num: add variable-width greedy int types

sx/__init__.py

@@ -11,6 +11,7 @@ from .types.num import (
     int16, uint16, int16be, int16le, uint16be, uint16le, word,
     int32, uint32, int32be, int32le, uint32be, uint32le, dword,
     int64, uint64, int64be, int64le, uint64be, uint64le, qword,
+    intbe, intle, uintbe, uintle,
     float16, float16le, float16be, binary16, binary16le, binary16be, half,
     float32, float32le, float32be, binary32, binary32le, binary32be, float_,
     float64, float64le, float64be, binary64, binary64le, binary64be, double,

sx/types/num.py

@@ -15,7 +15,7 @@ class Int(Type[int]):
 
     def parse(self, context: Context, stream: Stream) -> int:
         n = context.get(self.bits)
-        bs = stream.read(n // 8)
+        bs = stream.read(n // 8 if n is not None else -1)
         return int.from_bytes(bs, byteorder=context.get(self.endian).to_python(), signed=context.get(self.signed))
 
     def dump(self, context: Context, stream: Stream, value: U[int, float]) -> None:
@@ -40,7 +40,8 @@ class Int(Type[int]):
     def __str__(self) -> str:
         endian = {Endian.Big: 'be', Endian.Little: 'le'}.get(self.endian, self.endian) if self.bits != 8 else ''
         sign = {True: '', False: 'u'}.get(self.signed, self.signed)
-        return f'{sign}int{self.bits}{endian}'
+        bits = self.bits if self.bits is not None else ''
+        return f'{sign}int{bits}{endian}'
 
     def __repr__(self) -> str:
         return f'{__name__}.Int({self.bits!r}, endian={self.endian!r}, signed={self.signed!r})'
@@ -73,6 +74,11 @@ uint64   = \
 uint64le = Int(64, endian=Endian.Little, signed=False)
 uint64be = Int(64, endian=Endian.Big,    signed=False)
 
+intle    = Int(None, endian=Endian.Little, signed=True)
+intbe    = Int(None, endian=Endian.Big,    signed=True)
+uintle   = Int(None, endian=Endian.Little, signed=False)
+uintbe   = Int(None, endian=Endian.Big,    signed=False)
+
 
 T = TypeVar('T')