Added fast alternate io.BytesIO implementation and its test suite.

Removed old test suite for StringIO.
Modified truncate() to imply a seek to given argument value.

1 files changed, 66 insertions, 9 deletions

diff --git a/Lib/io.py b/Lib/io.py
index 3172554cf1..3a1546a4e1 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -490,6 +490,7 @@ class IOBase(metaclass=abc.ABCMeta):
         terminator(s) recognized.
         """
         # For backwards compatibility, a (slowish) readline().
+        self._checkClosed()
         if hasattr(self, "peek"):
             def nreadahead():
                 readahead = self.peek(1)
@@ -531,7 +532,7 @@ class IOBase(metaclass=abc.ABCMeta):
         lines will be read if the total size (in bytes/characters) of all
         lines so far exceeds hint.
         """
-        if hint is None:
+        if hint is None or hint <= 0:
             return list(self)
         n = 0
         lines = []
@@ -726,6 +727,8 @@ class _BufferedIOMixin(BufferedIOBase):
 
         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 ###
@@ -765,7 +768,7 @@ class _BufferedIOMixin(BufferedIOBase):
         return self.raw.isatty()
 
 
-class BytesIO(BufferedIOBase):
+class _BytesIO(BufferedIOBase):
 
     """Buffered I/O implementation using an in-memory bytes buffer."""
 
@@ -779,13 +782,19 @@ class BytesIO(BufferedIOBase):
     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 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 self._buffer[:0]
         newpos = min(len(self._buffer), self._pos + n)
         b = self._buffer[self._pos : newpos]
         self._pos = newpos
@@ -802,6 +811,8 @@ class BytesIO(BufferedIOBase):
         if isinstance(b, str):
             raise TypeError("can't write str to binary stream")
         n = len(b)
+        if n == 0:
+            return 0
         newpos = self._pos + n
         if newpos > len(self._buffer):
             # Inserts null bytes between the current end of the file
@@ -813,28 +824,38 @@ class BytesIO(BufferedIOBase):
         return n
 
     def seek(self, pos, whence=0):
+        if self.closed:
+            raise ValueError("seek on closed file")
         try:
             pos = pos.__index__()
         except AttributeError as err:
             raise TypeError("an integer is required") from err
         if whence == 0:
             self._pos = max(0, pos)
+            if pos < 0:
+                raise ValueError("negative seek position %r" % (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")
+            raise ValueError("invalid 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
+        elif pos < 0:
+            raise ValueError("negative truncate position %r" % (pos,))
         del self._buffer[pos:]
-        return pos
+        return self.seek(pos)
 
     def readable(self):
         return True
@@ -845,6 +866,16 @@ class BytesIO(BufferedIOBase):
     def seekable(self):
         return True
 
+# Use the faster implementation of BytesIO if available
+try:
+    import _bytesio
+
+    class BytesIO(_bytesio._BytesIO, BufferedIOBase):
+        __doc__ = _bytesio._BytesIO.__doc__
+
+except ImportError:
+    BytesIO = _BytesIO
+
 
 class BufferedReader(_BufferedIOMixin):
 
@@ -978,6 +1009,12 @@ class BufferedWriter(_BufferedIOMixin):
                     raise BlockingIOError(e.errno, e.strerror, overage)
         return written
 
+    def truncate(self, pos=None):
+        self.flush()
+        if pos is None:
+            pos = self.raw.tell()
+        return self.raw.truncate(pos)
+
     def flush(self):
         if self.closed:
             raise ValueError("flush of closed file")
@@ -1097,6 +1134,13 @@ class BufferedRandom(BufferedWriter, BufferedReader):
         else:
             return self.raw.tell() - len(self._read_buf)
 
+    def truncate(self, pos=None):
+        if pos is None:
+            pos = self.tell()
+        # Use seek to flush the read buffer.
+        self.seek(pos)
+        return BufferedWriter.truncate(self)
+
     def read(self, n=None):
         if n is None:
             n = -1
@@ -1145,11 +1189,7 @@ class TextIOBase(IOBase):
 
     def truncate(self, pos: int = None) -> int:
         """Truncate size to pos."""
-        self.flush()
-        if pos is None:
-            pos = self.tell()
-        self.seek(pos)
-        return self.buffer.truncate()
+        self._unsupported("truncate")
 
     def readline(self) -> str:
         """Read until newline or EOF.
@@ -1346,6 +1386,12 @@ class TextIOWrapper(TextIOBase):
     def seekable(self):
         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
@@ -1539,7 +1585,16 @@ class TextIOWrapper(TextIOBase):
         finally:
             decoder.setstate(saved_state)
 
+    def truncate(self, pos=None):
+        self.flush()
+        if pos is None:
+            pos = self.tell()
+        self.seek(pos)
+        return self.buffer.truncate()
+
     def seek(self, cookie, whence=0):
+        if self.closed:
+            raise ValueError("tell on closed file")
         if not self._seekable:
             raise IOError("underlying stream is not seekable")
         if whence == 1: # seek relative to current position
@@ -1626,6 +1681,8 @@ class TextIOWrapper(TextIOBase):
         return line
 
     def readline(self, limit=None):
+        if self.closed:
+            raise ValueError("read from closed file")
         if limit is None:
             limit = -1