exchange: improve computation of relevant markers for large repos
Compute the candidate nodes with relevant markers directly
from keys of the predecessors/successors/children dictionaries of
obsstore. This is faster than iterating over all nodes directly.
This test could be further improved for repositories with relative
few markers compared to the repository size, but this is no longer
hot already. With the current loop structure, the obshashrange use
works as well as before as it passes lists with a single node.
Adjust the interface by allowing revision lists as well as node lists.
This helps cases that computes ancestors as it reduces the
materialisation cost. Use this in _pushdiscoveryobsmarker and
_getbundleobsmarkerpart. Improve the latter further by directly using
ancestors().
Performance benchmarks show notable and welcome improvement to no-op push and
pull (that would also apply to other push/pull). This apply to push and pull
done without evolve.
### push/pull Benchmark parameter
# bin-env-vars.hg.flavor = default
# benchmark.variants.explicit-rev = none
# benchmark.variants.protocol = ssh
# benchmark.variants.revs = none
## benchmark.name = hg.command.pull
# data-env-vars.name = mercurial-devel-2024-03-22-zstd-sparse-revlog
before: 5.968537 seconds
after: 5.668507 seconds (-5.03%, -0.30)
# data-env-vars.name = tryton-devel-2024-03-22-zstd-sparse-revlog
before: 1.446232 seconds
after: 0.835553 seconds (-42.23%, -0.61)
# data-env-vars.name = netbsd-src-draft-2024-09-19-zstd-sparse-revlog
before: 5.777412 seconds
after: 2.523454 seconds (-56.32%, -3.25)
## benchmark.name = hg.command.push
# data-env-vars.name = mercurial-devel-2024-03-22-zstd-sparse-revlog
before: 6.155501 seconds
after: 5.885072 seconds (-4.39%, -0.27)
# data-env-vars.name = tryton-devel-2024-03-22-zstd-sparse-revlog
before: 1.491054 seconds
after: 0.934882 seconds (-37.30%, -0.56)
# data-env-vars.name = netbsd-src-draft-2024-09-19-zstd-sparse-revlog
before: 5.902494 seconds
after: 2.957644 seconds (-49.89%, -2.94)
There is not notable different in these result using the "rust" flavor instead
of the "default". The performance impact on the same operation when using
evolve were also tested and no impact was noted.
# encoding.py - character transcoding support for Mercurial
#
# Copyright 2005-2009 Olivia Mackall <olivia@selenic.com> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import annotations
import locale
import os
import re
import typing
import unicodedata
from typing import (
Any,
Callable,
Text,
TypeVar,
)
from . import (
error,
policy,
pycompat,
)
from .pure import charencode as charencodepure
_Tlocalstr = TypeVar('_Tlocalstr', bound='localstr')
charencode = policy.importmod('charencode')
isasciistr = charencode.isasciistr
asciilower = charencode.asciilower
asciiupper = charencode.asciiupper
_jsonescapeu8fast = charencode.jsonescapeu8fast
_sysstr = pycompat.sysstr
unichr = chr
if typing.TYPE_CHECKING:
# TODO: make a stub file for .cext.charencode, and import here
from .pure.charencode import (
asciilower,
asciiupper,
isasciistr,
jsonescapeu8fast as _jsonescapeu8fast,
)
# These unicode characters are ignored by HFS+ (Apple Technote 1150,
# "Unicode Subtleties"), so we need to ignore them in some places for
# sanity.
_ignore = [
unichr(int(x, 16)).encode("utf-8")
for x in b"200c 200d 200e 200f 202a 202b 202c 202d 202e "
b"206a 206b 206c 206d 206e 206f feff".split()
]
# verify the next function will work
assert all(i.startswith((b"\xe2", b"\xef")) for i in _ignore)
def hfsignoreclean(s: bytes) -> bytes:
"""Remove codepoints ignored by HFS+ from s.
