Edit: _pyio.py
""" Python implementation of the io module. """ import os import abc import codecs import errno # Import _thread instead of threading to reduce startup cost try: from _thread import allocate_lock as Lock except ImportError: from _dummy_thread import allocate_lock as Lock import io from io import (__all__, SEEK_SET, SEEK_CUR, SEEK_END) valid_seek_flags = {0, 1, 2} # Hardwired values if hasattr(os, 'SEEK_HOLE') : valid_seek_flags.add(os.SEEK_HOLE) valid_seek_flags.add(os.SEEK_DATA) # open() uses st_blksize whenever we can DEFAULT_BUFFER_SIZE = 8 * 1024 # bytes # NOTE: Base classes defined here are registered with the "official" ABCs # defined in io.py. We don't use real inheritance though, because we don't # want to inherit the C implementations. # Rebind for compatibility BlockingIOError = BlockingIOError def open(file, mode="r", buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None): r"""Open file and return a stream. Raise IOError upon failure. file is either a text or byte string giving the name (and the path if the file isn't in the current working directory) of the file to be opened or an integer file descriptor of the file to be wrapped. (If a file descriptor is given, it is closed when the returned I/O object is closed, unless closefd is set to False.) mode is an optional string that specifies the mode in which the file is opened. It defaults to 'r' which means open for reading in text mode. Other common values are 'w' for writing (truncating the file if it already exists), 'x' for exclusive creation of a new file, and 'a' for appending (which on some Unix systems, means that all writes append to the end of the file regardless of the current seek position). In text mode, if encoding is not specified the encoding used is platform dependent. (For reading and writing raw bytes use binary mode and leave encoding unspecified.) The available modes are: ========= =============================================================== Character Meaning --------- --------------------------------------------------------------- 'r' open for reading (default) 'w' open for writing, truncating the file first 'x' create a new file and open it for writing 'a' open for writing, appending to the end of the file if it exists 'b' binary mode 't' text mode (default) '+' open a disk file for updating (reading and writing) 'U' universal newline mode (for backwards compatibility; unneeded for new code) ========= =============================================================== The default mode is 'rt' (open for reading text). For binary random access, the mode 'w+b' opens and truncates the file to 0 bytes, while 'r+b' opens the file without truncation. The 'x' mode implies 'w' and raises an `FileExistsError` if the file already exists. Python distinguishes between files opened in binary and text modes, even when the underlying operating system doesn't. Files opened in binary mode (appending 'b' to the mode argument) return contents as bytes objects without any decoding. In text mode (the default, or when 't' is appended to the mode argument), the contents of the file are returned as strings, the bytes having been first decoded using a platform-dependent encoding or using the specified encoding if given. buffering is an optional integer used to set the buffering policy. Pass 0 to switch buffering off (only allowed in binary mode), 1 to select line buffering (only usable in text mode), and an integer > 1 to indicate the size of a fixed-size chunk buffer. When no buffering argument is given, the default buffering policy works as follows: * Binary files are buffered in fixed-size chunks; the size of the buffer is chosen using a heuristic trying to determine the underlying device's "block size" and falling back on `io.DEFAULT_BUFFER_SIZE`. On many systems, the buffer will typically be 4096 or 8192 bytes long. * "Interactive" text files (files for which isatty() returns True) use line buffering. Other text files use the policy described above for binary files. encoding is the str name of the encoding used to decode or encode the file. This should only be used in text mode. The default encoding is platform dependent, but any encoding supported by Python can be passed. See the codecs module for the list of supported encodings. errors is an optional string that specifies how encoding errors are to be handled---this argument should not be used in binary mode. Pass 'strict' to raise a ValueError exception if there is an encoding error (the default of None has the same effect), or pass 'ignore' to ignore errors. (Note that ignoring encoding errors can lead to data loss.) See the documentation for codecs.register for a list of the permitted encoding error strings. newline is a string controlling how universal newlines works (it only applies to text mode). It can be None, '', '\n', '\r', and '\r\n'. It works as follows: * On input, if newline is None, universal newlines mode is enabled. Lines in the input can end in '\n', '\r', or '\r\n', and these are translated into '\n' before being returned to the caller. If it is '', universal newline mode is enabled, but line endings are returned to the caller untranslated. If it has any of the other legal values, input lines are only terminated by the given string, and the line ending is returned to the caller untranslated. * On output, if newline is None, any '\n' characters written are translated to the system default line separator, os.linesep. If newline is '', no translation takes place. If newline is any of the other legal values, any '\n' characters written are translated to the given string. closedfd is a bool. If closefd is False, the underlying file descriptor will be kept open when the file is closed. This does not work when a file name is given and must be True in that case. A custom opener can be used by passing a callable as *opener*. The underlying file descriptor for the file object is then obtained by calling *opener* with (*file*, *flags*). *opener* must return an open file descriptor (passing os.open as *opener* results in functionality similar to passing None). open() returns a file object whose type depends on the mode, and through which the standard file operations such as reading and writing are performed. When open() is used to open a file in a text mode ('w', 'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open