pcm/PcmPack: add pcm_unpack_24be()

src/pcm/PcmPack.cxx

@@ -94,3 +94,12 @@ pcm_unpack_24(int32_t *dest, const uint8_t *src, const uint8_t *src_end)
 		src += 3;
 	}
 }
+
+void
+pcm_unpack_24be(int32_t *dest, const uint8_t *src, const uint8_t *src_end)
+{
+	while (src < src_end) {
+		*dest++ = ReadS24BE(src);
+		src += 3;
+	}
+}

src/pcm/PcmPack.hxx

@@ -49,4 +49,11 @@ pcm_pack_24(uint8_t *dest, const int32_t *src, const int32_t *src_end);
 void
 pcm_unpack_24(int32_t *dest, const uint8_t *src, const uint8_t *src_end);
 
+/**
+ * Like pcm_unpack_24(), but assume the source byte order is
+ * big-endian.  The destination byte order ia always native.
+ */
+void
+pcm_unpack_24be(int32_t *dest, const uint8_t *src, const uint8_t *src_end);
+
 #endif

test/test_pcm_all.hxx

@@ -40,11 +40,13 @@ class PcmPackTest : public CppUnit::TestFixture {
 	CPPUNIT_TEST_SUITE(PcmPackTest);
 	CPPUNIT_TEST(TestPack24);
 	CPPUNIT_TEST(TestUnpack24);
+	CPPUNIT_TEST(TestUnpack24BE);
 	CPPUNIT_TEST_SUITE_END();
 
 public:
 	void TestPack24();
 	void TestUnpack24();
+	void TestUnpack24BE();
 };
 
 class PcmChannelsTest : public CppUnit::TestFixture {

test/test_pcm_pack.cxx

@@ -70,3 +70,23 @@ PcmPackTest::TestUnpack24()
 		CPPUNIT_ASSERT_EQUAL(s, dest[i]);
 	}
 }
+
+void
+PcmPackTest::TestUnpack24BE()
+{
+	constexpr unsigned N = 509;
+	const auto src = TestDataBuffer<uint8_t, N * 3>();
+
+	int32_t dest[N];
+	pcm_unpack_24be(dest, src.begin(), src.end());
+
+	for (unsigned i = 0; i < N; ++i) {
+		int32_t s;
+		s = (src[i * 3] << 16) | (src[i * 3 + 1] << 8)
+			| src[i * 3 + 2];
+		if (s & 0x800000)
+			s |= 0xff000000;
+
+		CPPUNIT_ASSERT_EQUAL(s, dest[i]);
+	}
+}