// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Derived from google3/util/gtl/stl_util.h
#ifndef BASE_STL_UTIL_H_
#define BASE_STL_UTIL_H_
#include <algorithm>
#include <functional>
#include <iterator>
#include <string>
#include <vector>
#include "base/logging.h"
// Clears internal memory of an STL object.
// STL clear()/reserve(0) does not always free internal memory allocated
// This function uses swap/destructor to ensure the internal memory is freed.
template<class T>
void STLClearObject(T* obj) {
T tmp;
tmp.swap(*obj);
// Sometimes "T tmp" allocates objects with memory (arena implementation?).
// Hence using additional reserve(0) even if it doesn't always work.
obj->reserve(0);
}
// For a range within a container of pointers, calls delete (non-array version)
// on these pointers.
// NOTE: for these three functions, we could just implement a DeleteObject
// functor and then call for_each() on the range and functor, but this
// requires us to pull in all of algorithm.h, which seems expensive.
// For hash_[multi]set, it is important that this deletes behind the iterator
// because the hash_set may call the hash function on the iterator when it is
// advanced, which could result in the hash function trying to deference a
// stale pointer.
template <class ForwardIterator>
void STLDeleteContainerPointers(ForwardIterator begin, ForwardIterator end) {
while (begin != end) {
ForwardIterator temp = begin;
++begin;
delete *temp;
}
}
// For a range within a container of pairs, calls delete (non-array version) on
// BOTH items in the pairs.
// NOTE: Like STLDeleteContainerPointers, it is important that this deletes
// behind the iterator because if both the key and value are deleted, the
// container may call the hash function on the iterator when it is advanced,
// which could result in the hash function trying to dereference a stale
// pointer.
template <class ForwardIterator>
void STLDeleteContainerPairPointers(ForwardIterator begin,
ForwardIterator end) {
while (begin != end) {
ForwardIterator temp = begin;
++begin;
delete temp->first;
delete temp->second;
}
}
// For a range within a container of pairs, calls delete (non-array version) on
// the FIRST item in the pairs.
// NOTE: Like STLDeleteContainerPointers, deleting behind the iterator.
template <class ForwardIterator>
void STLDeleteContainerPairFirstPointers(ForwardIterator begin,
ForwardIterator end) {
while (begin != end) {
ForwardIterator temp = begin;
++begin;
delete temp->first;
}
}
// For a range within a container of pairs, calls delete.
// NOTE: Like STLDeleteContainerPointers, deleting behind the iterator.
// Deleting the value does not always invalidate the iterator, but it may
// do so if the key is a pointer into the value object.
template <class ForwardIterator>
void STLDeleteContainerPairSecondPointers(ForwardIterator begin,
ForwardIterator end) {
while (begin != end) {
ForwardIterator temp = begin;
++begin;
delete temp->second;
}
}
// To treat a possibly-empty vector as an array, use these functions.
// If you know the array will never be empty, you can use &*v.begin()
// directly, but that is undefined behaviour if |v| is empty.
template<typename T>
inline T* vector_as_array(std::vector<T>* v) {
return v->empty() ? NULL : &*v->begin();
}
template<typename T>
inline const T* vector_as_array(const std::vector<T>* v) {
return v->empty() ? NULL : &*v->begin();
}
// Return a mutable char* pointing to a string's internal buffer,
// which may not be null-terminated. Writing through this pointer will
// modify the string.
//
// string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
// next call to a string method that invalidates iterators.
//
// As of 2006-04, there is no standard-blessed way of getting a
// mutable reference to a string's internal buffer. However, issue 530
// (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#530)
// proposes this as the method. According to Matt Austern, this should
// already work on all current implementations.
inline char* string_as_array(std::string* str) {
// DO NOT USE const_cast<char*>(str->data())
return str->empty() ? NULL : &*str->begin();
}
// The following functions are useful for cleaning up STL containers whose
// elements point to allocated memory.
