python 中的 uuid
代码参考 cpython/Lib/uuid.py
版本 3.7
代码参考 cpython/Lib/uuid.py
版本 3.7
什么是 UUID
UUID 的全称是 Universal Unique Identifier，中文名是 通用唯一标识符；
wikipedia 上 UUID 的定义是
wikipedia 上 UUID 的定义是
a 128-bit number used to identify information in computer systems
UUID 需要满足两个条件：
- 128 bit
- 具有标识别计算机系统的能力
UUID 的规则
格式
- 将 16 个 8 位字节表示成 32 个十六进制数
- 按照 8-4-4-4-12 的格式加上 4 个连字符 “-‘
版本
UUID 应该是下面的这种格式
xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
其中 M 开始的 4 位表示版本，N 开始的 4 位表示变种
Name Length(bytes) Length(hex digits) Contents
time_low 4 8 integer giving the low 32 bits of the time
time_mid 2 4 integer giving the middle 16 bits of the time|
time_hi_and_version 2 4 4-bit “version” in the most significant bits, followed by the high 12 bits of the time
clock_seq_hi_and 2 4 1-3 bit “variant” in the most significant bits, _resclock_seq_low followed by the 13-15 bit clock sequence|
node 6 12 the 48-bit node id
Name Length(bytes) Length(hex digits) Contents
time_low 4 8 integer giving the low 32 bits of the time
time_mid 2 4 integer giving the middle 16 bits of the time|
time_hi_and_version 2 4 4-bit “version” in the most significant bits, followed by the high 12 bits of the time
clock_seq_hi_and 2 4 1-3 bit “variant” in the most significant bits, _resclock_seq_low followed by the 13-15 bit clock sequence|
node 6 12 the 48-bit node id
Nil UUID
Version 1(date-time and MAC address)
Version 2 (date-time and MAC address, DCE security version)
Versions 3 and 5 (namespace name-based)
Version 4 (random)
UUID 在 python 中的实现
Version2 实际应用的比较少，python 中没有实现；
UUID 的实现就是按照规则将代码写出来，但是 UUID 这个类的初始化与获得机器信息的代码还是可以看看的
UUID 的实现就是按照规则将代码写出来，但是 UUID 这个类的初始化与获得机器信息的代码还是可以看看的
class UUID
class UUID:
"""Instances of the UUID class represent UUIDs as specified in RFC 4122.
UUID objects are immutable, hashable, and usable as dictionary keys.
Converting a UUID to a string with str() yields something in the form
'12345678-1234-1234-1234-123456789abc'. The UUID constructor accepts
five possible forms: a similar string of hexadecimal digits, or a tuple
of six integer fields (with 32-bit, 16-bit, 16-bit, 8-bit, 8-bit, and
48-bit values respectively) as an argument named 'fields', or a string
of 16 bytes (with all the integer fields in big-endian order) as an
argument named 'bytes', or a string of 16 bytes (with the first three
fields in little-endian order) as an argument named 'bytes_le', or a
single 128-bit integer as an argument named 'int'.
UUIDs have these read-only attributes:
bytes the UUID as a 16-byte string (containing the six
integer fields in big-endian byte order)
bytes_le the UUID as a 16-byte string (with time_low, time_mid,
and time_hi_version in little-endian byte order)
fields a tuple of the six integer fields of the UUID,
which are also available as six individual attributes
and two derived attributes:
time_low the first 32 bits of the UUID
time_mid the next 16 bits of the UUID
time_hi_version the next 16 bits of the UUID
clock_seq_hi_variant the next 8 bits of the UUID
clock_seq_low the next 8 bits of the UUID
node the last 48 bits of the UUID
time the 60-bit timestamp
clock_seq the 14-bit sequence number
hex the UUID as a 32-character hexadecimal string
int the UUID as a 128-bit integer
urn the UUID as a URN as specified in RFC 4122
variant the UUID variant (one of the constants RESERVED_NCS,
RFC_4122, RESERVED_MICROSOFT, or RESERVED_FUTURE)
version the UUID version number (1 through 5, meaningful only
when the variant is RFC_4122)
is_safe An enum indicating whether the UUID has been generated in
a way that is safe for multiprocessing applications, via
uuid_generate_time_safe(3).
"""
def __init__(self, hex=None, bytes=None, bytes_le=None, fields=None,
int=None, version=None,
*, is_safe=SafeUUID.unknown):
r"""Create a UUID from either a string of 32 hexadecimal digits,
a string of 16 bytes as the 'bytes' argument, a string of 16 bytes
in little-endian order as the 'bytes_le' argument, a tuple of six
integers (32-bit time_low, 16-bit time_mid, 16-bit time_hi_version,
8-bit clock_seq_hi_variant, 8-bit clock_seq_low, 48-bit node) as
the 'fields' argument, or a single 128-bit integer as the 'int'
argument. When a string of hex digits is given, curly braces,
hyphens, and a URN prefix are all optional. For example, these
expressions all yield the same UUID:
UUID('{12345678-1234-5678-1234-567812345678}')
UUID('12345678123456781234567812345678')
UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
UUID(bytes='\x12\x34\x56\x78'*4)
UUID(bytes_le='\x78\x56\x34\x12\x34\x12\x78\x56' +
'\x12\x34\x56\x78\x12\x34\x56\x78')
UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
UUID(int=0x12345678123456781234567812345678)
Exactly one of 'hex', 'bytes', 'bytes_le', 'fields', or 'int' must
be given. The 'version' argument is optional; if given, the resulting
UUID will have its variant and version set according to RFC 4122,
overriding the given 'hex', 'bytes', 'bytes_le', 'fields', or 'int'.
is_safe is an enum exposed as an attribute on the instance. It
indicates whether the UUID has been generated in a way that is safe
for multiprocessing applications, via uuid_generate_time_safe(3).
"""
if [hex, bytes, bytes_le, fields, int].count(None) != 4:
raise TypeError('one of the hex, bytes, bytes_le, fields, '
'or int arguments must be given')
if hex is not None:
hex = hex.replace('urn:', '').replace('uuid:', '')
hex = hex.strip('{}').replace('-', '')
if len(hex) != 32:
raise ValueError('badly formed hexadecimal UUID string')
int = int_(hex, 16)
if bytes_le is not None:
if len(bytes_le) != 16:
raise ValueError('bytes_le is not a 16-char string')
bytes = (bytes_le[4-1::-1] + bytes_le[6-1:4-1:-1] +
bytes_le[8-1:6-1:-1] + bytes_le[8:])
if bytes is not None:
if len(bytes) != 16:
raise ValueError('bytes is not a 16-char string')
assert isinstance(bytes, bytes_), repr(bytes)
int = int_.from_bytes(bytes, byteorder='big')
if fields is not None:
if len(fields) != 6:
raise ValueError('fields is not a 6-tuple')
(time_low, time_mid, time_hi_version,
clock_seq_hi_variant, clock_seq_low, node) = fields
if not 0 <= time_low < 1<<32:
raise ValueError('field 1 out of range (need a 32-bit value)')
if not 0 <= time_mid < 1<<16:
raise ValueError('field 2 out of range (need a 16-bit value)')
if not 0 <= time_hi_version < 1<<16:
raise ValueError('field 3 out of range (need a 16-bit value)')
if not 0 <= clock_seq_hi_variant < 1<<8:
raise ValueError('field 4 out of range (need an 8-bit value)')
if not 0 <= clock_seq_low < 1<<8:
raise ValueError('field 5 out of range (need an 8-bit value)')
if not 0 <= node < 1<<48:
raise ValueError('field 6 out of range (need a 48-bit value)')
clock_seq = (clock_seq_hi_variant << 8) | clock_seq_low
int = ((time_low << 96) | (time_mid << 80) |
(time_hi_version << 64) | (clock_seq << 48) | node)
if int is not None:
if not 0 <= int < 1<<128:
raise ValueError('int is out of range (need a 128-bit value)')
if version is not None:
if not 1 <= version <= 5:
raise ValueError('illegal version number')
# Set the variant to RFC 4122.
int &= ~(0xc000 << 48)
int |= 0x8000 << 48
# Set the version number.
int &= ~(0xf000 << 64)
int |= version << 76
self.__dict__['int'] = int
self.__dict__['is_safe'] = is_safe
def __eq__(self, other):
if isinstance(other, UUID):
