From fea8242ea7635363f00823f9e24d689535825928 Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Sat, 7 Oct 2023 11:25:20 -0700
Subject: [PATCH] Reuse overlapped overhead on windows for something useful.

---
 src/core/ev.c       | 15 +++++++++------
 src/core/fiber.c    |  1 -
 src/core/marsh.c    |  1 -
 src/include/janet.h |  1 -
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/core/ev.c b/src/core/ev.c
index 39bff114..523a2724 100644
--- a/src/core/ev.c
+++ b/src/core/ev.c
@@ -1484,7 +1484,8 @@ void janet_loop1_impl(int has_timeout, JanetTimestamp to) {
             }
             if (fiber != NULL) {
                 fiber->ev_in_flight = 0;
-                fiber->ev_bytes = num_bytes_transfered;
+                /* System is done with this, we can reused this data */
+                overlapped->InternalHigh = (ULONG_PTR) num_bytes_transfered;
                 fiber->ev_callback(fiber, result ? JANET_ASYNC_EVENT_COMPLETE : JANET_ASYNC_EVENT_FAILED);
             } else {
                 janet_free((void *) overlapped);
@@ -2163,17 +2164,18 @@ void ev_callback_read(JanetFiber *fiber, JanetAsyncEvent event) {
         case JANET_ASYNC_EVENT_FAILED:
         case JANET_ASYNC_EVENT_COMPLETE: {
             /* Called when read finished */
-            state->bytes_read += fiber->ev_bytes;
+            uint32_t ev_bytes = state->overlapped.InternalHigh;
+            state->bytes_read += ev_bytes;
             if (state->bytes_read == 0 && (state->mode != JANET_ASYNC_READMODE_RECVFROM)) {
                 janet_schedule(fiber, janet_wrap_nil());
                 janet_async_end(fiber);
                 return;
             }
 
-            janet_buffer_push_bytes(state->buf, state->chunk_buf, fiber->ev_bytes);
-            state->bytes_left -= fiber->ev_bytes;
+            janet_buffer_push_bytes(state->buf, state->chunk_buf, ev_bytes);
+            state->bytes_left -= ev_bytes;
 
-            if (state->bytes_left == 0 || !state->is_chunk || fiber->ev_bytes == 0) {
+            if (state->bytes_left == 0 || !state->is_chunk || ev_bytes == 0) {
                 Janet resume_val;
 #ifdef JANET_NET
                 if (state->mode == JANET_ASYNC_READMODE_RECVFROM) {
@@ -2412,7 +2414,8 @@ void ev_callback_write(JanetFiber *fiber, JanetAsyncEvent event) {
         case JANET_ASYNC_EVENT_FAILED:
         case JANET_ASYNC_EVENT_COMPLETE: {
             /* Called when write finished */
-            if (fiber->ev_bytes == 0 && (state->mode != JANET_ASYNC_WRITEMODE_SENDTO)) {
+            uint32_t ev_bytes = state->overlapped.InternalHigh;
+            if (ev_bytes == 0 && (state->mode != JANET_ASYNC_WRITEMODE_SENDTO)) {
                 janet_cancel(fiber, janet_cstringv("disconnect"));
                 janet_async_end(fiber);
                 return;
diff --git a/src/core/fiber.c b/src/core/fiber.c
index fe558fb0..f733e7f6 100644
--- a/src/core/fiber.c
+++ b/src/core/fiber.c
@@ -43,7 +43,6 @@ static void fiber_reset(JanetFiber *fiber) {
     fiber->ev_callback = NULL;
     fiber->ev_state = NULL;
     fiber->ev_stream = NULL;
-    fiber->ev_bytes = 0;
     fiber->supervisor_channel = NULL;
     fiber->ev_in_flight = 0;
 #endif
diff --git a/src/core/marsh.c b/src/core/marsh.c
index 4332c6f7..9e032a2c 100644
--- a/src/core/marsh.c
+++ b/src/core/marsh.c
@@ -1051,7 +1051,6 @@ static const uint8_t *unmarshal_one_fiber(
     fiber->sched_id = 0;
     fiber->supervisor_channel = NULL;
     fiber->ev_state = NULL;
-    fiber->ev_bytes = 0;
     fiber->ev_callback = NULL;
     fiber->ev_stream = NULL;
     fiber->ev_in_flight = 0;
diff --git a/src/include/janet.h b/src/include/janet.h
index 0e2f5790..7288938d 100644
--- a/src/include/janet.h
+++ b/src/include/janet.h
@@ -927,7 +927,6 @@ struct JanetFiber {
     JanetStream *ev_stream; /* which stream we are waiting on */
     void *ev_state; /* Extra data for ev callback state. On windows, first element must be OVERLAPPED. */
     void *supervisor_channel; /* Channel to push self to when complete */
-    uint32_t ev_bytes; /* Number of bytes for completion event */
     int ev_in_flight; /* If overlapped operation is in flight */
 #endif
 };