Adding initial coroutine library with simple example/test.

test/coroutine.c

@@ -0,0 +1,92 @@
+/* printf, perror */
+#include <stdio.h>
+/* EXIT_SUCCESS, EXIT_FAILURE */
+#include <stdlib.h>
+
+/* ... */
+#include <threadless/coroutine.h>
+
+
+static void *fibonacci_generator(coroutine *coro, void *data)
+{
+    size_t x = 0;
+    size_t y = 1;
+
+    /* ignore initial input data */
+    (void) data;
+
+    /* generate Fibonacci sequence until overflow */
+    while (x <= y) {
+        size_t tmp = x;
+        /* yield next value, ignore new input data */
+        (void) coroutine_yield(coro, &tmp);
+        /* x, y = y, x + y */
+        tmp = y;
+        y += x;
+        x = tmp;
+    }
+
+    /* no more values */
+    return NULL;
+}
+
+
+static void *output_coroutine(coroutine *coro, void *data)
+{
+    size_t *value = data;
+
+    while (NULL != value) {
+        printf("%zu\n", *value);
+        value = coroutine_yield(coro, value);
+    }
+
+    return NULL;
+}
+
+
+static int run(void)
+{
+    int error = -1;
+    coroutine *fibonacci = NULL;
+    coroutine *output = NULL;
+
+    fibonacci = coroutine_create(fibonacci_generator, 1);
+    if (NULL == fibonacci) {
+        perror("coroutine_create");
+        goto fail;
+    }
+
+    output = coroutine_create(output_coroutine, 1);
+    if (NULL == output) {
+        perror("coroutine_create");
+        goto fail;
+    }
+
+    void *data;
+
+    while (!(coroutine_ended(fibonacci) || coroutine_ended(output))) {
+        data = coroutine_resume(fibonacci, NULL);
+        data = coroutine_resume(output, data);
+    }
+
+    error = 0;
+
+fail:
+    coroutine_destroy(output);
+    coroutine_destroy(fibonacci);
+
+    return error;
+}
+
+
+int main(int argc, char *argv[])
+{
+    int error;
+
+    (void) argc;
+    (void) argv;
+
+    error = run();
+
+    return !error ? EXIT_SUCCESS : EXIT_FAILURE;
+}