Re: [Xen-devel] [PATCH] tools/python: Python 3 compatibility

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Wed, Dec 18, 2019 at 03:05:22PM +0000, Andrew Cooper wrote:
> convert-legacy-stream is only used for incomming migration from pre Xen 4.7,
> and verify-stream-v2 appears to only be used by me during migration
> development - it is little surprise that they missed the main converstion
> effort in Xen 4.13.
> 
> Fix it all up.
> 
> Move open_file_or_fd() into a new util.py to avoid duplication, making it a
> more generic wrapper around open() or fdopen().
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Ian Jackson <Ian.Jackson@citrix.com>
> CC: Wei Liu <wl@xen.org>
> 
> This needs backporting to 4.13 ASAP
> ---
>  tools/python/scripts/convert-legacy-stream | 49 +++++++-----------------------
>  tools/python/scripts/verify-stream-v2      | 43 +++++---------------------
>  tools/python/xen/migration/libxc.py        |  2 +-
>  tools/python/xen/migration/libxl.py        |  2 +-
>  tools/python/xen/migration/verify.py       |  4 +--
>  tools/python/xen/util.py                   | 23 ++++++++++++++
>  6 files changed, 46 insertions(+), 77 deletions(-)
>  create mode 100644 tools/python/xen/util.py
> 
> diff --git a/tools/python/scripts/convert-legacy-stream b/tools/python/scripts/convert-legacy-stream
> index 5f80f13654..b0d81aa92e 100755
> --- a/tools/python/scripts/convert-legacy-stream
> +++ b/tools/python/scripts/convert-legacy-stream
> @@ -5,6 +5,8 @@
>  Convert a legacy migration stream to a v2 stream.
>  """
>  
> +from __future__ import print_function
> +
>  import sys
>  import os, os.path
>  import syslog
> @@ -12,6 +14,7 @@ import traceback
>  
>  from struct import calcsize, unpack, pack
>  
> +from xen.util import open_file_or_fd as open_file_or_fd
>  from xen.migration import legacy, public, libxc, libxl, xl
>  
>  __version__ = 1
> @@ -39,16 +42,16 @@ def info(msg):
>              for line in msg.split("\n"):
>                  syslog.syslog(syslog.LOG_INFO, line)
>          else:
> -            print msg
> +            print(msg)
>  
>  def err(msg):
>      """Error message, routed to appropriate destination"""
>      if log_to_syslog:
>          for line in msg.split("\n"):
>              syslog.syslog(syslog.LOG_ERR, line)
> -    print >> sys.stderr, msg
> +    print(msg, file = sys.stderr)
>  
> -class StreamError(StandardError):
> +class StreamError(Exception):
>      """Error with the incoming migration stream"""
>      pass
>  
> @@ -70,7 +73,7 @@ class VM(object):
>  
>          # libxl
>          self.libxl = fmt == "libxl"
> -        self.emu_xenstore = "" # NUL terminated key&val pairs from "toolstack" records
> +        self.emu_xenstore = b"" # NUL terminated key&val pairs from "toolstack" records
>  
>  def write_libxc_ihdr():
>      stream_write(pack(libxc.IHDR_FORMAT,

You also need to update write_record (string constants).
And few calls to it with string constants (write_libxl_end,
write_libxl_libxc_context, read_pv_tail, read_hvm_tail).
And blkid == ... in read_pv_extended_info().

