rw_hashmap(3C++) rw_hashmap(3C++)
Namerw_hashmap - Rogue Wave library class
Synopsis
#include <rw/rwstl/hashmap.h>
rw_hashmap<K,V,Hash,EQ> map;
Description
Class rw_hashmap<K,V,Hash,EQ> maintains a collection of mappings between
K and V, implemented as a hash table of pair<const K,V> . Pairs with
duplicate keys are not allowed. Two pairs having duplicate keys is the
result of the EQ comparison, applied to the first element of each, is
TRUE. Since this is a value based collection, objects are copied into
and out of the collection. As with all classes that meet the ANSI
associative container specification, rw_hashmap provides for iterators
that reference its elements. Operations that alter the contents of
rw_hashmap may invalidate other iterators that reference the container.
Since the contents of rw_hashmap are in pseudo-random order, the only
iterator ranges that will usually make sense are the results of calling
equal_range(key), and the entire range from begin() to end().
Persistence
None
Public Typedefs
typedef K key_type;
typedef Hash key_hash;
typedef EQ key_equal;
typedef pair<K,V> value_type; // or ... "const K"
typedef (unsigned) size_type; //from rw_slist
typedef (int) difference_type; // from rw_slist
typedef (value_type&) reference;
typedef (const value_type&) const_reference; //from rw_slist
Iterators over rw_hashmap<K,V,Hash,EQ> are forward iterators.
typedef (scoped Iterator) iterator;
typedef (scoped ConstIterator) const_iterator;
Public Constructors
rw_hashmap<K,V,Hash,EQ>(size_type sz = 1024,
const Hash& h = Hash(),
const EQ& eq = EQ());
Construct an empty rw_hashmap<K,V,Hash,EQ> with sz slots, using h as the
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hash object, and eq as the equality comparator.
rw_hashmap<K,V,Hash,EQ>(const rw_hashmap<K,V,Hash,EQ>& map);
Construct an rw_hashmap<K,V,Hash,EQ> which is a copy of map. Each
element from map will be copied into self.
rw_hashmap<K,V,Hash,EQ>(const_iterator first,
const_iterator bound
size_type sz=1024,
const Hash& h = Hash(),
const EQ& eq = EQ());
Construct an rw_hashmap<K,V,Hash,EQ> with sz slots, using h as the hash
object, and eq as the equality comparator, containing a copy of each pair
referenced by the range starting with first and bounded by bound.
rw_hashmap<K,V,Hash,EQ>(const value_type* first,
const value_type* bound
size_type sz=1024,
const Hash& h = Hash(),
const EQ& eq = EQ());
Construct an rw_hashmap<K,V,Hash,EQ> with sz slots, using h as the hash
object, and eq as the equality comparator, containing a copy of each pair
referenced by the range starting with first and bounded by bound. If
there are items in the range for which the K parts of the pairs match EQ,
then only the first such item will be inserted into self.
Public Destructor
~rw_hashmap<K,V,Hash,EQ>();
The destructor releases the memory used by the container's
implementation.
Public Operators
rw_hashmap<K,V,Hash,EQ>&
operator=(const rw_hashmap<K,V,Hash,EQ>& rhs);
Sets self to have the same capacity, Hash and EQ as rhs, removes all
self's current contents, and replaces them with copies of the elements in
rhs.
bool
operator==(const rw_hashmap<K,V,Hash,EQ> & rhs) const;
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Returns true if self and rhs have the same number of elements, and for
each value_type in self, there is a value_type in rhs that has a first
part for which the EQ object in self returns true, and a second part for
which operator==() returns true. The need to test both parts means that
this operator is slightly slower than the method equal_by_keys()
described below.
V&
operator[](const key_type& key);
Returns a reference to the V part of a pair held in self which has a part
EQ to key, either by finding such a pair, or inserting one (in which case
the reference is to an instance of V created by its default constructor).
