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Simplify and generalize implementation of align(). Should be very efficient on sensible platforms, and correct everywhere.

--- a/src/opus_private.h

+++ b/src/opus_private.h

@@ -33,6 +33,8 @@

 #include "opus.h"

 #include "celt.h"

+#include <stddef.h> /* offsetof */

+

 struct OpusRepacketizer {

    unsigned char toc;

    int nb_frames;

@@ -110,15 +112,13 @@

 /* Make sure everything is properly aligned. */

 static OPUS_INLINE int align(int i)

 {

-    int size;

-    /* Alignment is determined by the max size of void*, opus_int32 and opus_val32,

-       rounded up to the nearest power of two. */

-    int tmp = (sizeof(opus_int32)-1)|(sizeof(opus_val32)-1)|(sizeof(void*)-1);

-    if (tmp == 0)

-       size = 1;

-    else

-       size = 1 << EC_ILOG(tmp);

-    return (i+size-1)&-size;

+    struct foo {char c; union { void* p; opus_int32 i; opus_val32 v; } u;};

+

+    int alignment = offsetof(struct foo, u);

+

+    /* Optimizing compilers should optimize div and multiply into and

+       for all sensible alignment values. */

+    return ((i + alignment - 1) / alignment) * alignment;

 }

 int opus_packet_parse_impl(const unsigned char *data, opus_int32 len,