feat(C): Added C bindings

There is now a limited set of C bindings which will also be used to bind
to fotran

tests/extern/C/gridfire_evolve.c

@@ -0,0 +1,71 @@
+#include "gridfire/extern/gridfire_extern.h"
+#include <stdio.h>
+#define NUM_SPECIES 8
+
+// Define a macro to check return codes
+#define CHECK_RET_CODE(ret, ctx, msg) \
+    if (ret != 0 && ret != 1) { \
+        printf("Error %s: %s\n", msg, gf_get_last_error_message(ctx)); \
+        gf_free(ctx); \
+        return 1; \
+    }
+
+int main() {
+    void* ctx = gf_init();
+
+    const char* species_names[NUM_SPECIES];
+    species_names[0] = "H-1";
+    species_names[1] = "He-3";
+    species_names[2] = "He-4";
+    species_names[3] = "C-12";
+    species_names[4] = "N-14";
+    species_names[5] = "O-16";
+    species_names[6] = "Ne-20";
+    species_names[7] = "Mg-24";
+    const double abundances[NUM_SPECIES] = {0.702616602672027, 9.74791583949078e-06, 0.06895512307276903, 0.00025, 7.855418029399437e-05, 0.0006014411598306529, 8.103062886768109e-05, 2.151340851063217e-05};
+
+    int ret = gf_register_species(ctx, NUM_SPECIES, species_names);
+    CHECK_RET_CODE(ret, ctx, "SPECIES");
+
+    ret = gf_construct_engine_from_policy(ctx, "MAIN_SEQUENCE_POLICY", abundances, NUM_SPECIES);
+    CHECK_RET_CODE(ret, ctx, "MAIN_SEQUENCE_POLICY");
+
+    ret = gf_construct_solver_from_engine(ctx, "CVODE");
+    CHECK_RET_CODE(ret, ctx, "CVODE");
+
+    double Y_out[NUM_SPECIES];
+    double energy_out;
+    double dEps_dT;
+    double dEps_dRho;
+    double mass_lost;
+
+    ret = gf_evolve(
+        ctx,
+        abundances,
+        NUM_SPECIES,
+        1.5e7,    // Temperature in K
+        1.5e2,    // Density in g/cm^3
+        3e17,      // Time step in seconds
+        1e-12, // Initial time step in seconds
+        Y_out,
+        &energy_out,
+        &dEps_dT,
+        &dEps_dRho, &mass_lost
+    );
+
+    CHECK_RET_CODE(ret, ctx, "EVOLUTION");
+
+
+    printf("Evolved abundances:\n");
+    for (size_t i = 0; i < NUM_SPECIES; i++) {
+        printf("Species %s: %e\n", species_names[i], Y_out[i]);
+    }
+    printf("Energy output: %e\n", energy_out);
+    printf("dEps/dT: %e\n", dEps_dT);
+    printf("dEps/dRho: %e\n", dEps_dRho);
+    printf("Mass lost: %e\n", mass_lost);
+
+    gf_free(ctx);
+
+    return 0;
+}

tests/extern/C/meson.build

@@ -0,0 +1,5 @@
+executable('test_c_extern', 'gridfire_evolve.c',
+  install: false,
+  c_args: ['-Wall', '-Wextra'],
+  dependencies: [gridfire_extern_dep]
+)

tests/extern/meson.build

@@ -0,0 +1 @@
+subdir('C')

tests/meson.build

@@ -5,3 +5,4 @@ gtest_nomain_dep = dependency('gtest', main: false, required : true)
 
 # Subdirectories for unit and integration tests
 subdir('graphnet_sandbox')
+subdir('extern')