative, reads and returns all data until EOF. If the argument is positive, and the underlying raw stream is not 'interactive', multiple raw reads may be issued to satisfy the byte count (unless EOF is reached first). But for interactive raw streams (XXX and for pipes?), at most one raw read will be issued, and a short result does not imply that EOF is imminent. Returns an empty bytes array on EOF. Raises BlockingIOError if the underlying raw stream has no data at the moment. """ self._unsupported("read") def readinto(self, b: bytes) -> int: """readinto(b: bytes) -> int. Read up to len(b) bytes into b. Like read(), this may issue multiple reads to the underlying raw stream, unless the latter is 'interactive' (XXX or a pipe?). Returns the number of bytes read (0 for EOF). Raises BlockingIOError if the underlying raw stream has no data at the moment. """ self._unsupported("readinto") def write(self, b: bytes) -> int: """write(b: bytes) -> int. Write the given buffer to the IO stream. Returns the number of bytes written, which is never less than len(b). Raises BlockingIOError if the buffer is full and the underlying raw stream cannot accept more data at the moment. """ self._unsupported("write") class _BufferedIOMixin(BufferedIOBase): """A mixin implementation of BufferedIOBase with an underlying raw stream. This passes most requests on to the underlying raw stream. It does *not* provide implementations of read(), readinto() or write(). """ def __init__(self, raw): self.raw = raw ### Positioning ### def seek(self, pos, whence=0): self.raw.seek(pos, whence) def tell(self): return self.raw.tell() def truncate(self, pos=None): self.raw.truncate(pos) ### Flush and close ### def flush(self): self.raw.flush() def close(self): self.flush() self.raw.close() ### Inquiries ### def seekable(self): return self.raw.seekable() def readable(self): return self.raw.readable() def writable(self): return self.raw.writable() @property def closed(self): return self.raw.closed ### Lower-level APIs ### def fileno(self): return self.raw.fileno() def isatty(self): return self.raw.isatty() class _MemoryIOMixin(BufferedIOBase): # XXX docstring def __init__(self, buffer): self._buffer = buffer self._pos = 0 def getvalue(self): return self._buffer def read(self, n=-1): assert n is not None if n < 0: n = len(self._buffer) newpos = min(len(self._buffer), self._pos + n) b = self._buffer[self._pos : newpos] self._pos = newpos return b def readinto(self, b): tmp = self.read(len(b)) n = len(tmp) b[:n] = tmp return n def write(self, b): n = len(b) newpos = self._pos + n self._buffer[self._pos:newpos] = b self._pos = newpos return n def seek(self, pos, whence=0): if whence == 0: self._pos = max(0, pos) elif whence == 1: self._pos = max(0, self._pos + pos) elif whence == 2: self._pos = max(0, len(self._buffer) + pos) else: raise IOError("invalid whence value") def tell(self): return self._pos def truncate(self, pos=None): if pos is None: pos = self._pos else: self._pos = max(0, pos) del self._buffer[pos:] def readable(self): return True def writable(self): return True def seekable(self): return True class BytesIO(_MemoryIOMixin): """Buffered I/O implementation using a bytes buffer, like StringIO.""" # XXX More docs def __init__(self, inital_bytes=None): buffer = b"" if inital_bytes is not None: buffer += inital_bytes _MemoryIOMixin.__init__(self, buffer) # XXX This should inherit from TextIOBase class StringIO(_MemoryIOMixin): """Buffered I/O implementation using a string buffer, like StringIO.""" # XXX More docs # Reuses the same code as BytesIO, just with a string rather that # bytes as the _buffer value. # XXX This doesn't work; _MemoryIOMixin's write() and truncate() # methods assume the buffer is mutable. Simply redefining those # to use slice concatenation will make it awfully slow (in fact, # quadratic in the number of write() calls). def __init__(self, inital_string=None): buffer = "" if inital_string is not None: buffer += inital_string _MemoryIOMixin.__init__(self, buffer) def readinto(self, b: bytes) -> int: self._unsupported("readinto") class BufferedReader(_BufferedIOMixin): """Buffer for a readable sequential RawIO object.""" def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE): """Create a new buffered reader using the given readable raw IO object. """ assert raw.readable() _BufferedIOMixin.