"""New I/O library conforming to PEP 3116. This is a prototype; hopefully eventually some of this will be reimplemented in C. Conformance of alternative implementations: all arguments are intended to be positional-only except the arguments of the open() function. Argument names except those of the open() function are not part of the specification. Instance variables and methods whose name starts with a leading underscore are not part of the specification (except "magic" names like __iter__). Only the top-level names listed in the __all__ variable are part of the specification. XXX edge cases when switching between reading/writing XXX need to default buffer size to 1 if isatty() XXX need to support 1 meaning line-buffered XXX don't use assert to validate input requirements XXX whenever an argument is None, use the default value XXX read/write ops should check readable/writable XXX buffered readinto should work with arbitrary buffer objects XXX use incremental encoder for text output, at least for UTF-16 and UTF-8-SIG """ __author__ = ("Guido van Rossum , " "Mike Verdone , " "Mark Russell ") __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 # XXX Shouldn't we use st_blksize whenever we can? 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, newline=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. newline: optional newlines specifier; must be None, '\n' or '\r\n'; specifies the line ending expected on input and written on output. If None, use universal newlines on input and use os.linesep on output. (*) 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. """ # XXX Don't use asserts for these checks; raise TypeError or ValueError 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: if writing or appending: raise ValueError("can't use U and writing mode at once") 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 argument") if binary and newline is not None: raise ValueError("binary mode doesn't take a newline argument") raw = FileIO(file, (reading and "r" or "") + (writing and "w" or "") + (appending and "a" or "") + (updating and "+" or "")) if buffering is None: buffering = -1 if buffering < 0: 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: raw._name = file raw._mode = mode 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: buffer.name = file buffer.mode = mode return buffer text = TextIOWrapper(buffer, encoding, newline) text.name = file text.mode = mode return text class UnsupportedOperation(ValueError, IOError): pass 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. Not that calling any method (even inquiries) on a closed file is undefined. Implementations may raise IOError in this case. """ ### Internal ### def _unsupported(self, name: str) -> IOError: """Internal: raise an exception for unsupported operations.""" raise UnsupportedOperation("%s.%s() not supported" % (self.__class__.__name__, name)) ### Positioning ### def seek(self, pos: int, whence: int = 0) -> int: """seek(pos: int, whence: int = 0) -> int. 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. Returns the new absolute position. """ self._unsupported("seek") def tell(self) -> int: """tell() -> int. Return current stream position.""" return self.seek(0, 1) def truncate(self, pos: int = None) -> int: """truncate(size: int = None) -> int. Truncate file to size bytes. Size defaults to the current IO position as reported by tell(). Returns the new size. """ 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. """ # XXX Should this return the number of bytes written??? __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: try: self.flush() except IOError: pass # If flush() fails, just give up self.__closed = True 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. """ if self.closed: raise ValueError("isatty() on closed file") return False ### Readline[s] and writelines ### def readline(self, limit: int = -1) -> bytes: """For backwards compatibility, a (slowish) readline().""" if hasattr(self, "peek"): def nreadahead(): readahead = self.peek(1, unsafe=True) if not readahead: return 1 n = (readahead.find(b"\n") + 1) or len(readahead) if limit >= 0: n = min(n, limit) return n else: def nreadahead(): return 1 if limit is None: limit = -1 res = bytes() while limit < 0 or len(res) < limit: b = self.read(nreadahead()) if not b: break res += b if res.endswith(b"\n"): break return res def __iter__(self): if self.closed: raise ValueError("__iter__ on closed file") return self def __next__(self): line = self.readline() if not line: raise StopIteration return line def readlines(self, hint=None): if hint is None: return list(self) n = 0 lines = [] for line in self: lines.append(line) n += len(line) if n >= hint: break return lines def writelines(self, lines): if self.closed: raise ValueError("write to closed file") for line in lines: self.write(line) 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 = -1) -> 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. """ if n is None: n = -1 if n < 0: return self.readall() b = bytes(n.