Issue #16686: Fixed a lot of bugs in audioop module.

* avgpp() and maxpp() no more crash on empty and 1-samples input fragment. They now work when peak-peak values are greater INT_MAX.
* ratecv() no more crashes on empty input fragment.
* Fixed an integer overflow in ratecv().
* Fixed an integer overflow in add() and bias() for 32-bit samples.
* reverse(), lin2lin() and ratecv() no more lose precision for 32-bit samples.
* max() and rms() no more returns negative result for 32-bit sample -0x80000000.
* minmax() now returns correct max value for 32-bit sample -0x80000000.
* avg(), mul(), tomono() and tostereo() now round negative result down and can return 32-bit sample -0x80000000.
* add() now can return 32-bit sample -0x80000000.

Doc/library/audioop.rst

@@ -36,7 +36,7 @@ The module defines the following variables and functions:
 
    Return a fragment which is the addition of the two samples passed as parameters.
    *width* is the sample width in bytes, either ``1``, ``2`` or ``4``.  Both
-   fragments should have the same length.
+   fragments should have the same length.  Samples are truncated in case of overflow.
 
 
 .. function:: adpcm2lin(adpcmfragment, width, state)
@@ -67,7 +67,7 @@ The module defines the following variables and functions:
 .. function:: bias(fragment, width, bias)
 
    Return a fragment that is the original fragment with a bias added to each
-   sample.
+   sample.  Samples wrap around in case of overflow.
 
 
 .. function:: cross(fragment, width)
@@ -175,7 +175,7 @@ The module defines the following variables and functions:
 .. function:: mul(fragment, width, factor)
 
    Return a fragment that has all samples in the original fragment multiplied by
-   the floating-point value *factor*.  Overflow is silently ignored.
+   the floating-point value *factor*.  Samples are truncated in case of overflow.
 
 
 .. function:: ratecv(fragment, width, nchannels, inrate, outrate, state[, weightA[, weightB]])

Lib/test/test_audioop.py

 import audioop
+import sys
 import unittest
 from test.support import run_unittest
 
-endian = 'big' if audioop.getsample(b'\0\1', 2, 0) == 1 else 'little'
+def pack(width, data):
+    return b''.join(v.to_bytes(width, sys.byteorder, signed=True) for v in data)
 
-def gendata1():
-    return b'\0\1\2'
+packs = {w: (lambda *data, width=w: pack(width, data)) for w in (1, 2, 4)}
+maxvalues = {w: (1 << (8 * w - 1)) - 1 for w in (1, 2, 4)}
+minvalues = {w: -1 << (8 * w - 1) for w in (1, 2, 4)}
 
-def gendata2():
-    if endian == 'big':
-        return b'\0\0\0\1\0\2'
-    else:
-        return b'\0\0\1\0\2\0'
-
-def gendata4():
-    if endian == 'big':
-        return b'\0\0\0\0\0\0\0\1\0\0\0\2'
-    else:
-        return b'\0\0\0\0\1\0\0\0\2\0\0\0'
-
-data = [gendata1(), gendata2(), gendata4()]
+datas = {
+    1: b'\x00\x12\x45\xbb\x7f\x80\xff',
+    2: packs[2](0, 0x1234, 0x4567, -0x4567, 0x7fff, -0x8000, -1),
+    4: packs[4](0, 0x12345678, 0x456789ab, -0x456789ab,
+                0x7fffffff, -0x80000000, -1),
+}
 
 INVALID_DATA = [
     (b'abc', 0),
@@ -31,171 +27,320 @@ INVALID_DATA = [
 class TestAudioop(unittest.TestCase):
 
     def test_max(self):
-        self.assertEqual(audioop.max(data[0], 1), 2)
-        self.assertEqual(audioop.max(data[1], 2), 2)
-        self.assertEqual(audioop.max(data[2], 4), 2)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.max(b'', w), 0)
+            p = packs[w]
+            self.assertEqual(audioop.max(p(5), w), 5)
+            self.assertEqual(audioop.max(p(5, -8, -1), w), 8)
+            self.assertEqual(audioop.max(p(maxvalues[w]), w), maxvalues[w])
+            self.assertEqual(audioop.max(p(minvalues[w]), w), -minvalues[w])
+            self.assertEqual(audioop.max(datas[w], w), -minvalues[w])
 
     def test_minmax(self):
-        self.assertEqual(audioop.minmax(data[0], 1), (0, 2))
-        self.assertEqual(audioop.minmax(data[1], 2), (0, 2))
-        self.assertEqual(audioop.minmax(data[2], 4), (0, 2))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.minmax(b'', w),
+                             (0x7fffffff, -0x80000000))
+            p = packs[w]
+            self.assertEqual(audioop.minmax(p(5), w), (5, 5))
+            self.assertEqual(audioop.minmax(p(5, -8, -1), w), (-8, 5))
+            self.assertEqual(audioop.minmax(p(maxvalues[w]), w),
+                             (maxvalues[w], maxvalues[w]))
+            self.assertEqual(audioop.minmax(p(minvalues[w]), w),
+                             (minvalues[w], minvalues[w]))
+            self.assertEqual(audioop.minmax(datas[w], w),
+                             (minvalues[w], maxvalues[w]))
 
     def test_maxpp(self):
-        self.assertEqual(audioop.maxpp(data[0], 1), 0)
-        self.assertEqual(audioop.maxpp(data[1], 2), 0)
-        self.assertEqual(audioop.maxpp(data[2], 4), 0)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.maxpp(b'', w), 0)
+            self.assertEqual(audioop.maxpp(packs[w](*range(100)), w), 0)
+            self.assertEqual(audioop.maxpp(packs[w](9, 10, 5, 5, 0, 1), w), 10)
+            self.assertEqual(audioop.maxpp(datas[w], w),
+                             maxvalues[w] - minvalues[w])
 
     def test_avg(self):
-        self.assertEqual(audioop.avg(data[0], 1), 1)
-        self.assertEqual(audioop.avg(data[1], 2), 1)
-        self.assertEqual(audioop.avg(data[2], 4), 1)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.avg(b'', w), 0)
+            p = packs[w]
+            self.assertEqual(audioop.avg(p(5), w), 5)
+            self .assertEqual(audioop.avg(p(5, 8), w), 6)
+            self.assertEqual(audioop.avg(p(5, -8), w), -2)
+            self.assertEqual(audioop.avg(p(maxvalues[w], maxvalues[w]), w),
+                             maxvalues[w])
+            self.assertEqual(audioop.avg(p(minvalues[w], minvalues[w]), w),
+                             minvalues[w])
+        self.assertEqual(audioop.avg(packs[4](0x50000000, 0x70000000), 4),
+                         0x60000000)
+        self.assertEqual(audioop.avg(packs[4](-0x50000000, -0x70000000), 4),
+                         -0x60000000)
 