> @@ -336,7 +339,7 @@ def read_libxl_toolstack(vm, data):
>          if twidth == 64:
>              name = name[:-4]
>  
> -        if name[-1] != '\x00':
> +        if name[-1] != b'\x00':
>              raise StreamError("physmap name not NUL terminated")
>  
>          root = "physmap/%x" % (phys,)
> @@ -347,7 +350,7 @@ def read_libxl_toolstack(vm, data):
>          for key, val in zip(kv[0::2], kv[1::2]):
>              info("    '%s' = '%s'" % (key, val))
>  
> -        vm.emu_xenstore += '\x00'.join(kv) + '\x00'
> +        vm.emu_xenstore += b'\x00'.join(kv) + b'\x00'
>  
>  
>  def read_chunks(vm):
> @@ -534,7 +537,7 @@ def read_qemu(vm):
>      sig, = unpack("21s", rawsig)
>      info("Qemu signature: %s" % (sig, ))
>  
> -    if sig == "DeviceModelRecord0002":
> +    if sig == b"DeviceModelRecord0002":
>          rawsz = rdexact(4)
>          sz, = unpack("I", rawsz)
>          qdata = rdexact(sz)
> @@ -617,36 +620,6 @@ def read_legacy_stream(vm):
>          return 2
>      return 0
>  
> -def open_file_or_fd(val, mode):
> -    """
> -    If 'val' looks like a decimal integer, open it as an fd.  If not, try to
> -    open it as a regular file.
> -    """
> -
> -    fd = -1
> -    try:
> -        # Does it look like an integer?
> -        try:
> -            fd = int(val, 10)
> -        except ValueError:
> -            pass
> -
> -        # Try to open it...
> -        if fd != -1:
> -            return os.fdopen(fd, mode, 0)
> -        else:
> -            return open(val, mode, 0)
> -
> -    except StandardError, e:
> -        if fd != -1:
> -            err("Unable to open fd %d: %s: %s" %
> -                (fd, e.__class__.__name__, e))
> -        else:
> -            err("Unable to open file '%s': %s: %s" %
> -                (val, e.__class__.__name__, e))
> -
> -    raise SystemExit(1)
> -
>  
>  def main():
>      from optparse import OptionParser
> @@ -723,7 +696,7 @@ def main():
>  if __name__ == "__main__":
>      try:
>          sys.exit(main())
> -    except SystemExit, e:
> +    except SystemExit as e:
>          sys.exit(e.code)
>      except KeyboardInterrupt:
>          sys.exit(1)
> diff --git a/tools/python/scripts/verify-stream-v2 b/tools/python/scripts/verify-stream-v2
> index 3daf25791e..8355c2d206 100755
> --- a/tools/python/scripts/verify-stream-v2
> +++ b/tools/python/scripts/verify-stream-v2
> @@ -3,12 +3,15 @@
>  
>  """ Verify a v2 format migration stream """
>  
> +from __future__ import print_function
> +
>  import sys
>  import struct
>  import os, os.path
>  import syslog
>  import traceback
>  
> +from xen.util import open_file_or_fd as open_file_or_fd
>  from xen.migration.verify import StreamError, RecordError
>  from xen.migration.libxc import VerifyLibxc
>  from xen.migration.libxl import VerifyLibxl
> @@ -25,7 +28,7 @@ def info(msg):
>              for line in msg.split("\n"):
>                  syslog.syslog(syslog.LOG_INFO, line)
>          else:
> -            print msg
> +            print(msg)
>  
>  def err(msg):
>      """Error message, routed to appropriate destination"""
> @@ -33,7 +36,7 @@ def err(msg):
>          if log_to_syslog:
>              for line in msg.split("\n"):
>                  syslog.syslog(syslog.LOG_ERR, line)
> -        print >> sys.stderr, msg
> +        print(msg, file = sys.stderr)
>  
>  def stream_read(_ = None):
>      """Read from input"""
> @@ -56,7 +59,7 @@ def skip_xl_header():
>      """Skip over an xl header in the stream"""
>  
>      hdr = rdexact(32)
> -    if hdr != "Xen saved domain, xl format\n \0 \r":
> +    if hdr != b"Xen saved domain, xl format\n \0 \r":
>          raise StreamError("No xl header")
>  
>      _, mflags, _, optlen = unpack_exact("=IIII")
> @@ -86,7 +89,7 @@ def read_stream(fmt):
>          err(traceback.format_exc())
>          return 1
>  
> -    except StandardError:
> +    except Exception:
>          err("Script Error:")
>          err(traceback.format_exc())
>          err("Please fix me")
> @@ -94,36 +97,6 @@ def read_stream(fmt):
>  
>      return 0
>  
> -def open_file_or_fd(val, mode, buffering):
> -    """
> -    If 'val' looks like a decimal integer, open it as an fd.  If not, try to
> -    open it as a regular file.
