Implement long positioning (Unix only, probably).
Etc., etc.
diff --git a/Lib/io.py b/Lib/io.py
index 9f2a647..69c6c20 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -1,9 +1,15 @@
-"""New I/O library.
+"""New I/O library conforming to PEP 3116.
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.
+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 need to default buffer size to 1 if isatty()
XXX need to support 1 meaning line-buffered
@@ -142,6 +148,9 @@
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 ###
@@ -153,19 +162,20 @@
### Positioning ###
- def seek(self, pos: int, whence: int = 0) -> None:
- """seek(pos: int, whence: int = 0) -> None. Change stream position.
+ 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."""
- self._unsupported("tell")
+ return self.seek(0, 1)
def truncate(self, pos: int = None) -> None:
"""truncate(size: int = None) -> None. Truncate file to size bytes.
@@ -432,7 +442,7 @@
### Positioning ###
def seek(self, pos, whence=0):
- self.raw.seek(pos, whence)
+ return self.raw.seek(pos, whence)
def tell(self):
return self.raw.tell()
@@ -515,6 +525,7 @@
self._pos = max(0, len(self._buffer) + pos)
else:
raise IOError("invalid whence value")
+ return self._pos
def tell(self):
return self._pos
@@ -620,8 +631,9 @@
def seek(self, pos, whence=0):
if whence == 1:
pos -= len(self._read_buf)
- self.raw.seek(pos, whence)
+ pos = self.raw.seek(pos, whence)
self._read_buf = b""
+ return pos
class BufferedWriter(_BufferedIOMixin):
@@ -679,7 +691,7 @@
def seek(self, pos, whence=0):
self.flush()
- self.raw.seek(pos, whence)
+ return self.raw.seek(pos, whence)
class BufferedRWPair(BufferedIOBase):
@@ -750,13 +762,9 @@
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)
+ pos = 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.
+ return pos
def tell(self):
if (self._write_buf):