Switch on SFC_SET_CLIPPING in SoundFile.__init__()

See #104.
Incidentally, this closes #20.

pysoundfile.py

@@ -32,6 +32,7 @@
     SFC_GET_FORMAT_MAJOR            = 0x1031,
     SFC_GET_FORMAT_SUBTYPE_COUNT    = 0x1032,
     SFC_GET_FORMAT_SUBTYPE          = 0x1033,
+    SFC_SET_CLIPPING                = 0x10C0,
 } ;
 
 enum
@@ -690,6 +691,9 @@ def __init__(self, file, mode='r', samplerate=None, channels=None,
             # Move write position to 0 (like in Python file objects)
             self.seek(0)
 
+        _snd.sf_command(self._file, _snd.SFC_SET_CLIPPING, _ffi.NULL,
+                        _snd.SF_TRUE)
+
     name = property(lambda self: self._name)
     """The file name of the sound file."""
     mode = property(lambda self: self._mode)

tests/test_pysoundfile.py

@@ -1,6 +1,7 @@
 import pysoundfile as sf
 import numpy as np
 import os
+import io
 import shutil
 import pytest
 
@@ -74,6 +75,12 @@ def file_wplus(request):
     return _file_new(request, os.O_CREAT | os.O_RDWR, 'w+b')
 
 
+@pytest.yield_fixture
+def file_inmemory():
+    with io.BytesIO() as f:
+        yield f
+
+
 @pytest.yield_fixture
 def sf_stereo_r(file_stereo_r):
     with sf.SoundFile(file_stereo_r) as f:
@@ -423,6 +430,33 @@ def test_if_open_with_mode_w_truncates(file_stereo_rplus, mode):
             pass
 
 
+def test_clipping_float_to_int(file_inmemory):
+    float_to_clipped_int16 = [
+        (-1.0 - 2**-15, -2**15    ),
+        (-1.0         , -2**15    ),
+        (-1.0 + 2**-15, -2**15 + 1),
+        ( 0.0         ,  0        ),
+        ( 1.0 - 2**-14,  2**15 - 2),
+        ( 1.0 - 2**-15,  2**15 - 1),
+        ( 1.0         ,  2**15 - 1),
+    ]
+    written, expected = zip(*float_to_clipped_int16)
+    sf.write(written, file_inmemory, 44100, format='WAV', subtype='PCM_16')
+    file_inmemory.seek(0)
+    read, fs = sf.read(file_inmemory, always_2d=False, dtype='int16')
+    assert np.all(read == expected)
+    assert fs == 44100
+
+
+def test_non_clipping_float_to_float(file_inmemory):
+    data = -2.0, -1.0, 0.0, 1.0, 2.0
+    sf.write(data, file_inmemory, 44100, format='WAV', subtype='FLOAT')
+    file_inmemory.seek(0)
+    read, fs = sf.read(file_inmemory, always_2d=False)
+    assert np.all(read == data)
+    assert fs == 44100
+
+
 # -----------------------------------------------------------------------------
 # Test file metadata
 # -----------------------------------------------------------------------------