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util: add portable arithmetic shift right

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Add arithmetic_shift_right function, as the behaviour for shifting right a
negative signed value is implementation-defined (see ISO/IEC 9899 §6.5.7).

Change-Id: I05d930a96e8591dc248295bff853ed9e9cb263a2
Signed-off-by: Bogdan Davidoaia <bogdan.m.davidoaia@intel.com>
This commit is contained in:
Bogdan Davidoaia 2016-06-28 14:20:46 +03:00 • committed by Inaky Perez-Gonzalez
commit bcca0dcbbd
1 changed files with 21 additions and 0 deletions
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21
include/misc/util.h
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@ -30,6 +30,8 @@ extern "C" {
#ifndef _ASMLANGUAGE
#include <stdint.h>
/* Helper to pass a int as a pointer or vice-versa.
* Those are available for 32 bits architectures:
*/
@ -66,6 +68,25 @@ static inline int is_power_of_two(unsigned int x)
{
return (x != 0) && !(x & (x - 1));
}
static inline int64_t arithmetic_shift_right(int64_t value, uint8_t shift)
{
int64_t sign_ext;
if (shift == 0) {
return value;
}
/* extract sign bit */
sign_ext = (value >> 63) & 1;
/* make all bits of sign_ext be the same as the value's sign bit */
sign_ext = -sign_ext;
/* shift value and fill opened bit positions with sign bit */
return (value >> shift) | (sign_ext << (64 - shift));
}
#endif /* !_ASMLANGUAGE */
/* KB, MB, GB */