Pass the information of all native methods to the callback $macro. The input can be matched
with pattern {$({$func_name:ident, {$($ret:tt)*}, {$($args:tt)*}})*}
A macro that splits the input by comma and calls the callback $macro with the split result.
The each part of the split result is within a bracket, and the callback $macro can have its
first parameter as {$({$($args:tt)+})*} to match the split result.
Given the plain text of a list native methods, split the methods by semicolon (;), extract
the return type, argument list and name of the methods and pass the result to the callback
$macro with the extracted result as the first parameter. The result can be matched with
pattern {$({$func_name:ident, {$($ret:tt)*}, {$($args:tt)*}})*}
In most Jni interfaces, the first parameter is JNIEnv, and the second parameter is JClass.
This struct simply encapsulates the two common parameters into a single struct for simplicity.
Send messages to the channel received by CdcSplitReader.
If msg is null, just check whether the channel is closed.
Return true if sending is successful, otherwise, return false so that caller can stop
gracefully.