src/util/os_memory_aligned.h

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   3  * Copyright 2008-2010 VMware, Inc.
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  27
  28
  29 /*
  30  * Memory alignment wrappers.
  31  */
  32
  33
  34 #ifndef _OS_MEMORY_H_
  35 #error "Must not be included directly. Include os_memory.h instead"
  36 #endif
  37
  38
  39
  40 /**
  41  * Add two size_t values with integer overflow check.
  42  * TODO: leverage __builtin_add_overflow where available
  43  */
  44 static inline bool
  45 add_overflow_size_t(size_t a, size_t b, size_t *res)
  46 {
  47    *res = a + b;
  48    return *res < a || *res < b;
  49 }
  50
  51
  52 /**
  53  * Return memory on given byte alignment
  54  */
  55 static inline void *
  56 os_malloc_aligned(size_t size, size_t alignment)
  57 {
  58    char *ptr, *buf;
  59    size_t alloc_size;
  60
  61    /*
  62     * Calculate
  63     *
  64     *   alloc_size = size + alignment + sizeof(void *)
  65     *
  66     * while checking for overflow.
  67     */
  68    if (add_overflow_size_t(size, alignment, &alloc_size) ||
  69        add_overflow_size_t(alloc_size, sizeof(void *), &alloc_size)) {
  70       return NULL;
  71    }
  72
  73    ptr = (char *) os_malloc(alloc_size);
  74    if (!ptr)
  75       return NULL;
  76
  77    buf = (char *)(((uintptr_t)ptr + sizeof(void *) + alignment - 1) & ~((uintptr_t)(alignment - 1)));
  78    *(char **)(buf - sizeof(void *)) = ptr;
  79
  80    return buf;
  81 }
  82
  83
  84 /**
  85  * Free memory returned by os_malloc_aligned().
  86  */
  87 static inline void
  88 os_free_aligned(void *ptr)
  89 {
  90    if (ptr) {
  91       void **cubbyHole = (void **) ((char *) ptr - sizeof(void *));
  92       void *realAddr = *cubbyHole;
  93       os_free(realAddr);
  94    }
  95 }