     def test_avgpp(self):
-        self.assertEqual(audioop.avgpp(data[0], 1), 0)
-        self.assertEqual(audioop.avgpp(data[1], 2), 0)
-        self.assertEqual(audioop.avgpp(data[2], 4), 0)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.avgpp(b'', w), 0)
+            self.assertEqual(audioop.avgpp(packs[w](*range(100)), w), 0)
+            self.assertEqual(audioop.avgpp(packs[w](9, 10, 5, 5, 0, 1), w), 10)
+        self.assertEqual(audioop.avgpp(datas[1], 1), 196)
+        self.assertEqual(audioop.avgpp(datas[2], 2), 50534)
+        self.assertEqual(audioop.avgpp(datas[4], 4), 3311897002)
 
     def test_rms(self):
-        self.assertEqual(audioop.rms(data[0], 1), 1)
-        self.assertEqual(audioop.rms(data[1], 2), 1)
-        self.assertEqual(audioop.rms(data[2], 4), 1)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.rms(b'', w), 0)
+            p = packs[w]
+            self.assertEqual(audioop.rms(p(*range(100)), w), 57)
+            self.assertAlmostEqual(audioop.rms(p(maxvalues[w]) * 5, w),
+                                   maxvalues[w], delta=1)
+            self.assertAlmostEqual(audioop.rms(p(minvalues[w]) * 5, w),
+                                   -minvalues[w], delta=1)
+        self.assertEqual(audioop.rms(datas[1], 1), 77)
+        self.assertEqual(audioop.rms(datas[2], 2), 20001)
+        self.assertEqual(audioop.rms(datas[4], 4), 1310854152)
 
     def test_cross(self):
-        self.assertEqual(audioop.cross(data[0], 1), 0)
-        self.assertEqual(audioop.cross(data[1], 2), 0)
-        self.assertEqual(audioop.cross(data[2], 4), 0)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.cross(b'', w), -1)
+            p = packs[w]
+            self.assertEqual(audioop.cross(p(0, 1, 2), w), 0)
+            self.assertEqual(audioop.cross(p(1, 2, -3, -4), w), 1)
+            self.assertEqual(audioop.cross(p(-1, -2, 3, 4), w), 1)
+            self.assertEqual(audioop.cross(p(0, minvalues[w]), w), 1)
+            self.assertEqual(audioop.cross(p(minvalues[w], maxvalues[w]), w), 1)
 
     def test_add(self):
-        data2 = []
-        for d in data:
-            str = bytearray(len(d))
-            for i,b in enumerate(d):
-                str[i] = 2*b
-            data2.append(str)
-        self.assertEqual(audioop.add(data[0], data[0], 1), data2[0])
-        self.assertEqual(audioop.add(data[1], data[1], 2), data2[1])
-        self.assertEqual(audioop.add(data[2], data[2], 4), data2[2])
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.add(b'', b'', w), b'')
+            self.assertEqual(audioop.add(datas[w], b'\0' * len(datas[w]), w),
+                             datas[w])
+        self.assertEqual(audioop.add(datas[1], datas[1], 1),
+                         b'\x00\x24\x7f\x80\x7f\x80\xfe')
+        self.assertEqual(audioop.add(datas[2], datas[2], 2),
+                packs[2](0, 0x2468, 0x7fff, -0x8000, 0x7fff, -0x8000, -2))
+        self.assertEqual(audioop.add(datas[4], datas[4], 4),
+                packs[4](0, 0x2468acf0, 0x7fffffff, -0x80000000,
+                       0x7fffffff, -0x80000000, -2))
 
     def test_bias(self):
-        # Note: this test assumes that avg() works
-        d1 = audioop.bias(data[0], 1, 100)
-        d2 = audioop.bias(data[1], 2, 100)
-        d4 = audioop.bias(data[2], 4, 100)
-        self.assertEqual(audioop.avg(d1, 1), 101)
-        self.assertEqual(audioop.avg(d2, 2), 101)
-        self.assertEqual(audioop.avg(d4, 4), 101)
+        for w in 1, 2, 4:
+            for bias in 0, 1, -1, 127, -128, 0x7fffffff, -0x80000000:
+                self.assertEqual(audioop.bias(b'', w, bias), b'')
+        self.assertEqual(audioop.bias(datas[1], 1, 1),
+                         b'\x01\x13\x46\xbc\x80\x81\x00')
+        self.assertEqual(audioop.bias(datas[1], 1, -1),
+                         b'\xff\x11\x44\xba\x7e\x7f\xfe')
+        self.assertEqual(audioop.bias(datas[1], 1, 0x7fffffff),
+                         b'\xff\x11\x44\xba\x7e\x7f\xfe')
+        self.assertEqual(audioop.bias(datas[1], 1, -0x80000000),
+                         datas[1])
+        self.assertEqual(audioop.bias(datas[2], 2, 1),
+                packs[2](1, 0x1235, 0x4568, -0x4566, -0x8000, -0x7fff, 0))
+        self.assertEqual(audioop.bias(datas[2], 2, -1),
+                packs[2](-1, 0x1233, 0x4566, -0x4568, 0x7ffe, 0x7fff, -2))
+        self.assertEqual(audioop.bias(datas[2], 2, 0x7fffffff),
+                packs[2](-1, 0x1233, 0x4566, -0x4568, 0x7ffe, 0x7fff, -2))
+        self.assertEqual(audioop.bias(datas[2], 2, -0x80000000),
+                datas[2])
+        self.assertEqual(audioop.bias(datas[4], 4, 1),
+                packs[4](1, 0x12345679, 0x456789ac, -0x456789aa,
+                         -0x80000000, -0x7fffffff, 0))
+        self.assertEqual(audioop.bias(datas[4], 4, -1),
+                packs[4](-1, 0x12345677, 0x456789aa, -0x456789ac,
+                         0x7ffffffe, 0x7fffffff, -2))
+        self.assertEqual(audioop.bias(datas[4], 4, 0x7fffffff),
+                packs[4](0x7fffffff, -0x6dcba989, -0x3a987656, 0x3a987654,
+                         -2, -1, 0x7ffffffe))
+        self.assertEqual(audioop.bias(datas[4], 4, -0x80000000),
+                packs[4](-0x80000000, -0x6dcba988, -0x3a987655, 0x3a987655,
+                         -1, 0, 0x7fffffff))
 
