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MINOR: tools: make ptr_hash() support 0-bit outputs

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When dealing with macro-based size definitions, it is useful to be able
to hash pointers on zero bits so that the macro automatically returns a
constant 0. For now it only supports 1-32. Let's just add this special
case. It's automatically optimized out by the compiler since the function
is inlined.
This commit is contained in:
Willy Tarreau 2023-07-25 16:59:48 +02:00
parent 59c347c15e
commit ab6cb5dea0
1 changed files with 8 additions and 1 deletions
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9
include/haproxy/tools.h
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@ -1089,12 +1089,16 @@ static inline uint statistical_prng_range(uint range)
* fill ratio for 12 bits, ~1296 (~756 non-colliding) at 100% fill ratio for 11 * fill ratio for 12 bits, ~1296 (~756 non-colliding) at 100% fill ratio for 11
* bits, ~648 (~378 non-colliding) at 100% fill ratio for 10 bits, ~163 (95 non * bits, ~648 (~378 non-colliding) at 100% fill ratio for 10 bits, ~163 (95 non
* colliding) at 100% fill ratio for 8 bits, hence 1-1/e and 1/e respectively. * colliding) at 100% fill ratio for 8 bits, hence 1-1/e and 1/e respectively.
* It must be inlined so that <bits> is always a compile-time constant. * It must be inlined so that <bits> is always a compile-time constant. It
* supports output sizes from 0 to 32 bits.
*/ */
static forceinline uint ptr_hash(const void *p, const int bits) static forceinline uint ptr_hash(const void *p, const int bits)
{ {
unsigned long long x = (unsigned long)p; unsigned long long x = (unsigned long)p;
if (!bits)
return 0;
x *= 0xc1da9653U; x *= 0xc1da9653U;
if (sizeof(long) == 4) if (sizeof(long) == 4)
x ^= x >> 32; x ^= x >> 32;
@ -1111,6 +1115,9 @@ static forceinline uint ptr2_hash(const void *p1, const void *p2, const int bits
unsigned long long x = (unsigned long)p1; unsigned long long x = (unsigned long)p1;
unsigned long long y = (unsigned long)p2; unsigned long long y = (unsigned long)p2;
if (!bits)
return 0;
x *= 0xc1da9653U; x *= 0xc1da9653U;
y *= 0x96531cadU; y *= 0x96531cadU;
x ^= y; x ^= y;