array_selector.h

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// Ceres Solver - A fast non-linear least squares minimizer
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// Author: darius.rueckert@fau.de (Darius Rueckert)
//
 
#ifndef G2O_CERES_PUBLIC_INTERNAL_ARRAY_SELECTOR_H_
#define G2O_CERES_PUBLIC_INTERNAL_ARRAY_SELECTOR_H_
 
#include <array>
#include <vector>
 
#include "fixed_array.h"
#include "types.h"
 
namespace g2o {
namespace ceres {
namespace internal {
 
// StaticFixedArray selects the best array implementation based on template
// arguments. If the size is not known at compile-time, pass
// ceres::DYNAMIC as a size-template argument.
//
// Three different containers are selected in different scenarios:
//
//   num_elements == DYNAMIC:
//      -> ceres::internal::FixedArray<T, max_stack_size>(size)
 
//   num_elements != DYNAMIC  &&  num_elements <= max_stack_size
//      -> std::array<T,num_elements>
 
//   num_elements != DYNAMIC  &&  num_elements >  max_stack_size
//      -> std::vector<T>(num_elements)
//
template <typename T, int NumElements, int MaxNumElementsOnStack,
          bool Dynamic = (NumElements == kDynamic),
          bool FitsOnStack = (NumElements <= MaxNumElementsOnStack)>
struct ArraySelector {};
 
template <typename T, int NumElements, int MaxNumElementsOnStack,
          bool FitsOnStack>
struct ArraySelector<T, NumElements, MaxNumElementsOnStack, true, FitsOnStack>
    : ceres::internal::FixedArray<T, MaxNumElementsOnStack> {
  explicit ArraySelector(int s)
      : ceres::internal::FixedArray<T, MaxNumElementsOnStack>(s) {}
};
 
template <typename T, int NumElements, int MaxNumElementsOnStack>
struct ArraySelector<T, NumElements, MaxNumElementsOnStack, false, true>
    : std::array<T, NumElements> {
  explicit ArraySelector(int /*s*/) {}
};
 
template <typename T, int num_elements, int max_num_elements_on_stack>
struct ArraySelector<T, num_elements, max_num_elements_on_stack, false, false>
    : std::vector<T> {
  explicit ArraySelector(int s) : std::vector<T>(s) {}
};
 
}  // namespace internal
}  // namespace ceres
}  // namespace g2o
 
#endif  // G2O_CERES_PUBLIC_INTERNAL_ARRAY_SELECTOR_H_