start implementing the libretro interface. (not working yet)

libco/ucontext.c

@@ -0,0 +1,81 @@
+/*
+  libco.ucontext (2008-01-28)
+  author: Nach
+  license: public domain
+*/
+
+/*
+ * WARNING: the overhead of POSIX ucontext is very high,
+ * assembly versions of libco or libco_sjlj should be much faster
+ *
+ * This library only exists for two reasons:
+ * 1 - as an initial test for the viability of a ucontext implementation
+ * 2 - to demonstrate the power and speed of libco over existing implementations,
+ *     such as pth (which defaults to wrapping ucontext on unix targets)
+ *
+ * Use this library only as a *last resort*
+ */
+
+#define LIBCO_C
+#include <libco.h>
+#include <stdlib.h>
+#include <ucontext.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static thread_local ucontext_t co_primary;
+static thread_local ucontext_t *co_running = 0;
+
+cothread_t co_active(void)
+{
+   if (!co_running)
+      co_running = &co_primary;
+   return (cothread_t)co_running;
+}
+
+cothread_t co_create(unsigned int heapsize, void (*coentry)(void))
+{
+   if (!co_running)
+      co_running = &co_primary;
+   ucontext_t *thread = (ucontext_t*)malloc(sizeof(ucontext_t));
+
+   if(thread)
+   {
+      if((!getcontext(thread) && !(thread->uc_stack.ss_sp = 0)) && (thread->uc_stack.ss_sp = malloc(heapsize)))
+      {
+         thread->uc_link = co_running;
+         thread->uc_stack.ss_size = heapsize;
+         makecontext(thread, coentry, 0);
+      }
+      else
+      {
+         co_delete((cothread_t)thread);
+         thread = 0;
+      }
+   }
+   return (cothread_t)thread;
+}
+
+void co_delete(cothread_t cothread)
+{
+   if (!cothread)
+      return;
+
+   if(((ucontext_t*)cothread)->uc_stack.ss_sp)
+      free(((ucontext_t*)cothread)->uc_stack.ss_sp);
+   free(cothread);
+}
+
+void co_switch(cothread_t cothread)
+{
+   ucontext_t *old_thread = co_running;
+
+   co_running = (ucontext_t*)cothread;
+   swapcontext(old_thread, co_running);
+}
+
+#ifdef __cplusplus
+}
+#endif