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Mark static_empty_bucket_ptr storage as const(expr) #95

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Mark static_empty_bucket_ptr storage as const(expr) #95

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2 changes: 1 addition & 1 deletion include/tsl/robin_growth_policy.h
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Original file line number Diff line number Diff line change
Expand Up @@ -233,7 +233,7 @@ class mod_growth_policy {
private:
static constexpr double REHASH_SIZE_MULTIPLICATION_FACTOR =
1.0 * GrowthFactor::num / GrowthFactor::den;
static const std::size_t MAX_BUCKET_COUNT =
static constexpr std::size_t MAX_BUCKET_COUNT =
std::size_t(double(std::numeric_limits<std::size_t>::max() /
REHASH_SIZE_MULTIPLICATION_FACTOR));

Expand Down
36 changes: 27 additions & 9 deletions include/tsl/robin_hash.h
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Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,11 @@ class bucket_entry_hash<true> {
truncated_hash_type m_hash;
};

/**
* Tag type to select the constexpr bucket_entry constructor.
*/
struct constexpr_last_bucket_t {};

/**
* Each bucket entry has:
* - A value of type `ValueType`.
Expand Down Expand Up @@ -182,6 +187,12 @@ class bucket_entry : public bucket_entry_hash<StoreHash> {
tsl_rh_assert(empty());
}

constexpr bucket_entry(constexpr_last_bucket_t /* ignored */) noexcept
: bucket_hash(),
m_dist_from_ideal_bucket(EMPTY_MARKER_DIST_FROM_IDEAL_BUCKET),
m_last_bucket(true),
m_value() {}

bucket_entry(const bucket_entry& other) noexcept(
std::is_nothrow_copy_constructible<value_type>::value)
: bucket_hash(other),
Expand Down Expand Up @@ -233,16 +244,19 @@ class bucket_entry : public bucket_entry_hash<StoreHash> {

bucket_entry& operator=(bucket_entry&&) = delete;

#if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
constexpr
#endif
~bucket_entry() noexcept { clear(); }

void clear() noexcept {
constexpr void clear() noexcept {
if (!empty()) {
destroy_value();
m_dist_from_ideal_bucket = EMPTY_MARKER_DIST_FROM_IDEAL_BUCKET;
}
}

bool empty() const noexcept {
constexpr bool empty() const noexcept {
return m_dist_from_ideal_bucket == EMPTY_MARKER_DIST_FROM_IDEAL_BUCKET;
}

Expand Down Expand Up @@ -311,8 +325,8 @@ class bucket_entry : public bucket_entry_hash<StoreHash> {
}

public:
static const distance_type EMPTY_MARKER_DIST_FROM_IDEAL_BUCKET = -1;
static const distance_type DIST_FROM_IDEAL_BUCKET_LIMIT = 8192;
static constexpr distance_type EMPTY_MARKER_DIST_FROM_IDEAL_BUCKET = -1;
static constexpr distance_type DIST_FROM_IDEAL_BUCKET_LIMIT = 8192;
static_assert(DIST_FROM_IDEAL_BUCKET_LIMIT <=
std::numeric_limits<distance_type>::max() - 1,
"DIST_FROM_IDEAL_BUCKET_LIMIT must be <= "
Expand Down Expand Up @@ -1560,7 +1574,7 @@ class robin_hash : private Hash, private KeyEqual, private GrowthPolicy {
}

public:
static const size_type DEFAULT_INIT_BUCKETS_SIZE = 0;
static constexpr size_type DEFAULT_INIT_BUCKETS_SIZE = 0;

static constexpr float DEFAULT_MAX_LOAD_FACTOR = 0.5f;
static constexpr float MINIMUM_MAX_LOAD_FACTOR = 0.2f;
Expand All @@ -1581,16 +1595,20 @@ class robin_hash : private Hash, private KeyEqual, private GrowthPolicy {
/**
* Protocol version currenlty used for serialization.
*/
static const slz_size_type SERIALIZATION_PROTOCOL_VERSION = 1;
static constexpr slz_size_type SERIALIZATION_PROTOCOL_VERSION = 1;

/**
* Return an always valid pointer to an static empty bucket_entry with
* last_bucket() == true.
* last_bucket() == true. The bucket_entry must be treated as `const`.
*/
bucket_entry* static_empty_bucket_ptr() noexcept {
static bucket_entry empty_bucket(true);
#if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
static constexpr bucket_entry empty_bucket(constexpr_last_bucket_t{});
#else
static const bucket_entry empty_bucket(constexpr_last_bucket_t{});
#endif
tsl_rh_assert(empty_bucket.empty());
return &empty_bucket;
return const_cast<bucket_entry*>(&empty_bucket);
}

private:
Expand Down