     def test_lin2lin(self):
-        # too simple: we test only the size
-        for d1 in data:
-            for d2 in data:
-                got = len(d1)//3
-                wtd = len(d2)//3
-                self.assertEqual(len(audioop.lin2lin(d1, got, wtd)), len(d2))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.lin2lin(datas[w], w, w), datas[w])
+
+        self.assertEqual(audioop.lin2lin(datas[1], 1, 2),
+            packs[2](0, 0x1200, 0x4500, -0x4500, 0x7f00, -0x8000, -0x100))
+        self.assertEqual(audioop.lin2lin(datas[1], 1, 4),
+            packs[4](0, 0x12000000, 0x45000000, -0x45000000,
+                     0x7f000000, -0x80000000, -0x1000000))
+        self.assertEqual(audioop.lin2lin(datas[2], 2, 1),
+            b'\x00\x12\x45\xba\x7f\x80\xff')
+        self.assertEqual(audioop.lin2lin(datas[2], 2, 4),
+            packs[4](0, 0x12340000, 0x45670000, -0x45670000,
+                     0x7fff0000, -0x80000000, -0x10000))
+        self.assertEqual(audioop.lin2lin(datas[4], 4, 1),
+            b'\x00\x12\x45\xba\x7f\x80\xff')
+        self.assertEqual(audioop.lin2lin(datas[4], 4, 2),
+            packs[2](0, 0x1234, 0x4567, -0x4568, 0x7fff, -0x8000, -1))
 
     def test_adpcm2lin(self):
+        self.assertEqual(audioop.adpcm2lin(b'\x07\x7f\x7f', 1, None),
+                         (b'\x00\x00\x00\xff\x00\xff', (-179, 40)))
+        self.assertEqual(audioop.adpcm2lin(b'\x07\x7f\x7f', 2, None),
+                         (packs[2](0, 0xb, 0x29, -0x16, 0x72, -0xb3), (-179, 40)))
+        self.assertEqual(audioop.adpcm2lin(b'\x07\x7f\x7f', 4, None),
+                         (packs[4](0, 0xb0000, 0x290000, -0x160000, 0x720000,
+                                   -0xb30000), (-179, 40)))
+
         # Very cursory test
-        self.assertEqual(audioop.adpcm2lin(b'\0\0', 1, None), (b'\0' * 4, (0,0)))
-        self.assertEqual(audioop.adpcm2lin(b'\0\0', 2, None), (b'\0' * 8, (0,0)))
-        self.assertEqual(audioop.adpcm2lin(b'\0\0', 4, None), (b'\0' * 16, (0,0)))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.adpcm2lin(b'\0' * 5, w, None),
+                             (b'\0' * w * 10, (0, 0)))
 
     def test_lin2adpcm(self):
+        self.assertEqual(audioop.lin2adpcm(datas[1], 1, None),
+                         (b'\x07\x7f\x7f', (-221, 39)))
+        self.assertEqual(audioop.lin2adpcm(datas[2], 2, None),
+                         (b'\x07\x7f\x7f', (31, 39)))
+        self.assertEqual(audioop.lin2adpcm(datas[4], 4, None),
+                         (b'\x07\x7f\x7f', (31, 39)))
+
         # Very cursory test
-        self.assertEqual(audioop.lin2adpcm(b'\0\0\0\0', 1, None), (b'\0\0', (0,0)))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.lin2adpcm(b'\0' * w * 10, w, None),
+                             (b'\0' * 5, (0, 0)))
 
     def test_lin2alaw(self):
-        self.assertEqual(audioop.lin2alaw(data[0], 1), b'\xd5\xc5\xf5')
-        self.assertEqual(audioop.lin2alaw(data[1], 2), b'\xd5\xd5\xd5')
-        self.assertEqual(audioop.lin2alaw(data[2], 4), b'\xd5\xd5\xd5')
+        self.assertEqual(audioop.lin2alaw(datas[1], 1),
+                         b'\xd5\x87\xa4\x24\xaa\x2a\x5a')
+        self.assertEqual(audioop.lin2alaw(datas[2], 2),
+                         b'\xd5\x87\xa4\x24\xaa\x2a\x55')
+        self.assertEqual(audioop.lin2alaw(datas[4], 4),
+                         b'\xd5\x87\xa4\x24\xaa\x2a\x55')
 
     def test_alaw2lin(self):
-        # Cursory
-        d = audioop.lin2alaw(data[0], 1)
-        self.assertEqual(audioop.alaw2lin(d, 1), data[0])
-        if endian == 'big':
-            self.assertEqual(audioop.alaw2lin(d, 2),
-                             b'\x00\x08\x01\x08\x02\x10')
-            self.assertEqual(audioop.alaw2lin(d, 4),
-                             b'\x00\x08\x00\x00\x01\x08\x00\x00\x02\x10\x00\x00')
-        else:
-            self.assertEqual(audioop.alaw2lin(d, 2),
-                             b'\x08\x00\x08\x01\x10\x02')
-            self.assertEqual(audioop.alaw2lin(d, 4),
-                             b'\x00\x00\x08\x00\x00\x00\x08\x01\x00\x00\x10\x02')
+        encoded = b'\x00\x03\x24\x2a\x51\x54\x55\x58\x6b\x71\x7f'\
+                  b'\x80\x83\xa4\xaa\xd1\xd4\xd5\xd8\xeb\xf1\xff'
+        src = [-688, -720, -2240, -4032, -9, -3, -1, -27, -244, -82, -106,
+               688, 720, 2240, 4032, 9, 3, 1, 27, 244, 82, 106]
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.alaw2lin(encoded, w),
+                             packs[w](*(x << (w * 8) >> 13 for x in src)))
+
+        encoded = bytes(range(256))
+        for w in 2, 4:
+            decoded = audioop.alaw2lin(encoded, w)
+            self.assertEqual(audioop.lin2alaw(decoded, w), encoded)
 
     def test_lin2ulaw(self):
-        self.assertEqual(audioop.lin2ulaw(data[0], 1), b'\xff\xe7\xdb')
-        self.assertEqual(audioop.lin2ulaw(data[1], 2), b'\xff\xff\xff')
-        self.assertEqual(audioop.lin2ulaw(data[2], 4), b'\xff\xff\xff')
+        self.assertEqual(audioop.lin2ulaw(datas[1], 1),
+                         b'\xff\xad\x8e\x0e\x80\x00\x67')
+        self.assertEqual(audioop.lin2ulaw(datas[2], 2),
+                         b'\xff\xad\x8e\x0e\x80\x00\x7e')
+        self.assertEqual(audioop.lin2ulaw(datas[4], 4),
+                         b'\xff\xad\x8e\x0e\x80\x00\x7e')
 
