65 lines
1.7 KiB
Python
65 lines
1.7 KiB
Python
from typing import List
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from ..constants import FIELD_PRIME
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CairoData = List[int]
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MAX_UINT256 = (1 << 256) - 1
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MIN_UINT256 = 0
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def uint256_range_check(value: int):
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if not MIN_UINT256 <= value <= MAX_UINT256:
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raise ValueError(
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f"Uint256 is expected to be in range [0;2**256), got: {value}."
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)
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MIN_FELT = -FIELD_PRIME // 2
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MAX_FELT = FIELD_PRIME // 2
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def is_in_felt_range(value: int) -> bool:
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return 0 <= value < FIELD_PRIME
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def cairo_vm_range_check(value: int):
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if not is_in_felt_range(value):
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raise ValueError(
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f"Felt is expected to be in range [0; {FIELD_PRIME}), got: {value}."
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)
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def encode_shortstring(text: str) -> int:
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"""
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A function which encodes short string value (at most 31 characters) into cairo felt (MSB as first character)
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:param text: A short string value in python
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:return: Short string value encoded into felt
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"""
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if len(text) > 31:
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raise ValueError(
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f"Shortstring cannot be longer than 31 characters, got: {len(text)}."
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)
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try:
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text_bytes = text.encode("ascii")
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except UnicodeEncodeError as u_err:
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raise ValueError(f"Expected an ascii string. Found: {repr(text)}.") from u_err
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value = int.from_bytes(text_bytes, "big")
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cairo_vm_range_check(value)
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return value
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def decode_shortstring(value: int) -> str:
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"""
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A function which decodes a felt value to short string (at most 31 characters)
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:param value: A felt value
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:return: Decoded string which is corresponds to that felt
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"""
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cairo_vm_range_check(value)
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return "".join([chr(i) for i in value.to_bytes(31, byteorder="big")]).lstrip("\x00")
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