> -    """
> -
> -    fd = -1
> -    try:
> -        # Does it look like an integer?
> -        try:
> -            fd = int(val, 10)
> -        except ValueError:
> -            pass
> -
> -        # Try to open it...
> -        if fd != -1:
> -            return os.fdopen(fd, mode, buffering)
> -        else:
> -            return open(val, mode, buffering)
> -
> -    except StandardError, e:
> -        if fd != -1:
> -            err("Unable to open fd %d: %s: %s" %
> -                (fd, e.__class__.__name__, e))
> -        else:
> -            err("Unable to open file '%s': %s: %s" %
> -                (val, e.__class__.__name__, e))
> -
> -    raise SystemExit(2)
> -
>  def main():
>      """ main """
>      from optparse import OptionParser
> @@ -168,7 +141,7 @@ def main():
>  if __name__ == "__main__":
>      try:
>          sys.exit(main())
> -    except SystemExit, e:
> +    except SystemExit as e:
>          sys.exit(e.code)
>      except KeyboardInterrupt:
>          sys.exit(2)
> diff --git a/tools/python/xen/migration/libxc.py b/tools/python/xen/migration/libxc.py
> index f24448a9ef..cbffd1975e 100644
> --- a/tools/python/xen/migration/libxc.py
> +++ b/tools/python/xen/migration/libxc.py
> @@ -223,7 +223,7 @@ def verify_record(self):
>              self.squashed_pagedata_records += 1
>  
>          padding = content[length:]
> -        if padding != "\x00" * len(padding):
> +        if padding != b"\x00" * len(padding):
>              raise StreamError("Padding containing non0 bytes found")
>  
>          if rtype not in record_verifiers:
> diff --git a/tools/python/xen/migration/libxl.py b/tools/python/xen/migration/libxl.py
> index d5f54dc489..79f4024e72 100644
> --- a/tools/python/xen/migration/libxl.py
> +++ b/tools/python/xen/migration/libxl.py
> @@ -128,7 +128,7 @@ def verify_record(self):
>          content = self.rdexact(contentsz)
>  
>          padding = content[length:]
> -        if padding != "\x00" * len(padding):
> +        if padding != b"\x00" * len(padding):
>              raise StreamError("Padding containing non0 bytes found")
>  
>          if rtype not in record_verifiers:
> diff --git a/tools/python/xen/migration/verify.py b/tools/python/xen/migration/verify.py
> index 7a42dbfc58..1e38f4a3c0 100644
> --- a/tools/python/xen/migration/verify.py
> +++ b/tools/python/xen/migration/verify.py
> @@ -7,11 +7,11 @@
>  
>  from struct import calcsize, unpack
>  
> -class StreamError(StandardError):
> +class StreamError(Exception):
>      """Error with the stream"""
>      pass
>  
> -class RecordError(StandardError):
> +class RecordError(Exception):
>      """Error with a record in the stream"""
>      pass
>  
> diff --git a/tools/python/xen/util.py b/tools/python/xen/util.py
> new file mode 100644
> index 0000000000..a11358eefa
> --- /dev/null
> +++ b/tools/python/xen/util.py
> @@ -0,0 +1,23 @@
> +#!/usr/bin/env python
> +# -*- coding: utf-8 -*-
> +
> +import os
> +
> +def open_file_or_fd(val, *argl, **kwargs):
> +    """
> +    If 'val' looks like a decimal integer, open it as an fd.  If not, try to
> +    open it as a regular file.
> +    """
> +
> +    fd = -1
> +    try:
> +        # Does it look like an integer?
> +        fd = int(val, 10)
> +    except ValueError:
> +        pass
> +
> +    # Try to open it...
> +    if fd != -1:
> +        return os.fdopen(fd, *argl, **kwargs)
> +    else:
> +        return open(val, *argl, **kwargs)

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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