From 150bbf2e0ed5fff8aff5e073aff21db851e3d6a9 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Tue, 25 Oct 2016 23:40:09 +0200
Subject: [PATCH] Support for Windows fibers

---
 lib/libtask/context.c  | 20 ++++++++++++++++++++
 lib/libtask/task.c     | 30 ++++++++++++++++++++++++++++++
 lib/libtask/taskimpl.h | 24 ++++++++++++++++++++++++
 3 files changed, 74 insertions(+)

diff --git a/lib/libtask/context.c b/lib/libtask/context.c
index 9571996fd3a..db7d25cdfee 100644
--- a/lib/libtask/context.c
+++ b/lib/libtask/context.c
@@ -2,6 +2,15 @@
 
 #include "taskimpl.h"
 
+#ifdef LIBTASK_USE_FIBER
+
+#define STRICT
+#define NOMINMAX
+#define UNICODE
+#include <windows.h>
+
+#else
+
 #if defined(__APPLE__)
 #if defined(__i386__)
 #define NEEDX86MAKECONTEXT
@@ -35,6 +44,8 @@
 #define	NEEDMIPSMAKECONTEXT
 #endif
 
+#endif
+
 #ifdef NEEDPOWERMAKECONTEXT
 void
 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
@@ -139,3 +150,12 @@ swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
 	return 0;
 }
 #endif
+
+#ifdef LIBTASK_USE_FIBER
+int
+swapcontext (ucontext_t *oucp, const ucontext_t *ucp)
+{
+  SwitchToFiber (ucp->fiber);
+  return 0;
+}
+#endif
diff --git a/lib/libtask/task.c b/lib/libtask/task.c
index ebb868183b3..4e271f35071 100644
--- a/lib/libtask/task.c
+++ b/lib/libtask/task.c
@@ -4,6 +4,13 @@
 #include <fcntl.h>
 #include <stdio.h>
 
+#ifdef LIBTASK_USE_FIBER
+#define STRICT
+#define NOMINMAX
+#define UNICODE
+#include <windows.h>
+#endif
+
 int	taskdebuglevel;
 int	taskcount;
 int	tasknswitch;
@@ -55,6 +62,7 @@ return;
 		fprint(fd, "%d._: %s\n", getpid(), buf);
 }
 
+#ifndef LIBTASK_USE_FIBER
 static void
 taskstart(uint y, uint x)
 {
@@ -72,6 +80,7 @@ taskstart(uint y, uint x)
 	taskexit(0);
 //print("not reacehd\n");
 }
+#endif
 
 static int taskidgen;
 
@@ -83,23 +92,36 @@ taskalloc(void (*fn)(void*), void *arg, uint stack)
 	uint x, y;
 	ulong z;
 
+#ifdef LIBTASK_USE_FIBER
+        t = malloc (sizeof *t);
+#else
 	/* allocate the task and stack together */
 	t = malloc(sizeof *t+stack);
+#endif
 	if(t == nil){
 		fprint(2, "taskalloc malloc: %r\n");
 		abort();
 	}
 	memset(t, 0, sizeof *t);
+#ifdef LIBTASK_USE_FIBER
+        t->context.uc.fiber = CreateFiber (stack, fn, arg);
+        if (t->context.uc.fiber == NULL)
+          abort ();
+#else
 	t->stk = (uchar*)(t+1);
 	t->stksize = stack;
+#endif
 	t->id = ++taskidgen;
+#ifndef LIBTASK_USE_FIBER
 	t->startfn = fn;
 	t->startarg = arg;
+#endif
 
 #ifdef EMACS
         init_emacs_lisp_context (t->id == 1, &t->context.ec);
 #endif
 
+#ifndef LIBTASK_USE_FIBER
 	/* do a reasonable initialization */
 	memset(&t->context.uc, 0, sizeof t->context.uc);
 	sigemptyset(&zero);
@@ -133,6 +155,7 @@ taskalloc(void (*fn)(void*), void *arg, uint stack)
 	z >>= 16;	/* hide undefined 32-bit shift from 32-bit compilers */
 	x = z>>16;
 	makecontext(&t->context.uc, (void(*)())taskstart, 2, y, x);
+#endif
 
 	return t;
 }
@@ -308,6 +331,7 @@ taskgetstate(void)
 void
 needstack(int n)
 {
+#ifndef LIBTASK_USE_FIBER
 	Task *t;
 
 	t = taskrunning;
@@ -317,6 +341,7 @@ needstack(int n)
 		fprint(2, "task stack overflow: &t=%p tstk=%p n=%d\n", &t, t->stk, 256+n);
 		abort();
 	}
+#endif
 }
 
 static void
@@ -374,6 +399,11 @@ main(int argc, char **argv)
 	taskargc = argc;
 	taskargv = argv;
 
+#ifdef LIBTASK_USE_FIBER
+        if (ConvertThreadToFiber (NULL) == NULL)
+          return 2;
+#endif
+
 	if(mainstacksize == 0)
 		mainstacksize = 256*1024;
 #ifdef EMACS
diff --git a/lib/libtask/taskimpl.h b/lib/libtask/taskimpl.h
index 03a26c29fb0..2b1dd8f9f5e 100644
--- a/lib/libtask/taskimpl.h
+++ b/lib/libtask/taskimpl.h
@@ -27,6 +27,11 @@
 #ifdef EMACS
 #include <config.h>
 #include "lisp.h"
+#ifdef WINDOWSNT
+#undef USE_UCONTEXT
+#define USE_UCONTEXT 0
+#define LIBTASK_USE_FIBER
+#endif
 #endif
 
 #include <errno.h>
@@ -84,6 +89,19 @@ char *vsnprint(char*, uint, char*, va_list);
 char *vseprint(char*, char*, char*, va_list);
 char *strecpy(char*, char*, char*);
 
+#ifdef LIBTASK_USE_FIBER
+
+#undef ucontext
+#undef ucontext_t
+#define ucontext libtask_fiber_ucontext
+#define ucontext_t libtask_fiber_ucontext_t
+typedef struct libtask_fiber_ucontext {
+  void *fiber;
+} libtask_fiber_ucontext_t;
+extern int swapcontext(ucontext_t *, const ucontext_t *);
+
+#else
+
 #if defined(__FreeBSD__) && __FreeBSD__ < 5
 extern	int		getmcontext(mcontext_t*);
 extern	void		setmcontext(const mcontext_t*);
@@ -143,6 +161,8 @@ void setmcontext(const mcontext_t*);
 #define	getcontext(u)	getmcontext(&(u)->uc_mcontext)
 #endif
 
+#endif
+
 typedef struct Context Context;
 
 enum
@@ -169,14 +189,18 @@ struct Task
 	Context	context;
 	uvlong	alarmtime;
 	uint	id;
+#ifndef LIBTASK_USE_FIBER
 	uchar	*stk;
 	uint	stksize;
+#endif
 	int	exiting;
 	int	alltaskslot;
 	int	system;
 	int	ready;
+#ifndef LIBTASK_USE_FIBER
 	void	(*startfn)(void*);
 	void	*startarg;
+#endif
 	void	*udata;
 };
 
-- 
2.39.5