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+/* Ceres Solver - A fast non-linear least squares minimizer
+ * Copyright 2015 Google Inc. All rights reserved.
+ * http://ceres-solver.org/
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * - Neither the name of Google Inc. nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Author: mierle@gmail.com (Keir Mierle)
+ *
+ * A minimal C API for Ceres. Not all functionality is included. This API is
+ * not intended for clients of Ceres, but is instead intended for easing the
+ * process of binding Ceres to other languages.
+ *
+ * Currently this is a work in progress.
+ */
+
+#ifndef CERES_PUBLIC_C_API_H_
+#define CERES_PUBLIC_C_API_H_
+
+#include "ceres/internal/port.h"
+#include "ceres/internal/disable_warnings.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Init the Ceres private data. Must be called before anything else. */
+CERES_EXPORT void ceres_init();
+
+/* Equivalent to CostFunction::Evaluate() in the C++ API.
+ *
+ * The user may keep private information inside the opaque user_data object.
+ * The pointer here is the same one passed in the ceres_add_residual_block().
+ */
+typedef int (*ceres_cost_function_t)(void* user_data,
+                                     double** parameters,
+                                     double* residuals,
+                                     double** jacobians);
+
+/* Equivalent to LossFunction::Evaluate() from the C++ API. */
+typedef void (*ceres_loss_function_t)(void* user_data,
+                                      double squared_norm,
+                                      double out[3]);
+
+/* Create callback data for Ceres' stock loss functions.
+ *
+ * Ceres has several loss functions available by default, and these functions
+ * expose those to the C API. To use the stock loss functions, call
+ * ceres_create_*_loss_data(), which internally creates an instance of one of
+ * the stock loss functions (for example ceres::CauchyLoss), and pass the
+ * returned "loss_function_data" along with the ceres_stock_loss_function to
+ * ceres_add_residual_block().
+ *
+ * For example:
+ *
+ *   void* cauchy_loss_function_data =
+ *       ceres_create_cauchy_loss_function_data(1.2, 0.0);
+ *   ceres_problem_add_residual_block(
+ *       problem,
+ *       my_cost_function,
+ *       my_cost_function_data,
+ *       ceres_stock_loss_function,
+ *       cauchy_loss_function_data,
+ *       1,
+ *       2,
+ *       parameter_sizes,
+ *       parameter_pointers);
+ *    ...
+ *    ceres_free_stock_loss_function_data(cauchy_loss_function_data);
+ *
+ * See loss_function.h for the details of each loss function.
+ */
+CERES_EXPORT void* ceres_create_huber_loss_function_data(double a);
+CERES_EXPORT void* ceres_create_softl1_loss_function_data(double a);
+CERES_EXPORT void* ceres_create_cauchy_loss_function_data(double a);
+CERES_EXPORT void* ceres_create_arctan_loss_function_data(double a);
+CERES_EXPORT void* ceres_create_tolerant_loss_function_data(double a, double b);
+
+/* Free the given stock loss function data. */
+CERES_EXPORT void ceres_free_stock_loss_function_data(void* loss_function_data);
+
+/* This is an implementation of ceres_loss_function_t contained within Ceres
+ * itself, intended as a way to access the various stock Ceres loss functions
+ * from the C API. This should be passed to ceres_add_residual() below, in
+ * combination with a user_data pointer generated by
+ * ceres_create_stock_loss_function() above. */
+CERES_EXPORT void ceres_stock_loss_function(void* user_data,
+                                            double squared_norm,
+                                            double out[3]);
+
+/* Equivalent to Problem from the C++ API. */
+struct ceres_problem_s;
+typedef struct ceres_problem_s ceres_problem_t;
+
+struct ceres_residual_block_id_s;
+typedef struct ceres_residual_block_id_s ceres_residual_block_id_t;
+
+/* Create and destroy a problem */
+/* TODO(keir): Add options for the problem. */
+CERES_EXPORT ceres_problem_t* ceres_create_problem();
+CERES_EXPORT void ceres_free_problem(ceres_problem_t* problem);
+
+/* Add a residual block. */
+CERES_EXPORT ceres_residual_block_id_t* ceres_problem_add_residual_block(
+    ceres_problem_t* problem,
+    ceres_cost_function_t cost_function,
+    void* cost_function_data,
+    ceres_loss_function_t loss_function,
+    void* loss_function_data,
+    int num_residuals,
+    int num_parameter_blocks,
+    int* parameter_block_sizes,
+    double** parameters);
+
+CERES_EXPORT void ceres_solve(ceres_problem_t* problem);
+
+/* TODO(keir): Figure out a way to pass a config in. */
+
+#ifdef __cplusplus
+}
+#endif
+
+#include "ceres/internal/reenable_warnings.h"
+
+#endif  /* CERES_PUBLIC_C_API_H_ */