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