a file in a binary mode, the returned class varies: in read binary mode, it returns a BufferedReader; in write binary and append binary modes, it returns a BufferedWriter, and in read/write mode, it returns a BufferedRandom. It is also possible to use a string or bytearray as a file for both reading and writing. For strings StringIO can be used like a file opened in a text mode, and for bytes a BytesIO can be used like a file opened in a binary mode. """ if not isinstance(file, (str, bytes, int)): raise TypeError("invalid file: %r" % file) if not isinstance(mode, str): raise TypeError("invalid mode: %r" % mode) if not isinstance(buffering, int): raise TypeError("invalid buffering: %r" % buffering) if encoding is not None and not isinstance(encoding, str): raise TypeError("invalid encoding: %r" % encoding) if errors is not None and not isinstance(errors, str): raise TypeError("invalid errors: %r" % errors) modes = set(mode) if modes - set("axrwb+tU") or len(mode) > len(modes): raise ValueError("invalid mode: %r" % mode) creating = "x" in modes 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 creating or 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 creating + reading + writing + appending > 1: raise ValueError("can't have read/write/append mode at once") if not (creating or 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 errors is not None: raise ValueError("binary mode doesn't take an errors argument") if binary and newline is not None: raise ValueError("binary mode doesn't take a newline argument") raw = FileIO(file, (creating and "x" or "") + (reading and "r" or "") + (writing and "w" or "") + (appending and "a" or "") + (updating and "+" or ""), closefd, opener=opener) line_buffering = False if buffering == 1 or buffering < 0 and raw.isatty(): buffering = -1 line_buffering = True if buffering < 0: buffering = DEFAULT_BUFFER_SIZE 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 creating or writing or appending: buffer = BufferedWriter(raw, buffering) elif reading: buffer = BufferedReader(raw, buffering) else: raise ValueError("unknown mode: %r" % mode) if binary: return buffer text = TextIOWrapper(buffer, encoding, errors, newline, line_buffering) text.mode = mode return text class DocDescriptor: """Helper for builtins.open.__doc__ """ def __get__(self, obj, typ): return ( "open(file, mode='r', buffering=-1, encoding=None, " "errors=None, newline=None, closefd=True)\n\n" + open.__doc__) class OpenWrapper: """Wrapper for builtins.open Trick so that open won't become a bound method when stored as a class variable (as dbm.dumb does). See initstdio() in Python/pythonrun.c. """ __doc__ = DocDescriptor() def __new__(cls, *args, **kwargs): return open(*args, **kwargs) # In normal operation, both `UnsupportedOperation`s should be bound to the # same object. try: UnsupportedOperation = io.UnsupportedOperation except AttributeError: class UnsupportedOperation(ValueError, IOError): pass class IOBase(metaclass=abc.ABCMeta): """The abstract base class for all I/O classes, acting on streams of bytes. There is no public constructor. 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. Even though IOBase does not declare read, readinto, or write because their signatures will vary, implementations and clients should consider those methods part of the interface. Also, implementations may raise UnsupportedOperation when operations they do not support are called. The basic type used for binary data read from or written to a file is bytes. bytearrays are accepted too, and in some cases (such as readinto) needed. Text I/O classes work with str data. Note that calling any method (even inquiries) on a closed stream is undefined. Implementations may raise IOError in this case. IOBase (and its subclasses) support the iterator protocol, meaning that an IOBase object can be iterated over yielding the lines in a stream. IOBase also supports the :keyword:`with` statement. In this example, fp is closed after the suite of the with statement is complete: with open('spam.txt', 'r') as fp: fp.write('Spam and eggs!') """ ### Internal ### def _unsupported(self, name): """Internal: raise an IOError exception for unsupported operations.""" raise UnsupportedOperation("%s.%s() not supported" % (self.__class__.__name__, name)) ### Positioning ### def seek(self, pos, whence=0): """Change stream position. Change the stream position to byte offset pos. Argument pos is interpreted relative to the position indicated by whence. Values for whence are ints: * 0 -- start of stream (the default); offset should be zero or positive * 1 -- current stream position; offset may be negative * 2 -- end of stream; offset is usually negative Some operating systems / file systems could provide additional values. Return an int indicating the new absolute position. """ self._unsupported("seek") def tell(self): """Return an int indicating the current stream position.""" return self.seek(0, 1) def truncate(self, pos=None): """Truncate file to size bytes. Size defaults to the current IO position as reported by tell(). Return the new size. """ self._unsupported("truncate") ### Flush and close ### def flush(self): """Flush write buffers, if applicable. This is not implemented for read-only and non-blocking streams. """ self._checkClosed() # XXX Should this return the number of bytes written??? __closed = False def close(self): """Flush and close the IO object. This method has no effect if the file is already closed. """ if not self.__closed: try: self.flush() finally: self.