>>> hfsignoreclean(u'.h\u200cg'.encode('utf-8'))
'.hg'
>>> hfsignoreclean(u'.h\ufeffg'.encode('utf-8'))
'.hg'
"""
if b"\xe2" in s or b"\xef" in s:
for c in _ignore:
s = s.replace(c, b'')
return s
# encoding.environ is provided read-only, which may not be used to modify
# the process environment
_nativeenviron = os.supports_bytes_environ
if _nativeenviron:
environ = os.environb # re-exports
if pycompat.sysplatform == b'OpenVMS':
# workaround for a bug in VSI 3.10 port
# os.environb is only populated with a few Predefined symbols
def newget(self, key, default=None):
# pytype on linux does not understand OpenVMS special modules
import _decc # pytype: disable=import-error
v = _decc.getenv(key, None)
if isinstance(key, bytes):
return default if v is None else v.encode('latin-1')
else:
return default if v is None else v
environ.__class__.get = newget
else:
# preferred encoding isn't known yet; use utf-8 to avoid unicode error
# and recreate it once encoding is settled
environ = {
k.encode('utf-8'): v.encode('utf-8')
for k, v in os.environ.items() # re-exports
}
_encodingrewrites = {
b'646': b'ascii',
b'ANSI_X3.4-1968': b'ascii',
}
# cp65001 is a Windows variant of utf-8, which isn't supported on Python 2.
# No idea if it should be rewritten to the canonical name 'utf-8' on Python 3.
# https://bugs.python.org/issue13216
if pycompat.iswindows:
_encodingrewrites[b'cp65001'] = b'utf-8'
encoding: bytes = b'' # help pytype avoid seeing None value
try:
encoding = environ.get(b"HGENCODING", b'')
if not encoding:
encoding = locale.getpreferredencoding().encode('ascii') or b'ascii'
encoding = _encodingrewrites.get(encoding, encoding)
except locale.Error:
encoding = b'ascii'
encodingmode: bytes = environ.get(b"HGENCODINGMODE", b"strict")
fallbackencoding = b'ISO-8859-1'
class localstr(bytes):
"""This class allows strings that are unmodified to be
round-tripped to the local encoding and back"""
def __new__(cls, u, l):
s = bytes.__new__(cls, l)
s._utf8 = u
return s
if typing.TYPE_CHECKING:
# pseudo implementation to help pytype see localstr() constructor
def __init__(self, u: bytes, l: bytes) -> None:
super(localstr, self).__init__(l)
self._utf8 = u
def __hash__(self):
return hash(self._utf8) # avoid collisions in local string space
class safelocalstr(bytes):
"""Tagged string denoting it was previously an internal UTF-8 string,
and can be converted back to UTF-8 losslessly
>>> assert safelocalstr(b'\\xc3') == b'\\xc3'
>>> assert b'\\xc3' == safelocalstr(b'\\xc3')
>>> assert b'\\xc3' in {safelocalstr(b'\\xc3'): 0}
>>> assert safelocalstr(b'\\xc3') in {b'\\xc3': 0}
"""
def tolocal(s: bytes) -> bytes:
"""
Convert a string from internal UTF-8 to local encoding
All internal strings should be UTF-8 but some repos before the
implementation of locale support may contain latin1 or possibly
other character sets. We attempt to decode everything strictly
using UTF-8, then Latin-1, and failing that, we use UTF-8 and
replace unknown characters.
The localstr class is used to cache the known UTF-8 encoding of
strings next to their local representation to allow lossless
round-trip conversion back to UTF-8.
>>> u = b'foo: \\xc3\\xa4' # utf-8
>>> l = tolocal(u)
>>> l
'foo: ?'
>>> fromlocal(l)
'foo: \\xc3\\xa4'
>>> u2 = b'foo: \\xc3\\xa1'
>>> d = { l: 1, tolocal(u2): 2 }
>>> len(d) # no collision
2
>>> b'foo: ?' in d
False
>>> l1 = b'foo: \\xe4' # historical latin1 fallback
>>> l = tolocal(l1)
>>> l
'foo: ?'
>>> fromlocal(l) # magically in utf-8
'foo: \\xc3\\xa4'
"""
if isasciistr(s):
return s
try:
try:
# make sure string is actually stored in UTF-8
u = s.decode('UTF-8')
if encoding == b'UTF-8':
# fast path
return s
r = u.encode(_sysstr(encoding), "replace")
if u == r.decode(_sysstr(encoding)):
# r is a safe, non-lossy encoding of s
return safelocalstr(r)
return localstr(s, r)
except UnicodeDecodeError:
# we should only get here if we're looking at an ancient changeset
try:
u = s.decode(_sysstr(fallbackencoding))
r = u.encode(_sysstr(encoding), "replace")
if u == r.decode(_sysstr(encoding)):
# r is a safe, non-lossy encoding of s
return safelocalstr(r)
return localstr(u.encode('UTF-8'), r)
except UnicodeDecodeError:
u = s.decode("utf-8", "replace") # last ditch
# can't round-trip
return u.encode(_sysstr(encoding), "replace")
except LookupError as k:
raise error.Abort(
pycompat.bytestr(k), hint=b"please check your locale settings"
)
def fromlocal(s: bytes) -> bytes:
"""
Convert a string from the local character encoding to UTF-8
We attempt to decode strings using the encoding mode set by
HGENCODINGMODE, which defaults to 'strict'. In this mode, unknown
characters will cause an error message. Other modes include
'replace', which replaces unknown characters with a special
Unicode character, and 'ignore', which drops the character.