Accessors
iterator
begin();
The iterator returned references the first item in self. If self is
empty, the iterator is equal to end(). Note that because items are
stored in pseudo-random order, this iterator might reference any item
that has been stored in self.
const_iterator
begin() const;
The iterator returned references the first item in self. If self is
empty, the iterator is equal to end(). Note that because items are
stored in pseudo-random order, this iterator might reference any item
that has been stored in self.
iterator
end();
The iterator returned marks the location "off the end" of self. It may
not be dereferenced.
const_iterator
end() const;
The iterator returned marks the location "off the end" of self. It may
not be dereferenced.
pair<const_iterator, const_iterator>
equal_range(const key_type key) const;
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Returns pair<const_iterator, const_iterator>(lower_bound(key),
upper_bound(key)). Upper and lower bound have special meaning for hash-
based collections. See discussion elsewhere.
pair<iterator, iterator>
equal_range(const key_type key);
Returns pair<iterator, iterator>(lower_bound(key), upper_bound(key)).
Upper and lower bound have special meaning for hash-based collections.
See discussion elsewhere.
const_iterator
lower_bound(const key_type& key) const;
Returns the lower bound of key in self. This has a special meaning for
hash-based collections. See discussion elsewhere.
iterator
lower_bound(const key_type& key);
Returns the lower bound of key in self. This has a special meaning for
hash-based collections. See discussion elsewhere.
const_iterator
upper_bound(const key_type& key) const;
Returns the upper bound of key in self. This has a special meaning for
hash-based collections. See discussion elsewhere.
iterator
upper_bound(const key_type& key);
Returns the upper bound of key in self. This has a special meaning for
hash-based collections. See discussion elsewhere.
Const Public Member Functions
size_type
capacity() const;
Returns the number of slots in the hash table that self uses.
bool
empty() const;
Returns true if self is empty.
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float
fill_ratio() const;
Returns the result of calculating size()/capacity().
size_type
size() const;
Returns the number of pairs currently held in self.
Mutators
void
clear();
A synonym for erase(begin(),end());
size_type
erase(const key_type& key);
If there is a pair in self for which the first part is EQ to key, that
pair is removed, and 1 is returned. Otherwise, 0 is returned.
iterator
erase(iterator iter);
Removes the element referenced by iter and returns an iterator
referencing the "next" element. If iter does not reference an item in
self, the result is undefined.
iterator
erase(iterator first, iterator bound);
Removes each element in the range which begins with first and is bound by
bound. Returns an iterator referencing bound. If first does not
reference an item in self (and if first and bound are not equal), the
effect is undefined.
pair<iterator,bool>
insert(const value_type& val);
If there is no pair in self with first part EQ to the first part of val
then inserts val, returning a pair with an iterator referencing the new
element and true. Otherwise, returns a pair with an iterator referencing
the matching value_type and false.
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size_type
insert(iterator ignore, const value_type& val);
If there is no pair in self with first part EQ to the first part of val
then inserts val, returning 1. Otherwise, does nothing and returns 0.
Note that the first argument is provided only for conformance with the
ANSI associative container specification, and is ignored by the method,
since hash table look up can be done in constant time.
size_type
insert(const value_type* first, const value_type* bound);
For each element in the range beginning with first and bounded by bound,
if there is no pair in self with first part EQ to the first part of that
element, the element is copied into self, or if there is such a pair, the
element is skipped. Returns the number of elements inserted.
size_type
insert(const_iterator first, const_iterator bound);
For each element in the range beginning with first and bounded by bound,
if there is no pair in self with first part EQ to the first part of that
element, the element is copied into self, or if there is such a pair, the
element is skipped. Returns the number of elements inserted.
void
swap(rw_hashmap<K,V,Hash,EQ>& other);
Exchanges the contents of self with other including the Hash and EQ
objects. This method does not copy or destroy any of the items exchanged
but exchanges the underlying hash tables.
Special Methods for Maps
size_type
count(const key_type& key) const;
Returns 1 if self contains a pair with its first element EQ to key, else
0.
bool
equal_by_keys(const rw_hashmap<K,V,Hash,EQ>& rhs) const;
Returns true if self and rhs have the same size, and if for each
value_type in self, there is a value_type in rhs such that the EQ object
in self returns true when called for the first parts of those pairs.
Note that this method does not compare the V (second) part of the pair of
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the items, so it will run slightly faster than operator==().
const_iterator
find(const key_type& key) const;
Returns a const_iterator referencing the pair with key as its first
element if such a pair is contained in self, else returns end().
iterator
find(const key_type& key);
Returns an iterator referencing the pair with key as its first element,
if such a pair is contained in self, else returns end().
void
resize(size_type sz);
Resizes self's hash table to have sz slots; and re-hashes all self's
elements into the new table. Can be very expensive if self holds many
elements.
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