net/quic/quic_utils_chromium.h

// Copyright 2014 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.
//
// Some helpers for quic that are for chromium codebase.

#ifndef NET_QUIC_QUIC_UTILS_CHROMIUM_H_
#define NET_QUIC_QUIC_UTILS_CHROMIUM_H_

#include "base/basictypes.h"
#include "base/logging.h"

namespace net {

//
// Find*()
//

// Returns a const reference to the value associated with the given key if it
// exists. Crashes otherwise.
//
// This is intended as a replacement for operator[] as an rvalue (for reading)
// when the key is guaranteed to exist.
//
// operator[] for lookup is discouraged for several reasons:
//  * It has a side-effect of inserting missing keys
//  * It is not thread-safe (even when it is not inserting, it can still
//      choose to resize the underlying storage)
//  * It invalidates iterators (when it chooses to resize)
//  * It default constructs a value object even if it doesn't need to
//
// This version assumes the key is printable, and includes it in the fatal log
// message.
template <class Collection>
const typename Collection::value_type::second_type&
FindOrDie(const Collection& collection,
          const typename Collection::value_type::first_type& key) {
  typename Collection::const_iterator it = collection.find(key);
  CHECK(it != collection.end()) << "Map key not found: " << key;
  return it->second;
}

// Same as above, but returns a non-const reference.
template <class Collection>
typename Collection::value_type::second_type&
FindOrDie(Collection& collection,  // NOLINT
          const typename Collection::value_type::first_type& key) {
  typename Collection::iterator it = collection.find(key);
  CHECK(it != collection.end()) << "Map key not found: " << key;
  return it->second;
}

// Returns a pointer to the const value associated with the given key if it
// exists, or NULL otherwise.
template <class Collection>
const typename Collection::value_type::second_type*
FindOrNull(const Collection& collection,
           const typename Collection::value_type::first_type& key) {
  typename Collection::const_iterator it = collection.find(key);
  if (it == collection.end()) {
    return 0;
  }
  return &it->second;
}

// Same as above but returns a pointer to the non-const value.
template <class Collection>
typename Collection::value_type::second_type*
FindOrNull(Collection& collection,  // NOLINT
           const typename Collection::value_type::first_type& key) {
  typename Collection::iterator it = collection.find(key);
  if (it == collection.end()) {
    return 0;
  }
  return &it->second;
}

}  // namespace net

#endif  // NET_QUIC_QUIC_UTILS_CHROMIUM_H_