backtrace sink and refactoring

include/spdlog/details/log_msg_buffer.h

@@ -0,0 +1,62 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+#include "spdlog/details/log_msg.h"
+#include "spdlog/fmt/bundled/core.h"
+
+namespace spdlog {
+namespace details {
+
+// regular log_msgs only holds string_views to stack data - so the cannot be stored for later use.
+// this one can, since it contains and owns the payload buffer.
+struct log_msg_buffer : log_msg
+{
+    fmt::basic_memory_buffer<char, 40> loggername_buf;
+    fmt::basic_memory_buffer<char, 200> payload_buf;
+    log_msg_buffer() = default;
+
+    log_msg_buffer(const log_msg &orig_msg): log_msg(orig_msg)
+    {
+        update_buffers();
+    }
+
+    log_msg_buffer(const log_msg_buffer& other):log_msg(other)
+    {
+        update_buffers();
+    }
+
+    log_msg_buffer(const log_msg_buffer&& other):log_msg(std::move(other))
+    {
+        update_buffers();
+    }
+
+    log_msg_buffer& operator=(log_msg_buffer &other) SPDLOG_NOEXCEPT
+    {
+        *static_cast<log_msg*>(this) = other;
+        update_buffers();
+        return *this;
+    }
+
+    log_msg_buffer& operator=(log_msg_buffer &&other) SPDLOG_NOEXCEPT
+    {
+        *static_cast<log_msg*>(this) = std::move(other);
+        update_buffers();
+        return *this;
+    }
+
+    void update_buffers() SPDLOG_NOEXCEPT
+    {
+        loggername_buf.clear();
+        loggername_buf.append(logger_name.data(), logger_name.data() + logger_name.size());
+        logger_name = string_view_t{loggername_buf.data(), loggername_buf.size()};
+
+        payload_buf.clear();
+        payload_buf.append(payload.data(),payload.data() + payload.size());
+        payload = string_view_t{payload_buf.data(), payload_buf.size()};
+    }
+};
+
+}
+}