add

ccxt/static_dependencies/starknet/cairo/felt.py

@@ -0,0 +1,64 @@
+from typing import List
+
+from ..constants import FIELD_PRIME
+
+CairoData = List[int]
+
+
+MAX_UINT256 = (1 << 256) - 1
+MIN_UINT256 = 0
+
+
+def uint256_range_check(value: int):
+    if not MIN_UINT256 <= value <= MAX_UINT256:
+        raise ValueError(
+            f"Uint256 is expected to be in range [0;2**256), got: {value}."
+        )
+
+
+MIN_FELT = -FIELD_PRIME // 2
+MAX_FELT = FIELD_PRIME // 2
+
+
+def is_in_felt_range(value: int) -> bool:
+    return 0 <= value < FIELD_PRIME
+
+
+def cairo_vm_range_check(value: int):
+    if not is_in_felt_range(value):
+        raise ValueError(
+            f"Felt is expected to be in range [0; {FIELD_PRIME}), got: {value}."
+        )
+
+
+def encode_shortstring(text: str) -> int:
+    """
+    A function which encodes short string value (at most 31 characters) into cairo felt (MSB as first character)
+
+    :param text: A short string value in python
+    :return: Short string value encoded into felt
+    """
+    if len(text) > 31:
+        raise ValueError(
+            f"Shortstring cannot be longer than 31 characters, got: {len(text)}."
+        )
+
+    try:
+        text_bytes = text.encode("ascii")
+    except UnicodeEncodeError as u_err:
+        raise ValueError(f"Expected an ascii string. Found: {repr(text)}.") from u_err
+    value = int.from_bytes(text_bytes, "big")
+
+    cairo_vm_range_check(value)
+    return value
+
+
+def decode_shortstring(value: int) -> str:
+    """
+    A function which decodes a felt value to short string (at most 31 characters)
+
+    :param value: A felt value
+    :return: Decoded string which is corresponds to that felt
+    """
+    cairo_vm_range_check(value)
+    return "".join([chr(i) for i in value.to_bytes(31, byteorder="big")]).lstrip("\x00")