__init__(self, raw) self._read_buf = b"" self.buffer_size = buffer_size def read(self, n=-1): """Read n bytes. Returns exactly n bytes of data unless the underlying raw IO stream reaches EOF of if the call would block in non-blocking mode. If n is negative, read until EOF or until read() would block. """ assert n is not None nodata_val = b"" while n < 0 or len(self._read_buf) < n: to_read = max(self.buffer_size, n if n is not None else 2*len(self._read_buf)) current = self.raw.read(to_read) if current in (b"", None): nodata_val = current break self._read_buf += current if self._read_buf: if n < 0: n = len(self._read_buf) out = self._read_buf[:n] self._read_buf = self._read_buf[n:] else: out = nodata_val return out def tell(self): return self.raw.tell() - len(self._read_buf) def seek(self, pos, whence=0): if whence == 1: pos -= len(self._read_buf) self.raw.seek(pos, whence) self._read_buf = b"" class BufferedWriter(_BufferedIOMixin): # XXX docstring def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None): assert raw.writable() _BufferedIOMixin.__init__(self, raw) self.buffer_size = buffer_size self.max_buffer_size = (2*buffer_size if max_buffer_size is None else max_buffer_size) self._write_buf = b"" def write(self, b): # XXX we can implement some more tricks to try and avoid partial writes ##assert issubclass(type(b), bytes) if len(self._write_buf) > self.buffer_size: # We're full, so let's pre-flush the buffer try: self.flush() except BlockingIOError as e: # We can't accept anything else. # XXX Why not just let the exception pass through? raise BlockingIOError(e.errno, e.strerror, 0) self._write_buf.extend(b) if len(self._write_buf) > self.buffer_size: try: self.flush() except BlockingIOError as e: if (len(self._write_buf) > self.max_buffer_size): # We've hit max_buffer_size. We have to accept a partial # write and cut back our buffer. overage = len(self._write_buf) - self.max_buffer_size self._write_buf = self._write_buf[:self.max_buffer_size] raise BlockingIOError(e.errno, e.strerror, overage) def flush(self): written = 0 try: while self._write_buf: n = self.raw.write(self._write_buf) del self._write_buf[:n] written += n except BlockingIOError as e: n = e.characters_written del self._write_buf[:n] written += n raise BlockingIOError(e.errno, e.strerror, written) def tell(self): return self.raw.tell() + len(self._write_buf) def seek(self, pos, whence=0): self.flush() self.raw.seek(pos, whence) class BufferedRWPair(BufferedIOBase): """A buffered reader and writer object together. A buffered reader object and buffered writer object put together to form a sequential IO object that can read and write. This is typically used with a socket or two-way pipe. XXX The usefulness of this (compared to having two separate IO objects) is questionable. """ def __init__(self, reader, writer, buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None): """Constructor. The arguments are two RawIO instances. """ assert reader.readable() assert writer.writable() self.reader = BufferedReader(reader, buffer_size) self.writer = BufferedWriter(writer, buffer_size, max_buffer_size) def read(self, n=-1): return self.reader.read(n) def readinto(self, b): return self.reader.readinto(b) def write(self, b): return self.writer.write(b) def readable(self): return self.reader.readable() def writable(self): return self.writer.writable() def flush(self): return self.writer.flush() def close(self): self.writer.close() self.reader.close() def isatty(self): return self.reader.isatty() or self.writer.isatty() @property def closed(self): return self.writer.closed() class BufferedRandom(BufferedWriter, BufferedReader): # XXX docstring def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None): assert raw.seekable() BufferedReader.__init__(self, raw, buffer_size) BufferedWriter.__init__(self, raw, buffer_size, max_buffer_size) def seek(self, pos, whence=0): self.flush() # First do the raw seek, then empty the read buffer, so that # if the raw seek fails, we don't lose buffered data forever. self.raw.seek(pos, whence) self._read_buf = b"" # XXX I suppose we could implement some magic here to move through the # existing read buffer in the case of seek(<some small +ve number>, 1) # XXX OTOH it might be good to *guarantee* that the buffer is # empty after a seek or flush; for small relative forward # seeks one might as well use small reads instead. def tell(self): if (self._write_buf): return self.raw.tell() + len(self._write_buf) else: return self.raw.tell() - len(self._read_buf) def read(self, n=-1): self.flush() return