From 174e57e51da8035b6c69f8b3287c94feb7b9344f Mon Sep 17 00:00:00 2001
From: Milo Turner <iitalics@gmail.com>
Date: Tue, 18 Feb 2020 16:53:31 -0500
Subject: [PATCH] [backend] message queue

---
 src/backend.h         |  8 +++---
 src/backend/sdl.c     | 46 ++++++++++++++++++++++++++++------
 src/concurrent/msgq.c | 57 +++++++++++++++++++++++++++++++++++++++++++
 src/concurrent/msgq.h | 29 ++++++++++++++++++++++
 4 files changed, 128 insertions(+), 12 deletions(-)
 create mode 100644 src/concurrent/msgq.c
 create mode 100644 src/concurrent/msgq.h

diff --git a/src/backend.h b/src/backend.h
index 03461c3..9fcdbcb 100644
--- a/src/backend.h
+++ b/src/backend.h
@@ -4,9 +4,7 @@
 #include <stdint.h>
 
 struct rgn;
-
 struct ax_backend;
-struct ax_font_h;
 
 extern const char* ax__backend_impl_name;
 
@@ -15,5 +13,7 @@ int ax__backend_new(
     struct ax_backend** out_bac,
     const char** out_err);
 
-const char* ax__backend_get_error(
-    struct ax_backend* bac);
+void ax__backend_enqueue_font(
+    struct ax_backend* bac,
+    const char* font_path,
+    size_t font_size);
diff --git a/src/backend/sdl.c b/src/backend/sdl.c
index 53536a0..d6eb406 100644
--- a/src/backend/sdl.c
+++ b/src/backend/sdl.c
@@ -1,14 +1,34 @@
 #include "../backend.h"
 #include "../util/region.h"
+#include "../concurrent/msgq.h"
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_ttf.h>
 
-struct ax_backend {
-};
+/* --- Backend data type --- */
 
 const char* ax__backend_impl_name = "SDL";
 
-static void shutdown_backend(struct ax_backend* bac);
+struct ax_backend {
+    struct msgq* mq;
+};
+
+/* --- Async messages --- */
+
+enum {
+    msg_close_TAG,
+    msg_load_font_TAG,
+};
+
+struct msg_close {};
+
+struct msg_load_font {
+    const char* path;
+    size_t size;
+};
+
+/* --- Functions --- */
+
+static void backend_cleanup(struct ax_backend* bac);
 
 int ax__backend_new(
     struct rgn* init_rgn,
@@ -26,7 +46,9 @@ int ax__backend_new(
     }
 
     struct ax_backend* bac = ralloc_typed(init_rgn, struct ax_backend, 1);
-    rgn_pin(init_rgn, bac, (void*) shutdown_backend);
+    rgn_pin(init_rgn, bac, (void*) backend_cleanup);
+
+    bac->mq = msgq_new(init_rgn);
 
     if (out_bac != NULL) {
         *out_bac = bac;
@@ -40,15 +62,23 @@ fail:
     return 1;
 }
 
-static void shutdown_backend(struct ax_backend* bac)
+static void backend_cleanup(struct ax_backend* bac)
 {
+    msgq_begin_send_typed(bac->mq, msg_close);
+    msgq_end_send(bac->mq);
+
     // printf("bye, from SDL\n");
     TTF_Quit();
     SDL_Quit();
 }
 
-const char* ax__backend_get_error(struct ax_backend* bac)
+void ax__backend_enqueue_font(
+    struct ax_backend* bac,
+    const char* font_path,
+    size_t font_size)
 {
-    (void) bac;
-    return NULL;
+    struct msg_load_font* m = msgq_begin_send_typed(bac->mq, msg_load_font);
+    m->path = rstrdup(&bac->mq->rgn, font_path);
+    m->size = font_size;
+    msgq_end_send(bac->mq);
 }
diff --git a/src/concurrent/msgq.c b/src/concurrent/msgq.c
new file mode 100644
index 0000000..3f94e8d
--- /dev/null
+++ b/src/concurrent/msgq.c
@@ -0,0 +1,57 @@
+#include "msgq.h"
+
+static void msgq_cleanup(struct msgq* mq);
+
+struct msgq* msgq_new(struct rgn* init_rgn)
+{
+    struct msgq* mq = ralloc_typed(init_rgn, struct msgq, 1);
+    rgn_init(&mq->rgn, SMALL);
+    mq->head = mq->tail = NULL;
+    rgn_pin(init_rgn, mq, (void*) msgq_cleanup);
+    return mq;
+}
+
+static void msgq_cleanup(struct msgq* mq)
+{
+    msgq_begin_recv(mq);
+    rgn_cleanup(&mq->rgn);
+}
+
+void* msgq_begin_send(struct msgq* mq, int type, size_t payload_size)
+{
+    struct msgq_msg* msg = ralloc(&mq->rgn, sizeof(struct msgq_msg) + payload_size);
+    msg->next = NULL;
+    msg->type = type;
+    if (mq->head == NULL) {
+        mq->head = mq->tail = msg;
+    } else {
+        mq->tail->next = msg;
+        mq->tail = msg;
+    }
+    return msg->payload;
+}
+
+void msgq_end_send(struct msgq* mq)
+{
+}
+
+void msgq_begin_recv(struct msgq* mq)
+{
+}
+
+void* msgq_recv1(struct msgq* mq, int* out_type)
+{
+    if (mq->head == NULL) {
+        return NULL;
+    } else {
+        void* pl = mq->head->payload;
+        mq->head = mq->head->next;
+        return pl;
+    }
+}
+
+void msgq_end_recv(struct msgq* mq)
+{
+    mq->head = mq->tail = NULL;
+    rgn_clear(&mq->rgn);
+}
diff --git a/src/concurrent/msgq.h b/src/concurrent/msgq.h
new file mode 100644
index 0000000..3acdc8d
--- /dev/null
+++ b/src/concurrent/msgq.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include "../util/region.h"
+
+struct msgq_msg;
+
+struct msgq {
+    struct rgn rgn;
+    struct msgq_msg* head;
+    struct msgq_msg* tail;
+};
+
+struct msgq_msg {
+    struct msgq_msg* next;
+    int type;
+    char payload[0];
+};
+
+struct msgq* msgq_new(struct rgn* init_rgn);
+
+void* msgq_begin_send(struct msgq* mq, int type, size_t payload_size);
+void msgq_end_send(struct msgq* mq);
+
+#define msgq_begin_send_typed(_mq, _ty)                                  \
+    ((struct _ty*) msgq_begin_send(_mq, _ty ## _TAG, sizeof(struct _ty)))
+
+void msgq_begin_recv(struct msgq* mq);
+void* msgq_recv1(struct msgq* mq, int* out_type);
+void msgq_end_recv(struct msgq* mq);