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 // Copyright (c) 2006-2008 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.

 // STL utility functions.  Usually, these replace built-in, but slow(!),

 // STL functions with more efficient versions.

 #ifndef BASE_STL_UTIL_INL_H_

 #define BASE_STL_UTIL_INL_H_

 #include <string.h>  // for memcpy

 #include <functional>

 #include <set>

 #include <string>

 #include <vector>

 #include <cassert>

 // Clear 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);

   obj->reserve(0);  // this is because sometimes "T tmp" allocates objects with

                     // memory (arena implementation?).  use reserve()

                     // to clear() even if it doesn't always work

 }

 // Reduce memory usage on behalf of object if it is using more than

 // "bytes" bytes of space.  By default, we clear objects over 1MB.

 template <class T> inline void STLClearIfBig(T* obj, size_t limit = 1<<20) {

   if (obj->capacity() >= limit) {

     STLClearObject(obj);

   } else {

     obj->clear();

   }

 }

 // Reserve space for STL object.

 // STL's reserve() will always copy.

 // This function avoid the copy if we already have capacity

 template<class T> void STLReserveIfNeeded(T* obj, int new_size) {

   if (obj->capacity() < new_size)   // increase capacity

     obj->reserve(new_size);

   else if (obj->size() > new_size)  // reduce size

     obj->resize(new_size);

 }

 // STLDeleteContainerPointers()

 //  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;

   }

 }

 // STLDeleteContainerPairPointers()

 //  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;

   }

 }

 // STLDeleteContainerPairFirstPointers()

 //  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;

   }

 }

 // STLDeleteContainerPairSecondPointers()

 //  For a range within a container of pairs, calls delete

 //  (non-array version) on the SECOND item in the pairs.

 template <class ForwardIterator>

 void STLDeleteContainerPairSecondPointers(ForwardIterator begin,

                                           ForwardIterator end) {

   while (begin != end) {

     delete begin->second;

     ++begin;

   }

 }

 template<typename T>

 inline void STLAssignToVector(std::vector<T>* vec,

                               const T* ptr,

                               size_t n) {

   vec->resize(n);

   memcpy(&vec->front(), ptr, n*sizeof(T));

 }

 /***** Hack to allow faster assignment to a vector *****/

 // This routine speeds up an assignment of 32 bytes to a vector from

 // about 250 cycles per assignment to about 140 cycles.

 //

 // Usage:

 //      STLAssignToVectorChar(&vec, ptr, size);

 //      STLAssignToString(&str, ptr, size);

 inline void STLAssignToVectorChar(std::vector<char>* vec,

                                   const char* ptr,

                                   size_t n) {

   STLAssignToVector(vec, ptr, n);

 }

 inline void STLAssignToString(std::string* str, const char* ptr, size_t n) {

   str->resize(n);

   memcpy(&*str->begin(), ptr, n);

 }

 // 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 allowed to dump core if v is empty.  This

 // function is the most efficient code that will work, taking into

 // account how our STL is actually implemented.  THIS IS NON-PORTABLE

 // CODE, so call us instead of repeating the nonportable code

 // everywhere.  If our STL implementation changes, we will need to

 // change this as well.

 template<typename T>

 inline T* vector_as_array(std::vector<T>* v) {

 # ifdef NDEBUG

   return &*v->begin();

 # else

   return v->empty() ? NULL : &*v->begin();

 # endif

 }

 template<typename T>

 inline const T* vector_as_array(const std::vector<T>* v) {

 # ifdef NDEBUG

   return &*v->begin();

 # else

   return v->empty() ? NULL : &*v->begin();

 # endif

 }

 // 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())! See the unittest for why.

   return str->empty() ? NULL : &*str->begin();

 }

 // These are methods that test two hash maps/sets for equality.  These exist

 // because the == operator in the STL can return false when the maps/sets

 // contain identical elements.  This is because it compares the internal hash

 // tables which may be different if the order of insertions and deletions

 // differed.

 template <class HashSet>

 inline bool

 HashSetEquality(const HashSet& set_a,

                 const HashSet& set_b) {

   if (set_a.size() != set_b.size()) return false;

   for (typename HashSet::const_iterator i = set_a.begin();

        i != set_a.end();

        ++i) {

     if (set_b.find(*i) == set_b.end())

       return false;

   }

   return true;

 }

 template <class HashMap>

 inline bool

 HashMapEquality(const HashMap& map_a,

                 const HashMap& map_b) {

   if (map_a.size() != map_b.size()) return false;

   for (typename HashMap::const_iterator i = map_a.begin();

        i != map_a.end(); ++i) {

     typename HashMap::const_iterator j = map_b.find(i->first);

     if (j == map_b.end()) return false;

     if (i->second != j->second) return false;

   }

   return true;

 }

 // 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 *v) {

   if (!v) return;

   for (typename T::iterator i = v->begin(); i != v->end(); ++i) {

     delete i->second;

   }

   v->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 STLContainer> class STLElementDeleter {

  public:

   STLElementDeleter(STLContainer *ptr) : container_ptr_(ptr) {}

   ~STLElementDeleter() { STLDeleteElements(container_ptr_); }

  private:

   STLContainer *container_ptr_;

 };

 // Given a pointer to an STL container this class will delete all the value

 // pointers when it goes out of scope.

 template<class STLContainer> class STLValueDeleter {

  public:

   STLValueDeleter(STLContainer *ptr) : container_ptr_(ptr) {}

   ~STLValueDeleter() { STLDeleteValues(container_ptr_); }

  private:

   STLContainer *container_ptr_;

 };

 // Forward declare some callback classes in callback.h for STLBinaryFunction

 template <class R, class T1, class T2>

 class ResultCallback2;

 // STLBinaryFunction is a wrapper for the ResultCallback2 class in callback.h

 // It provides an operator () method instead of a Run method, so it may be

 // passed to STL functions in <algorithm>.