__index__()) n = self.readinto(b) del b[n:] return b def readall(self): """readall() -> bytes. Read until EOF, using multiple read() call.""" res = bytes() while True: data = self.read(DEFAULT_BUFFER_SIZE) if not data: break res += data return res 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). """ def close(self): _fileio._FileIO.close(self) RawIOBase.close(self) @property def name(self): return self._name @property def mode(self): return self._mode 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 = None) -> bytes: """read(n: int = None) -> bytes. Read and return up to n bytes. If the argument is omitted, None, 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. """ # XXX This ought to work with anything that supports the buffer API data = self.read(len(b)) n = len(data) try: b[:n] = data except TypeError as err: import array if not isinstance(b, array.array): raise err b[:n] = array.array('b', data) return n 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): return self.raw.seek(pos, whence) def tell(self): return self.raw.tell() def truncate(self, pos=None): if pos is None: pos = self.tell() return self.raw.truncate(pos) ### Flush and close ### def flush(self): self.raw.flush() def close(self): if not self.closed: try: self.flush() except IOError: pass # If flush() fails, just give up 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 BytesIO(BufferedIOBase): """Buffered I/O implementation using an in-memory bytes buffer.""" # XXX More docs def __init__(self, initial_bytes=None): buffer = b"" if initial_bytes is not None: buffer += initial_bytes self._buffer = buffer self._pos = 0 def getvalue(self): return self._buffer def read(self, n=None): if n is None: n = -1 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 read1(self, n): return self.read(n) def write(self, b): if self.closed: raise ValueError("write to closed file") n = len(b) newpos = self._pos + n if newpos > len(self._buffer): # Inserts null bytes between the current end of the file # and the new write position. padding = '\x00' * (newpos - len(self._buffer) - n) self._buffer[self._pos:newpos - n] = padding 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") return self._pos def tell(self): return self._pos def truncate(self, pos=None): if pos is None: pos = self._pos del self._buffer[pos:] return pos def readable(self): return True def writable(self): return True def seekable(self): return True 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=None): """Read n bytes. Returns exactly n bytes of data unless the underlying raw IO stream reaches EOF or if the call would block in non-blocking mode. If n is negative, read until EOF or until read() would block. """ if n is None: n = -1 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 peek(self, n=0, *, unsafe=False): """Returns buffered bytes without advancing the position. The argument indicates a desired minimal number of bytes; we do at most one raw read to satisfy it. We never return more than self.buffer_size. Unless unsafe=True is passed, we return a copy. """ want = min(n, self.buffer_size) have = len(self._read_buf) if have < want: to_read = self.buffer_size - have current = self.raw.read(to_read) if current: self._read_buf += current result = self._read_buf if unsafe: result = result[:] return result def read1(self, n): """Reads up to n bytes. Returns up to n bytes. If at least one byte is buffered, we only return buffered bytes. Otherwise, we do one raw read. """ if n <= 0: return b"" self.peek(1, unsafe=True) return self.read(min(n, len(self._read_buf))) 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) pos = self.raw.seek(pos, whence) self._read_buf = b"" return pos 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): if self.closed: raise ValueError("write to closed file") if not isinstance(b, bytes): if hasattr(b, "__index__"): raise TypeError("Can't write object of type %s" % type(b).__name__) b = bytes(b) # XXX we can implement some more tricks to try and avoid partial writes 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) before = len(self._write_buf) self._write_buf.extend(b) written = len(self._write_buf) - before 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) return written def flush(self): if self.closed: raise ValueError("flush of closed file") 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() return 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=None): if n is None: 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 peek(self, n=0, *, unsafe=False): return self.reader.peek(n, unsafe=unsafe) def read1(self, n): return self.reader.read1(n) 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. pos = self.raw.seek(pos, whence) self._read_buf = b"" return pos 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=None): if n is None: n = -1 self.flush() return BufferedReader.read(self, n) def readinto(self, b): self.flush() return BufferedReader.readinto(self, b) def peek(self, n=0, *, unsafe=False): self.flush() return BufferedReader.peek(self, n, unsafe=unsafe) def read1(self, n): self.flush() return BufferedReader.read1(self, n) 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. There is no readinto() method, as character strings are immutable. """ 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) -> int: """write(s: str) -> int. Write string s to stream.""" self._unsupported("write") def truncate(self, pos: int = None) -> int: """truncate(pos: int = None) -> int. Truncate size to pos.""" self.flush() if pos is None: pos = self.tell() self.seek(pos) return self.buffer.truncate() def readline(self) -> str: """readline() -> str. Read until newline or EOF. Returns an empty string if EOF is hit immediately. """ self._unsupported("readline") @property def encoding(self): """Subclasses should override.""" return None class TextIOWrapper(TextIOBase): """Buffered text stream. Character and line based layer over a BufferedIOBase object. """ _CHUNK_SIZE = 128 def __init__(self, buffer, encoding=None, newline=None): if newline not in (None, "\n", "\r\n"): raise ValueError("illegal newline value: %r" % (newline,)) if encoding is None: try: encoding = os.device_encoding(buffer.fileno()) except AttributeError: pass if encoding is None: try: import locale except ImportError: # Importing