__closed = True def __del__(self): """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): """Return a bool indicating whether object supports random access. If False, seek(), tell() and truncate() will raise UnsupportedOperation. This method may need to do a test seek(). """ return False def _checkSeekable(self, msg=None): """Internal: raise UnsupportedOperation if file is not seekable """ if not self.seekable(): raise UnsupportedOperation("File or stream is not seekable." if msg is None else msg) def readable(self): """Return a bool indicating whether object was opened for reading. If False, read() will raise UnsupportedOperation. """ return False def _checkReadable(self, msg=None): """Internal: raise UnsupportedOperation if file is not readable """ if not self.readable(): raise UnsupportedOperation("File or stream is not readable." if msg is None else msg) def writable(self): """Return a bool indicating whether object was opened for writing. If False, write() and truncate() will raise UnsupportedOperation. """ return False def _checkWritable(self, msg=None): """Internal: raise UnsupportedOperation if file is not writable """ if not self.writable(): raise UnsupportedOperation("File or stream is not writable." if msg is None else msg) @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 def _checkClosed(self, msg=None): """Internal: raise an ValueError if file is closed """ if self.closed: raise ValueError("I/O operation on closed file." if msg is None else msg) ### Context manager ### def __enter__(self): # That's a forward reference """Context management protocol. Returns self (an instance of IOBase).""" self._checkClosed() return self def __exit__(self, *args): """Context management protocol. Calls close()""" self.close() ### Lower-level APIs ### # XXX Should these be present even if unimplemented? def fileno(self): """Returns underlying file descriptor (an int) if one exists. An IOError is raised if the IO object does not use a file descriptor. """ self._unsupported("fileno") def isatty(self): """Return a bool indicating whether this is an 'interactive' stream. Return False if it can't be determined. """ self._checkClosed() return False ### Readline[s] and writelines ### def readline(self, limit=-1): r"""Read and return a line of bytes from the stream. If limit is specified, at most limit bytes will be read. Limit should be an int. The line terminator is always b'\n' for binary files; for text files, the newlines argument to open can be used to select the line terminator(s) recognized. """ # For backwards compatibility, a (slowish) readline(). if hasattr(self, "peek"): def nreadahead(): readahead = self.peek(1) 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 elif not isinstance(limit, int): raise TypeError("limit must be an integer") res = bytearray() while limit < 0 or len(res) < limit: b = self.read(nreadahead()) if not b: break res += b if res.endswith(b"\n"): break return bytes(res) def __iter__(self): self._checkClosed() return self def __next__(self): line = self.readline() if not line: raise StopIteration return line def readlines(self, hint=None): """Return a list of lines from the stream. hint can be specified to control the number of lines read: no more lines will be read if the total size (in bytes/characters) of all lines so far exceeds hint. """ if hint is None or hint <= 0: 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): self._checkClosed() for line in lines: self.write(line) io.IOBase.register(IOBase) 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=-1): """Read and return up to n bytes, where n is an int. Returns an empty bytes object 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 = bytearray(n.__index__()) n = self.readinto(b) if n is None: return None del b[n:] return bytes(b) def readall(self): """Read until EOF, using multiple read() call.""" res = bytearray() while True: data = self.read(DEFAULT_BUFFER_SIZE) if not data: break res += data if res: return bytes(res) else: # b'' or None return data def readinto(self, b): """Read up to len(b) bytes into bytearray b. Returns an int representing the number of bytes read (0 for EOF), or None if the object is set not to block and has no data to read. """ self._unsupported("readinto") def write(self, b): """Write the given buffer to the IO stream. Returns the number of bytes written, which may be less than len(b). """ self._unsupported("write") io.RawIOBase.register(RawIOBase) from _io import FileIO RawIOBase.register(FileIO) 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=None): """Read and return up to n bytes, where n is an int. 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 read1(self, n=None): """Read up to n bytes with at most one read() system call, where n is an int. """ self._unsupported("read1") def readinto(self, b): """Read up to len(b) bytes into bytearray b. Like read(), this may issue multiple reads to the underlying raw stream, unless the latter is 'interactive'. Returns an int representing 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): """Write the given bytes buffer to the IO stream. Return 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") def detach(self): """ Separate the underlying raw stream from the buffer and return it. After the raw stream has been detached, the buffer is in an unusable state. """ self._unsupported("detach") io.BufferedIOBase.register(BufferedIOBase) 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): new_position = self.raw.seek(pos, whence) if new_position < 0: raise IOError("seek() returned an invalid position") return new_position def tell(self): pos = self.raw.tell() if pos < 0: raise IOError("tell() returned an invalid position") return pos def truncate(self, pos=None): # Flush the stream. We're mixing buffered I/O with lower-level I/O, # and a flush may be necessary to synch both views of the current # file state. self.flush() if pos is None: pos = self.tell() # XXX: Should seek() be used, instead of passing the position # XXX directly to truncate? return self.raw.truncate(pos) ### Flush and close ### def flush(self): if self.closed: raise ValueError("flush of closed file") self.raw.flush() def close(self): if self.raw is not None and not self.closed: try: # may raise BlockingIOError or BrokenPipeError etc self.flush() finally: self.raw.close() def detach(self): if self.raw is None: raise ValueError("raw stream already detached") self.flush() raw = self._raw self._raw = None return raw ### Inquiries ### def seekable(self): return self.raw.seekable() def readable(self): return self.raw.readable() def writable(self): return self.raw.writable() @property def raw(self): return self._raw @property def closed(self): return self.raw.closed @property def name(self): return self.raw.name @property def mode(self): return self.raw.mode def __getstate__(self): raise TypeError("can not serialize a '{0}' object" .format(self.__class__.__name__)) def __repr__(self): clsname = self.__class__.__name__ try: name = self.name except AttributeError: return "<_pyio.{0}>".format(clsname) else: return "<_pyio.