/* Buffered input/output */ #ifndef _io_#define _io_  #include "misc.h"#include "mlvalues.h" #ifndef IO_BUFFER_SIZE#define IO_BUFFER_SIZE 4096#endif struct channel {  int fd;                       /* Unix file descriptor */  long offset;                  /* Absolute position of fd in the file */  char * curr;                  /* Current position in the buffer */  char * max;                   /* Logical end of the buffer */  char * end;                   /* Physical end of the buffer */  char buff[IO_BUFFER_SIZE];    /* The buffer itself */}; /* For an output channel:     [offset] is the absolute position of the beginning of the buffer [buff].   For an input channel:     [offset] is the absolute position of the logical end of the buffer [max].*/ #define putch(channel, ch)                                                    \  { if ((channel)->curr >= (channel)->end) flush(channel);                    \    *((channel)->curr)++ = (ch);                                              \    if ((channel)->curr > (channel)->max) (channel)->max = (channel)->curr; } #define getch(channel)                                                        \  ((channel)->curr >= (channel)->max                                          \   ? refill(channel)                                                          \   : (unsigned char) *((channel))->curr++) struct channel * open_descr (int);value flush (struct channel *);void putword (struct channel *, uint32);void putblock (struct channel *, char *, unsigned);unsigned char refill (struct channel *);uint32 getword (struct channel *);int getblock (struct channel *, char *, unsigned, int);int really_getblock (struct channel *, char *, unsigned long);value close_in (struct channel *);void close_stdouterr(void);void flush_stdouterr(void);value pos_out(struct channel * channel);value seek_out(struct channel * channel, value pos);#endif /* _io_ */