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atomic_cell: add COUNTER_IN_PLACE_REVERT flag

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The general algorithm for merging counter cells involves allocating a
new buffer for the shards. However, it is expected that most of the
applies are just updating the values of existing shards and not adding
new ones, therefore can be done in place.
However, reverting the general and in-place applies requires different
logic, hence the need for an additional flag to differentiate between
them.
This commit is contained in:
Paweł Dziepak
2017-02-22 11:27:11 +00:00
parent 1e3fbddb3a
commit 7604b926e1
1 changed files with 14 additions and 0 deletions
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14
atomic_cell.hh
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@@ -59,6 +59,7 @@ private:
static constexpr int8_t EXPIRY_FLAG = 0x02; // When present, expiry field is present. Set only for live cells
static constexpr int8_t REVERT_FLAG = 0x04; // transient flag used to efficiently implement ReversiblyMergeable for atomic cells.
static constexpr int8_t COUNTER_UPDATE_FLAG = 0x08; // Cell is a counter update.
static constexpr int8_t COUNTER_IN_PLACE_REVERT = 0x10;
static constexpr unsigned flags_size = 1;
static constexpr unsigned timestamp_offset = flags_size;
static constexpr unsigned timestamp_size = 8;
@@ -76,10 +77,17 @@ private:
static bool is_revert_set(bytes_view cell) {
return cell[0] & REVERT_FLAG;
}
static bool is_counter_in_place_revert_set(bytes_view cell) {
return cell[0] & COUNTER_IN_PLACE_REVERT;
}
template<typename BytesContainer>
static void set_revert(BytesContainer& cell, bool revert) {
cell[0] = (cell[0] & ~REVERT_FLAG) | (revert * REVERT_FLAG);
}
template<typename BytesContainer>
static void set_counter_in_place_revert(BytesContainer& cell, bool flag) {
cell[0] = (cell[0] & ~COUNTER_IN_PLACE_REVERT) | (flag * COUNTER_IN_PLACE_REVERT);
}
static bool is_live(const bytes_view& cell) {
return cell[0] & LIVE_FLAG;
}
@@ -211,6 +219,9 @@ public:
bool is_revert_set() const {
return atomic_cell_type::is_revert_set(_data);
}
bool is_counter_in_place_revert_set() const {
return atomic_cell_type::is_counter_in_place_revert_set(_data);
}
bool is_live() const {
return atomic_cell_type::is_live(_data);
}
@@ -266,6 +277,9 @@ public:
void set_revert(bool revert) {
atomic_cell_type::set_revert(_data, revert);
}
void set_counter_in_place_revert(bool flag) {
atomic_cell_type::set_counter_in_place_revert(_data, flag);
}
};
class atomic_cell_view final : public atomic_cell_base<bytes_view> {