{0} name={1!r}>".format(clsname, name) ### 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.""" def __init__(self, initial_bytes=None): buf = bytearray() if initial_bytes is not None: buf += initial_bytes self._buffer = buf self._pos = 0 def __getstate__(self): if self.closed: raise ValueError("__getstate__ on closed file") return self.__dict__.copy() def getvalue(self): """Return the bytes value (contents) of the buffer """ if self.closed: raise ValueError("getvalue on closed file") return bytes(self._buffer) def getbuffer(self): """Return a readable and writable view of the buffer. """ return memoryview(self._buffer) def read(self, n=None): if self.closed: raise ValueError("read from closed file") if n is None: n = -1 if n < 0: n = len(self._buffer) if len(self._buffer) <= self._pos: return b"" newpos = min(len(self._buffer), self._pos + n) b = self._buffer[self._pos : newpos] self._pos = newpos return bytes(b) def read1(self, n): """This is the same as read. """ return self.read(n) def write(self, b): if self.closed: raise ValueError("write to closed file") if isinstance(b, str): raise TypeError("can't write str to binary stream") n = len(b) if n == 0: return 0 pos = self._pos if pos > len(self._buffer): # Inserts null bytes between the current end of the file # and the new write position. padding = b'\x00' * (pos - len(self._buffer)) self._buffer += padding self._buffer[pos:pos + n] = b self._pos += n return n def seek(self, pos, whence=0): if self.closed: raise ValueError("seek on closed file") try: pos.__index__ except AttributeError as err: raise TypeError("an integer is required") from err if whence == 0: if pos < 0: raise ValueError("negative seek position %r" % (pos,)) self._pos = pos elif whence == 1: self._pos = max(0, self._pos + pos) elif whence == 2: self._pos = max(0, len(self._buffer) + pos) else: raise ValueError("unsupported whence value") return self._pos def tell(self): if self.closed: raise ValueError("tell on closed file") return self._pos def truncate(self, pos=None): if self.closed: raise ValueError("truncate on closed file") if pos is None: pos = self._pos else: try: pos.__index__ except AttributeError as err: raise TypeError("an integer is required") from err if pos < 0: raise ValueError("negative truncate position %r" % (pos,)) del self._buffer[pos:] return pos def readable(self): if self.closed: raise ValueError("I/O operation on closed file.") return True def writable(self): if self.closed: raise ValueError("I/O operation on closed file.") return True def seekable(self): if self.closed: raise ValueError("I/O operation on closed file.") return True class BufferedReader(_BufferedIOMixin): """BufferedReader(raw[, buffer_size]) A buffer for a readable, sequential BaseRawIO object. The constructor creates a BufferedReader for the given readable raw stream and buffer_size. If buffer_size is omitted, DEFAULT_BUFFER_SIZE is used. """ def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE): """Create a new buffered reader using the given readable raw IO object. """ if not raw.readable(): raise IOError('"raw" argument must be readable.') _BufferedIOMixin.__init__(self, raw) if buffer_size <= 0: raise ValueError("invalid buffer size") self.buffer_size = buffer_size self._reset_read_buf() self._read_lock = Lock() def _reset_read_buf(self): self._read_buf = b"" self._read_pos = 0 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 not None and n < -1: raise ValueError("invalid number of bytes to read") with self._read_lock: return self._read_unlocked(n) def _read_unlocked(self, n=None): nodata_val = b"" empty_values = (b"", None) buf = self._read_buf pos = self._read_pos # Special case for when the number of bytes to read is unspecified. if n is None or n == -1: self._reset_read_buf() if hasattr(self.raw, 'readall'): chunk = self.raw.readall() if chunk is None: return buf[pos:] or None else: return buf[pos:] + chunk chunks = [buf[pos:]] # Strip the consumed bytes. current_size = 0 while True: # Read until EOF or until read() would block. try: chunk = self.raw.read() except InterruptedError: continue if chunk in empty_values: nodata_val = chunk break current_size += len(chunk) chunks.append(chunk) return b"".join(chunks) or nodata_val # The number of bytes to read is specified, return at most n bytes. avail = len(buf) - pos # Length of the available buffered data. if n <= avail: # Fast path: the data to read is fully buffered. self._read_pos += n return buf[pos:pos+n] # Slow path: read from the stream until enough bytes are read, # or until an EOF occurs or until read() would block. chunks = [buf[pos:]] wanted = max(self.buffer_size, n) while avail < n: try: chunk = self.raw.read(wanted) except InterruptedError: continue if chunk in empty_values: nodata_val = chunk break avail += len(chunk) chunks.append(chunk) # n is more then avail only when an EOF occurred or when # read() would have blocked. n = min(n, avail) out = b"".join(chunks) self._read_buf = out[n:] # Save the extra data in the buffer. self._read_pos = 0 return out[:n] if out else nodata_val def peek(self, n=0): """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. """ with self._read_lock: return self._peek_unlocked(n) def _peek_unlocked(self, n=0): want = min(n, self.buffer_size) have = len(self._read_buf) - self._read_pos if have < want or have <= 0: to_read = self.buffer_size - have while True: try: current = self.raw.read(to_read) except InterruptedError: continue break if current: self._read_buf = self._read_buf[self._read_pos:] + current self._read_pos = 0 return self._read_buf[self._read_pos:] def read1(self, n): """Reads up to n bytes, with at most one read() system call.""" # 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: raise ValueError("number of bytes to read must be positive") if n == 0: return b"" with self._read_lock: self._peek_unlocked(1) return self._read_unlocked( min(n, len(self._read_buf) - self._read_pos)) def tell(self): return _BufferedIOMixin.tell(self) - len(self._read_buf) + self._read_pos def seek(self, pos, whence=0): if whence not in valid_seek_flags: raise ValueError("invalid whence value") with self._read_lock: if whence == 1: pos -= len(self._read_buf) - self._read_pos pos = _BufferedIOMixin.seek(self, pos, whence) self._reset_read_buf() return pos class BufferedWriter(_BufferedIOMixin): """A buffer for a writeable sequential RawIO object. The constructor creates a BufferedWriter for the given writeable raw stream. If the buffer_size is not given, it defaults to DEFAULT_BUFFER_SIZE. """ def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE): if not raw.writable(): raise IOError('"raw" argument must be writable.') _BufferedIOMixin.__init__(self, raw) if buffer_size <= 0: raise ValueError("invalid buffer size") self.buffer_size = buffer_size self._write_buf = bytearray() self._write_lock = Lock() def write(self, b): if self.closed: raise ValueError("write to closed file") if isinstance(b, str): raise TypeError("can't write str to binary stream") with self._write_lock: # 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. (This may # raise BlockingIOError with characters_written == 0.) self._flush_unlocked() 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_unlocked() except BlockingIOError as e: if len(self._write_buf) > self.buffer_size: # We've hit the buffer_size. We have to accept a partial # write and cut back our buffer. overage = len(self._write_buf) - self.buffer_size written -= overage self._write_buf = self._write_buf[:self.buffer_size] raise BlockingIOError(e.errno, e.strerror, written) return written def truncate(self, pos=None): with self._write_lock: self._flush_unlocked() if pos is None: pos = self.raw.tell() return self.raw.truncate(pos) def flush(self): with self._write_lock: self._flush_unlocked() def _flush_unlocked(self): if self.closed: raise ValueError("flush of closed file") while self._write_buf: try: n = self.raw.write(self._write_buf) except InterruptedError: continue except BlockingIOError: raise RuntimeError("self.raw should implement RawIOBase: it " "should not raise BlockingIOError") if n is None: raise BlockingIOError( errno.EAGAIN, "write could not complete without blocking", 0) if n > len(self._write_buf) or n < 0: raise IOError("write() returned incorrect number of bytes") del self._write_buf[:n] def tell(self): return _BufferedIOMixin.tell(self) + len(self._write_buf) def seek(self, pos, whence=0): if whence not in valid_seek_flags: raise ValueError("invalid whence value") with self._write_lock: self._flush_unlocked() return _BufferedIOMixin.seek(self, 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. reader and writer are RawIOBase objects that are readable and writeable respectively. If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE. """ # XXX The usefulness of this (compared to having two separate IO # objects) is questionable. def __init__(self, reader, writer, buffer_size=DEFAULT_BUFFER_SIZE): """Constructor. The arguments are two RawIO instances. """ if not reader.readable(): raise IOError('"reader" argument must be readable.') if not writer.writable(): raise IOError('"writer" argument must be writable.') self.reader = BufferedReader(reader, buffer_size) self.writer = BufferedWriter(writer, 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): return self.reader.peek(n) 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): """A buffered interface to random access streams. The constructor creates a reader and writer for a seekable stream, raw, given in the first argument. If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE. """ def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE): raw._checkSeekable() BufferedReader.__init__(self, raw, buffer_size) BufferedWriter.__init__(self, raw, buffer_size) def seek(self, pos, whence=0): if whence not in valid_seek_flags: raise ValueError("invalid whence value") self.flush() if self._read_buf: # Undo read ahead. with self._read_lock: self.raw.seek(self._read_pos - len(self._read_buf), 1) # 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) with self._read_lock: self._reset_read_buf() if pos < 0: raise IOError("seek() returned invalid position") return pos def tell(self): if self._write_buf: return BufferedWriter.tell(self) else: return BufferedReader.tell(self) def truncate(self, pos=None): if pos is None: pos = self.tell() # Use seek to flush the read buffer. return BufferedWriter.truncate(self, pos) 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): self.flush() return BufferedReader.peek(self, n) def read1(self, n): self.flush() return BufferedReader.read1(self, n) def write(self, b): if self._read_buf: # Undo readahead with self._read_lock: self.raw.seek(self._read_pos - len(self._read_buf), 1) self._reset_read_buf() 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 because Python's character strings are immutable. There is no public constructor. """ def read(self, n=-1): """Read at most n characters from stream, where n is an int. Read from underlying buffer until we have n characters or we hit EOF. If n is negative or omitted, read until EOF. Returns a string. """ self._unsupported("read") def write(self, s): """Write string s to stream and returning an int.""" self._unsupported("write") def truncate(self, pos=None): """Truncate size to pos, where pos is an int.""" self._unsupported("truncate") def readline(self): """Read until newline or EOF. Returns an empty string if EOF is hit immediately. """ self._unsupported("readline") def detach(self): """ Separate the underlying buffer from the TextIOBase and return it. After the underlying buffer has been detached, the TextIO is in an unusable state. """ self._unsupported("detach") @property def encoding(self): """Subclasses should override.""" return None @property def newlines(self): """Line endings translated so far. Only line endings translated during reading are considered. Subclasses should override. """ return None @property def errors(self): """Error setting of the decoder or encoder. Subclasses should override.""" return None io.TextIOBase.register(TextIOBase) class IncrementalNewlineDecoder(codecs.IncrementalDecoder): r"""Codec used when reading a file in universal newlines mode. It wraps another incremental decoder, translating \r\n and \r into \n. It also records the types of newlines encountered. When used with translate=False, it ensures that the newline sequence is returned in one piece. """ def __init__(self, decoder, translate, errors='strict'): codecs.IncrementalDecoder.