text: #ifndef GRAPHDATA_H
  #define GRAPHDATA_H
  
  #include <stdint.h>
  #include <pthread.h>
  
  typedef struct graphdata_t graphdata_t;
  
  typedef graphdata_t* graphdata_handle_t;
  typedef uint64_t graphdata_cursor_t;
  typedef int64_t graphdata_datapoint_t;
  
  void graphdata_advance_cursor(graphdata_handle_t, graphdata_cursor_t*);
  graphdata_datapoint_t graphdata_read_datapoint(graphdata_handle_t, graphdata_cursor_t);
  int  graphdata_cursor_at_end(graphdata_handle_t, graphdata_cursor_t);
  graphdata_cursor_t  graphdata_current_head(graphdata_handle_t);
  void graphdata_add_datapoint(graphdata_handle_t, int64_t);
  void graphdata_initialize(graphdata_handle_t, int);
  void graphdata_destroy(graphdata_handle_t);
  
  #endif
  