Make int.from_bytes recognize __bytes__ in all cases (#970)

Author: BCSharp

Src/IronPython/Runtime/Bytes.cs

@@ -165,6 +165,8 @@ internal static Bytes FromObject(CodeContext context, object? o) {
                 return (Bytes)o;
             } else if (TryInvokeBytesOperator(context, o, out Bytes? res)) {
                 return res;
+            } else if (o is IBufferProtocol bp) {
+                return new Bytes(bp);
             } else if (o is string || o is ExtensibleString) {
                 throw PythonOps.TypeError("cannot convert unicode object to bytes");
             } else {

Src/IronPython/Runtime/Operations/IntOps.cs

@@ -528,30 +528,20 @@ public static Bytes to_bytes(Int32 value, int length, string byteorder, bool sig
             return Bytes.Make(res.ToArray());
         }
 
-        public static BigInteger from_bytes([NotNull, BytesLike]IList<byte> bytes, string byteorder, bool signed=false) {
+        public static BigInteger from_bytes(CodeContext context, object bytes, [NotNull] string byteorder, bool signed = false) {
             // TODO: signed should be a keyword only argument
             // TODO: return int when possible?
+            // TODO: if called on a subclass of Extensible<BigInteger>, return that subclass
 
             bool isLittle = byteorder == "little";
             if (!isLittle && byteorder != "big") throw PythonOps.ValueError("byteorder must be either 'little' or 'big'");
 
-            return FromBytes(bytes, isLittle, signed);
-        }
-
-        public static BigInteger from_bytes(CodeContext context, object bytes, string byteorder, bool signed = false) {
-            // TODO: signed should be a keyword only argument
-            // TODO: return int when possible?
-
-            bool isLittle = byteorder == "little";
-            if (!isLittle && byteorder != "big") throw PythonOps.ValueError("byteorder must be either 'little' or 'big'");
-
-            return FromBytes(Bytes.FromObject(context, bytes), isLittle, signed);
-        }
-
-        private static BigInteger FromBytes(IList<byte> bytes, bool isLittle, bool signed) {
-            if (!bytes.Any()) return 0;
+            byte[] bytesArr = Bytes.FromObject(context, bytes).UnsafeByteArray;
+            if (bytesArr.Length == 0) return 0;
 
-            byte[] bytesArr = bytes as byte[] ?? ((bytes is Bytes) ? ((Bytes)bytes).UnsafeByteArray : bytes.ToArray());
+#if NETCOREAPP
+            return new BigInteger(bytesArr.AsSpan(), isUnsigned: !signed, isBigEndian: !isLittle);
+#else
 
             if (isLittle) {
                 bool msbSet = (bytesArr[bytesArr.Length - 1] & 0x80) == 0x80;
@@ -562,6 +552,7 @@ private static BigInteger FromBytes(IList<byte> bytes, bool isLittle, bool signe
                 if (!msbSet) return new BigInteger(bytesArr.Reverse());
                 return new BigInteger(bytesArr.Reverse().Concat(Enumerable.Repeat<byte>(signed ? (byte)0xff : (byte)0, 1)).ToArray());
             }
+#endif
         }
 
         public static int __round__(int self) {

Tests/test_bytes.py

@@ -213,6 +213,7 @@ def __bytes__(self):
         self.assertEqual(bytes(BytesBytesSubclass(b"JUST BYTES")), b"BYTES FROM BYTES")
         self.assertIs(type(bytes(BytesBytesSubclass(b"JUST BYTES"))), BytesBytesSubclass)
         self.assertEqual(int.from_bytes(bytes(BytesBytesSubclass(b"JUST BYTES")), 'big'), int.from_bytes(b"BYTES FROM BYTES", 'big'))
+        self.assertEqual(int.from_bytes(BytesBytesSubclass(b"JUST BYTES"), 'big'), int.from_bytes(b"BYTES FROM BYTES", 'big'))
 
         class ListSubclass(bytes):
             def __bytes__(self):

Tests/test_memoryview.py

@@ -247,6 +247,11 @@ def test_unicode_array(self):
             with self.assertRaisesRegex(TypeError, "^memoryview: cannot cast between two non-byte formats$"):
                 mv.cast('H')
 
+    def test_conv(self):
+        self.assertEqual(int.from_bytes(memoryview(b'abcd'), 'big'), 0x61626364)
+        self.assertEqual(int.from_bytes(memoryview(b'abcd')[::2], 'big'), 0x6163)
+        self.assertEqual(int.from_bytes(memoryview(b'abcd')[::-2], 'big'), 0x6462)
+
 class CastTests(unittest.TestCase):
     def test_get_int_alignment(self):
         a = array.array('b', range(8))