     def test_ulaw2lin(self):
-        # Cursory
-        d = audioop.lin2ulaw(data[0], 1)
-        self.assertEqual(audioop.ulaw2lin(d, 1), data[0])
-        if endian == 'big':
-            self.assertEqual(audioop.ulaw2lin(d, 2),
-                             b'\x00\x00\x01\x04\x02\x0c')
-            self.assertEqual(audioop.ulaw2lin(d, 4),
-                             b'\x00\x00\x00\x00\x01\x04\x00\x00\x02\x0c\x00\x00')
-        else:
-            self.assertEqual(audioop.ulaw2lin(d, 2),
-                             b'\x00\x00\x04\x01\x0c\x02')
-            self.assertEqual(audioop.ulaw2lin(d, 4),
-                             b'\x00\x00\x00\x00\x00\x00\x04\x01\x00\x00\x0c\x02')
+        encoded = b'\x00\x0e\x28\x3f\x57\x6a\x76\x7c\x7e\x7f'\
+                  b'\x80\x8e\xa8\xbf\xd7\xea\xf6\xfc\xfe\xff'
+        src = [-8031, -4447, -1471, -495, -163, -53, -18, -6, -2, 0,
+               8031, 4447, 1471, 495, 163, 53, 18, 6, 2, 0]
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.ulaw2lin(encoded, w),
+                             packs[w](*(x << (w * 8) >> 14 for x in src)))
+
+        # Current u-law implementation has two codes fo 0: 0x7f and 0xff.
+        encoded = bytes(range(127)) + bytes(range(128, 256))
+        for w in 2, 4:
+            decoded = audioop.ulaw2lin(encoded, w)
+            self.assertEqual(audioop.lin2ulaw(decoded, w), encoded)
 
     def test_mul(self):
-        data2 = []
-        for d in data:
-            str = bytearray(len(d))
-            for i,b in enumerate(d):
-                str[i] = 2*b
-            data2.append(str)
-        self.assertEqual(audioop.mul(data[0], 1, 2), data2[0])
-        self.assertEqual(audioop.mul(data[1],2, 2), data2[1])
-        self.assertEqual(audioop.mul(data[2], 4, 2), data2[2])
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.mul(b'', w, 2), b'')
+            self.assertEqual(audioop.mul(datas[w], w, 0),
+                             b'\0' * len(datas[w]))
+            self.assertEqual(audioop.mul(datas[w], w, 1),
+                             datas[w])
+        self.assertEqual(audioop.mul(datas[1], 1, 2),
+                         b'\x00\x24\x7f\x80\x7f\x80\xfe')
+        self.assertEqual(audioop.mul(datas[2], 2, 2),
+                packs[2](0, 0x2468, 0x7fff, -0x8000, 0x7fff, -0x8000, -2))
+        self.assertEqual(audioop.mul(datas[4], 4, 2),
+                packs[4](0, 0x2468acf0, 0x7fffffff, -0x80000000,
+                         0x7fffffff, -0x80000000, -2))
 
     def test_ratecv(self):
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.ratecv(b'', w, 1, 8000, 8000, None),
+                             (b'', (-1, ((0, 0),))))
+            self.assertEqual(audioop.ratecv(b'', w, 5, 8000, 8000, None),
+                             (b'', (-1, ((0, 0),) * 5)))
+            self.assertEqual(audioop.ratecv(b'', w, 1, 8000, 16000, None),
+                             (b'', (-2, ((0, 0),))))
+            self.assertEqual(audioop.ratecv(datas[w], w, 1, 8000, 8000, None)[0],
+                             datas[w])
         state = None
-        d1, state = audioop.ratecv(data[0], 1, 1, 8000, 16000, state)
-        d2, state = audioop.ratecv(data[0], 1, 1, 8000, 16000, state)
+        d1, state = audioop.ratecv(b'\x00\x01\x02', 1, 1, 8000, 16000, state)
+        d2, state = audioop.ratecv(b'\x00\x01\x02', 1, 1, 8000, 16000, state)
         self.assertEqual(d1 + d2, b'\000\000\001\001\002\001\000\000\001\001\002')
 
+        for w in 1, 2, 4:
+            d0, state0 = audioop.ratecv(datas[w], w, 1, 8000, 16000, None)
+            d, state = b'', None
+            for i in range(0, len(datas[w]), w):
+                d1, state = audioop.ratecv(datas[w][i:i + w], w, 1,
+                                           8000, 16000, state)
+                d += d1
+            self.assertEqual(d, d0)
+            self.assertEqual(state, state0)
+
     def test_reverse(self):
-        self.assertEqual(audioop.reverse(data[0], 1), b'\2\1\0')
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.reverse(b'', w), b'')
+            self.assertEqual(audioop.reverse(packs[w](0, 1, 2), w),
+                             packs[w](2, 1, 0))
 
     def test_tomono(self):
-        data2 = bytearray()
-        for d in data[0]:
-            data2.append(d)
-            data2.append(d)
-        self.assertEqual(audioop.tomono(data2, 1, 0.5, 0.5), data[0])
+        for w in 1, 2, 4:
+            data1 = datas[w]
+            data2 = bytearray(2 * len(data1))
+            for k in range(w):
+                data2[k::2*w] = data1[k::w]
+            self.assertEqual(audioop.tomono(data2, w, 1, 0), data1)
+            self.assertEqual(audioop.tomono(data2, w, 0, 1), b'\0' * len(data1))
+            for k in range(w):
+                data2[k+w::2*w] = data1[k::w]
+            self.assertEqual(audioop.tomono(data2, w, 0.5, 0.5), data1)
 
     def test_tostereo(self):
-        data2 = bytearray()
-        for d in data[0]:
-            data2.append(d)
-            data2.append(d)
-        self.assertEqual(audioop.tostereo(data[0], 1, 1, 1), data2)
+        for w in 1, 2, 4:
+            data1 = datas[w]
+            data2 = bytearray(2 * len(data1))
+            for k in range(w):
+                data2[k::2*w] = data1[k::w]
+            self.assertEqual(audioop.tostereo(data1, w, 1, 0), data2)
+            self.assertEqual(audioop.tostereo(data1, w, 0, 0), b'\0' * len(data2))
+            for k in range(w):
+                data2[k+w::2*w] = data1[k::w]
+            self.assertEqual(audioop.tostereo(data1, w, 1, 1), data2)
 
     def test_findfactor(self):
-        self.assertEqual(audioop.findfactor(data[1], data[1]), 1.0)
+        self.assertEqual(audioop.findfactor(datas[2], datas[2]), 1.0)
+        self.assertEqual(audioop.findfactor(b'\0' * len(datas[2]), datas[2]),
+                         0.0)
 
