NAME

getc, getw, fopen  −  buffered input

SYNOPSIS

mov$filename,r0
jsrr5,fopen; iobuf fopen(filename, iobuf)
char *filename;
struct buf *iobuf; jsrr5,getc; iobuf
(character in r0) getc(iobuf)
struct buf *iobuf; jsrr5,getw; iobuf
(word in r0) getw(iobuf)
struct buf *iobuf;

DESCRIPTION

These routines provide a buffered input facility.  Iobuf is the address of a 518(10) byte buffer area whose contents are maintained by these routines.  Its structure is

struct buf {
int fildes;/* File descriptor */
int nleft;/* Chars left in buffer */
char *nextp;/* Ptr to next character */
char buff[512];/* The buffer */
};

Fopen may be called initially to open the file.  On return, the error bit (c-bit) is set if the open failed.  If fopen is never called, get will read from the standard input file.  From C, the value is negative if the open failed.  Getc returns the next byte from the file in r0.  The error bit is set on end of file or a read error.  From C, the character is returned as an integer, without sign extension; it is −1 on end-of-file or error.  Getw returns the next word in r0.  Getc and getw may be used alternately; there are no odd/even problems.  Getw is may be called from C; −1 is returned on end-of-file or error, but of course is also a legitimate value.  Iobuf must be provided by the user; it must be on a word boundary.  To reuse the same buffer for another file, it is sufficient to close the original file and call fopen again. 

SEE ALSO

open (II), read (II), getchar (III), putc (III)

DIAGNOSTICS

c-bit set on EOF or error; from C, negative return indicates error or EOF.  Moreover, errno is set by this routine just as it is for a system call (see introduction (II)). 

BUGS