__init__(self, errors=errors) self.translate = translate self.decoder = decoder self.seennl = 0 self.pendingcr = False def decode(self, input, final=False): # decode input (with the eventual \r from a previous pass) if self.decoder is None: output = input else: output = self.decoder.decode(input, final=final) if self.pendingcr and (output or final): output = "\r" + output self.pendingcr = False # retain last \r even when not translating data: # then readline() is sure to get \r\n in one pass if output.endswith("\r") and not final: output = output[:-1] self.pendingcr = True # Record which newlines are read crlf = output.count('\r\n') cr = output.count('\r') - crlf lf = output.count('\n') - crlf self.seennl |= (lf and self._LF) | (cr and self._CR) \ | (crlf and self._CRLF) if self.translate: if crlf: output = output.replace("\r\n", "\n") if cr: output = output.replace("\r", "\n") return output def getstate(self): if self.decoder is None: buf = b"" flag = 0 else: buf, flag = self.decoder.getstate() flag <<= 1 if self.pendingcr: flag |= 1 return buf, flag def setstate(self, state): buf, flag = state self.pendingcr = bool(flag & 1) if self.decoder is not None: self.decoder.setstate((buf, flag >> 1)) def reset(self): self.seennl = 0 self.pendingcr = False if self.decoder is not None: self.decoder.reset() _LF = 1 _CR = 2 _CRLF = 4 @property def newlines(self): return (None, "\n", "\r", ("\r", "\n"), "\r\n", ("\n", "\r\n"), ("\r", "\r\n"), ("\r", "\n", "\r\n") )[self.seennl] class TextIOWrapper(TextIOBase): r"""Character and line based layer over a BufferedIOBase object, buffer. encoding gives the name of the encoding that the stream will be decoded or encoded with. It defaults to locale.getpreferredencoding(False). errors determines the strictness of encoding and decoding (see the codecs.register) and defaults to "strict". newline can be None, '', '\n', '\r', or '\r\n'. It controls the handling of line endings. If it is None, universal newlines is enabled. With this enabled, on input, the lines endings '\n', '\r', or '\r\n' are translated to '\n' before being returned to the caller. Conversely, on output, '\n' is translated to the system default line separator, os.linesep. If newline is any other of its legal values, that newline becomes the newline when the file is read and it is returned untranslated. On output, '\n' is converted to the newline. If line_buffering is True, a call to flush is implied when a call to write contains a newline character. """ _CHUNK_SIZE = 2048 # The write_through argument has no effect here since this # implementation always writes through. The argument is present only # so that the signature can match the signature of the C version. def __init__(self, buffer, encoding=None, errors=None, newline=None, line_buffering=False, write_through=False): if newline is not None and not isinstance(newline, str): raise TypeError("illegal newline type: %r" % (type(newline),)) if newline not in (None, "", "\n", "\r", "\r\n"): raise ValueError("illegal newline value: %r" % (newline,)) if encoding is None: try: encoding = os.device_encoding(buffer.fileno()) except (AttributeError, UnsupportedOperation): 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(False) if not isinstance(encoding, str): raise ValueError("invalid encoding: %r" % encoding) if not codecs.lookup(encoding)._is_text_encoding: msg = ("%r is not a text encoding; " "use codecs.open() to handle arbitrary codecs") raise LookupError(msg % encoding) if errors is None: errors = "strict" else: if not isinstance(errors, str): raise ValueError("invalid errors: %r" % errors) self._buffer = buffer self._line_buffering = line_buffering self._encoding = encoding self._errors = errors self._readuniversal = not newline self._readtranslate = newline is None self._readnl = newline self._writetranslate = newline != '' self._writenl = newline or os.linesep self._encoder = None self._decoder = None self._decoded_chars = '' # buffer for text returned from decoder self._decoded_chars_used = 0 # offset into _decoded_chars for read() self._snapshot = None # info for reconstructing decoder state self._seekable = self._telling = self.buffer.seekable() self._has_read1 = hasattr(self.buffer, 'read1') self._b2cratio = 0.0 if self._seekable and self.writable(): position = self.buffer.tell() if position != 0: try: self._get_encoder().setstate(0) except LookupError: # Sometimes the encoder doesn't exist pass # self._snapshot is either None, or a tuple (dec_flags, next_input) # where dec_flags is the second (integer) item of the decoder state # and next_input is the chunk of input bytes that comes next after the # snapshot point. We use this to reconstruct decoder states in tell(). # Naming convention: # - "bytes_..." for integer variables that count input bytes # - "chars_..." for integer variables that count decoded characters def __repr__(self): result = "<_pyio.TextIOWrapper" try: name = self.name except AttributeError: pass else: result += " name={0!r}".format(name) try: mode = self.mode except AttributeError: pass else: result += " mode={0!r}".format(mode) return result + " encoding={0!r}>".format(self.encoding) @property def encoding(self): return self._encoding @property def errors(self): return self._errors @property def line_buffering(self): return self._line_buffering @property def buffer(self): return self._buffer def seekable(self): if self.closed: raise ValueError("I/O operation on closed file.") return self._seekable def readable(self): return self.buffer.readable() def writable(self): return self.buffer.writable() def flush(self): self.buffer.flush() self._telling = self._seekable def close(self): if self.buffer is not None and not self.closed: try: self.flush() finally: self.buffer.close() @property def closed(self): return self.buffer.closed @property def name(self): return self.buffer.name def fileno(self): return self.buffer.fileno() def isatty(self): return self.buffer.isatty() def write(self, s): 'Write data, where s is a str' if self.closed: raise ValueError("write to closed file") if not isinstance(s, str): raise TypeError("can't write %s to text stream" % s.__class__.__name__) length = len(s) haslf = (self._writetranslate or self._line_buffering) and "\n" in s if haslf and self._writetranslate and self._writenl != "\n": s = s.replace("\n", self._writenl) encoder = self._encoder or self._get_encoder() # XXX What if we were just reading? b = encoder.encode(s) self.buffer.write(b) if self._line_buffering and (haslf or "\r" in s): self.flush() self._snapshot = None if self._decoder: self._decoder.reset() return length def _get_encoder(self): make_encoder = codecs.getincrementalencoder(self._encoding) self._encoder = make_encoder(self._errors) return self._encoder def _get_decoder(self): make_decoder = codecs.getincrementaldecoder(self._encoding) decoder = make_decoder(self._errors) if self._readuniversal: decoder = IncrementalNewlineDecoder(decoder, self._readtranslate) self._decoder = decoder return decoder # The following three methods implement an ADT for _decoded_chars. # Text returned from the decoder is buffered here until the client # requests it by calling our read() or readline() method. def _set_decoded_chars(self, chars): """Set the _decoded_chars buffer.""" self._decoded_chars = chars self._decoded_chars_used = 0 def _get_decoded_chars(self, n=None): """Advance into the _decoded_chars buffer.""" offset = self._decoded_chars_used if n is None: chars = self._decoded_chars[offset:] else: chars = self._decoded_chars[offset:offset + n] self._decoded_chars_used += len(chars) return chars def _rewind_decoded_chars(self, n): """Rewind the _decoded_chars buffer.""" if self._decoded_chars_used < n: raise AssertionError("rewind decoded_chars out of bounds") self._decoded_chars_used -= n def _read_chunk(self): """ Read and decode the next chunk of data from the BufferedReader. """ # The return value is True unless EOF was reached. The decoded # string is placed in self._decoded_chars (replacing its previous # value). The entire input chunk is sent to the decoder, though # some of it may remain buffered in the decoder, yet to be # converted. if self._decoder is None: raise ValueError("no decoder") if self._telling: # To prepare for tell(), we need to snapshot a point in the # file where the decoder's input buffer is empty. dec_buffer, dec_flags = self._decoder.getstate() # Given this, we know there was a valid snapshot point # len(dec_buffer) bytes ago with decoder state (b'', dec_flags). # Read a chunk, decode it, and put the result in self._decoded_chars. if self._has_read1: input_chunk = self.buffer.read1(self._CHUNK_SIZE) else: input_chunk = self.buffer.read(self._CHUNK_SIZE) eof = not input_chunk decoded_chars = self._decoder.decode(input_chunk, eof) self._set_decoded_chars(decoded_chars) if decoded_chars: self._b2cratio = len(input_chunk) / len(self._decoded_chars) else: self._b2cratio = 0.0 if self._telling: # At the snapshot point, len(dec_buffer) bytes before the read, # the next input to be decoded is dec_buffer + input_chunk. self._snapshot = (dec_flags, dec_buffer + input_chunk) return not eof def _pack_cookie(self, position, dec_flags=0, bytes_to_feed=0, need_eof=0, chars_to_skip=0): # The meaning of a tell() cookie is: seek to position, set the # decoder flags to dec_flags, read bytes_to_feed bytes, feed them # into the decoder with need_eof as the EOF flag, then skip # chars_to_skip characters of the decoded result. For most simple # decoders, tell() will often just give a byte offset in the file. return (position | (dec_flags<<64) | (bytes_to_feed<<128) | (chars_to_skip<<192) | bool(need_eof)<<256) def _unpack_cookie(self, bigint): rest, position = divmod(bigint, 1<<64) rest, dec_flags = divmod(rest, 1<<64) rest, bytes_to_feed = divmod(rest, 1<<64) need_eof, chars_to_skip = divmod(rest, 1<<64) return position, dec_flags, bytes_to_feed, need_eof, chars_to_skip def tell(self): if not self._seekable: raise UnsupportedOperation("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: if self._decoded_chars: # This should never happen. raise AssertionError("pending decoded text") return position # Skip backward to the snapshot point (see _read_chunk). dec_flags, next_input = self._snapshot position -= len(next_input) # How many decoded characters have been used up since the snapshot? chars_to_skip = self._decoded_chars_used if chars_to_skip == 0: # We haven't moved from the snapshot point. return self._pack_cookie(position, dec_flags) # Starting from the snapshot position, we will walk the decoder # forward until it gives us enough decoded characters. saved_state = decoder.getstate() try: # Fast search for an acceptable start point, close to our # current pos. # Rationale: calling decoder.decode() has a large overhead # regardless of chunk size; we want the number of such calls to # be O(1) in most situations (common decoders, non-crazy input). # Actually, it will be exactly 1 for fixed-size codecs (all # 8-bit codecs, also UTF-16 and UTF-32). skip_bytes = int(self._b2cratio * chars_to_skip) skip_back = 1 assert skip_bytes <= len(next_input) while skip_bytes > 0: decoder.setstate((b'', dec_flags)) # Decode up to temptative start point n = len(decoder.decode(next_input[:skip_bytes])) if n <= chars_to_skip: b, d = decoder.getstate() if not b: # Before pos and no bytes buffered in decoder => OK dec_flags = d chars_to_skip -= n break # Skip back by buffered amount and reset heuristic skip_bytes -= len(b) skip_back = 1 else: # We're too far ahead, skip back a bit skip_bytes -= skip_back skip_back = skip_back * 2 else: skip_bytes = 0 decoder.setstate((b'', dec_flags)) # Note our initial start point. start_pos = position + skip_bytes start_flags = dec_flags if chars_to_skip == 0: # We haven't moved from the start point. return self._pack_cookie(start_pos, start_flags) # Feed the decoder one byte at a time. As we go, note the # nearest "safe start point" before the current location # (a point where the decoder has nothing buffered, so seek() # can safely start from there and advance to this location). bytes_fed = 0 need_eof = 0 # Chars decoded since `start_pos` chars_decoded = 0 for i in range(skip_bytes, len(next_input)): bytes_fed += 1 chars_decoded += len(decoder.decode(next_input[i:i+1])) dec_buffer, dec_flags = decoder.getstate() if not dec_buffer and chars_decoded <= chars_to_skip: # Decoder buffer is empty, so this is a safe start point. start_pos += bytes_fed chars_to_skip -= chars_decoded start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0 if chars_decoded >= chars_to_skip: break else: # We didn't get enough decoded data; signal EOF to get more. chars_decoded += len(decoder.decode(b'', final=True)) need_eof = 1 if chars_decoded < chars_to_skip: raise IOError("can't reconstruct logical file position") # The returned cookie corresponds to the last safe start point. return self._pack_cookie( start_pos, start_flags, bytes_fed, need_eof, chars_to_skip) finally: decoder.setstate(saved_state) def