#include <bson/bson.h>
typedef enum {
   BSON_SUBTYPE_BINARY = 0x00,
   BSON_SUBTYPE_FUNCTION = 0x01,
   BSON_SUBTYPE_BINARY_DEPRECATED = 0x02,
   BSON_SUBTYPE_UUID_DEPRECATED = 0x03,
   BSON_SUBTYPE_UUID = 0x04,
   BSON_SUBTYPE_MD5 = 0x05,
   BSON_SUBTYPE_COLUMN = 0x07,
   BSON_SUBTYPE_SENSITIVE = 0x08,
   BSON_SUBTYPE_USER = 0x80,
} bson_subtype_t;

bson_t doc = BSON_INITIALIZER;
BSON_APPEND_BINARY (&doc, "binary", BSON_SUBTYPE_BINARY, data, data_len);