     def test_findfit(self):
-        self.assertEqual(audioop.findfit(data[1], data[1]), (0, 1.0))
+        self.assertEqual(audioop.findfit(datas[2], datas[2]), (0, 1.0))
+        self.assertEqual(audioop.findfit(datas[2], packs[2](1, 2, 0)),
+                         (1, 8038.8))
+        self.assertEqual(audioop.findfit(datas[2][:-2] * 5 + datas[2], datas[2]),
+                         (30, 1.0))
 
     def test_findmax(self):
-        self.assertEqual(audioop.findmax(data[1], 1), 2)
+        self.assertEqual(audioop.findmax(datas[2], 1), 5)
 
     def test_getsample(self):
-        for i in range(3):
-            self.assertEqual(audioop.getsample(data[0], 1, i), i)
-            self.assertEqual(audioop.getsample(data[1], 2, i), i)
-            self.assertEqual(audioop.getsample(data[2], 4, i), i)
+        for w in 1, 2, 4:
+            data = packs[w](0, 1, -1, maxvalues[w], minvalues[w])
+            self.assertEqual(audioop.getsample(data, w, 0), 0)
+            self.assertEqual(audioop.getsample(data, w, 1), 1)
+            self.assertEqual(audioop.getsample(data, w, 2), -1)
+            self.assertEqual(audioop.getsample(data, w, 3), maxvalues[w])
+            self.assertEqual(audioop.getsample(data, w, 4), minvalues[w])
 
     def test_negativelen(self):
         # from issue 3306, previously it segfaulted
         self.assertRaises(audioop.error,
-            audioop.findmax, ''.join(chr(x) for x in range(256)), -2392392)
+            audioop.findmax, bytes(range(256)), -2392392)
 
     def test_issue7673(self):
         state = None
@@ -222,9 +367,9 @@ class TestAudioop(unittest.TestCase):
             self.assertRaises(audioop.error, audioop.lin2adpcm, data, size, state)
 
     def test_wrongsize(self):
-        data = b'abc'
+        data = b'abcdefgh'
         state = None
-        for size in (-1, 3, 5):
+        for size in (-1, 0, 3, 5, 1024):
             self.assertRaises(audioop.error, audioop.ulaw2lin, data, size)
             self.assertRaises(audioop.error, audioop.alaw2lin, data, size)
             self.assertRaises(audioop.error, audioop.adpcm2lin, data, size, state)

Misc/NEWS

@@ -215,6 +215,12 @@ Core and Builtins
 Library
 -------
 
+- Issue #16686: Fixed a lot of bugs in audioop module.  Fixed crashes in
+  avgpp(), maxpp() and ratecv().  Fixed an integer overflow in add(), bias(),
+  and ratecv().  reverse(), lin2lin() and ratecv() no more lose precision for
+  32-bit samples.  max() and rms() no more returns a negative result and
+  various other functions now work correctly with 32-bit sample -0x80000000.
+
 - Issue #17073: Fix some integer overflows in sqlite3 module.
 
 - Issue #17114: IDLE now uses non-strict config parser.

Modules/audioop.c

@@ -26,6 +26,21 @@ typedef short PyInt16;
 #endif
 #endif
 
+static const int maxvals[] = {0, 0x7F, 0x7FFF, 0x7FFFFF, 0x7FFFFFFF};
+static const int minvals[] = {0, -0x80, -0x8000, -0x800000, -0x80000000};
+static const unsigned int masks[] = {0, 0xFF, 0xFFFF, 0xFFFFFF, 0xFFFFFFFF};
+
+static int
+fbound(double val, double minval, double maxval)
+{
+    if (val > maxval)
+        val = maxval;
+    else if (val < minval + 1)
+        val = minval;
+    return val;
+}
+
+
 /* Code shamelessly stolen from sox, 12.17.7, g711.c
 ** (c) Craig Reese, Joe Campbell and Jeff Poskanzer 1989 */
 
@@ -347,7 +362,7 @@ audioop_max(PyObject *self, PyObject *args)
     signed char *cp;
     Py_ssize_t len, i;
     int size, val = 0;
-    int max = 0;
+    unsigned int absval, max = 0;
 
     if ( !PyArg_ParseTuple(args, "s#i:max", &cp, &len, &size) )
         return 0;
@@ -357,10 +372,11 @@ audioop_max(PyObject *self, PyObject *args)
         if ( size == 1 )      val = (int)*CHARP(cp, i);
         else if ( size == 2 ) val = (int)*SHORTP(cp, i);
         else if ( size == 4 ) val = (int)*LONGP(cp, i);
-        if ( val < 0 ) val = (-val);
-        if ( val > max ) max = val;
+        if (val < 0) absval = (-val);
+        else absval = val;
+        if (absval > max) max = absval;
     }
-    return PyLong_FromLong(max);
+    return PyLong_FromUnsignedLong(max);
 }
 
 static PyObject *
@@ -369,7 +385,7 @@ audioop_minmax(PyObject *self, PyObject *args)
     signed char *cp;
     Py_ssize_t len, i;
     int size, val = 0;
-    int min = 0x7fffffff, max = -0x7fffffff;
+    int min = 0x7fffffff, max = -0x80000000;
 
     if (!PyArg_ParseTuple(args, "s#i:minmax", &cp, &len, &size))
         return NULL;
@@ -406,7 +422,7 @@ audioop_avg(PyObject *self, PyObject *args)
     if ( len == 0 )
         val = 0;
     else
-        val = (int)(avg / (double)(len/size));
+        val = (int)floor(avg / (double)(len/size));
     return PyLong_FromLong(val);
 }
 
@@ -416,6 +432,7 @@ audioop_rms(PyObject *self, PyObject *args)
     signed char *cp;
     Py_ssize_t len, i;
     int size, val = 0;
+    unsigned int res;
     double sum_squares = 0.0;
 
     if ( !PyArg_ParseTuple(args, "s#i:rms", &cp, &len, &size) )
@@ -429,10 +446,10 @@ audioop_rms(PyObject *self, PyObject *args)
         sum_squares += (double)val*(double)val;
     }
     if ( len == 0 )
-        val = 0;
+        res = 0;
     else
-        val = (int)sqrt(sum_squares / (double)(len/size));
-    return PyLong_FromLong(val);
+        res = (unsigned int)sqrt(sum_squares / (double)(len/size));
+    return PyLong_FromUnsignedLong(res);
 }
 
 static double _sum2(short *a, short *b, Py_ssize_t len)
@@ -624,52 +641,46 @@ audioop_avgpp(PyObject *self, PyObject *args)
     Py_ssize_t len, i;
     int size, val = 0, prevval = 0, prevextremevalid = 0,
         prevextreme = 0;
-    double avg = 0.0;
-    int diff, prevdiff, extremediff, nextreme = 0;
+    double sum = 0.0;
+    unsigned int avg;
+    int diff, prevdiff, nextreme = 0;
 
