Asink sink (#3309)

Replace async logger with async sink

src/details/async_log_msg.cpp

@@ -0,0 +1,61 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#include "spdlog/details/async_log_msg.h"
+
+namespace spdlog {
+namespace details {
+
+
+async_log_msg::async_log_msg(const type type)
+    : msg_type_{type} {}
+
+// copy logger name and payload to buffer so can be used asynchronously
+// note: source location pointers are copied without allocation since they
+// are compiler generated const chars* (__FILE__, __LINE__, __FUNCTION__)
+// if you pass custom strings to source location, make sure they outlive the async_log_msg
+async_log_msg::async_log_msg(const type type, const log_msg &orig_msg)
+    : log_msg{orig_msg}, msg_type_(type) {
+    buffer_.append(logger_name);
+    buffer_.append(payload);
+    update_string_views();
+}
+
+async_log_msg::async_log_msg(const async_log_msg &other)
+    : log_msg{other}, msg_type_{other.msg_type_} {
+    buffer_.append(logger_name);
+    buffer_.append(payload);
+    update_string_views();
+}
+
+async_log_msg::async_log_msg(async_log_msg &&other) noexcept
+    : log_msg{other}, msg_type_{other.msg_type_}, buffer_{std::move(other.buffer_)} {
+    update_string_views();
+}
+
+async_log_msg &async_log_msg::operator=(const async_log_msg &other) {
+    if (this == &other) return *this;
+    log_msg::operator=(other);
+    msg_type_ = other.msg_type_;
+    buffer_.clear();
+    buffer_.append(other.buffer_.data(), other.buffer_.data() + other.buffer_.size());
+    update_string_views();
+    return *this;
+}
+
+async_log_msg &async_log_msg::operator=(async_log_msg &&other) noexcept {
+    if (this == &other) return *this;
+    log_msg::operator=(other);
+    msg_type_ = other.msg_type_;
+    buffer_ = std::move(other.buffer_);
+    update_string_views();
+    return *this;
+}
+
+void async_log_msg::update_string_views() {
+    logger_name = string_view_t{buffer_.data(), logger_name.size()};
+    payload = string_view_t{buffer_.data() + logger_name.size(), payload.size()};
+}
+
+}  // namespace details
+}  // namespace spdlog