from decimal import Decimal, Context, Inexact
from typing import Union
_ONE = Decimal(10 ** 7)
[docs]def to_xdr_amount(value: Union[str, Decimal]) -> int:
"""Converts an amount to the appropriate value to send over the network
as a part of an XDR object.
Each asset amount is encoded as a signed 64-bit integer in the XDR
structures. An asset amount unit (that which is seen by end users) is
scaled down by a factor of ten million (10,000,000) to arrive at the
native 64-bit integer representation. For example, the integer amount
value 25,123,456 equals 2.5123456 units of the asset. This scaling
allows for seven decimal places of precision in human-friendly amount
units.
This static method correctly multiplies the value by the scaling factor
in order to come to the integer value used in XDR structures.
See `Stellar's documentation on Asset Precision
<https://www.stellar.org/developers/guides/concepts/assets.html#amount-precision-and-representation>`_
for more information.
:param value: The amount to convert to an integer for XDR
serialization.
"""
if not (isinstance(value, str) or isinstance(value, Decimal)):
raise TypeError(
f"Value of type '{value}' must be of type {str} or {Decimal}, but got {type(value)}."
)
# throw exception if value * ONE has decimal places (it can't be represented as int64)
try:
amount = int(
(Decimal(value) * _ONE).to_integral_exact(context=Context(traps=[Inexact]))
)
except Inexact:
raise ValueError(
f"Value of '{value}' must have at most 7 digits after the decimal."
)
if amount < 0 or amount > 9223372036854775807:
raise ValueError(
f"Value of '{value}' must represent a positive number "
"and the max valid value is 922337203685.4775807."
)
return amount
[docs]def from_xdr_amount(value: int) -> str:
"""Converts an str amount from an XDR amount object
:param value: The amount to convert to a string from an XDR int64
amount.
"""
return str(Decimal(value) / _ONE)