 //

 // The client should create callback with NewPermanentCallback, and should

 // delete callback after it is done using the STLBinaryFunction.

 template <class Result, class Arg1, class Arg2>

 class STLBinaryFunction : public std::binary_function<Arg1, Arg2, Result> {

  public:

   typedef ResultCallback2<Result, Arg1, Arg2> Callback;

   STLBinaryFunction(Callback* callback)

     : callback_(callback) {

     assert(callback_);

   }

   Result operator() (Arg1 arg1, Arg2 arg2) {

     return callback_->Run(arg1, arg2);

   }

  private:

   Callback* callback_;

 };

 // STLBinaryPredicate is a specialized version of STLBinaryFunction, where the

 // return type is bool and both arguments have type Arg.  It can be used

 // wherever STL requires a StrictWeakOrdering, such as in sort() or

 // lower_bound().

 //

 // templated typedefs are not supported, so instead we use inheritance.

 template <class Arg>

 class STLBinaryPredicate : public STLBinaryFunction<bool, Arg, Arg> {

  public:

   typedef typename STLBinaryPredicate<Arg>::Callback Callback;

   STLBinaryPredicate(Callback* callback)

     : STLBinaryFunction<bool, Arg, Arg>(callback) {

   }

 };

 // Functors that compose arbitrary unary and binary functions with a

 // function that "projects" one of the members of a pair.

 // Specifically, if p1 and p2, respectively, are the functions that

 // map a pair to its first and second, respectively, members, the

 // table below summarizes the functions that can be constructed:

 //

 // * UnaryOperate1st<pair>(f) returns the function x -> f(p1(x))

 // * UnaryOperate2nd<pair>(f) returns the function x -> f(p2(x))

 // * BinaryOperate1st<pair>(f) returns the function (x,y) -> f(p1(x),p1(y))

 // * BinaryOperate2nd<pair>(f) returns the function (x,y) -> f(p2(x),p2(y))

 //

 // A typical usage for these functions would be when iterating over

 // the contents of an STL map. For other sample usage, see the unittest.

 template<typename Pair, typename UnaryOp>

 class UnaryOperateOnFirst

     : public std::unary_function<Pair, typename UnaryOp::result_type> {

  public:

   UnaryOperateOnFirst() {

   }

   UnaryOperateOnFirst(const UnaryOp& f) : f_(f) {

   }

   typename UnaryOp::result_type operator()(const Pair& p) const {

     return f_(p.first);

   }

  private:

   UnaryOp f_;

 };

 template<typename Pair, typename UnaryOp>

 UnaryOperateOnFirst<Pair, UnaryOp> UnaryOperate1st(const UnaryOp& f) {

   return UnaryOperateOnFirst<Pair, UnaryOp>(f);

 }

 template<typename Pair, typename UnaryOp>

 class UnaryOperateOnSecond

     : public std::unary_function<Pair, typename UnaryOp::result_type> {

  public:

   UnaryOperateOnSecond() {

   }

   UnaryOperateOnSecond(const UnaryOp& f) : f_(f) {

   }

   typename UnaryOp::result_type operator()(const Pair& p) const {

     return f_(p.second);

   }

  private:

   UnaryOp f_;

 };

 template<typename Pair, typename UnaryOp>

 UnaryOperateOnSecond<Pair, UnaryOp> UnaryOperate2nd(const UnaryOp& f) {

   return UnaryOperateOnSecond<Pair, UnaryOp>(f);

 }

 template<typename Pair, typename BinaryOp>

 class BinaryOperateOnFirst

     : public std::binary_function<Pair, Pair, typename BinaryOp::result_type> {

  public:

   BinaryOperateOnFirst() {

   }

   BinaryOperateOnFirst(const BinaryOp& f) : f_(f) {

   }

   typename BinaryOp::result_type operator()(const Pair& p1,

                                             const Pair& p2) const {

     return f_(p1.first, p2.first);

   }

  private:

   BinaryOp f_;

 };

 template<typename Pair, typename BinaryOp>

 BinaryOperateOnFirst<Pair, BinaryOp> BinaryOperate1st(const BinaryOp& f) {

   return BinaryOperateOnFirst<Pair, BinaryOp>(f);

 }

 template<typename Pair, typename BinaryOp>

 class BinaryOperateOnSecond

     : public std::binary_function<Pair, Pair, typename BinaryOp::result_type> {

  public:

   BinaryOperateOnSecond() {

   }

   BinaryOperateOnSecond(const BinaryOp& f) : f_(f) {

   }

   typename BinaryOp::result_type operator()(const Pair& p1,

                                             const Pair& p2) const {

     return f_(p1.second, p2.second);

   }

  private:

   BinaryOp f_;

 };

 template<typename Pair, typename BinaryOp>

 BinaryOperateOnSecond<Pair, BinaryOp> BinaryOperate2nd(const BinaryOp& f) {

   return BinaryOperateOnSecond<Pair, BinaryOp>(f);

 }

 // Translates a set into a vector.

 template<typename T>

 std::vector<T> SetToVector(const std::set<T>& values) {

   std::vector<T> result;

   result.reserve(values.size());

   result.insert(result.begin(), values.begin(), values.end());

   return result;

 }

 #endif  // BASE_STL_UTIL_INL_H_