mpg123-1.32.4

src/common/swap_bytes_impl.h

@@ -0,0 +1,103 @@
+/*
+	swap_bytes: Swap byte order of samples in a buffer.
+
+	copyright 2018 by the mpg123 project
+	licensed under the terms of the LGPL 2.1
+	see COPYING and AUTHORS files in distribution or http://mpg123.org
+
+	initially written by Thomas Orgis
+
+	This is C source to include in your code to get the function named
+	swap_bytes. It is serves intentional duplication in libmpg123 and
+	libsyn123 to avoid introducing a dependency between them. This function
+	is too small for that.
+*/
+
+/* Other headers are already included! */
+
+/* Optionally use platform-specific byteswap macros. */
+#ifdef HAVE_BYTESWAP_H
+#include <byteswap.h>
+#endif
+
+/* Plain stupid swapping of elements in a byte array. */
+/* This is the fallback when there is no native bswap macro. */
+#define SWAP(a,b) tmp = p[a]; p[a] = p[b]; p[b] = tmp;
+
+/* Convert samplecount elements of samplesize bytes each in buffer buf. */
+static void swap_bytes(void *buf, size_t samplesize, size_t samplecount)
+{
+	unsigned char *p = buf;
+	unsigned char *pend = (unsigned char*)buf+samplesize*samplecount;
+	unsigned char tmp;
+
+	if(samplesize < 2)
+		return;
+	switch(samplesize)
+	{
+		case 2: /* AB -> BA */
+#ifdef HAVE_BYTESWAP_H
+		{
+			uint16_t* pp = (uint16_t*)p;
+			for(; pp<(uint16_t*)pend; ++pp)
+				*pp = bswap_16(*pp);
+		}
+#else
+			for(; p<pend; p+=2)
+			{
+				SWAP(0,1)
+			}
+#endif
+		break;
+		case 3: /* ABC -> CBA */
+			for(; p<pend; p+=3)
+			{
+				SWAP(0,2)
+			}
+		break;
+		case 4: /* ABCD -> DCBA */
+#ifdef HAVE_BYTESWAP_H
+		{
+			uint32_t* pp = (uint32_t*)p;
+			for(; pp<(uint32_t*)pend; ++pp)
+				*pp = bswap_32(*pp);
+		}
+#else
+			for(; p<pend; p+=4)
+			{
+				SWAP(0,3)
+				SWAP(1,2)
+			}
+#endif
+		break;
+		case 8: /* ABCDEFGH -> HGFEDCBA */
+#ifdef HAVE_BYTESWAP_H
+		{
+			uint64_t* pp = (uint64_t*)p;
+			for(; pp<(uint64_t*)pend; ++pp)
+				*pp = bswap_64(*pp);
+		}
+#else
+			for(; p<pend; p+=8)
+			{
+				SWAP(0,7)
+				SWAP(1,6)
+				SWAP(2,5)
+				SWAP(3,4)
+			}
+#endif
+		break;
+		/* All the weird choices with the full nested loop. */
+		default:
+			for(; p<pend; p+=samplesize)
+			{
+				size_t j;
+				for(j=0; j<samplesize/2; ++j)
+				{
+					SWAP(j, samplesize-j-1)
+				}
+			}
+	}
+}
+
+#undef SWAP