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pbd: clarify int62_t comments

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Mads Kiilerich 2022-11-18 22:56:55 +01:00 committed by Paul Davis
parent 3478acfcf9
commit c5e7e5c4df
1 changed files with 4 additions and 2 deletions
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6
libs/pbd/pbd/int62.h
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@ -26,7 +26,7 @@
#include <exception> #include <exception>
#include <limits> #include <limits>
/* int62_t is a class the functions as a 62 bit signed integer complete with a flag that can be used to indicate a boolean property of /* int62_t is a class that functions as a 63 bit signed integer with a flag that can be used to indicate a boolean property of
* the object. The flag is stored inside the 64 bit integer used by the object (as a single bit), and all operations on the object that * the object. The flag is stored inside the 64 bit integer used by the object (as a single bit), and all operations on the object that
* change either the flag or the value are atomic. * change either the flag or the value are atomic.
* *
@ -38,10 +38,12 @@ class alignas(16) int62_t {
protected: protected:
/* std::atomic<> takes care of memory barriers for us; the actual load and stores /* std::atomic<> takes care of memory barriers for us; the actual load and stores
are atomic on architectures that we're likely to care about. are atomic on architectures that we're likely to care about.
The 2nd highest bit is used for the flag, and the highest bit is used for the sign.
Watch out for the impact of two's complement and overflow to and from the flag bit.
*/ */
std::atomic<int64_t> v; std::atomic<int64_t> v;
/* this defines the bit used to indicate "flag" or not */ /* this defines the bit used to indicate "flag" or not: the 2nd highest bit */
static const int64_t flagbit_mask = (1LL<<62); static const int64_t flagbit_mask = (1LL<<62);
protected: protected: