http_parser能够支持多线程

https://github.com/nodejs/http-parser

用C++封装一个类，其中setting中注册的解析http head的函数为static，此函数须要访问存储header数据的指针，因为注册的函数不能变，不能加this指针。一种是直接将指针搞成static，这样在多线程场景就会出问题；另一种就是将指针做为http_parser的私有数据

 

Mul-thread Example:

typedef struct {
  socket_t sock;
  void* buffer;
  int buf_len;
 } custom_data_t;


int my_url_callback(http_parser* parser, const char *at, size_t length) {
  /* access to thread local custom_data_t struct.
  Use this access save parsed data for later use into thread local
  buffer, or communicate over socket
  */
  parser->data;
  ...
  return 0;
}

...

void http_parser_thread(socket_t sock) {
 int nparsed = 0;
 /* allocate memory for user data */
 custom_data_t *my_data = malloc(sizeof(custom_data_t));

 /* some information for use by callbacks.
 * achieves thread -> callback information flow */
 my_data->sock = sock;

 /* instantiate a thread-local parser */
 http_parser *parser = malloc(sizeof(http_parser));
 http_parser_init(parser, HTTP_REQUEST); /* initialise parser */
 /* this custom data reference is accessible through the reference to the
 parser supplied to callback functions */
 parser->data = my_data;

 http_parser_settings settings; /* set up callbacks */
 settings.on_url = my_url_callback;

 /* execute parser */
 nparsed = http_parser_execute(parser, &settings, buf, recved);

 ...
 /* parsed information copied from callback.
 can now perform action on data copied into thread-local memory from callbacks.
 achieves callback -> thread information flow */
 my_data->buffer;
 ...
}