"""
# can we do a lossless round-trip?
if isinstance(s, localstr):
return s._utf8
if isasciistr(s):
return s
try:
u = s.decode(_sysstr(encoding), _sysstr(encodingmode))
return u.encode("utf-8")
except UnicodeDecodeError as inst:
sub = s[max(0, inst.start - 10) : inst.start + 10]
raise error.Abort(
b"decoding near '%s': %s!" % (sub, pycompat.bytestr(inst))
)
except LookupError as k:
raise error.Abort(
pycompat.bytestr(k), hint=b"please check your locale settings"
)
def unitolocal(u: str) -> bytes:
"""Convert a unicode string to a byte string of local encoding"""
return tolocal(u.encode('utf-8'))
def unifromlocal(s: bytes) -> str:
"""Convert a byte string of local encoding to a unicode string"""
return fromlocal(s).decode('utf-8')
def unimethod(bytesfunc: Callable[[Any], bytes]) -> Callable[[Any], str]:
"""Create a proxy method that forwards __unicode__() and __str__() of
Python 3 to __bytes__()"""
def unifunc(obj):
return unifromlocal(bytesfunc(obj))
return unifunc
# converter functions between native str and byte string. use these if the
# character encoding is not aware (e.g. exception message) or is known to
# be locale dependent (e.g. date formatting.)
strtolocal = unitolocal
strfromlocal = unifromlocal
strmethod = unimethod
def lower(s: bytes) -> bytes:
"""best-effort encoding-aware case-folding of local string s"""
try:
return asciilower(s)
except UnicodeDecodeError:
pass
try:
if isinstance(s, localstr):
u = s._utf8.decode("utf-8")
else:
u = s.decode(_sysstr(encoding), _sysstr(encodingmode))
lu = u.lower()
if u == lu:
return s # preserve localstring
return lu.encode(_sysstr(encoding))
except UnicodeError:
return s.lower() # we don't know how to fold this except in ASCII
except LookupError as k:
raise error.Abort(
pycompat.bytestr(k), hint=b"please check your locale settings"
)
def upper(s: bytes) -> bytes:
"""best-effort encoding-aware case-folding of local string s"""
try:
return asciiupper(s)
except UnicodeDecodeError:
return upperfallback(s)
def upperfallback(s: Any) -> Any:
try:
if isinstance(s, localstr):
u = s._utf8.decode("utf-8")
else:
u = s.decode(_sysstr(encoding), _sysstr(encodingmode))
uu = u.upper()
if u == uu:
return s # preserve localstring
return uu.encode(_sysstr(encoding))
except UnicodeError:
return s.upper() # we don't know how to fold this except in ASCII
except LookupError as k:
raise error.Abort(
pycompat.bytestr(k), hint=b"please check your locale settings"
)
if not _nativeenviron:
# now encoding and helper functions are available, recreate the environ
# dict to be exported to other modules
if pycompat.iswindows:
class WindowsEnviron(dict):
"""`os.environ` normalizes environment variables to uppercase on windows"""
def get(self, key, default=None):
return super().get(upper(key), default)
environ = WindowsEnviron()
for k, v in os.environ.items(): # re-exports
environ[tolocal(k.encode('utf-8'))] = tolocal(v.encode('utf-8'))
DRIVE_RE = re.compile(b'^[a-z]:')
# os.getcwd() on Python 3 returns string, but it has os.getcwdb() which
# returns bytes.
if pycompat.iswindows:
# Python 3 on Windows issues a DeprecationWarning about using the bytes
# API when os.getcwdb() is called.
#
# Additionally, py3.8+ uppercases the drive letter when calling
# os.path.realpath(), which is used on ``repo.root``. Since those
# strings are compared in various places as simple strings, also call
# realpath here. See https://bugs.python.org/issue40368
#
# However this is not reliable, so lets explicitly make this drive
# letter upper case.
#
# note: we should consider dropping realpath here since it seems to
# change the semantic of `getcwd`.
def getcwd():
cwd = os.getcwd() # re-exports
cwd = os.path.realpath(cwd)
cwd = strtolocal(cwd)
if DRIVE_RE.match(cwd):
cwd = cwd[0:1].upper() + cwd[1:]
return cwd
else:
getcwd = os.getcwdb # re-exports
# How to treat ambiguous-width characters. Set to 'wide' to treat as wide.
_wide = _sysstr(
environ.get(b"HGENCODINGAMBIGUOUS", b"narrow") == b"wide"
and b"WFA"
or b"WF"
)
def colwidth(s: bytes) -> int:
"""Find the column width of a string for display in the local encoding"""
return ucolwidth(s.decode(_sysstr(encoding), 'replace'))
def ucolwidth(d: Text) -> int:
"""Find the column width of a Unicode string for display"""
eaw = getattr(unicodedata, 'east_asian_width', None)
if eaw is not None:
return sum([eaw(c) in _wide and 2 or 1 for c in d])
return len(d)
def getcols(s: bytes, start: int, c: int) -> bytes:
"""Use colwidth to find a c-column substring of s starting at byte
index start"""
for x in range(start + c, len(s)):
t = s[start:x]
if colwidth(t) == c:
return t
raise ValueError('substring not found')
def trim(
s: bytes,
width: int,
ellipsis: bytes = b'',
leftside: bool = False,
) -> bytes:
"""Trim string 's' to at most 'width' columns (including 'ellipsis').
If 'leftside' is True, left side of string 's' is trimmed.
'ellipsis' is always placed at trimmed side.
>>> from .node import bin
>>> def bprint(s):
... print(pycompat.sysstr(s))
>>> ellipsis = b'+++'
>>> from . import encoding
>>> encoding.encoding = b'utf-8'
>>> t = b'1234567890'
>>> bprint(trim(t, 12, ellipsis=ellipsis))
1234567890
>>> bprint(trim(t, 10, ellipsis=ellipsis))
1234567890
>>> bprint(trim(t, 8, ellipsis=ellipsis))
12345+++
>>> bprint(trim(t, 8, ellipsis=ellipsis, leftside=True))
+++67890
>>> bprint(trim(t, 8))
12345678
>>> bprint(trim(t, 8, leftside=True))
34567890
>>> bprint(trim(t, 3, ellipsis=ellipsis))
+++
>>> bprint(trim(t, 1, ellipsis=ellipsis))
+
>>> u = u'\u3042\u3044\u3046\u3048\u304a' # 2 x 5 = 10 columns
>>> t = u.encode(pycompat.sysstr(encoding.encoding))
>>> bprint(trim(t, 12, ellipsis=ellipsis))
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\xe3\x81\x8a
>>> bprint(trim(t, 10, ellipsis=ellipsis))
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\xe3\x81\x8a
>>> bprint(trim(t, 8, ellipsis=ellipsis))
\xe3\x81\x82\xe3\x81\x84+++
>>> bprint(trim(t, 8, ellipsis=ellipsis, leftside=True))
+++\xe3\x81\x88\xe3\x81\x8a
>>> bprint(trim(t, 5))
\xe3\x81\x82\xe3\x81\x84
>>> bprint(trim(t, 5, leftside=True))
\xe3\x81\x88\xe3\x81\x8a
>>> bprint(trim(t, 4, ellipsis=ellipsis))
+++
>>> bprint(trim(t, 4, ellipsis=ellipsis, leftside=True))
+++
>>> t = bin(b'112233445566778899aa') # invalid byte sequence
>>> bprint(trim(t, 12, ellipsis=ellipsis))
\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa
>>> bprint(trim(t, 10, ellipsis=ellipsis))
\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa
>>> bprint(trim(t, 8, ellipsis=ellipsis))
\x11\x22\x33\x44\x55+++
>>> bprint(trim(t, 8, ellipsis=ellipsis, leftside=True))
+++\x66\x77\x88\x99\xaa
>>> bprint(trim(t, 8))
\x11\x22\x33\x44\x55\x66\x77\x88
