Cleanup base/stl_util

base/stl_util-inl.h

-// 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_