net/quic/quic_utils_chromium.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // Some helpers for quic that are for chromium codebase.
   6
   7 #ifndef NET_QUIC_QUIC_UTILS_CHROMIUM_H_
   8 #define NET_QUIC_QUIC_UTILS_CHROMIUM_H_
   9
  10 #include "base/basictypes.h"
  11 #include "base/logging.h"
  12
  13 namespace net {
  14
  15 //
  16 // Find*()
  17 //
  18
  19 // Returns a const reference to the value associated with the given key if it
  20 // exists. Crashes otherwise.
  21 //
  22 // This is intended as a replacement for operator[] as an rvalue (for reading)
  23 // when the key is guaranteed to exist.
  24 //
  25 // operator[] for lookup is discouraged for several reasons:
  26 //  * It has a side-effect of inserting missing keys
  27 //  * It is not thread-safe (even when it is not inserting, it can still
  28 //      choose to resize the underlying storage)
  29 //  * It invalidates iterators (when it chooses to resize)
  30 //  * It default constructs a value object even if it doesn't need to
  31 //
  32 // This version assumes the key is printable, and includes it in the fatal log
  33 // message.
  34 template <class Collection>
  35 const typename Collection::value_type::second_type&
  36 FindOrDie(const Collection& collection,
  37           const typename Collection::value_type::first_type& key) {
  38   typename Collection::const_iterator it = collection.find(key);
  39   CHECK(it != collection.end()) << "Map key not found: " << key;
  40   return it->second;
  41 }
  42
  43 // Same as above, but returns a non-const reference.
  44 template <class Collection>
  45 typename Collection::value_type::second_type&
  46 FindOrDie(Collection& collection,  // NOLINT
  47           const typename Collection::value_type::first_type& key) {
  48   typename Collection::iterator it = collection.find(key);
  49   CHECK(it != collection.end()) << "Map key not found: " << key;
  50   return it->second;
  51 }
  52
  53 // Returns a pointer to the const value associated with the given key if it
  54 // exists, or NULL otherwise.
  55 template <class Collection>
  56 const typename Collection::value_type::second_type*
  57 FindOrNull(const Collection& collection,
  58            const typename Collection::value_type::first_type& key) {
  59   typename Collection::const_iterator it = collection.find(key);
  60   if (it == collection.end()) {
  61     return 0;
  62   }
  63   return &it->second;
  64 }
  65
  66 // Same as above but returns a pointer to the non-const value.
  67 template <class Collection>
  68 typename Collection::value_type::second_type*
  69 FindOrNull(Collection& collection,  // NOLINT
  70            const typename Collection::value_type::first_type& key) {
  71   typename Collection::iterator it = collection.find(key);
  72   if (it == collection.end()) {
  73     return 0;
  74   }
  75   return &it->second;
  76 }
  77
  78 }  // namespace net
  79
  80 #endif  // NET_QUIC_QUIC_UTILS_CHROMIUM_H_