xref: /external/chromium_org/third_party/protobuf/src/google/protobuf/stubs/map-util.h

// Protocol Buffers - Google's data interchange format
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// http://code.google.com/p/protobuf/
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// from google3/util/gtl/map-util.h
// Author: Anton Carver

#ifndef GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
#define GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__

#include <google/protobuf/stubs/common.h>

namespace google {
namespace protobuf {

// Perform a lookup in a map or hash_map.
// If the key is present in the map then the value associated with that
// key is returned, otherwise the value passed as a default is returned.
template <class Collection>
const typename Collection::value_type::second_type&
FindWithDefault(const Collection& collection,
                const typename Collection::value_type::first_type& key,
                const typename Collection::value_type::second_type& value) {
  typename Collection::const_iterator it = collection.find(key);
  if (it == collection.end()) {
    return value;
  }
  return it->second;
}

// Perform a lookup in a map or hash_map.
// If the key is present a const pointer to the associated value is returned,
// otherwise a NULL pointer is returned.
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;
}

// Perform a lookup in a map or hash_map, assuming that the key exists.
// Crash if it does not.
//
// This is intended as a replacement for operator[] as an rvalue (for reading)
// when the key is guaranteed to exist.
//
// operator[] 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);
  GOOGLE_CHECK(it != collection.end()) << "Map key not found: " << key;
  return it->second;
}

// Perform a lookup in a map or hash_map whose values are pointers.
// If the key is present a const pointer to the associated value is returned,
// otherwise a NULL pointer is returned.
// This function does not distinguish between a missing key and a key mapped
// to a NULL value.
template <class Collection>
const typename Collection::value_type::second_type
FindPtrOrNull(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;
}

// Change the value associated with a particular key in a map or hash_map.
// If the key is not present in the map the key and value are inserted,
// otherwise the value is updated to be a copy of the value provided.
// True indicates that an insert took place, false indicates an update.
template <class Collection, class Key, class Value>
bool InsertOrUpdate(Collection * const collection,
                   const Key& key, const Value& value) {
  pair<typename Collection::iterator, bool> ret =
    collection->insert(typename Collection::value_type(key, value));
  if (!ret.second) {
    // update
    ret.first->second = value;
    return false;
  }
  return true;
}

// Insert a new key and value into a map or hash_map.
// If the key is not present in the map the key and value are
// inserted, otherwise nothing happens. True indicates that an insert
// took place, false indicates the key was already present.
template <class Collection, class Key, class Value>
bool InsertIfNotPresent(Collection * const collection,
                        const Key& key, const Value& value) {
  pair<typename Collection::iterator, bool> ret =
    collection->insert(typename Collection::value_type(key, value));
  return ret.second;
}

}  // namespace protobuf
}  // namespace google

#endif  // GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__