Line data    Source code

       1             : /*
       2             :  *
       3             :  *    Copyright (c) 2020 Project CHIP Authors
       4             :  *
       5             :  *    Licensed under the Apache License, Version 2.0 (the "License");
       6             :  *    you may not use this file except in compliance with the License.
       7             :  *    You may obtain a copy of the License at
       8             :  *
       9             :  *        http://www.apache.org/licenses/LICENSE-2.0
      10             :  *
      11             :  *    Unless required by applicable law or agreed to in writing, software
      12             :  *    distributed under the License is distributed on an "AS IS" BASIS,
      13             :  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      14             :  *    See the License for the specific language governing permissions and
      15             :  *    limitations under the License.
      16             :  */
      17             : 
      18             : #pragma once
      19             : 
      20             : #include "QName.h"
      21             : 
      22             : namespace mdns {
      23             : namespace Minimal {
      24             : 
      25             : /// A void* implementation that stores QNames as
      26             : ///   [ptr array] [name1] #0 [name2] #0 .... [namen] #0
      27             : ///
      28             : /// Usage:
      29             : ///   - RequiredStorageSize("some", "name", "here") provides the memory block
      30             : ///   - Build(ptr, "some", "name", "here") stores all data in [ptr]
      31             : ///
      32             : namespace FlatAllocatedQName {
      33             : 
      34         117 : inline size_t RequiredStorageSize()
      35             : {
      36         117 :     return 0;
      37             : }
      38             : 
      39             : /// Determines the memory size required to store the given qname parts.
      40             : ///
      41             : /// Example:
      42             : ///   malloc(RequiredStorageSize("myhostname", "local"));
      43             : template <typename... Args>
      44         465 : inline size_t RequiredStorageSize(QNamePart name, Args &&... rest)
      45             : {
      46             :     static_assert(CHAR_BIT == 8, "Assumption is that names can be stored in 1 byte");
      47             : 
      48             :     // need to store a pointer entry in the array, the name and null terminator plus
      49             :     // the rest of the data
      50         465 :     return sizeof(QNamePart) + strlen(name) + 1 + RequiredStorageSize(std::forward<Args>(rest)...);
      51             : }
      52             : 
      53          20 : inline size_t RequiredStorageSizeFromArray(char const * const * names, size_t num)
      54             : {
      55          20 :     size_t ret = 0;
      56         108 :     for (size_t i = 0; i < num; ++i)
      57             :     {
      58          88 :         ret += sizeof(QNamePart) + strlen(names[i]) + 1;
      59             :     }
      60          20 :     return ret;
      61             : }
      62             : namespace Internal {
      63             : 
      64             : // nothing left to initialize
      65         205 : inline void Initialize(QNamePart * ptrLocation, char * nameLocation) {}
      66             : 
      67             : template <typename... Args>
      68         553 : inline void Initialize(QNamePart * ptrLocation, char * nameLocation, const char * name, Args &&... rest)
      69             : {
      70         553 :     *ptrLocation = nameLocation;
      71         553 :     strcpy(nameLocation, name);
      72             : 
      73         553 :     Initialize(ptrLocation + 1, nameLocation + strlen(nameLocation) + 1, std::forward<Args>(rest)...);
      74         553 : }
      75             : 
      76             : } // namespace Internal
      77             : 
      78             : /// Builds a qname inside the given storage.
      79             : ///
      80             : /// storage MUST be aligned to hold pointers
      81             : ///
      82             : /// Example:
      83             : ///   void * data = malloc(RequiredStorageSize("myhostname", "local"));
      84             : ///   FullQName value = Build(data, "myhostname", "local");
      85             : template <typename... Args>
      86         117 : inline FullQName Build(void * storage, Args &&... args)
      87             : {
      88         117 :     QNamePart * names = reinterpret_cast<QNamePart *>(storage);
      89         117 :     char * nameOut    = reinterpret_cast<char *>(names + sizeof...(args));
      90             : 
      91         117 :     Internal::Initialize(names, nameOut, std::forward<Args>(args)...);
      92             : 
      93         117 :     FullQName result;
      94         117 :     result.names     = names;
      95         117 :     result.nameCount = sizeof...(args);
      96         117 :     return result;
      97             : }
      98             : 
      99          20 : inline FullQName BuildFromArray(void * storage, char const * const * parts, size_t num)
     100             : {
     101             :     // Storage memory holds pointers to each name, then copies of the names after
     102          20 :     QNamePart * names = reinterpret_cast<QNamePart *>(storage);
     103          20 :     char * nameOut    = reinterpret_cast<char *>(names + num);
     104         108 :     for (size_t i = 0; i < num; ++i)
     105             :     {
     106          88 :         QNamePart * ptrLocation = names + i;
     107          88 :         Internal::Initialize(ptrLocation, nameOut, parts[i]);
     108          88 :         nameOut += strlen(parts[i]) + 1;
     109             :     }
     110          20 :     FullQName result;
     111          20 :     result.names     = names;
     112          20 :     result.nameCount = num;
     113          20 :     return result;
     114             : }
     115             : 
     116             : } // namespace FlatAllocatedQName
     117             : 
     118             : } // namespace Minimal
     119             : } // namespace mdns