From 0132b3ca1dba9ec31c9fc8a94fb6a998818a5666 Mon Sep 17 00:00:00 2001
From: blankie <blankie@nixnetmail.com>
Date: Wed, 18 Jan 2023 23:34:17 +0700
Subject: [PATCH] Add inter-thread communication

---
 arb.h             | 49 +++++++++++++++++++++++++++++++++++++++++++++++
 event_loop.cpp    | 21 +++++++++++++++++++-
 event_loop.h      |  3 ++-
 logcat_thread.cpp |  5 ++++-
 logcat_thread.h   |  6 ++++++
 main.cpp          |  2 +-
 6 files changed, 82 insertions(+), 4 deletions(-)
 create mode 100644 arb.h

diff --git a/arb.h b/arb.h
new file mode 100644
index 0000000..df26ae0
--- /dev/null
+++ b/arb.h
@@ -0,0 +1,49 @@
+#pragma once
+
+#include <atomic>
+#include "logcat_thread.h"
+
+#define ARB_MAX_SIZE 16
+
+template<typename T>
+class AtomicRingBuffer {
+public:
+    T* get();
+    void increment_read();
+    void put_and_increment_write(T item);
+
+private:
+    size_t _read = 0;
+    size_t _write = 0;
+    std::atomic<size_t> _used = 0;
+    T _items[ARB_MAX_SIZE];
+};
+
+// function bodies must be in the header because https://stackoverflow.com/a/999383
+
+template<typename T>
+T* AtomicRingBuffer<T>::get() {
+    if (this->_used.load() == 0) {
+        return nullptr;
+    }
+    return &this->_items[this->_read];
+}
+
+template<typename T>
+void AtomicRingBuffer<T>::increment_read() {
+    if (this->_used.load() == 0) {
+        return;
+    }
+    --this->_used;
+    this->_read = (this->_read + 1) % ARB_MAX_SIZE;
+}
+
+template<typename T>
+void AtomicRingBuffer<T>::put_and_increment_write(T item) {
+    while (this->_used.load() == ARB_MAX_SIZE) {
+        printf("spinlocking!!!\n");
+    }
+    this->_items[this->_write] = std::move(item);
+    ++this->_used;
+    this->_write = (this->_write + 1) % ARB_MAX_SIZE;
+}
diff --git a/event_loop.cpp b/event_loop.cpp
index bcd89a1..00f3b92 100644
--- a/event_loop.cpp
+++ b/event_loop.cpp
@@ -3,6 +3,7 @@
 
 #include "log.h"
 #include "config.h"
+#include "logcat_thread.h"
 
 static inline void write_config_and_update_structures(const Config& config) {
     try {
@@ -13,6 +14,22 @@ static inline void write_config_and_update_structures(const Config& config) {
     }
 }
 
+static inline void check_for_logcat_items(LogcatThread& logcat_thread) {
+    LogcatThreadItem* logcat_thread_item;
+
+    while ((logcat_thread_item = logcat_thread.atomic_ring_buffer.get())) {
+        if (std::holds_alternative<std::string>(*logcat_thread_item)) {
+            if (!log_entries.empty()) {
+                log_entries += '\n';
+            }
+            log_entries += std::move(std::get<std::string>(*logcat_thread_item));
+        } else {
+            throw std::runtime_error("Cannot handle all possible logcat thread item variants");
+        }
+        logcat_thread.atomic_ring_buffer.increment_read();
+    }
+}
+
 
 static inline void settings_window(Config& config, float* config_write_timer, bool* show_settings_window) {
     if (!ImGui::Begin("Settings", show_settings_window)) {
@@ -132,11 +149,13 @@ static inline void debug_window() {
     ImGui::End();
 }
 
-void event_loop(ImFont* monospace_font, Config& config, float* config_write_timer, bool* run_event_loop) {
+void event_loop(ImFont* monospace_font, Config& config, float* config_write_timer, LogcatThread& logcat_thread, bool* run_event_loop) {
     static bool show_settings_window = false;
     static bool show_logs_window = false;
     static size_t log_entries_read = 0;
 
+    check_for_logcat_items(logcat_thread);
+
     debug_window();
 
     if (show_settings_window) {
diff --git a/event_loop.h b/event_loop.h
index 56adbc9..c9a4103 100644
--- a/event_loop.h
+++ b/event_loop.h
@@ -3,5 +3,6 @@
 #include <imgui.h>
 
 #include "config.h"
+#include "logcat_thread.h"
 
-void event_loop(ImFont* monospace_font, Config& config, float* config_write_timer, bool* run_event_loop);
+void event_loop(ImFont* monospace_font, Config& config, float* config_write_timer, LogcatThread& logcat_thread, bool* run_event_loop);
diff --git a/logcat_thread.cpp b/logcat_thread.cpp
index 120c215..86c097c 100644
--- a/logcat_thread.cpp
+++ b/logcat_thread.cpp
@@ -106,9 +106,12 @@ void LogcatThread::_run(std::stop_token stoken) {
 
     while (!stoken.stop_requested()) {
         printf("(boop)\n");
+
         int ready_fds = epoll_wait(this->_epoll_fd, events, EPOLL_MAX_EVENTS, 1000);
         if (ready_fds == -1) {
-            printf("%s\n", format_log(std::string("epoll_wait(): ") + strerror(errno)).c_str());
+            std::string log_entry = format_log(std::string("epoll_wait(): ") + strerror(errno));
+            printf("%s\n", log_entry.c_str());
+            this->atomic_ring_buffer.put_and_increment_write(std::move(log_entry));
             break;
         }
 
diff --git a/logcat_thread.h b/logcat_thread.h
index d2f2496..c9dee9c 100644
--- a/logcat_thread.h
+++ b/logcat_thread.h
@@ -1,6 +1,10 @@
 #pragma once
 
 #include <thread>
+#include <variant>
+#include "arb.h"
+
+typedef std::variant<std::string> LogcatThreadItem;
 
 class LogcatThread {
 public:
@@ -13,6 +17,8 @@ public:
     void request_stop();
     void join();
 
+    AtomicRingBuffer<LogcatThreadItem> atomic_ring_buffer;
+
 private:
     void _run(std::stop_token stoken);
 
diff --git a/main.cpp b/main.cpp
index f21ac4f..55cd87c 100644
--- a/main.cpp
+++ b/main.cpp
@@ -161,7 +161,7 @@ int main(int, char**) {
         ImGui_ImplSDL2_NewFrame();
         ImGui::NewFrame();
 
-        event_loop(monospace_font, config, &config_write_timer, &run_event_loop);
+        event_loop(monospace_font, config, &config_write_timer, logcat_thread, &run_event_loop);
 
         // Rendering
         ImGui::Render();