[PATCH 1/2] add COPY_ARRAY
- From
René Scharfe <l.s.r@web.de>
- Date
- Sep 25, 2016, 07:15 UTC
- Message-ID
- <6f402d35-b483-7552-2fb2-a5350112b8a6@web.de>
Add COPY_ARRAY, a safe and convenient helper for copying arrays, complementing ALLOC_ARRAY and REALLOC_ARRAY. Users just specify source, destination and the number of elements; the size of an element is inferred automatically.
It checks if the multiplication of size and element count overflows. The inferred size is passed first to st_mult, which allows the division there to be done at compilation time.
As a basic type safety check it makes sure the sizes of source and destination elements are the same. That's evaluated at compilation time as well.
COPY_ARRAY is safe to use with NULL as source pointer iff 0 elements are to be copied. That convention is used in some cases for initializing arrays. Raw memcpy(3) does not support it -- compilers are allowed to assume that only valid pointers are passed to it and can optimize away NULL checks after such a call.
Signed-off-by: Rene Scharfe <l.s.r@web.de> --- git-compat-util.h | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/git-compat-util.h b/git-compat-util.h index 37cce07..91775ce 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -801,6 +801,14 @@ extern FILE *fopen_for_writing(const char *path); #define ALLOC_ARRAY(x, alloc) (x) = xmalloc(st_mult(sizeof(*(x)), (alloc))) #define REALLOC_ARRAY(x, alloc) (x) = xrealloc((x), st_mult(sizeof(*(x)), (alloc))) +#define COPY_ARRAY(dst, src, n) copy_array((dst), (src), (n), sizeof(*(dst)) + \ + BUILD_ASSERT_OR_ZERO(sizeof(*(dst)) == sizeof(*(src)))) +static inline void copy_array(void *dst, const void *src, size_t n, size_t size) +{ + if (n) + memcpy(dst, src, st_mult(size, n)); +} + /* * These functions help you allocate structs with flex arrays, and copy * the data directly into the array. For example, if you had:
-- 2.10.0