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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef V4L2_CAMERA_HAL_METADATA_MAP_CONVERTER_H_
     18 #define V4L2_CAMERA_HAL_METADATA_MAP_CONVERTER_H_
     19 
     20 #include <errno.h>
     21 
     22 #include <map>
     23 #include <memory>
     24 
     25 #include "../common.h"
     26 #include "converter_interface.h"
     27 
     28 namespace v4l2_camera_hal {
     29 
     30 // A MapConverter fits values converted by a wrapped converter
     31 // to a map entry corresponding to the key with the nearest value.
     32 template <typename TMetadata, typename TV4L2, typename TMapKey>
     33 class MapConverter : public ConverterInterface<TMetadata, TV4L2> {
     34  public:
     35   MapConverter(
     36       std::shared_ptr<ConverterInterface<TMetadata, TMapKey>> wrapped_converter,
     37       std::map<TMapKey, TV4L2> conversion_map);
     38 
     39   virtual int MetadataToV4L2(TMetadata value, TV4L2* conversion) override;
     40   virtual int V4L2ToMetadata(TV4L2 value, TMetadata* conversion) override;
     41 
     42  private:
     43   std::shared_ptr<ConverterInterface<TMetadata, TMapKey>> wrapped_converter_;
     44   std::map<TMapKey, TV4L2> conversion_map_;
     45 
     46   DISALLOW_COPY_AND_ASSIGN(MapConverter);
     47 };
     48 
     49 // -----------------------------------------------------------------------------
     50 
     51 template <typename TMetadata, typename TV4L2, typename TMapKey>
     52 MapConverter<TMetadata, TV4L2, TMapKey>::MapConverter(
     53     std::shared_ptr<ConverterInterface<TMetadata, TMapKey>> wrapped_converter,
     54     std::map<TMapKey, TV4L2> conversion_map)
     55     : wrapped_converter_(std::move(wrapped_converter)),
     56       conversion_map_(conversion_map) {
     57   HAL_LOG_ENTER();
     58 }
     59 
     60 template <typename TMetadata, typename TV4L2, typename TMapKey>
     61 int MapConverter<TMetadata, TV4L2, TMapKey>::MetadataToV4L2(TMetadata value,
     62                                                             TV4L2* conversion) {
     63   HAL_LOG_ENTER();
     64 
     65   if (conversion_map_.empty()) {
     66     HAL_LOGE("Empty conversion map.");
     67     return -EINVAL;
     68   }
     69 
     70   TMapKey raw_conversion = 0;
     71   int res = wrapped_converter_->MetadataToV4L2(value, &raw_conversion);
     72   if (res) {
     73     HAL_LOGE("Failed to perform underlying conversion.");
     74     return res;
     75   }
     76 
     77   // Find nearest key.
     78   auto kv = conversion_map_.lower_bound(raw_conversion);
     79   // lower_bound finds the first >= element.
     80   if (kv == conversion_map_.begin()) {
     81     // Searching for less than the smallest key, so that will be the nearest.
     82     *conversion = kv->second;
     83   } else if (kv == conversion_map_.end()) {
     84     // Searching for greater than the largest key, so that will be the nearest.
     85     --kv;
     86     *conversion = kv->second;
     87   } else {
     88     // Since kv points to the first >= element, either that or the previous
     89     // element will be nearest.
     90     *conversion = kv->second;
     91     TMapKey diff = kv->first - raw_conversion;
     92 
     93     // Now compare to the previous. This element will be < raw conversion,
     94     // so reverse the order of the subtraction.
     95     --kv;
     96     if (raw_conversion - kv->first < diff) {
     97       *conversion = kv->second;
     98     }
     99   }
    100 
    101   return 0;
    102 }
    103 
    104 template <typename TMetadata, typename TV4L2, typename TMapKey>
    105 int MapConverter<TMetadata, TV4L2, TMapKey>::V4L2ToMetadata(
    106     TV4L2 value, TMetadata* conversion) {
    107   HAL_LOG_ENTER();
    108 
    109   // Unfortunately no bi-directional map lookup in C++.
    110   // Breaking on second, not first found so that a warning
    111   // can be given if there are multiple values.
    112   size_t count = 0;
    113   int res;
    114   for (auto kv : conversion_map_) {
    115     if (kv.second == value) {
    116       ++count;
    117       if (count == 1) {
    118         // First match.
    119         res = wrapped_converter_->V4L2ToMetadata(kv.first, conversion);
    120       } else {
    121         // second match.
    122         break;
    123       }
    124     }
    125   }
    126 
    127   if (count == 0) {
    128     HAL_LOGE("Couldn't find map conversion of V4L2 value %d.", value);
    129     return -EINVAL;
    130   } else if (count > 1) {
    131     HAL_LOGW("Multiple map conversions found for V4L2 value %d, using first.",
    132              value);
    133   }
    134   return res;
    135 }
    136 
    137 }  // namespace v4l2_camera_hal
    138 
    139 #endif  // V4L2_CAMERA_HAL_METADATA_MAP_CONVERTER_H_
    140