The stream-operations structure

The following code fragment shows the declaration of the stream-operations structure, mi_st_ops. For the most current definition, see the mistream.h header file.

#define OPS_NAME_LENGTH 40

struct mi_stream_operations {
   /* the pointers to the functions */
   mi_integer (*close)(MI_STREAM *strm_desc);
   mi_integer (*read)(MI_STREAM *strm_desc, void *buf, 
      mi_integer nbytes);
   mi_integer (*write)(MI_STREAM *strm_desc, void *buf,
      mi_integer nbytes);
   mi_integer (*seek)(MI_STREAM *strm_desc, 
      mi_int8 *offset, mi_integer whence);
   mi_int8 *  (*tell)(MI_STREAM *strm_desc);
   mi_integer (*setpos)(MI_STREAM *strm_desc, 
      mi_int8 *pos);
   mi_integer (*getpos)(MI_STREAM *strm_desc, 
      mi_int8 *pos);
   mi_integer (*length)(MI_STREAM *strm_desc, 
      mi_int8 *length);
   /* names of the functions above */
   char close_name [OPS_NAME_LENGTH];
   char read_name  [OPS_NAME_LENGTH];
   char write_name [OPS_NAME_LENGTH];
   char seek_name  [OPS_NAME_LENGTH];
   char tell_name  [OPS_NAME_LENGTH];
   char setpos_name[OPS_NAME_LENGTH];
   char getpos_name[OPS_NAME_LENGTH];
   char length_name[OPS_NAME_LENGTH];
   /* the function handles for the functions above */
   void *close_fhandle;
   void *read_fhandle;
   void *write_fhandle;
   void *seek_fhandle;
   void *tell_fhandle;
   void *setpos_fhandle;
   void *getpos_fhandle;
   void *length_fhandle;
} mi_st_ops;

As preceding code fragment shows, the stream-operations structure consists of the following parts:

• The function pointers to the generic stream I/O functions
• The names of the generic stream I/O functions
• The function handles of the generic stream I/O functions

The following code fragment shows a sample stream-operations structure that provides function pointers for the type-specific implementations of the mi_stream_close(), mi_stream_read(), and mi_stream_write() functions for a stream on a user-defined type named newstream.