Modernize ProductParameterization.

This CL modernizes ProductParameterization in the following ways:
- It uses std::unique_ptr for memory handling instead of using raw
  pointers and handmade memory management.
- Replaces the constructors with a variadic template.

Change-Id: I5c9fe42ac935b6c26e867dbd3369a4c766623047

include/ceres/local_parameterization.h

@@ -32,9 +32,11 @@
 #ifndef CERES_PUBLIC_LOCAL_PARAMETERIZATION_H_
 #define CERES_PUBLIC_LOCAL_PARAMETERIZATION_H_
 
+#include <array>
+#include <memory>
 #include <vector>
-#include "ceres/internal/port.h"
 #include "ceres/internal/disable_warnings.h"
+#include "ceres/internal/port.h"
 
 namespace ceres {
 
@@ -269,9 +271,6 @@ class CERES_EXPORT HomogeneousVectorParameterization :
 // manifolds. For example the parameters of a camera consist of a
 // rotation and a translation, i.e., SO(3) x R^3.
 //
-// Currently this class supports taking the cartesian product of up to
-// four local parameterizations.
-//
 // Example usage:
 //
 // ProductParameterization product_param(new QuaterionionParameterization(),
@@ -282,22 +281,37 @@ class CERES_EXPORT HomogeneousVectorParameterization :
 class CERES_EXPORT ProductParameterization : public LocalParameterization {
  public:
   //
-  // NOTE: All the constructors take ownership of the input local
+  // NOTE: The constructor takes ownership of the input local
   // parameterizations.
   //
-  ProductParameterization(LocalParameterization* local_param1,
-                          LocalParameterization* local_param2);
+  template <typename... LocalParams>
+  ProductParameterization(LocalParams*... local_params)
+      : local_params_(sizeof...(LocalParams)),
+        local_size_{0},
+        global_size_{0},
+        buffer_size_{0} {
+    constexpr int kNumLocalParams = sizeof...(LocalParams);
+    static_assert(kNumLocalParams >= 2,
+                  "At least two local parameterizations must be specified.");
+
+    using LocalParameterizationPtr = std::unique_ptr<LocalParameterization>;
 
-  ProductParameterization(LocalParameterization* local_param1,
-                          LocalParameterization* local_param2,
-                          LocalParameterization* local_param3);
+    // Wrap all raw pointers into std::unique_ptr for exception safety.
+    std::array<LocalParameterizationPtr, kNumLocalParams> local_params_array{
+        LocalParameterizationPtr(local_params)...};
 
-  ProductParameterization(LocalParameterization* local_param1,
-                          LocalParameterization* local_param2,
-                          LocalParameterization* local_param3,
-                          LocalParameterization* local_param4);
+    // Initialize internal state.
+    for (int i = 0; i < kNumLocalParams; ++i) {
+      LocalParameterizationPtr& param = local_params_[i];
+      param = std::move(local_params_array[i]);
+
+      buffer_size_ =
+          std::max(buffer_size_, param->LocalSize() * param->GlobalSize());
+      global_size_ += param->GlobalSize();
+      local_size_ += param->LocalSize();
+    }
+  }
 
-  virtual ~ProductParameterization();
   virtual bool Plus(const double* x,
                     const double* delta,
                     double* x_plus_delta) const;
@@ -307,9 +321,7 @@ class CERES_EXPORT ProductParameterization : public LocalParameterization {
   virtual int LocalSize() const { return local_size_; }
 
  private:
-  void Init();
-
-  std::vector<LocalParameterization*> local_params_;
+  std::vector<std::unique_ptr<LocalParameterization>> local_params_;
   int local_size_;
   int global_size_;
   int buffer_size_;

internal/ceres/local_parameterization.cc

@@ -287,62 +287,12 @@ bool HomogeneousVectorParameterization::ComputeJacobian(
   return true;
 }
 
-ProductParameterization::ProductParameterization(
-    LocalParameterization* local_param1,
-    LocalParameterization* local_param2) {
-  local_params_.push_back(local_param1);
-  local_params_.push_back(local_param2);
-  Init();
-}
-
-ProductParameterization::ProductParameterization(
-    LocalParameterization* local_param1,
-    LocalParameterization* local_param2,
-    LocalParameterization* local_param3) {
-  local_params_.push_back(local_param1);
-  local_params_.push_back(local_param2);
-  local_params_.push_back(local_param3);
-  Init();
-}
-
-ProductParameterization::ProductParameterization(
-    LocalParameterization* local_param1,
-    LocalParameterization* local_param2,
-    LocalParameterization* local_param3,
-    LocalParameterization* local_param4) {
-  local_params_.push_back(local_param1);
-  local_params_.push_back(local_param2);
-  local_params_.push_back(local_param3);
-  local_params_.push_back(local_param4);
-  Init();
-}
-
-ProductParameterization::~ProductParameterization() {
-  for (int i = 0; i < local_params_.size(); ++i) {
-    delete local_params_[i];
-  }
-}
-
-void ProductParameterization::Init() {
-  global_size_ = 0;
-  local_size_ = 0;
-  buffer_size_ = 0;
-  for (int i = 0; i < local_params_.size(); ++i) {
-    const LocalParameterization* param = local_params_[i];
-    buffer_size_ = std::max(buffer_size_,
-                            param->LocalSize() * param->GlobalSize());
-    global_size_ += param->GlobalSize();
-    local_size_ += param->LocalSize();
-  }
-}
-
 bool ProductParameterization::Plus(const double* x,
                                    const double* delta,
                                    double* x_plus_delta) const {
   int x_cursor = 0;
   int delta_cursor = 0;
-  for (int i = 0; i < local_params_.size(); ++i) {
-    const LocalParameterization* param = local_params_[i];
+  for (const auto& param : local_params_) {
     if (!param->Plus(x + x_cursor,
                      delta + delta_cursor,
                      x_plus_delta + x_cursor)) {
@@ -363,8 +313,7 @@ bool ProductParameterization::ComputeJacobian(const double* x,
 
   int x_cursor = 0;
   int delta_cursor = 0;
-  for (int i = 0; i < local_params_.size(); ++i) {
-    const LocalParameterization* param = local_params_[i];
+  for (const auto& param : local_params_) {
     const int local_size = param->LocalSize();
     const int global_size = param->GlobalSize();