>>> bprint(trim(t, 8, leftside=True))
\x33\x44\x55\x66\x77\x88\x99\xaa
>>> bprint(trim(t, 3, ellipsis=ellipsis))
+++
>>> bprint(trim(t, 1, ellipsis=ellipsis))
+
"""
try:
u = s.decode(_sysstr(encoding))
except UnicodeDecodeError:
if len(s) <= width: # trimming is not needed
return s
width -= len(ellipsis)
if width <= 0: # no enough room even for ellipsis
return ellipsis[: width + len(ellipsis)]
if leftside:
return ellipsis + s[-width:]
return s[:width] + ellipsis
if ucolwidth(u) <= width: # trimming is not needed
return s
width -= len(ellipsis)
if width <= 0: # no enough room even for ellipsis
return ellipsis[: width + len(ellipsis)]
chars = list(u)
if leftside:
chars.reverse()
width_so_far = 0
for i, c in enumerate(chars):
width_so_far += ucolwidth(c)
if width_so_far > width:
break
chars = chars[:i]
if leftside:
chars.reverse()
u = u''.join(chars).encode(_sysstr(encoding))
if leftside:
return ellipsis + u
return u + ellipsis
class normcasespecs:
"""what a platform's normcase does to ASCII strings
This is specified per platform, and should be consistent with what normcase
on that platform actually does.
lower: normcase lowercases ASCII strings
upper: normcase uppercases ASCII strings
other: the fallback function should always be called
This should be kept in sync with normcase_spec in util.h."""
lower = -1
upper = 1
other = 0
def jsonescape(s: bytes, paranoid: bool = False) -> bytes:
"""returns a string suitable for JSON
JSON is problematic for us because it doesn't support non-Unicode
bytes. To deal with this, we take the following approach:
- localstr/safelocalstr objects are converted back to UTF-8
- valid UTF-8/ASCII strings are passed as-is
- other strings are converted to UTF-8b surrogate encoding
- apply JSON-specified string escaping
(escapes are doubled in these tests)
>>> jsonescape(b'this is a test')
'this is a test'
>>> jsonescape(b'escape characters: \\0 \\x0b \\x7f')
'escape characters: \\\\u0000 \\\\u000b \\\\u007f'
>>> jsonescape(b'escape characters: \\b \\t \\n \\f \\r \\" \\\\')
'escape characters: \\\\b \\\\t \\\\n \\\\f \\\\r \\\\" \\\\\\\\'
>>> jsonescape(b'a weird byte: \\xdd')
'a weird byte: \\xed\\xb3\\x9d'
>>> jsonescape(b'utf-8: caf\\xc3\\xa9')
'utf-8: caf\\xc3\\xa9'
>>> jsonescape(b'')
''
If paranoid, non-ascii and common troublesome characters are also escaped.
This is suitable for web output.
>>> s = b'escape characters: \\0 \\x0b \\x7f'
>>> assert jsonescape(s) == jsonescape(s, paranoid=True)
>>> s = b'escape characters: \\b \\t \\n \\f \\r \\" \\\\'
>>> assert jsonescape(s) == jsonescape(s, paranoid=True)
>>> jsonescape(b'escape boundary: \\x7e \\x7f \\xc2\\x80', paranoid=True)
'escape boundary: ~ \\\\u007f \\\\u0080'
>>> jsonescape(b'a weird byte: \\xdd', paranoid=True)
'a weird byte: \\\\udcdd'
>>> jsonescape(b'utf-8: caf\\xc3\\xa9', paranoid=True)
'utf-8: caf\\\\u00e9'
>>> jsonescape(b'non-BMP: \\xf0\\x9d\\x84\\x9e', paranoid=True)
'non-BMP: \\\\ud834\\\\udd1e'
>>> jsonescape(b'<foo@example.org>', paranoid=True)
'\\\\u003cfoo@example.org\\\\u003e'
"""
u8chars = toutf8b(s)
try:
return _jsonescapeu8fast(u8chars, paranoid)
except ValueError:
pass
return charencodepure.jsonescapeu8fallback(u8chars, paranoid)
# We need to decode/encode U+DCxx codes transparently since invalid UTF-8
# bytes are mapped to that range.
_utf8strict = r'surrogatepass'
_utf8len = [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 4]
def getutf8char(s: bytes, pos: int) -> bytes:
"""get the next full utf-8 character in the given string, starting at pos
Raises a UnicodeError if the given location does not start a valid
utf-8 character.