truncate(self, pos=None): self.flush() if pos is None: pos = self.tell() return self.buffer.truncate(pos) def detach(self): if self.buffer is None: raise ValueError("buffer is already detached") self.flush() buffer = self._buffer self._buffer = None return buffer def seek(self, cookie, whence=0): if self.closed: raise ValueError("tell on closed file") if not self._seekable: raise UnsupportedOperation("underlying stream is not seekable") if whence == 1: # seek relative to current position if cookie != 0: raise UnsupportedOperation("can't do nonzero cur-relative seeks") # Seeking to the current position should attempt to # sync the underlying buffer with the current position. whence = 0 cookie = self.tell() if whence == 2: # seek relative to end of file if cookie != 0: raise UnsupportedOperation("can't do nonzero end-relative seeks") self.flush() position = self.buffer.seek(0, 2) self._set_decoded_chars('') self._snapshot = None if self._decoder: self._decoder.reset() return position if whence != 0: raise ValueError("unsupported whence (%r)" % (whence,)) if cookie < 0: raise ValueError("negative seek position %r" % (cookie,)) self.flush() # The strategy of seek() is to go back to the safe start point # and replay the effect of read(chars_to_skip) from there. start_pos, dec_flags, bytes_to_feed, need_eof, chars_to_skip = \ self._unpack_cookie(cookie) # Seek back to the safe start point. self.buffer.seek(start_pos) self._set_decoded_chars('') self._snapshot = None # Restore the decoder to its state from the safe start point. if cookie == 0 and self._decoder: self._decoder.reset() elif self._decoder or dec_flags or chars_to_skip: self._decoder = self._decoder or self._get_decoder() self._decoder.setstate((b'', dec_flags)) self._snapshot = (dec_flags, b'') if chars_to_skip: # Just like _read_chunk, feed the decoder and save a snapshot. input_chunk = self.buffer.read(bytes_to_feed) self._set_decoded_chars( self._decoder.decode(input_chunk, need_eof)) self._snapshot = (dec_flags, input_chunk) # Skip chars_to_skip of the decoded characters. if len(self._decoded_chars) < chars_to_skip: raise IOError("can't restore logical file position") self._decoded_chars_used = chars_to_skip # Finally, reset the encoder (merely useful for proper BOM handling) try: encoder = self._encoder or self._get_encoder() except LookupError: # Sometimes the encoder doesn't exist pass else: if cookie != 0: encoder.setstate(0) else: encoder.reset() return cookie def read(self, n=None): self._checkReadable() if n is None: n = -1 decoder = self._decoder or self._get_decoder() try: n.__index__ except AttributeError as err: raise TypeError("an integer is required") from err if n < 0: # Read everything. result = (self._get_decoded_chars() + decoder.decode(self.buffer.read(), final=True)) self._set_decoded_chars('') self._snapshot = None return result else: # Keep reading chunks until we have n characters to return. eof = False result = self._get_decoded_chars(n) while len(result) < n and not eof: eof = not self._read_chunk() result += self._get_decoded_chars(n - len(result)) return result 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 self.closed: raise ValueError("read from closed file") if limit is None: limit = -1 elif not isinstance(limit, int): raise TypeError("limit must be an integer") # Grab all the decoded text (we will rewind any extra bits later). line = self._get_decoded_chars() start = 0 # Make the decoder if it doesn't already exist. if not self._decoder: self._get_decoder() pos = endpos = None while True: if self._readtranslate: # Newlines are already translated, only search for \n pos = line.find('\n', start) if pos >= 0: endpos = pos + 1 break else: start = len(line) elif self._readuniversal: # Universal newline search. Find any of \r, \r\n, \n # The decoder ensures that \r\n are not split in two pieces # In C we'd look for these in parallel of course. nlpos = line.find("\n", start) crpos = line.find("\r", start) if crpos == -1: if nlpos == -1: # Nothing found start = len(line) else: # Found \n endpos = nlpos + 1 break elif nlpos == -1: # Found lone \r endpos = crpos + 1 break elif nlpos < crpos: # Found \n endpos = nlpos + 1 break elif nlpos == crpos + 1: # Found \r\n endpos = crpos + 2 break else: # Found \r endpos = crpos + 1 break else: # non-universal pos = line.find(self._readnl) if pos >= 0: endpos = pos + len(self._readnl) break if limit >= 0 and len(line) >= limit: endpos = limit # reached length limit break # No line ending seen yet - get more data' while self._read_chunk(): if self._decoded_chars: break if self._decoded_chars: line += self._get_decoded_chars() else: # end of file self._set_decoded_chars('') self._snapshot = None return line if limit >= 0 and endpos > limit: endpos = limit # don't exceed limit # Rewind _decoded_chars to just after the line ending we found. self._rewind_decoded_chars(len(line) - endpos) return line[:endpos] @property def newlines(self): return self._decoder.newlines if self._decoder else None class StringIO(TextIOWrapper): """Text I/O implementation using an in-memory buffer. The initial_value argument sets the value of object. The newline argument is like the one of TextIOWrapper's constructor. """ def __init__(self, initial_value="", newline="\n"): super(StringIO, self).__init__(BytesIO(), encoding="utf-8", errors="surrogatepass", newline=newline) # Issue #5645: make universal newlines semantics the same as in the # C version, even under Windows. if newline is None: self._writetranslate = False if initial_value is not None: if not isinstance(initial_value, str): raise TypeError("initial_value must be str or None, not {0}" .format(type(initial_value).__name__)) initial_value = str(initial_value) self.write(initial_value) self.seek(0) def getvalue(self): self.flush() decoder = self._decoder or self._get_decoder() old_state = decoder.getstate() decoder.reset() try: return decoder.decode(self.buffer.getvalue(), final=True) finally: decoder.setstate(old_state) def __repr__(self): # TextIOWrapper tells the encoding in its repr. In StringIO, # that's a implementation detail. return object.__repr__(self) @property def errors(self): return None @property def encoding(self): return None def detach(self): # This doesn't make sense on StringIO. self._unsupported("detach")
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