Implement read for Decimal

csla_binary/binary_reader.py

@@ -14,10 +14,12 @@
 #   You should have received a copy of the GNU Affero General Public License
 #   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+from decimal import Decimal
 import io
 import struct
 from typing import List
 
+from .decimal import int32_to_decimal
 from .known_types import CslaKnownTypes
 from .serialization_info import ChildData, FieldData, SerializationInfo
 
@@ -112,6 +114,14 @@ class CslaBinaryReader:
 			
 			shift += 7
 	
+	def read_decimal(self):
+		length = self.read_int32()
+		if length != 4:
+			raise ValueError('Unexpected length of Decimal, expected 4, got {}'.format(length))
+		
+		decimal_parts = [self.read_int32() for _ in range(length)]
+		return int32_to_decimal(decimal_parts)
+	
 	def read_int32(self):
 		# BinaryReader.ReadInt32
 		return struct.unpack('<i', self.stream.read(4))[0]
@@ -158,7 +168,7 @@ class CslaBinaryReader:
 			raise NotImplementedError()
 		
 		if known_type == CslaKnownTypes.Decimal.value:
-			raise NotImplementedError()
+			return self.read_decimal()
 		
 		if known_type == CslaKnownTypes.DateTime.value:
 			raise NotImplementedError()

csla_binary/decimal.py

@@ -0,0 +1,57 @@
+#   pycsla-binary: Python implementation of CSLA .NET binary serialisation
+#   Copyright (C) 2025  Lee Yingtong Li (RunasSudo)
+#
+#   This program is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU Affero General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU Affero General Public License for more details.
+#
+#   You should have received a copy of the GNU Affero General Public License
+#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+from decimal import Decimal, getcontext
+from typing import List
+
+def int32_to_decimal(decimal_parts: List[int]) -> Decimal:
+	# System.Decimal(Int32[])
+	# The binary representation of a Decimal number consists of a 1-bit sign, a 96-bit integer number, and a scaling factor used to divide the integer number and specify what portion of it is a decimal fraction. The scaling factor is implicitly the number 10, raised to an exponent ranging from 0 to 28.
+	# bits is a four-element long array of 32-bit signed integers.
+	# bits [0], bits [1], and bits [2] contain the low, middle, and high 32 bits of the 96-bit integer number.
+	# bits [3] contains the scale factor and sign, and consists of following parts:
+	# - Bits 0 to 15, the lower word, are unused and must be zero.
+	# - Bits 16 to 23 must contain an exponent between 0 and 28, which indicates the power of 10 to divide the integer number.
+	# - Bits 24 to 30 are unused and must be zero.
+	# - Bit 31 contains the sign; 0 meaning positive, and 1 meaning negative.
+	
+	getcontext().prec = 29
+	
+	if decimal_parts[3] & 0b1111111111111111 != 0:
+		raise ValueError('Invalid Decimal: Nonzero unused bits')
+	if decimal_parts[3] & 0b1111111000000000000000000000000 != 0:
+		raise ValueError('Invalid Decimal: Nonzero unused bits')
+	
+	mantissa = (decimal_parts[2] << 64) | (decimal_parts[1] << 32) | decimal_parts[0]
+	exponent = (decimal_parts[3] >> 16) & 0b11111111
+	sign = (decimal_parts[3] >> 31) & 0b1
+	
+	if exponent < 0 or exponent > 28:
+		raise ValueError('Invalid Decimal: Invalid exponent')
+	
+	return Decimal(mantissa * (-1 if sign == 1 else 1)) / (Decimal(10) ** exponent)
+
+def test_int32_to_decimal():
+	# https://learn.microsoft.com/en-us/dotnet/api/system.decimal.-ctor?view=net-9.0#system-decimal-ctor(system-int32())
+	assert int32_to_decimal([0x0, 0x0, 0x0, 0x0]) == Decimal('0')
+	assert int32_to_decimal([0x3B9ACA00, 0x0, 0x0, 0x0]) == Decimal('1000000000')
+	assert int32_to_decimal([0x0, 0x3B9ACA00, 0x0, 0x0]) == Decimal('4294967296000000000')
+	assert int32_to_decimal([0x0, 0x0, 0x3B9ACA00, 0x0]) == Decimal('18446744073709551616000000000')
+	assert int32_to_decimal([0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x0]) == Decimal('79228162514264337593543950335')
+	assert int32_to_decimal([0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x80000000]) == Decimal('-79228162514264337593543950335')
+	assert int32_to_decimal([0xFFFFFFFF, 0x0, 0x0, 0x100000]) == Decimal('0.0000004294967295')
+	assert int32_to_decimal([0xFFFFFFFF, 0x0, 0x0, 0x1C0000]) == Decimal('0.0000000000000000004294967295')
+	assert int32_to_decimal([0xF0000, 0xF0000, 0xF0000, 0xF0000]) == Decimal('18133887298.441562272235520')