locale may fail if Python is being built encoding = "ascii" else: encoding = locale.getpreferredencoding() self.buffer = buffer self._encoding = encoding self._newline = newline or os.linesep self._fix_newlines = newline is None self._decoder = None self._pending = "" self._snapshot = None self._seekable = self._telling = self.buffer.seekable() @property def encoding(self): return self._encoding # A word about _snapshot. This attribute is either None, or a # tuple (decoder_state, readahead, pending) where decoder_state is # the second (integer) item of the decoder state, readahead is the # chunk of bytes that was read, and pending is the characters that # were rendered by the decoder after feeding it those bytes. We # use this to reconstruct intermediate decoder states in tell(). def _seekable(self): return self._seekable def flush(self): self.buffer.flush() self._telling = self._seekable def close(self): try: self.flush() except: pass # If flush() fails, just give up self.buffer.close() @property def closed(self): return self.buffer.closed def fileno(self): return self.buffer.fileno() def isatty(self): return self.buffer.isatty() def write(self, s: str): if self.closed: raise ValueError("write to closed file") # XXX What if we were just reading? b = s.encode(self._encoding) if isinstance(b, str): b = bytes(b) n = self.buffer.write(b) if "\n" in s: # XXX only if isatty self.flush() self._snapshot = self._decoder = None return len(s) def _get_decoder(self): make_decoder = codecs.getincrementaldecoder(self._encoding) if make_decoder is None: raise IOError("Can't find an incremental decoder for encoding %s" % self._encoding) decoder = self._decoder = make_decoder() # XXX: errors return decoder def _read_chunk(self): assert self._decoder is not None if not self._telling: readahead = self.buffer.read1(self._CHUNK_SIZE) pending = self._decoder.decode(readahead, not readahead) return readahead, pending decoder_buffer, decoder_state = self._decoder.getstate() readahead = self.buffer.read1(self._CHUNK_SIZE) pending = self._decoder.decode(readahead, not readahead) self._snapshot = (decoder_state, decoder_buffer + readahead, pending) return readahead, pending def _encode_decoder_state(self, ds, pos): x = 0 for i in bytes(ds): x = x<<8 | i return (x<<64) | pos def _decode_decoder_state(self, pos): x, pos = divmod(pos, 1<<64) if not x: return None, pos b = b"" while x: b.append(x&0xff) x >>= 8 return str(b[::-1]), pos def tell(self): if not self._seekable: raise IOError("Underlying stream is not seekable") if not self._telling: raise IOError("Telling position disabled by next() call") self.flush() position = self.buffer.tell() decoder = self._decoder if decoder is None or self._snapshot is None: assert self._pending == "" return position decoder_state, readahead, pending = self._snapshot position -= len(readahead) needed = len(pending) - len(self._pending) if not needed: return self._encode_decoder_state(decoder_state, position) saved_state = decoder.getstate() try: decoder.setstate((b"", decoder_state)) n = 0 bb = bytes(1) for i, bb[0] in enumerate(readahead): n += len(decoder.decode(bb)) if n >= needed: decoder_buffer, decoder_state = decoder.getstate() return self._encode_decoder_state( decoder_state, position + (i+1) - len(decoder_buffer)) raise IOError("Can't reconstruct logical file position") finally: decoder.setstate(saved_state) def seek(self, pos, whence=0): if not self._seekable: raise IOError("Underlying stream is not seekable") if whence == 1: if pos != 0: raise IOError("Can't do nonzero cur-relative seeks") pos = self.tell() whence = 0 if whence == 2: if pos != 0: raise IOError("Can't do nonzero end-relative seeks") self.flush() pos = self.buffer.seek(0, 2) self._snapshot = None self._pending = "" self._decoder = None return pos if whence != 0: raise ValueError("Invalid whence (%r, should be 0, 1 or 2)" % (whence,)) if pos < 0: raise ValueError("Negative seek position %r" % (pos,)) self.flush() orig_pos = pos ds, pos = self._decode_decoder_state(pos) if not ds: self.buffer.seek(pos) self._snapshot = None self._pending = "" self._decoder = None return pos decoder = self._decoder or self._get_decoder() decoder.set_state(("", ds)) self.buffer.seek(pos) self._snapshot = (ds, b"", "") self._pending = "" self._decoder = decoder return orig_pos def read(self, n=None): if n is None: n = -1 decoder = self._decoder or self._get_decoder() res = self._pending if n < 0: res += decoder.decode(self.buffer.read(), True) self._pending = "" self._snapshot = None return res.replace("\r\n", "\n") else: while len(res) < n: readahead, pending = self._read_chunk() res += pending if not readahead: break self._pending = res[n:] return res[:n].replace("\r\n", "\n") def __next__(self): self._telling = False line = self.readline() if not line: self._snapshot = None self._telling = self._seekable raise StopIteration return line def readline(self, limit=None): if limit is not None: # XXX Hack to support limit argument, for backwards compatibility 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: readahead, pending = self._read_chunk() more_line = pending if more_line or not readahead: 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] class StringIO(TextIOWrapper): # XXX This is really slow, but fully functional def __init__(self, initial_value="", encoding="utf-8", newline=None): super(StringIO, self).__init__(BytesIO(), encoding=encoding, newline=newline) if initial_value: if not isinstance(initial_value, basestring): initial_value = str(initial_value) self.write(initial_value) self.seek(0) def getvalue(self): self.flush() return self.buffer.getvalue().decode(self._encoding)