// STLDeleteElements() deletes all the elements in an STL container and clears
// the container. This function is suitable for use with a vector, set,
// hash_set, or any other STL container which defines sensible begin(), end(),
// and clear() methods.
//
// If container is NULL, this function is a no-op.
//
// As an alternative to calling STLDeleteElements() directly, consider
// STLElementDeleter (defined below), which ensures that your container's
// elements are deleted when the STLElementDeleter goes out of scope.
template <class T>
void STLDeleteElements(T* container) {
if (!container)
return;
STLDeleteContainerPointers(container->begin(), container->end());
container->clear();
}
// Given an STL container consisting of (key, value) pairs, STLDeleteValues
// deletes all the "value" components and clears the container. Does nothing
// in the case it's given a NULL pointer.
template <class T>
void STLDeleteValues(T* container) {
if (!container)
return;
for (typename T::iterator i(container->begin()); i != container->end(); ++i)
delete i->second;
container->clear();
}
// The following classes provide a convenient way to delete all elements or
// values from STL containers when they goes out of scope. This greatly
// simplifies code that creates temporary objects and has multiple return
// statements. Example:
//
// vector<MyProto *> tmp_proto;
// STLElementDeleter<vector<MyProto *> > d(&tmp_proto);
// if (...) return false;
// ...
// return success;
// Given a pointer to an STL container this class will delete all the element
// pointers when it goes out of scope.
template<class T>
class STLElementDeleter {
public:
STLElementDeleter<T>(T* container) : container_(container) {}
~STLElementDeleter<T>() { STLDeleteElements(container_); }
private:
T* container_;
};
// Given a pointer to an STL container this class will delete all the value
// pointers when it goes out of scope.
template<class T>
class STLValueDeleter {
public:
STLValueDeleter<T>(T* container) : container_(container) {}
~STLValueDeleter<T>() { STLDeleteValues(container_); }
private:
T* container_;
};
// Test to see if a set, map, hash_set or hash_map contains a particular key.
// Returns true if the key is in the collection.
template <typename Collection, typename Key>
bool ContainsKey(const Collection& collection, const Key& key) {
return collection.find(key) != collection.end();
}
namespace base {
// Returns true if the container is sorted.
template <typename Container>
bool STLIsSorted(const Container& cont) {
// Note: Use reverse iterator on container to ensure we only require
// value_type to implement operator<.
return std::adjacent_find(cont.rbegin(), cont.rend(),
std::less<typename Container::value_type>())
== cont.rend();
}
// Returns a new ResultType containing the difference of two sorted containers.
template <typename ResultType, typename Arg1, typename Arg2>
ResultType STLSetDifference(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
ResultType difference;
std::set_difference(a1.begin(), a1.end(),
a2.begin(), a2.end(),
std::inserter(difference, difference.end()));
return difference;
}
// Returns a new ResultType containing the union of two sorted containers.
template <typename ResultType, typename Arg1, typename Arg2>
ResultType STLSetUnion(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
ResultType result;
std::set_union(a1.begin(), a1.end(),
a2.begin(), a2.end(),
std::inserter(result, result.end()));
return result;
}
// Returns a new ResultType containing the intersection of two sorted
// containers.
template <typename ResultType, typename Arg1, typename Arg2>
ResultType STLSetIntersection(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
ResultType result;
std::set_intersection(a1.begin(), a1.end(),
a2.begin(), a2.end(),
std::inserter(result, result.end()));
return result;
}
// Returns true if the sorted container |a1| contains all elements of the sorted
// container |a2|.
template <typename Arg1, typename Arg2>
bool STLIncludes(const Arg1& a1, const Arg2& a2) {
DCHECK(STLIsSorted(a1));
DCHECK(STLIsSorted(a2));
return std::includes(a1.begin(), a1.end(),
a2.begin(), a2.end());
}
} // namespace base
#endif // BASE_STL_UTIL_H_