log_strdup requested for a piece of memory, with the first 4 bytes as
the number of references and the next used to copy strings. In the
implementation of this function, the memory is managed by user and
is a little hard to understand.
Rewriting this part of code, using structure to manage the memory
requested, make it easier to understand.
Signed-off-by: qianfan Zhao <qianfanguijin@163.com>