use klamath_rs_ext if available

klamath/basic.py

@@ -17,6 +17,11 @@ logger = logging.getLogger(__name__)
 class KlamathError(Exception):
     pass
 
+try:
+    from klamath_rs_ext import pack_int2, pack_int4
+    _USE_RS_EXT = True
+except ImportError:
+    _USE_RS_EXT = False
 
 #
 # Parse functions
@@ -93,14 +98,14 @@ def pack_bitarray(data: int) -> bytes:
     return struct.pack('>H', data)
 
 
-def pack_int2(data: NDArray[numpy.integer] | Sequence[int] | int) -> bytes:
+def _pack_int2(data: NDArray[numpy.integer] | Sequence[int] | int) -> bytes:
     arr = numpy.asarray(data)
     if (arr > 32767).any() or (arr < -32768).any():
         raise KlamathError(f'int2 data out of range: {arr}')
     return arr.astype('>i2').tobytes()
 
 
-def pack_int4(data: NDArray[numpy.integer] | Sequence[int] | int) -> bytes:
+def _pack_int4(data: NDArray[numpy.integer] | Sequence[int] | int) -> bytes:
     arr = numpy.asarray(data)
     if (arr > 2147483647).any() or (arr < -2147483648).any():
         raise KlamathError(f'int4 data out of range: {arr}')
@@ -189,3 +194,9 @@ def read(stream: IO[bytes], size: int) -> bytes:
     if len(data) != size:
         raise EOFError
     return data
+
+
+if not _USE_RS_EXT:
+    pack_int2 = _pack_int2
+    pack_int4 = _pack_int4
+