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// Copyright (c) 2010 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_
#pragma once
#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>(STLContainer *ptr) : container_ptr_(ptr) {}
~STLElementDeleter<STLContainer>() { 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>(STLContainer *ptr) : container_ptr_(ptr) {}
~STLValueDeleter<STLContainer>() { 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;
}
// 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();
}
#endif // BASE_STL_UTIL_INL_H_