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* Copyright (C) 2011 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <algorithm>
#include <sstream>
#include "base/logging.h"
namespace art {
// Sort and remove duplicates of an STL vector or deque.
template<class T>
void STLSortAndRemoveDuplicates(T* v) {
std::sort(v->begin(), v->end());
v->erase(std::unique(v->begin(), v->end()), v->end());
// 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;
delete *temp;
// 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
// using a container of std::unique_ptr, which ensures that your container's
// elements are deleted when the container goes out of scope.
template <class T>
void STLDeleteElements(T *container) {
if (container != nullptr) {
STLDeleteContainerPointers(container->begin(), container->end());
// 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 != nullptr) {
for (typename T::iterator i = v->begin(); i != v->end(); ++i) {
delete i->second;
template <class T>
std::string ToString(const T& v) {
std::ostringstream os;
os << "[";
for (size_t i = 0; i < v.size(); ++i) {
os << v[i];
if (i < v.size() - 1) {
os << ", ";
os << "]";
return os.str();
// Deleter using free() for use with std::unique_ptr<>. See also UniqueCPtr<> below.
struct FreeDelete {
// NOTE: Deleting a const object is valid but free() takes a non-const pointer.
void operator()(const void* ptr) const {
// Alias for std::unique_ptr<> that uses the C function free() to delete objects.
template <typename T>
using UniqueCPtr = std::unique_ptr<T, FreeDelete>;
// C++14 from-the-future import (std::make_unique)
// Invoke the constructor of 'T' with the provided args, and wrap the result in a unique ptr.
template <typename T, typename ... Args>
std::unique_ptr<T> MakeUnique(Args&& ... args) {
return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
// Find index of the first element with the specified value known to be in the container.
template <typename Container, typename T>
size_t IndexOfElement(const Container& container, const T& value) {
auto it = std::find(container.begin(), container.end(), value);
DCHECK(it != container.end()); // Must exist.
return std::distance(container.begin(), it);
// Remove the first element with the specified value known to be in the container.
template <typename Container, typename T>
void RemoveElement(Container& container, const T& value) {
auto it = std::find(container.begin(), container.end(), value);
DCHECK(it != container.end()); // Must exist.
// Replace the first element with the specified old_value known to be in the container.
template <typename Container, typename T>
void ReplaceElement(Container& container, const T& old_value, const T& new_value) {
auto it = std::find(container.begin(), container.end(), old_value);
DCHECK(it != container.end()); // Must exist.
*it = new_value;
// Search for an element with the specified value and return true if it was found, false otherwise.
template <typename Container, typename T>
bool ContainsElement(const Container& container, const T& value, size_t start_pos = 0u) {
DCHECK_LE(start_pos, container.size());
auto start = container.begin();
std::advance(start, start_pos);
auto it = std::find(start, container.end(), value);
return it != container.end();
// const char* compare function suitable for std::map or std::set.
struct CStringLess {
bool operator()(const char* lhs, const char* rhs) const {
return strcmp(lhs, rhs) < 0;
// 32-bit FNV-1a hash function suitable for std::unordered_map.
// It can be used with any container which works with range-based for loop.
// See
template <typename Vector>
struct FNVHash {
size_t operator()(const Vector& vector) const {
uint32_t hash = 2166136261u;
for (const auto& value : vector) {
hash = (hash ^ value) * 16777619u;
return hash;
// Use to suppress type deduction for a function argument.
// See std::identity<> for more background:
// - move/forward helpers
// e.g. "template <typename X> void bar(identity<X>::type foo);
// bar(5); // compilation error
// bar<int>(5); // ok
// or "template <typename T> void foo(T* x, typename Identity<T*>::type y);
// Base b;
// Derived d;
// foo(&b, &d); // Use implicit Derived* -> Base* conversion.
// If T was deduced from both &b and &d, there would be a mismatch, i.e. deduction failure.
template <typename T>
struct Identity {
using type = T;
} // namespace art