Closes #10142: Support for SEEK_HOLE/SEEK_DATA
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index b684a9f..c06f4b8 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -16,6 +16,11 @@
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
@@ -306,6 +311,7 @@
* 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.
"""
@@ -866,7 +872,7 @@
elif whence == 2:
self._pos = max(0, len(self._buffer) + pos)
else:
- raise ValueError("invalid whence value")
+ raise ValueError("unsupported whence value")
return self._pos
def tell(self):
@@ -1041,7 +1047,7 @@
return _BufferedIOMixin.tell(self) - len(self._read_buf) + self._read_pos
def seek(self, pos, whence=0):
- if not (0 <= whence <= 2):
+ if whence not in valid_seek_flags:
raise ValueError("invalid whence value")
with self._read_lock:
if whence == 1:
@@ -1138,8 +1144,8 @@
return _BufferedIOMixin.tell(self) + len(self._write_buf)
def seek(self, pos, whence=0):
- if not (0 <= whence <= 2):
- raise ValueError("invalid whence")
+ 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)
@@ -1235,8 +1241,8 @@
BufferedWriter.__init__(self, raw, buffer_size, max_buffer_size)
def seek(self, pos, whence=0):
- if not (0 <= whence <= 2):
- raise ValueError("invalid whence")
+ if whence not in valid_seek_flags:
+ raise ValueError("invalid whence value")
self.flush()
if self._read_buf:
# Undo read ahead.
@@ -1852,8 +1858,7 @@
self._decoder.reset()
return position
if whence != 0:
- raise ValueError("invalid whence (%r, should be 0, 1 or 2)" %
- (whence,))
+ raise ValueError("unsupported whence (%r)" % (whence,))
if cookie < 0:
raise ValueError("negative seek position %r" % (cookie,))
self.flush()
diff --git a/Lib/os.py b/Lib/os.py
index 11e4d60..261a39e 100644
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -121,6 +121,7 @@
# Python uses fixed values for the SEEK_ constants; they are mapped
# to native constants if necessary in posixmodule.c
+# Other possible SEEK values are directly imported from posixmodule.c
SEEK_SET = 0
SEEK_CUR = 1
SEEK_END = 2
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 1951a06..54ba179 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -706,7 +706,7 @@
bufio = self.tp(rawio)
# Invalid whence
self.assertRaises(ValueError, bufio.seek, 0, -1)
- self.assertRaises(ValueError, bufio.seek, 0, 3)
+ self.assertRaises(ValueError, bufio.seek, 0, 9)
def test_override_destructor(self):
tp = self.tp
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 21473fc..ae46866 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1015,6 +1015,26 @@
posix.RTLD_GLOBAL
posix.RTLD_LOCAL
+ @unittest.skipUnless(hasattr(os, 'SEEK_HOLE'),
+ "test needs an OS that reports file holes")
+ def test_fs_holes(self) :
+ # Even if the filesystem doesn't report holes,
+ # if the OS supports it the SEEK_* constants
+ # will be defined and will have a consistent
+ # behaviour:
+ # os.SEEK_DATA = current position
+ # os.SEEK_HOLE = end of file position
+ with open(support.TESTFN, 'r+b') as fp :
+ fp.write(b"hello")
+ fp.flush()
+ size = fp.tell()
+ fno = fp.fileno()
+ for i in range(size) :
+ self.assertEqual(i, os.lseek(fno, i, os.SEEK_DATA))
+ self.assertLessEqual(size, os.lseek(fno, i, os.SEEK_HOLE))
+ self.assertRaises(OSError, os.lseek, fno, size, os.SEEK_DATA)
+ self.assertRaises(OSError, os.lseek, fno, size, os.SEEK_HOLE)
+
class PosixGroupsTester(unittest.TestCase):
def setUp(self):