GzipFile.peek improvements, suggested by Nir Aides.
diff --git a/Doc/library/gzip.rst b/Doc/library/gzip.rst
index 0ae23d2..82f10b9 100644
--- a/Doc/library/gzip.rst
+++ b/Doc/library/gzip.rst
@@ -70,6 +70,17 @@
including iteration and the :keyword:`with` statement. Only the
:meth:`truncate` method isn't implemented.
+ :class:`GzipFile` also provides the following method:
+
+ .. method:: peek([n])
+
+ Read *n* uncompressed bytes without advancing the file position.
+ At most one single read on the compressed stream is done to satisfy
+ the call. The number of bytes returned may be more or less than
+ requested.
+
+ .. versionadded:: 3.2
+
.. versionchanged:: 3.1
Support for the :keyword:`with` statement was added.
@@ -79,9 +90,6 @@
.. versionchanged:: 3.2
Support for unseekable files was added.
- .. versionchanged:: 3.2
- The :meth:`peek` method was implemented.
-
.. function:: open(filename, mode='rb', compresslevel=9)
diff --git a/Lib/gzip.py b/Lib/gzip.py
index 58e866b..7c3fd51 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -342,16 +342,18 @@
def peek(self, n):
if self.mode != READ:
import errno
- raise IOError(errno.EBADF, "read() on write-only GzipFile object")
+ raise IOError(errno.EBADF, "peek() on write-only GzipFile object")
- # Do not return ridiculously small buffers
+ # Do not return ridiculously small buffers, for one common idiom
+ # is to call peek(1) and expect more bytes in return.
if n < 100:
n = 100
if self.extrasize == 0:
if self.fileobj is None:
return b''
try:
- self._read(max(self.max_read_chunk, n))
+ # 1024 is the same buffering heuristic used in read()
+ self._read(max(n, 1024))
except EOFError:
pass
offset = self.offset - self.extrastart