Add source code of d3plot example

.gitignore

@@ -4,6 +4,7 @@ binout
 d3plot
 d3plot*
 !examples/*
+!examples/d3plot/d3plot.odin
 examples/binout/binout0000
 .xmake/
 build/

examples/d3plot/d3plot.odin

@@ -0,0 +1,61 @@
+package main
+
+import dro "../../."
+import "core:c"
+import "core:c/libc"
+import "core:fmt"
+import "core:os"
+
+main :: proc() {
+    d := dro.d3plot_open("./examples/d3plot/d3plot")
+    defer dro.d3plot_close(&d)
+    if err := d.error_string; err != nil {
+        fmt.eprintf("failed to open d3plot: {}\n", err)
+        os.exit(1)
+    }
+
+    num_nodes: c.size_t
+    node_ids := dro.d3plot_read_node_ids(&d, &num_nodes)
+    defer libc.free(rawptr(node_ids))
+
+    fmt.printf("Number of Nodes: {}\n", num_nodes)
+    fmt.printf("[")
+    for i: c.size_t; i < num_nodes; i += 1 {
+        fmt.printf("{}", node_ids[i])
+        if i != num_nodes - 1 {
+            fmt.printf(", ")
+        }
+    }
+    fmt.printf("]\n")
+
+    num_shells: c.size_t
+    shell_ids := dro.d3plot_read_shell_element_ids(&d, &num_shells)
+    defer libc.free(rawptr(shell_ids))
+
+    fmt.printf("Num Shells: {}\n", num_shells)
+    fmt.printf("[")
+    for i: c.size_t; i < num_shells; i += 1 {
+        fmt.printf("{}", shell_ids[i])
+        if i != num_shells - 1 {
+            fmt.printf(", ")
+        }
+    }
+    fmt.printf("]\n")
+
+    fmt.printf("Num States: {}\n", d.num_states)
+    for i: c.size_t; i < d.num_states; i += 1 {
+        fmt.printf("State {}={}\n", i, dro.d3plot_read_time(&d, i))
+
+        num_els, num_his: c.size_t
+        shells := dro.d3plot_read_shells_state(&d, i, &num_els, &num_his)
+        defer dro.d3plot_free_shells_state(shells)
+
+        for j: c.size_t; j < num_els; j += 1 {
+            mean := dro.d3plot_get_shell_mean(&shells[j])
+            defer dro.d3plot_free_surface(mean)
+
+            fmt.printf("Shell {}={}: {}\n", j, shell_ids[j], mean.stress)
+        }
+    }
+}
+