25 lines
992 B
C
25 lines
992 B
C
/* Code fragment of how to get a buffer from the heap that has a specific
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* alignment. The typical alignment is to a "page" whose size is often
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* 4096 bytes. */
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uint8_t * wrkBuff; /* will get pointer to heap allocation */
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uint8_t * wrkPos; /* will get aligned pointer within wrkBuff */
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uint32_t sz_of_aligned = 1234; /* number of aligned bytes required */
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int psz;
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#if defined(HAVE_SYSCONF) && defined(_SC_PAGESIZE)
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psz = sysconf(_SC_PAGESIZE); /* POSIX.1 (was getpagesize()) */
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#else
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psz = 4096; /* give up, pick likely figure */
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#endif
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/* perhaps use posix_memalign() instead. Yes but not always available */
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wrkBuff = (uint8_t *)malloc(sz_of_aligned + psz);
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wrkPos = (uint8_t *)(((sg_uintptr_t)wrkBuff + psz - 1) & (~(psz - 1)));
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/* The disadvantage of this approach is that it needs both wrkBuff and wrkPos
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* to be held by the application. The wrkBuff is only needed for the
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* corresponding free(), all other uses should be via wrkPos. */
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