"""
# find how many bytes to attempt decoding from first nibble
l = _utf8len[ord(s[pos : pos + 1]) >> 4]
if not l: # ascii
return s[pos : pos + 1]
c = s[pos : pos + l]
# validate with attempted decode
c.decode("utf-8", _utf8strict)
return c
def toutf8b(s: bytes) -> bytes:
"""convert a local, possibly-binary string into UTF-8b
This is intended as a generic method to preserve data when working
with schemes like JSON and XML that have no provision for
arbitrary byte strings. As Mercurial often doesn't know
what encoding data is in, we use so-called UTF-8b.
If a string is already valid UTF-8 (or ASCII), it passes unmodified.
Otherwise, unsupported bytes are mapped to UTF-16 surrogate range,
uDC00-uDCFF.
Principles of operation:
- ASCII and UTF-8 data successfully round-trips and is understood
by Unicode-oriented clients
- filenames and file contents in arbitrary other encodings can have
be round-tripped or recovered by clueful clients
- local strings that have a cached known UTF-8 encoding (aka
localstr) get sent as UTF-8 so Unicode-oriented clients get the
Unicode data they want
- non-lossy local strings (aka safelocalstr) get sent as UTF-8 as well
- because we must preserve UTF-8 bytestring in places such as
filenames, metadata can't be roundtripped without help
(Note: "UTF-8b" often refers to decoding a mix of valid UTF-8 and
arbitrary bytes into an internal Unicode format that can be
re-encoded back into the original. Here we are exposing the
internal surrogate encoding as a UTF-8 string.)
"""
if isinstance(s, localstr):
# assume that the original UTF-8 sequence would never contain
# invalid characters in U+DCxx range
return s._utf8
elif isinstance(s, safelocalstr):
# already verified that s is non-lossy in legacy encoding, which
# shouldn't contain characters in U+DCxx range
return fromlocal(s)
elif isasciistr(s):
return s
if b"\xed" not in s:
try:
s.decode('utf-8', _utf8strict)
return s
except UnicodeDecodeError:
pass
s = pycompat.bytestr(s)
r = bytearray()
pos = 0
l = len(s)
while pos < l:
try:
c = getutf8char(s, pos)
if b"\xed\xb0\x80" <= c <= b"\xed\xb3\xbf":
# have to re-escape existing U+DCxx characters
c = unichr(0xDC00 + ord(s[pos])).encode('utf-8', _utf8strict)
pos += 1
else:
pos += len(c)
except UnicodeDecodeError:
c = unichr(0xDC00 + ord(s[pos])).encode('utf-8', _utf8strict)
pos += 1
r += c
return bytes(r)
def fromutf8b(s: bytes) -> bytes:
"""Given a UTF-8b string, return a local, possibly-binary string.
return the original binary string. This
is a round-trip process for strings like filenames, but metadata
that's was passed through tolocal will remain in UTF-8.
>>> roundtrip = lambda x: fromutf8b(toutf8b(x)) == x
>>> m = b"\\xc3\\xa9\\x99abcd"
>>> toutf8b(m)
'\\xc3\\xa9\\xed\\xb2\\x99abcd'
>>> roundtrip(m)
True
>>> roundtrip(b"\\xc2\\xc2\\x80")
True
>>> roundtrip(b"\\xef\\xbf\\xbd")
True
>>> roundtrip(b"\\xef\\xef\\xbf\\xbd")
True
>>> roundtrip(b"\\xf1\\x80\\x80\\x80\\x80")
True
"""
if isasciistr(s):
return s
# fast path - look for uDxxx prefixes in s
if b"\xed" not in s:
return s
# We could do this with the unicode type but some Python builds
# use UTF-16 internally (issue5031) which causes non-BMP code
# points to be escaped. Instead, we use our handy getutf8char
# helper again to walk the string without "decoding" it.
s = pycompat.bytestr(s)
r = bytearray()
pos = 0
l = len(s)
while pos < l:
c = getutf8char(s, pos)
pos += len(c)
# unescape U+DCxx characters
if b"\xed\xb0\x80" <= c <= b"\xed\xb3\xbf":
c = pycompat.bytechr(ord(c.decode("utf-8", _utf8strict)) & 0xFF)
r += c
return bytes(r)