BufferedReader.read(self, n) def readinto(self, b): self.flush() return BufferedReader.readinto(self, b) def write(self, b): if self._read_buf: self.raw.seek(-len(self._read_buf), 1) # Undo readahead self._read_buf = b"" return BufferedWriter.write(self, b) class TextIOBase(IOBase): """Base class for text I/O. This class provides a character and line based interface to stream I/O. """ def read(self, n: int = -1) -> str: """read(n: int = -1) -> str. Read at most n characters from stream. Read from underlying buffer until we have n characters or we hit EOF. If n is negative or omitted, read until EOF. """ self._unsupported("read") def write(self, s: str): """write(s: str) -> None. Write string s to stream.""" self._unsupported("write") def readline(self) -> str: """readline() -> str. Read until newline or EOF. Returns an empty string if EOF is hit immediately. """ self._unsupported("readline") def __iter__(self): """__iter__() -> Iterator. Return line iterator (actually just self). """ return self def next(self): """Same as readline() except raises StopIteration on immediate EOF.""" line = self.readline() if not line: raise StopIteration return line # The following are provided for backwards compatibility def readlines(self, hint=None): if hint is None: return list(self) n = 0 lines = [] while not lines or n < hint: line = self.readline() if not line: break lines.append(line) n += len(line) return lines def writelines(self, lines): for line in lines: self.write(line) class TextIOWrapper(TextIOBase): """Buffered text stream. Character and line based layer over a BufferedIOBase object. """ # XXX tell(), seek() def __init__(self, buffer, encoding=None, newline=None): if newline not in (None, '\n', '\r\n'): raise IOError("illegal newline %s" % newline) # XXX: ValueError? if encoding is None: # XXX This is questionable encoding = sys.getfilesystemencoding() or "latin-1" self.buffer = buffer self._encoding = encoding self._newline = newline or os.linesep self._fix_newlines = newline is None self._decoder = None self._pending = '' def flush(self): self.buffer.flush() def close(self): self.flush() self.buffer.close() @property def closed(self): return self.buffer.closed def fileno(self): return self.buffer.fileno() def write(self, s: str): b = s.encode(self._encoding) if isinstance(b, str): b = bytes(b) n = self.buffer.write(b) if "\n" in s: self.flush() return n def _get_decoder(self): make_decoder = codecs.getincrementaldecoder(self._encoding) if make_decoder is None: raise IOError(".readline() not supported for encoding %s" % self._encoding) decoder = self._decoder = make_decoder() # XXX: errors if isinstance(decoder, codecs.BufferedIncrementalDecoder): # XXX Hack: make the codec use bytes instead of strings decoder.buffer = b"" return decoder def read(self, n: int = -1): decoder = self._decoder or self._get_decoder() res = self._pending if n < 0: res += decoder.decode(self.buffer.read(), True) self._pending = "" return res else: while len(res) < n: data = self.buffer.read(64) res += decoder.decode(data, not data) if not data: break self._pending = res[n:] return res[:n] def readline(self, limit=None): if limit is not None: # XXX Hack to support limit arg line = self.readline() if len(line) <= limit: return line line, self._pending = line[:limit], line[limit:] + self._pending return line line = self._pending start = 0 decoder = self._decoder or self._get_decoder() while True: # In C we'd look for these in parallel of course. nlpos = line.find("\n", start) crpos = line.find("\r", start) if nlpos >= 0 and crpos >= 0: endpos = min(nlpos, crpos) else: endpos = nlpos if nlpos >= 0 else crpos if endpos != -1: endc = line[endpos] if endc == "\n": ending = "\n" break # We've seen \r - is it standalone, \r\n or \r at end of line? if endpos + 1 < len(line): if line[endpos+1] == '\n': ending = "\r\n" else: ending = "\r" break # There might be a following \n in the next block of data ... start = endpos else: start = len(line) # No line ending seen yet - get more data while True: data = self.buffer.read(64) more_line = decoder.decode(data, not data) if more_line or not data: break if not more_line: ending = "" endpos = len(line) break line += more_line nextpos = endpos + len(ending) self._pending = line[nextpos:] # XXX Update self.newlines here if we want to support that if self._fix_newlines and ending not in ("\n", ""): return line[:endpos] + "\n" else: return line[:nextpos]