From 9acc8a43b44565c100fe53f23058d46828886ad6 Mon Sep 17 00:00:00 2001
From: "Justin R. Cutler" <justin.r.cutler@gmail.com>
Date: Sun, 10 Apr 2016 21:45:20 -0400
Subject: [PATCH] Adding coroutine_defer() (with test)

---
 src/coroutine.c        | 49 ++++++++++++++++++++++++++++++++++++++++++
 test/coroutine.c       | 13 +++++++++++
 threadless/coroutine.h | 17 +++++++++++++++
 3 files changed, 79 insertions(+)

diff --git a/src/coroutine.c b/src/coroutine.c
index ea35c02..a12f296 100644
--- a/src/coroutine.c
+++ b/src/coroutine.c
@@ -29,6 +29,13 @@ enum {
     COROUTINE_ENDED = 1,
 };
 
+typedef struct deferred deferred_t;
+struct deferred {
+    allocation_t allocation;
+    coroutine_deferred_function_t *function;
+    void *data;
+    deferred_t *next;
+};
 
 struct coroutine {
     allocation_t allocation;
@@ -36,6 +43,7 @@ struct coroutine {
     ucontext_t   caller;
     void         *data;
     int          status;
+    deferred_t   *deferred;
 };
 
 
@@ -78,6 +86,7 @@ coroutine_t *coroutine_create(allocator_t *allocator,
     coro = allocation.memory;
     memset(coro, 0, alloc_size);
     coro->allocation = allocation;
+    coro->deferred = NULL;
     (void) getcontext(&coro->context);
     coro->context.uc_stack.ss_sp = coro + 1;
     coro->context.uc_stack.ss_size = stack_size;
@@ -94,9 +103,22 @@ fail:
 }
 
 
+static void coroutine_run_deferred(coroutine_t *coro)
+{
+    deferred_t *deferred = coro->deferred;
+    while (NULL != deferred) {
+        allocation_t allocation = deferred->allocation;
+        deferred->function(deferred->data);
+        deferred = deferred->next;
+        allocation_free(&allocation);
+    }
+}
+
+
 void coroutine_destroy(coroutine_t *coro)
 {
     if (NULL != coro) {
+        coroutine_run_deferred(coro);
         allocation_t allocation = coro->allocation;
         allocation_free(&allocation);
     }
@@ -129,3 +151,30 @@ void *coroutine_yield(coroutine_t *coro, void *value)
     (void) swapcontext(&coro->context, &coro->caller);
     return coro->data;
 }
+
+
+int coroutine_defer(coroutine_t *coro, coroutine_deferred_function_t *function,
+    void *data)
+{
+    int error;
+    deferred_t *deferred = NULL;
+    allocation_t allocation;
+
+    /* allocate memory */
+    allocation_init(&allocation, coro->allocation.allocator);
+    error = allocation_realloc_array(&allocation, 1, sizeof(*deferred));
+
+    if (!error) {
+       /* initialize deferred work */
+        deferred = allocation.memory;
+        deferred->allocation = allocation;
+        deferred->function = function;
+        deferred->data = data;
+
+        /* push deferred work to front of list */
+        deferred->next = coro->deferred;
+        coro->deferred = deferred;
+    }
+
+    return error;
+}
diff --git a/test/coroutine.c b/test/coroutine.c
index 46d6658..934bcdf 100644
--- a/test/coroutine.c
+++ b/test/coroutine.c
@@ -52,10 +52,23 @@ static void *fibonacci_generator(coroutine_t *coro, void *data)
 }
 
 
+static void deferred_puts(void *data)
+{
+    puts(data);
+}
+
+
 static void *output_coroutine(coroutine_t *coro, void *data)
 {
     size_t *value = data;
 
+    if (coroutine_defer(coro, deferred_puts, "deferred output 0")) {
+        return NULL;
+    }
+    if (coroutine_defer(coro, deferred_puts, "deferred output 1")) {
+        return NULL;
+    }
+
     while (NULL != value) {
         printf("%zu\n", *value);
         value = coroutine_yield(coro, value);
diff --git a/threadless/coroutine.h b/threadless/coroutine.h
index b018a58..f4de52b 100644
--- a/threadless/coroutine.h
+++ b/threadless/coroutine.h
@@ -29,6 +29,11 @@ typedef struct coroutine coroutine_t;
  */
 typedef void *(coroutine_function_t)(coroutine_t *coro, void *data);
 
+/** Coroutine deferred function type
+ * @param[in,out] data user-defined data
+ */
+typedef void (coroutine_deferred_function_t)(void *data);
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
@@ -77,6 +82,18 @@ void *coroutine_resume(coroutine_t *coro, void *value);
  */
 void *coroutine_yield(coroutine_t *coro, void *value);
 
+/** Defer a function call until coroutine termination
+ * @param[in,out] coro     coroutine
+ * @param         function function to call when @p coro terminates
+ * @param         data     user-defined point to pass to @p function
+ * @retval 0  success
+ * @retval -1 error
+ * @post @p function will be called with @p data when @p coro terminates
+ * @note Registered functions will be called in reverse order of registration
+ */
+int coroutine_defer(coroutine_t *coro, coroutine_deferred_function_t *function,
+    void *data);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */