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#ifndef UTIL_PROBING_HASH_TABLE__
#define UTIL_PROBING_HASH_TABLE__
#include "util/exception.hh"
#include <algorithm>
#include <cstddef>
#include <functional>
#include <vector>
#include <assert.h>
#include <stdint.h>
namespace util {
/* Thrown when table grows too large */
class ProbingSizeException : public Exception {
public:
ProbingSizeException() throw() {}
~ProbingSizeException() throw() {}
};
// std::identity is an SGI extension :-(
struct IdentityHash {
template <class T> T operator()(T arg) const { return arg; }
};
/* Non-standard hash table
* Buckets must be set at the beginning and must be greater than maximum number
* of elements, else it throws ProbingSizeException.
* Memory management and initialization is externalized to make it easier to
* serialize these to disk and load them quickly.
* Uses linear probing to find value.
* Only insert and lookup operations.
*/
template <class EntryT, class HashT, class EqualT = std::equal_to<typename EntryT::Key> > class ProbingHashTable {
public:
typedef EntryT Entry;
typedef typename Entry::Key Key;
typedef const Entry *ConstIterator;
typedef Entry *MutableIterator;
typedef HashT Hash;
typedef EqualT Equal;
public:
static uint64_t Size(uint64_t entries, float multiplier) {
uint64_t buckets = std::max(entries + 1, static_cast<uint64_t>(multiplier * static_cast<float>(entries)));
return buckets * sizeof(Entry);
}
// Must be assigned to later.
ProbingHashTable() : entries_(0)
#ifdef DEBUG
, initialized_(false)
#endif
{}
ProbingHashTable(void *start, std::size_t allocated, const Key &invalid = Key(), const Hash &hash_func = Hash(), const Equal &equal_func = Equal())
: begin_(reinterpret_cast<MutableIterator>(start)),
buckets_(allocated / sizeof(Entry)),
end_(begin_ + buckets_),
invalid_(invalid),
hash_(hash_func),
equal_(equal_func),
entries_(0)
#ifdef DEBUG
, initialized_(true)
#endif
{}
template <class T> MutableIterator Insert(const T &t) {
#ifdef DEBUG
assert(initialized_);
#endif
UTIL_THROW_IF(++entries_ >= buckets_, ProbingSizeException, "Hash table with " << buckets_ << " buckets is full.");
return UncheckedInsert(t);
}
// Return true if the value was found (and not inserted). This is consistent with Find but the opposite if hash_map!
template <class T> bool FindOrInsert(const T &t, MutableIterator &out) {
#ifdef DEBUG
assert(initialized_);
#endif
for (MutableIterator i(begin_ + (hash_(t.GetKey()) % buckets_));;) {
Key got(i->GetKey());
if (equal_(got, t.GetKey())) { out = i; return true; }
if (equal_(got, invalid_)) {
UTIL_THROW_IF(++entries_ >= buckets_, ProbingSizeException, "Hash table with " << buckets_ << " buckets is full.");
*i = t;
out = i;
return false;
}
if (++i == end_) i = begin_;
}
}
void FinishedInserting() {}
void LoadedBinary() {}
// Don't change anything related to GetKey,
template <class Key> bool UnsafeMutableFind(const Key key, MutableIterator &out) {
#ifdef DEBUG
assert(initialized_);
#endif
for (MutableIterator i(begin_ + (hash_(key) % buckets_));;) {
Key got(i->GetKey());
if (equal_(got, key)) { out = i; return true; }
if (equal_(got, invalid_)) return false;
if (++i == end_) i = begin_;
}
}
template <class Key> bool Find(const Key key, ConstIterator &out) const {
#ifdef DEBUG
assert(initialized_);
#endif
for (ConstIterator i(begin_ + (hash_(key) % buckets_));;) {
Key got(i->GetKey());
if (equal_(got, key)) { out = i; return true; }
if (equal_(got, invalid_)) return false;
if (++i == end_) i = begin_;
}
}
void Clear() {
Entry invalid;
invalid.SetKey(invalid_);
std::fill(begin_, end_, invalid);
entries_ = 0;
}
// Return number of entries assuming no serialization went on.
std::size_t SizeNoSerialization() const {
return entries_;
}
// Return memory size expected by Double.
std::size_t DoubleTo() const {
return buckets_ * 2 * sizeof(Entry);
}
// Inform the table that it has double the amount of memory.
// Pass clear_new = false if you are sure the new memory is initialized
// properly (to invalid_) i.e. by mremap.
void Double(void *new_base, bool clear_new = true) {
begin_ = static_cast<MutableIterator>(new_base);
MutableIterator old_end = begin_ + buckets_;
buckets_ *= 2;
end_ = begin_ + buckets_;
if (clear_new) {
Entry invalid;
invalid.SetKey(invalid_);
std::fill(old_end, end_, invalid);
}
std::vector<Entry> rolled_over;
// Move roll-over entries to a buffer because they might not roll over anymore. This should be small.
for (MutableIterator i = begin_; i != old_end && !equal_(i->GetKey(), invalid_); ++i) {
rolled_over.push_back(*i);
i->SetKey(invalid_);
}
/* Re-insert everything. Entries might go backwards to take over a
* recently opened gap, stay, move to new territory, or wrap around. If
* an entry wraps around, it might go to a pointer greater than i (which
* can happen at the beginning) and it will be revisited to possibly fill
* in a gap created later.
*/
Entry temp;
for (MutableIterator i = begin_; i != old_end; ++i) {
if (!equal_(i->GetKey(), invalid_)) {
temp = *i;
i->SetKey(invalid_);
UncheckedInsert(temp);
}
}
// Put the roll-over entries back in.
for (typename std::vector<Entry>::const_iterator i(rolled_over.begin()); i != rolled_over.end(); ++i) {
UncheckedInsert(*i);
}
}
// Mostly for tests, check consistency of every entry.
void CheckConsistency() {
MutableIterator last;
for (last = end_ - 1; last >= begin_ && !equal_(last->GetKey(), invalid_); --last) {}
UTIL_THROW_IF(last == begin_, ProbingSizeException, "Completely full");
MutableIterator i;
// Beginning can be wrap-arounds.
for (i = begin_; !equal_(i->GetKey(), invalid_); ++i) {
MutableIterator ideal = Ideal(*i);
UTIL_THROW_IF(ideal > i && ideal <= last, Exception, "Inconsistency at position " << (i - begin_) << " should be at " << (ideal - begin_));
}
MutableIterator pre_gap = i;
for (; i != end_; ++i) {
if (equal_(i->GetKey(), invalid_)) {
pre_gap = i;
continue;
}
MutableIterator ideal = Ideal(*i);
UTIL_THROW_IF(ideal > i || ideal <= pre_gap, Exception, "Inconsistency at position " << (i - begin_) << " with ideal " << (ideal - begin_));
}
}
private:
template <class T> MutableIterator Ideal(const T &t) {
return begin_ + (hash_(t.GetKey()) % buckets_);
}
template <class T> MutableIterator UncheckedInsert(const T &t) {
for (MutableIterator i(Ideal(t));;) {
if (equal_(i->GetKey(), invalid_)) { *i = t; return i; }
if (++i == end_) { i = begin_; }
}
}
MutableIterator begin_;
std::size_t buckets_;
MutableIterator end_;
Key invalid_;
Hash hash_;
Equal equal_;
std::size_t entries_;
#ifdef DEBUG
bool initialized_;
#endif
};
} // namespace util
#endif // UTIL_PROBING_HASH_TABLE__
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