return self.int == other.int
return NotImplemented
# Q. What's the value of being able to sort UUIDs?
# A. Use them as keys in a B-Tree or similar mapping.
def __lt__(self, other):
if isinstance(other, UUID):
return self.int < other.int
return NotImplemented
def __gt__(self, other):
if isinstance(other, UUID):
return self.int > other.int
return NotImplemented
def __le__(self, other):
if isinstance(other, UUID):
return self.int <= other.int
return NotImplemented
def __ge__(self, other):
if isinstance(other, UUID):
return self.int >= other.int
return NotImplemented
def __hash__(self):
return hash(self.int)
def __int__(self):
return self.int
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__, str(self))
def __setattr__(self, name, value):
raise TypeError('UUID objects are immutable')
def __str__(self):
hex = '%032x' % self.int
return '%s-%s-%s-%s-%s' % (
hex[:8], hex[8:12], hex[12:16], hex[16:20], hex[20:])
@property
def bytes(self):
return self.int.to_bytes(16, 'big')
@property
def bytes_le(self):
bytes = self.bytes
return (bytes[4-1::-1] + bytes[6-1:4-1:-1] + bytes[8-1:6-1:-1] +
bytes[8:])
@property
def fields(self):
return (self.time_low, self.time_mid, self.time_hi_version,
self.clock_seq_hi_variant, self.clock_seq_low, self.node)
@property
def time_low(self):
return self.int >> 96
@property
def time_mid(self):
return (self.int >> 80) & 0xffff
@property
def time_hi_version(self):
return (self.int >> 64) & 0xffff
@property
def clock_seq_hi_variant(self):
return (self.int >> 56) & 0xff
@property
def clock_seq_low(self):
return (self.int >> 48) & 0xff
@property
def time(self):
return (((self.time_hi_version & 0x0fff) << 48) |
(self.time_mid << 32) | self.time_low)
@property
def clock_seq(self):
return (((self.clock_seq_hi_variant & 0x3f) << 8) |
self.clock_seq_low)
@property
def node(self):
return self.int & 0xffffffffffff
@property
def hex(self):
return '%032x' % self.int
@property
def urn(self):
return 'urn:uuid:' + str(self)
@property
def variant(self):
if not self.int & (0x8000 << 48):
return RESERVED_NCS
elif not self.int & (0x4000 << 48):
return RFC_4122
elif not self.int & (0x2000 << 48):
return RESERVED_MICROSOFT
else:
return RESERVED_FUTURE
@property
def version(self):
# The version bits are only meaningful for RFC 4122 UUIDs.
if self.variant == RFC_4122:
return int((self.int >> 76) & 0xf)
getnode
getnode 区别了 windows 与 unix
windows 的时候会从 windll、netbios 、ipconfig 中获取机器信息
uinx 的时候会从 ifconfig、ip、arp、lanscan、netstat 中获取机器信息
如果都失败了就会生成一个随机的 48 bit 的数字并将第八位至为 1
windows 的时候会从 windll、netbios 、ipconfig 中获取机器信息
uinx 的时候会从 ifconfig、ip、arp、lanscan、netstat 中获取机器信息
如果都失败了就会生成一个随机的 48 bit 的数字并将第八位至为 1
def getnode(*, getters=None):
global _node
if _node is not None:
return _node
if sys.platform == 'win32':
getters = _NODE_GETTERS_WIN32
else:
getters = _NODE_GETTERS_UNIX
for getter in getters + [_random_getnode]:
try:
_node = getter()
except:
continue
if (_node is not None) and (0 <= _node < (1 << 48)):
return _node
assert False, '_random_getnode() returned invalid value: {}'.format(_node)
_popen
为了执行 ifconfig 等命令
python 中写了一个 _popen 的函数来完成命令的执行
python 中写了一个 _popen 的函数来完成命令的执行
def _popen(command, *args):
import os, shutil, subprocess
executable = shutil.which(command)
if executable is None:
path = os.pathsep.join(('/sbin', '/usr/sbin'))
executable = shutil.which(command, path=path)
if executable is None:
return None
env = dict(os.environ)
env['LC_ALL'] = 'C'
proc = subprocess.Popen((executable,) + args,
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL,
env=env)
return proc
评论
发表评论