/*
 * Interface to unix's read function.  Provide for buffered input files.
 */

#include "defs.h"
public
#include <sys/file.h>
public
#include <stdio.h>

public
#define	ENDOFFILE	0	 /* return value for GetChar on end-of-file */

public typedef	struct			/* open file information */
  {
    int    fd;				/* file descriptor */
    int    nChars;			/* characters left in buffer */
    char   *buffp;			/* pointer to next char. in buffer */
    char   *buff;			/* begining address of the buffer */
  } File;



/*
 * Open a file for reading, return the file descriptor as obtained from open.
 */
public int OpenFile( fname, buff, file )
  char   *fname;
  char   *buff;
  File   *file;
  {
    file->fd = open( fname, O_RDONLY, 0 );
    file->buff = buff;
				    file->buffp = buff;
    file->nChars = 0;
    return( file->fd );
  }

/*
 * A lot of data gets read during CIF parsing: inline this procedure
 */
public
#define GetChar( c, f )						\
  {								\
    if( --(f).nChars >= 0 )					\
	c = *(f).buffp++;					\
    else							\
      {								\
	(f).nChars = read( (f).fd, (f).buff, BUFSIZ );		\
	if( (f).nChars > 0 )					\
	  {							\
	    (f).buffp = (f).buff;				\
	    (f).nChars--;					\
	    c = *(f).buffp++;					\
	  }							\
	else							\
	    c = ENDOFFILE;					\
      }								\
  }								\


public
#define UngetChar( f )	(f).buffp--; (f).nChars++

public
#define CloseFile( f )	close( (f).fd )



/*
 * Move back in the file to find the begining of the current line.  Display
 * the line in question and a pointer to the current position within the line
 * Then restore the file buffer to its initial state.
 */
public int PrintErrLine( f )
  File  *f;
  {
    char   *cp, c;
    int    col, nc;
    long   fpos, savePos;
    char   *buff;
    File   f1;
    
    savePos = fpos = BUFSIZ * ((lseek( f->fd, 0, L_INCR ) - 1) / BUFSIZ);
    cp = f->buffp;
    nc = f->nChars;
    buff = f->buff;
    if( *cp == '\n' )
      {
	cp--;
	nc++;
      }

    for( col = 0; *cp != '\n' and cp > buff; cp--, col++, nc++ );
    while( *cp != '\n' and fpos >= BUFSIZ )
      {
	fpos -= BUFSIZ;
	(void) lseek( f->fd, fpos, L_SET );
	(void) read( f->fd, buff, BUFSIZ );
	col++;
	for( cp = buff+BUFSIZ-1; cp > buff and *cp != '\n'; cp--, col++ );
	nc = buff + BUFSIZ - cp;
      }
    if( *cp == '\n' )
      {
	cp++;
	col--;
	nc--;
      }

    f1.fd = f->fd;
    f1.buff = f->buff;
    f1.nChars = nc;
    f1.buffp = cp;
    do
      {
	GetChar( c, f1 );
	fputc( c, stderr );
      } while( c != '\n' and c != ENDOFFILE );

    if( c != '\n' )
	fputc( '\n', stderr );

    /* put it back the way you found it */

    (void) lseek( f->fd, savePos, L_SET );
    (void) read( f->fd, buff, BUFSIZ );

    return( col );
  }