     if ( !PyArg_ParseTuple(args, "s#i:avgpp", &cp, &len, &size) )
         return 0;
     if (!audioop_check_parameters(len, size))
         return NULL;
-    /* Compute first delta value ahead. Also automatically makes us
-    ** skip the first extreme value
-    */
+    if (len <= size)
+        return PyLong_FromLong(0);
     if ( size == 1 )      prevval = (int)*CHARP(cp, 0);
     else if ( size == 2 ) prevval = (int)*SHORTP(cp, 0);
     else if ( size == 4 ) prevval = (int)*LONGP(cp, 0);
-    if ( size == 1 )      val = (int)*CHARP(cp, size);
-    else if ( size == 2 ) val = (int)*SHORTP(cp, size);
-    else if ( size == 4 ) val = (int)*LONGP(cp, size);
-    prevdiff = val - prevval;
-
+    prevdiff = 17; /* Anything != 0, 1 */
     for ( i=size; i<len; i+= size) {
         if ( size == 1 )      val = (int)*CHARP(cp, i);
         else if ( size == 2 ) val = (int)*SHORTP(cp, i);
         else if ( size == 4 ) val = (int)*LONGP(cp, i);
-        diff = val - prevval;
-        if ( diff*prevdiff < 0 ) {
+        if (val != prevval) {
+            diff = val < prevval;
+            if (prevdiff == !diff) {
                 /* Derivative changed sign. Compute difference to last
                 ** extreme value and remember.
                 */
-            if ( prevextremevalid ) {
-                extremediff = prevval - prevextreme;
-                if ( extremediff < 0 )
-                    extremediff = -extremediff;
-                avg += extremediff;
+                if (prevextremevalid) {
+                    sum += fabs((double)prevval - (double)prevextreme);
                     nextreme++;
                 }
                 prevextremevalid = 1;
                 prevextreme = prevval;
             }
             prevval = val;
-        if ( diff != 0 )
             prevdiff = diff;
         }
+    }
     if ( nextreme == 0 )
-        val = 0;
+        avg = 0;
     else
-        val = (int)(avg / (double)nextreme);
-    return PyLong_FromLong(val);
+        avg = (unsigned int)(sum / (double)nextreme);
+    return PyLong_FromUnsignedLong(avg);
 }
 
 static PyObject *
@@ -679,37 +690,36 @@ audioop_maxpp(PyObject *self, PyObject *args)
     Py_ssize_t len, i;
     int size, val = 0, prevval = 0, prevextremevalid = 0,
         prevextreme = 0;
-    int max = 0;
-    int diff, prevdiff, extremediff;
+    unsigned int max = 0, extremediff;
+    int diff, prevdiff;
 
     if ( !PyArg_ParseTuple(args, "s#i:maxpp", &cp, &len, &size) )
         return 0;
     if (!audioop_check_parameters(len, size))
         return NULL;
-    /* Compute first delta value ahead. Also automatically makes us
-    ** skip the first extreme value
-    */
+    if (len <= size)
+        return PyLong_FromLong(0);
     if ( size == 1 )      prevval = (int)*CHARP(cp, 0);
     else if ( size == 2 ) prevval = (int)*SHORTP(cp, 0);
     else if ( size == 4 ) prevval = (int)*LONGP(cp, 0);
-    if ( size == 1 )      val = (int)*CHARP(cp, size);
-    else if ( size == 2 ) val = (int)*SHORTP(cp, size);
-    else if ( size == 4 ) val = (int)*LONGP(cp, size);
-    prevdiff = val - prevval;
-
+    prevdiff = 17; /* Anything != 0, 1 */
     for ( i=size; i<len; i+= size) {
         if ( size == 1 )      val = (int)*CHARP(cp, i);
         else if ( size == 2 ) val = (int)*SHORTP(cp, i);
         else if ( size == 4 ) val = (int)*LONGP(cp, i);
-        diff = val - prevval;
-        if ( diff*prevdiff < 0 ) {
+        if (val != prevval) {
+            diff = val < prevval;
+            if (prevdiff == !diff) {
                 /* Derivative changed sign. Compute difference to
                 ** last extreme value and remember.
                 */
-            if ( prevextremevalid ) {
-                extremediff = prevval - prevextreme;
-                if ( extremediff < 0 )
-                    extremediff = -extremediff;
+                if (prevextremevalid) {
+                    if (prevval < prevextreme)
+                        extremediff = (unsigned int)prevextreme -
+                                      (unsigned int)prevval;
+                    else
+                        extremediff = (unsigned int)prevval -
+                                      (unsigned int)prevextreme;
                     if ( extremediff > max )
                         max = extremediff;
                 }
@@ -717,10 +727,10 @@ audioop_maxpp(PyObject *self, PyObject *args)
                 prevextreme = prevval;
             }
             prevval = val;
-        if ( diff != 0 )
             prevdiff = diff;
         }
-    return PyLong_FromLong(max);
+    }
+    return PyLong_FromUnsignedLong(max);
 }
 
 static PyObject *
@@ -755,7 +765,7 @@ audioop_mul(PyObject *self, PyObject *args)
     signed char *cp, *ncp;
     Py_ssize_t len, i;
     int size, val = 0;
-    double factor, fval, maxval;
+    double factor, fval, maxval, minval;
     PyObject *rv;
 
     if ( !PyArg_ParseTuple(args, "s#id:mul", &cp, &len, &size, &factor ) )
@@ -763,13 +773,8 @@ audioop_mul(PyObject *self, PyObject *args)
     if (!audioop_check_parameters(len, size))
         return NULL;
 
-    if ( size == 1 ) maxval = (double) 0x7f;
-    else if ( size == 2 ) maxval = (double) 0x7fff;
-    else if ( size == 4 ) maxval = (double) 0x7fffffff;
-    else {
-        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
-        return 0;
-    }
+    maxval = (double) maxvals[size];
+    minval = (double) minvals[size];
 
     rv = PyBytes_FromStringAndSize(NULL, len);
     if ( rv == 0 )
@@ -782,9 +787,7 @@ audioop_mul(PyObject *self, PyObject *args)
         else if ( size == 2 ) val = (int)*SHORTP(cp, i);
         else if ( size == 4 ) val = (int)*LONGP(cp, i);
         fval = (double)val*factor;
-        if ( fval > maxval ) fval = maxval;
-        else if ( fval < -maxval ) fval = -maxval;
-        val = (int)fval;
+        val = (int)floor(fbound(fval, minval, maxval));
         if ( size == 1 )      *CHARP(ncp, i) = (signed char)val;
         else if ( size == 2 ) *SHORTP(ncp, i) = (short)val;
         else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)val;
@@ -799,7 +802,7 @@ audioop_tomono(PyObject *self, PyObject *args)
     signed char *cp, *ncp;
     Py_ssize_t len, i;
     int size, val1 = 0, val2 = 0;
-    double fac1, fac2, fval, maxval;
+    double fac1, fac2, fval, maxval, minval;
     PyObject *rv;
 
     if ( !PyArg_ParseTuple(args, "s*idd:tomono",
@@ -817,14 +820,8 @@ audioop_tomono(PyObject *self, PyObject *args)
         return NULL;
     }
 
