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"""
event-stream library for `awscrt`.
"""
# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0.
from collections.abc import ByteString
from enum import IntEnum
from typing import Any
from uuid import UUID
__all__ = ['HeaderType', 'Header']
_BYTE_MIN = -2**7
_BYTE_MAX = 2**7 - 1
_INT16_MIN = -2**15
_INT16_MAX = 2**15 - 1
_INT32_MIN = -2**31
_INT32_MAX = 2**31 - 1
_INT64_MIN = -2**63
_INT64_MAX = 2**63 - 1
class HeaderType(IntEnum):
"""Supported types for the value within a Header"""
BOOL_TRUE = 0
"""Value is True.
No actual value is transmitted on the wire."""
BOOL_FALSE = 1
"""Value is False.
No actual value is transmitted on the wire."""
BYTE = 2
"""Value is signed 8-bit int."""
INT16 = 3
"""Value is signed 16-bit int."""
INT32 = 4
"""Value is signed 32-bit int."""
INT64 = 5
"""Value is signed 64-bit int."""
BYTE_BUF = 6
"""Value is raw bytes."""
STRING = 7
"""Value is a str.
Transmitted on the wire as utf-8"""
TIMESTAMP = 8
"""Value is a posix timestamp (seconds since Unix epoch).
Transmitted on the wire as a 64-bit int"""
UUID = 9
"""Value is a UUID.
Transmitted on the wire as 16 bytes"""
def __format__(self, format_spec):
# override so formatted string doesn't simply look like an int
return str(self)
class Header:
"""A header in an event-stream message.
Each header has a name, value, and type.
:class:`HeaderType` enumerates the supported value types.
Create a header with one of the Header.from_X() functions.
"""
def __init__(self, name: str, value: Any, header_type: HeaderType):
# do not call directly, use Header.from_xyz() methods.
self._name = name
self._value = value
self._type = header_type
@classmethod
def from_bool(cls, name: str, value: bool) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.BOOL_TRUE` or :attr:`~HeaderType.BOOL_FALSE`"""
if value:
return cls(name, True, HeaderType.BOOL_TRUE)
else:
return cls(name, False, HeaderType.BOOL_FALSE)
@classmethod
def from_byte(cls, name: str, value: int) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.BYTE`
The value must fit in an 8-bit signed int"""
value = int(value)
if value < _BYTE_MIN or value > _BYTE_MAX:
raise ValueError("Value {} cannot fit in signed 8-bit byte".format(value))
return cls(name, value, HeaderType.BYTE)
@classmethod
def from_int16(cls, name: str, value: int) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.INT16`
The value must fit in an 16-bit signed int"""
value = int(value)
if value < _INT16_MIN or value > _INT16_MAX:
raise ValueError("Value {} cannot fit in signed 16-bit int".format(value))
return cls(name, value, HeaderType.INT16)
@classmethod
def from_int32(cls, name: str, value: int) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.INT32`
The value must fit in an 32-bit signed int"""
value = int(value)
if value < _INT32_MIN or value > _INT32_MAX:
raise ValueError("Value {} cannot fit in signed 32-bit int".format(value))
return cls(name, value, HeaderType.INT32)
@classmethod
def from_int64(cls, name: str, value: int) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.INT64`
The value must fit in an 64-bit signed int"""
value = int(value)
if value < _INT64_MIN or value > _INT64_MAX:
raise ValueError("Value {} cannot fit in signed 64-bit int".format(value))
return cls(name, value, HeaderType.INT64)
@classmethod
def from_byte_buf(cls, name: str, value: ByteString) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.BYTE_BUF`
The value must be a bytes-like object"""
return cls(name, value, HeaderType.BYTE_BUF)
@classmethod
def from_string(cls, name: str, value: str) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.STRING`"""
value = str(value)
return cls(name, value, HeaderType.STRING)
@classmethod
def from_timestamp(cls, name: str, value: int) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.TIMESTAMP`
Value must be a posix timestamp (seconds since Unix epoch)"""
value = int(value)
if value < _INT64_MIN or value > _INT64_MAX:
raise ValueError("Value {} exceeds timestamp limits".format(value))
return cls(name, value, HeaderType.TIMESTAMP)
@classmethod
def from_uuid(cls, name: str, value: UUID) -> 'Header':
"""Create a Header of type :attr:`~HeaderType.UUID`
The value must be a UUID"""
if not isinstance(value, UUID):
raise TypeError("Value must be UUID, not {}".format(type(value)))
return cls(name, value, HeaderType.UUID)
@classmethod
def _from_binding_tuple(cls, binding_tuple):
# native code deals with a simplified tuple, rather than full class
name, value, header_type = binding_tuple
header_type = HeaderType(header_type)
if header_type == HeaderType.UUID:
value = UUID(bytes=value)
return cls(name, value, header_type)
def _as_binding_tuple(self):
# native code deals with a simplified tuple, rather than full class
if self._type == HeaderType.UUID:
value = self._value.bytes
else:
value = self._value
return (self._name, value, self._type)
@property
def name(self) -> str:
"""Header name"""
return self._name
@property
def type(self) -> HeaderType:
"""Header type"""
return self._type
@property
def value(self) -> Any:
"""Header value
The header's type determines the value's type.
Use the value_as_X() methods for type-checked queries."""
return self._value
def _value_as(self, header_type: HeaderType) -> Any:
if self._type != header_type:
raise TypeError("Header type is {}, not {}".format(self._type, header_type))
return self._value
def value_as_bool(self) -> bool:
"""Return bool value
Raises an exception if type is not :attr:`~HeaderType.BOOL_TRUE` or :attr:`~HeaderType.BOOL_FALSE`"""
if self._type == HeaderType.BOOL_TRUE:
return True
if self._type == HeaderType.BOOL_FALSE:
return False
raise TypeError(
"Header type is {}, not {} or {}".format(
self._type,
HeaderType.BOOL_TRUE,
HeaderType.BOOL_FALSE))
def value_as_byte(self) -> int:
"""Return value of 8-bit signed int
Raises an exception if type is not :attr:`~HeaderType.BYTE`"""
return self._value_as(HeaderType.BYTE)
def value_as_int16(self) -> int:
"""Return value of 16-bit signed int
Raises an exception if type is not :attr:`~HeaderType.INT16`"""
return self._value_as(HeaderType.INT16)
def value_as_int32(self) -> int:
"""Return value of 32-bit signed int
Raises an exception if type is not :attr:`~HeaderType.INT32`"""
return self._value_as(HeaderType.INT32)
def value_as_int64(self) -> int:
"""Return value of 64-bit signed int
Raises an exception if type is not :attr:`~HeaderType.INT64`"""
return self._value_as(HeaderType.INT64)
def value_as_byte_buf(self) -> ByteString:
"""Return value of bytes
Raises an exception if type is not :attr:`~HeaderType.BYTE_BUF`"""
return self._value_as(HeaderType.BYTE_BUF)
def value_as_string(self) -> str:
"""Return value of string
Raises an exception if type is not :attr:`~HeaderType.STRING`"""
return self._value_as(HeaderType.STRING)
def value_as_timestamp(self) -> int:
"""Return value of timestamp (seconds since Unix epoch)
Raises an exception if type is not :attr:`~HeaderType.TIMESTAMP`"""
return self._value_as(HeaderType.TIMESTAMP)
def value_as_uuid(self) -> UUID:
"""Return value of UUID
Raises an exception if type is not :attr:`~HeaderType.UUID`"""
return self._value_as(HeaderType.UUID)
def __str__(self):
return "{}: {} <{}>".format(
self._name,
repr(self._value),
self._type.name)
def __repr__(self):
return "{}({}, {}, {})".format(
self.__class__.__name__,
repr(self._name),
repr(self._value),
repr(self._type))
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