dart::SimpleHashMap Class Reference

#include <hashmap.h>

Classes
struct	Entry

Public Types
typedef bool(*	MatchFun) (void *key1, void *key2)
typedef void(*	ClearFun) (void *value)

Public Member Functions
	SimpleHashMap (MatchFun match, uint32_t initial_capacity)
	~SimpleHashMap ()
Entry *	Lookup (void *key, uint32_t hash, bool insert)
void	Remove (void *key, uint32_t hash)
void	Clear (ClearFun clear=nullptr)
intptr_t	size () const
intptr_t	capacity () const
Entry *	Start () const
Entry *	Next (Entry *p) const

Static Public Member Functions
static bool	SamePointerValue (void *key1, void *key2)
static uint32_t	StringHash (const char *key)
static bool	SameStringValue (void *key1, void *key2)

Friends
class	IntSet

Detailed Description

Definition at line 12 of file hashmap.h.

Member Typedef Documentation

ClearFun

typedef void(* dart::SimpleHashMap::ClearFun) (void *value)

Definition at line 16 of file hashmap.h.

MatchFun

typedef bool(* dart::SimpleHashMap::MatchFun) (void *key1, void *key2)

Definition at line 14 of file hashmap.h.

Constructor & Destructor Documentation

SimpleHashMap()

dart::SimpleHashMap::SimpleHashMap	(	MatchFun	match,
		uint32_t	initial_capacity
	)

Definition at line 11 of file hashmap.cc.

                                                                      {
  match_ = match;
  Initialize(initial_capacity);
}

~SimpleHashMap()

dart::SimpleHashMap::~SimpleHashMap

(

)

Definition at line 16 of file hashmap.cc.

                              {
  delete[] map_;
}

Member Function Documentation

capacity()

intptr_t dart::SimpleHashMap::capacity ( ) const

inline

Definition at line 79 of file hashmap.h.

{ return capacity_; }

Clear()

void dart::SimpleHashMap::Clear

(

ClearFun

clear = nullptr

)

Definition at line 111 of file hashmap.cc.

                                        {
  // Mark all entries as empty.
  const Entry* end = map_end();
  for (Entry* p = map_; p < end; p++) {
    if ((clear != nullptr) && (p->key != nullptr)) {
      clear(p->value);
    }
    p->key = nullptr;
  }
  occupancy_ = 0;
}

Lookup()

SimpleHashMap::Entry * dart::SimpleHashMap::Lookup	(	void *	key,
		uint32_t	hash,
		bool	insert
	)

Definition at line 20 of file hashmap.cc.

                                                         {
  // Find a matching entry.
  Entry* p = Probe(key, hash);
  if (p->key != nullptr) {
    return p;
  }
 
  // No entry found; insert one if necessary.
  if (insert) {
    p->key = key;
    p->value = nullptr;
    p->hash = hash;
    occupancy_++;
 
    // Grow the map if we reached >= 80% occupancy.
    if ((occupancy_ + (occupancy_ / 4)) >= capacity_) {
      Resize();
      p = Probe(key, hash);
    }
 
    return p;
  }
 
  // No entry found and none inserted.
  return nullptr;
}

Next()

SimpleHashMap::Entry * dart::SimpleHashMap::Next

(

Entry *

p

)

const

Definition at line 127 of file hashmap.cc.

                                                      {
  const Entry* end = map_end();
  ASSERT(map_ - 1 <= p && p < end);
  for (p++; p < end; p++) {
    if (p->key != nullptr) {
      return p;
    }
  }
  return nullptr;
}

Remove()

void dart::SimpleHashMap::Remove	(	void *	key,
		uint32_t	hash
	)

Definition at line 49 of file hashmap.cc.

                                                   {
  // Lookup the entry for the key to remove.
  Entry* candidate = Probe(key, hash);
  if (candidate->key == nullptr) {
    // Key not found nothing to remove.
    return;
  }
 
  // To remove an entry we need to ensure that it does not create an empty
  // entry that will cause the search for another entry to stop too soon. If all
  // the entries between the entry to remove and the next empty slot have their
  // initial position inside this interval, clearing the entry to remove will
  // not break the search. If, while searching for the next empty entry, an
  // entry is encountered which does not have its initial position between the
  // entry to remove and the position looked at, then this entry can be moved to
  // the place of the entry to remove without breaking the search for it. The
  // entry made vacant by this move is now the entry to remove and the process
  // starts over.
  // Algorithm from http://en.wikipedia.org/wiki/Open_addressing.
 
  // This guarantees loop termination as there is at least one empty entry so
  // eventually the removed entry will have an empty entry after it.
  ASSERT(occupancy_ < capacity_);
 
  // "candidate" is the candidate entry to clear. "next" is used to scan
  // forwards.
  Entry* next = candidate;  // Start at the entry to remove.
  while (true) {
    // Move "next" to the next entry. Wrap when at the end of the array.
    next = next + 1;
    if (next == map_end()) {
      next = map_;
    }
 
    // All entries between "candidate" and "next" have their initial position
    // between candidate and entry and the entry candidate can be cleared
    // without breaking the search for these entries.
    if (next->key == nullptr) {
      break;
    }
 
    // Find the initial position for the entry at position "next". That is
    // the entry where searching for the entry at position "next" will
    // actually start.
    Entry* start = map_ + (next->hash & (capacity_ - 1));
 
    // If the entry at position "next" has its initial position outside the
    // range between "candidate" and "next" it can be moved forward to
    // position "candidate" and will still be found. There is now the new
    // candidate entry for clearing.
    if ((next > candidate && (start <= candidate || start > next)) ||
        (next < candidate && (start <= candidate && start > next))) {
      *candidate = *next;
      candidate = next;
    }
  }
 
  // Clear the candidate which will not break searching the hash table.
  candidate->key = nullptr;
  occupancy_--;
}

SamePointerValue()

static bool dart::SimpleHashMap::SamePointerValue ( void *  key1, void *  key2  )

inlinestatic

Definition at line 24 of file hashmap.h.

{ return key1 == key2; }

SameStringValue()

static bool dart::SimpleHashMap::SameStringValue ( void *  key1, void *  key2  )

inlinestatic

Definition at line 41 of file hashmap.h.

                                                      {
    return strcmp(reinterpret_cast<char*>(key1),
                  reinterpret_cast<char*>(key2)) == 0;
  }

size()

intptr_t dart::SimpleHashMap::size ( ) const

inline

Definition at line 74 of file hashmap.h.

{ return occupancy_; }

Start()

SimpleHashMap::Entry * dart::SimpleHashMap::Start

(

)

const

Definition at line 123 of file hashmap.cc.

                                               {
  return Next(map_ - 1);
}

StringHash()

static uint32_t dart::SimpleHashMap::StringHash ( const char *  key )

inlinestatic

Definition at line 26 of file hashmap.h.

                                              {
    uint32_t hash_ = 0;
    if (key == nullptr) return hash_;
    int len = strlen(key);
    for (int i = 0; i < len; i++) {
      hash_ += key[i];
      hash_ += hash_ << 10;
      hash_ ^= hash_ >> 6;
    }
    hash_ += hash_ << 3;
    hash_ ^= hash_ >> 11;
    hash_ += hash_ << 15;
    return hash_ == 0 ? 1 : hash_;
  }

Friends And Related Symbol Documentation

IntSet

friend class IntSet

friend

Definition at line 103 of file hashmap.h.

---

The documentation for this class was generated from the following files:

• third_party/dart-lang/sdk/runtime/platform/hashmap.h
• third_party/dart-lang/sdk/runtime/platform/hashmap.cc