-    if ( size == 1 ) maxval = (double) 0x7f;
-    else if ( size == 2 ) maxval = (double) 0x7fff;
-    else if ( size == 4 ) maxval = (double) 0x7fffffff;
-    else {
-        PyBuffer_Release(&pcp);
-        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
-        return 0;
-    }
+    maxval = (double) maxvals[size];
+    minval = (double) minvals[size];
 
     rv = PyBytes_FromStringAndSize(NULL, len/2);
     if ( rv == 0 ) {
@@ -842,9 +839,7 @@ audioop_tomono(PyObject *self, PyObject *args)
         else if ( size == 2 ) val2 = (int)*SHORTP(cp, i+2);
         else if ( size == 4 ) val2 = (int)*LONGP(cp, i+4);
         fval = (double)val1*fac1 + (double)val2*fac2;
-        if ( fval > maxval ) fval = maxval;
-        else if ( fval < -maxval ) fval = -maxval;
-        val1 = (int)fval;
+        val1 = (int)floor(fbound(fval, minval, maxval));
         if ( size == 1 )      *CHARP(ncp, i/2) = (signed char)val1;
         else if ( size == 2 ) *SHORTP(ncp, i/2) = (short)val1;
         else if ( size == 4 ) *LONGP(ncp, i/2)= (Py_Int32)val1;
@@ -859,7 +854,7 @@ audioop_tostereo(PyObject *self, PyObject *args)
     signed char *cp, *ncp;
     Py_ssize_t len, i;
     int size, val1, val2, val = 0;
-    double fac1, fac2, fval, maxval;
+    double fac1, fac2, fval, maxval, minval;
     PyObject *rv;
 
     if ( !PyArg_ParseTuple(args, "s#idd:tostereo",
@@ -868,13 +863,8 @@ audioop_tostereo(PyObject *self, PyObject *args)
     if (!audioop_check_parameters(len, size))
         return NULL;
 
-    if ( size == 1 ) maxval = (double) 0x7f;
-    else if ( size == 2 ) maxval = (double) 0x7fff;
-    else if ( size == 4 ) maxval = (double) 0x7fffffff;
-    else {
-        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
-        return 0;
-    }
+    maxval = (double) maxvals[size];
+    minval = (double) minvals[size];
 
     if (len > PY_SSIZE_T_MAX/2) {
         PyErr_SetString(PyExc_MemoryError,
@@ -894,14 +884,10 @@ audioop_tostereo(PyObject *self, PyObject *args)
         else if ( size == 4 ) val = (int)*LONGP(cp, i);
 
         fval = (double)val*fac1;
-        if ( fval > maxval ) fval = maxval;
-        else if ( fval < -maxval ) fval = -maxval;
-        val1 = (int)fval;
+        val1 = (int)floor(fbound(fval, minval, maxval));
 
         fval = (double)val*fac2;
-        if ( fval > maxval ) fval = maxval;
-        else if ( fval < -maxval ) fval = -maxval;
-        val2 = (int)fval;
+        val2 = (int)floor(fbound(fval, minval, maxval));
 
         if ( size == 1 )      *CHARP(ncp, i*2) = (signed char)val1;
         else if ( size == 2 ) *SHORTP(ncp, i*2) = (short)val1;
@@ -919,7 +905,7 @@ audioop_add(PyObject *self, PyObject *args)
 {
     signed char *cp1, *cp2, *ncp;
     Py_ssize_t len1, len2, i;
-    int size, val1 = 0, val2 = 0, maxval, newval;
+    int size, val1 = 0, val2 = 0, minval, maxval, newval;
     PyObject *rv;
 
     if ( !PyArg_ParseTuple(args, "s#s#i:add",
@@ -932,13 +918,8 @@ audioop_add(PyObject *self, PyObject *args)
         return 0;
     }
 
-    if ( size == 1 ) maxval = 0x7f;
-    else if ( size == 2 ) maxval = 0x7fff;
-    else if ( size == 4 ) maxval = 0x7fffffff;
-    else {
-        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
-        return 0;
-    }
+    maxval = maxvals[size];
+    minval = minvals[size];
 
     rv = PyBytes_FromStringAndSize(NULL, len1);
     if ( rv == 0 )
@@ -954,12 +935,19 @@ audioop_add(PyObject *self, PyObject *args)
         else if ( size == 2 ) val2 = (int)*SHORTP(cp2, i);
         else if ( size == 4 ) val2 = (int)*LONGP(cp2, i);
 
+        if (size < 4) {
             newval = val1 + val2;
             /* truncate in case of overflow */
-        if (newval > maxval) newval = maxval;
-        else if (newval < -maxval) newval = -maxval;
-        else if (size == 4 && (newval^val1) < 0 && (newval^val2) < 0)
-            newval = val1 > 0 ? maxval : - maxval;
+            if (newval > maxval)
+                newval = maxval;
+            else if (newval < minval)
+                newval = minval;
+        }
+        else {
+            double fval = (double)val1 + (double)val2;
+            /* truncate in case of overflow */
+            newval = (int)floor(fbound(fval, minval, maxval));
+        }
 
         if ( size == 1 )      *CHARP(ncp, i) = (signed char)newval;
         else if ( size == 2 ) *SHORTP(ncp, i) = (short)newval;
@@ -973,9 +961,9 @@ audioop_bias(PyObject *self, PyObject *args)
 {
     signed char *cp, *ncp;
     Py_ssize_t len, i;
-    int size, val = 0;
+    int size, bias;
+    unsigned int val = 0, mask;
     PyObject *rv;
-    int bias;
 
     if ( !PyArg_ParseTuple(args, "s#ii:bias",
                       &cp, &len, &size , &bias) )
@@ -989,15 +977,20 @@ audioop_bias(PyObject *self, PyObject *args)
         return 0;
     ncp = (signed char *)PyBytes_AsString(rv);
 
+    mask = masks[size];
 
     for ( i=0; i < len; i += size ) {
-        if ( size == 1 )      val = (int)*CHARP(cp, i);
-        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
-        else if ( size == 4 ) val = (int)*LONGP(cp, i);
+        if ( size == 1 )      val = (unsigned int)(unsigned char)*CHARP(cp, i);
+        else if ( size == 2 ) val = (unsigned int)(unsigned short)*SHORTP(cp, i);
+        else if ( size == 4 ) val = (unsigned int)(Py_UInt32)*LONGP(cp, i);
+
+        val += (unsigned int)bias;
+        /* wrap around in case of overflow */
+        val &= mask;
 
-        if ( size == 1 )      *CHARP(ncp, i) = (signed char)(val+bias);
-        else if ( size == 2 ) *SHORTP(ncp, i) = (short)(val+bias);
-        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)(val+bias);
+        if ( size == 1 )      *CHARP(ncp, i) = (signed char)(unsigned char)val;
+        else if ( size == 2 ) *SHORTP(ncp, i) = (short)(unsigned short)val;
+        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)(Py_UInt32)val;
     }
     return rv;
 }
@@ -1024,15 +1017,15 @@ audioop_reverse(PyObject *self, PyObject *args)
     ncp = (unsigned char *)PyBytes_AsString(rv);
 
     for ( i=0; i < len; i += size ) {
-        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
-        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
-        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;
+        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 24;
+        else if ( size == 2 ) val = ((int)*SHORTP(cp, i)) << 16;
+        else if ( size == 4 ) val = (int)*LONGP(cp, i);
 
         j = len - i - size;
 
-        if ( size == 1 )      *CHARP(ncp, j) = (signed char)(val >> 8);
-        else if ( size == 2 ) *SHORTP(ncp, j) = (short)(val);
-        else if ( size == 4 ) *LONGP(ncp, j) = (Py_Int32)(val<<16);
+        if ( size == 1 )      *CHARP(ncp, j) = (signed char)(val >> 24);
+        else if ( size == 2 ) *SHORTP(ncp, j) = (short)(val >> 16);
+        else if ( size == 4 ) *LONGP(ncp, j) = (Py_Int32)val;
     }
     return rv;
 }
@@ -1066,13 +1059,13 @@ audioop_lin2lin(PyObject *self, PyObject *args)
     ncp = (unsigned char *)PyBytes_AsString(rv);
 
     for ( i=0, j=0; i < len; i += size, j += size2 ) {
-        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
-        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
-        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;
+        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 24;
+        else if ( size == 2 ) val = ((int)*SHORTP(cp, i)) << 16;
+        else if ( size == 4 ) val = (int)*LONGP(cp, i);
 
-        if ( size2 == 1 )  *CHARP(ncp, j) = (signed char)(val >> 8);
-        else if ( size2 == 2 ) *SHORTP(ncp, j) = (short)(val);
-        else if ( size2 == 4 ) *LONGP(ncp, j) = (Py_Int32)(val<<16);
+        if ( size2 == 1 )  *CHARP(ncp, j) = (signed char)(val >> 24);
+        else if ( size2 == 2 ) *SHORTP(ncp, j) = (short)(val >> 16);
+        else if ( size2 == 4 ) *LONGP(ncp, j) = (Py_Int32)val;
     }
     return rv;
 }
@@ -1136,6 +1129,10 @@ audioop_ratecv(PyObject *self, PyObject *args)
     d = gcd(inrate, outrate);
     inrate /= d;
     outrate /= d;
+    /* divide weightA and weightB by their greatest common divisor */
+    d = gcd(weightA, weightB);
+    weightA /= d;
+    weightA /= d;
 
     if ((size_t)nchannels > PY_SIZE_MAX/sizeof(int)) {
         PyErr_SetString(PyExc_MemoryError,
@@ -1175,7 +1172,9 @@ audioop_ratecv(PyObject *self, PyObject *args)
     }
 
     /* str <- Space for the output buffer. */
-    {
+    if (len == 0)
+        str = PyBytes_FromStringAndSize(NULL, 0);
+    else {
         /* There are len input frames, so we need (mathematically)
            ceiling(len*outrate/inrate) output frames, and each frame
            requires bytes_per_frame bytes.  Computing this
@@ -1190,13 +1189,12 @@ audioop_ratecv(PyObject *self, PyObject *args)
         else
             str = PyBytes_FromStringAndSize(NULL,
                                             q * outrate * bytes_per_frame);
-
+    }
     if (str == NULL) {
         PyErr_SetString(PyExc_MemoryError,
             "not enough memory for output buffer");
         goto exit;
     }
-    }
     ncp = PyBytes_AsString(str);
 
     for (;;) {
@@ -1229,32 +1227,32 @@ audioop_ratecv(PyObject *self, PyObject *args)
             for (chan = 0; chan < nchannels; chan++) {
                 prev_i[chan] = cur_i[chan];
                 if (size == 1)
-                    cur_i[chan] = ((int)*CHARP(cp, 0)) << 8;
+                    cur_i[chan] = ((int)*CHARP(cp, 0)) << 24;
                 else if (size == 2)
-                    cur_i[chan] = (int)*SHORTP(cp, 0);
+                    cur_i[chan] = ((int)*SHORTP(cp, 0)) << 16;
                 else if (size == 4)
-                    cur_i[chan] = ((int)*LONGP(cp, 0)) >> 16;
+                    cur_i[chan] = (int)*LONGP(cp, 0);
                 cp += size;
                 /* implements a simple digital filter */
-                cur_i[chan] =
-                    (weightA * cur_i[chan] +
-                     weightB * prev_i[chan]) /
-                    (weightA + weightB);
+                cur_i[chan] = (int)(
+                    ((double)weightA * (double)cur_i[chan] +
+                     (double)weightB * (double)prev_i[chan]) /
+                    ((double)weightA + (double)weightB));
             }
             len--;
             d += outrate;
         }
         while (d >= 0) {
             for (chan = 0; chan < nchannels; chan++) {
-                cur_o = (prev_i[chan] * d +
-                         cur_i[chan] * (outrate - d)) /
-                    outrate;
+                cur_o = (int)(((double)prev_i[chan] * (double)d +
+                         (double)cur_i[chan] * (double)(outrate - d)) /
+                    (double)outrate);
                 if (size == 1)
-                    *CHARP(ncp, 0) = (signed char)(cur_o >> 8);
+                    *CHARP(ncp, 0) = (signed char)(cur_o >> 24);
                 else if (size == 2)
-                    *SHORTP(ncp, 0) = (short)(cur_o);
+                    *SHORTP(ncp, 0) = (short)(cur_o >> 16);
                 else if (size == 4)
-                    *LONGP(ncp, 0) = (Py_Int32)(cur_o<<16);
+                    *LONGP(ncp, 0) = (Py_Int32)(cur_o);
                 ncp += size;
             }
             d -= inrate;