android: Support __android_log_write_log_message based logging

This function has been introduced in API Level 30. This commit
enables support for dynamic use of the new API (in case the
application would run on older OS versions).

Signed-off-by: Jarosław Pelczar <jarek@jpelczar.com>

include/spdlog/sinks/android_sink.h

@@ -22,6 +22,10 @@
         #define SPDLOG_ANDROID_RETRIES 2
     #endif
 
+    #if __ANDROID_API__ >= 30
+        #define SPDLOG_ANDROID_ENABLE_LOG_WRITE
+    #endif
+
 namespace spdlog {
 namespace sinks {
 
@@ -35,7 +39,12 @@ class android_sink final : public base_sink<Mutex> {
 public:
     explicit android_sink(std::string tag = "spdlog", bool use_raw_msg = false)
         : tag_(std::move(tag)),
-          use_raw_msg_(use_raw_msg) {}
+          use_raw_msg_(use_raw_msg) {
+        // Available since API level 30
+    #ifdef SPDLOG_ANDROID_ENABLE_LOG_WRITE
+        write_message_ = (write_log_message_t)dlsym(nullptr, "__android_log_write_log_message");
+    #endif
+    }
 
 protected:
     void sink_it_(const details::log_msg &msg) override {
@@ -49,6 +58,21 @@ protected:
         formatted.push_back('\0');
         const char *msg_output = formatted.data();
 
+    #ifdef SPDLOG_ANDROID_ENABLE_LOG_WRITE
+        if (write_message_) {
+            __android_log_message logMessage{};
+            logMessage.struct_size = sizeof(logMessage);
+            logMessage.buffer_id = BufferID;
+            logMessage.priority = priority;
+            logMessage.tag = tag_.c_str();
+            logMessage.file = msg.source.filename;
+            logMessage.line = static_cast<uint32_t>(msg.source.line);
+            logMessage.message = msg_output;
+            write_message_(&logMessage);
+            return;
+        }
+    #endif
+
         // See system/core/liblog/logger_write.c for explanation of return value
         int ret = android_log(priority, tag_.c_str(), msg_output);
         if (ret == -EPERM) {
@@ -104,8 +128,15 @@ private:
         }
     }
 
+    #ifdef SPDLOG_ANDROID_ENABLE_LOG_WRITE
+    typedef void (*write_log_message_t)(struct __android_log_message *log_message);
+    #endif
+
     std::string tag_;
     bool use_raw_msg_;
+    #ifdef SPDLOG_ANDROID_ENABLE_LOG_WRITE
+    write_log_message_t write_message_;
+    #endif
 };
 
 using android_sink_mt = android_sink<std::mutex>;