/*
 *   Input scanner.
 *
 *   Function are SetSrc() to redirect input, and GetToken() to
 *   get a token.  This automatically adds the token to the
 *   symbol table.  GetToken uses ; as a statement separator.
 *
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "glob.h"

static FILE *src = NULL;
static int nextch = 0;

int SetSrc(char *fn)
{
  if (src != NULL) fclose(src);

  if (strcmp(fn,"stdin")) {
    src = fopen(fn,"r");
    if (src == NULL)
      eprintf("An error occurred opening '%s' for input.",fn,0,0);
  }
  else src = NULL;

  nextch = 0;
  return 0;
}

#define SYMB "!&()-,:;<=>?{|}\[]^"
#define MAXW 80
#define more nextch=((src == NULL) ? getchar() : putchar(getc(src)))
#define eof (nextch==-1 || ((src == NULL) ? feof(stdin) : feof(src)))

int GetToken(void)
{
  static char buffer[MAXW];
  static int i;

  while (nextch <= ' ')
    if (eof) src==NULL||printf("eof in stdin\n"),SetSrc("stdin");
    else more;

  if (strchr(SYMB,nextch) != NULL) {
    buffer[0] = nextch;
    buffer[1] = 0;
    more;
    return AddSymbol(buffer);
  }

  for (i=0; i<MAXW; ++i) {
    buffer[i] = nextch;
    more;
    if (nextch <= ' ' || strchr(SYMB,nextch)!=NULL) break;
  }
  if (i==MAXW) {
    eprintf("The token '%.20s...' has been truncated to %d chars.",
         buffer,MAXW,0);
    --i;
  }
  buffer[i+1] = 0;
  return AddSymbol(buffer);
}

/*---------------------------------------------------------------------------
  This returns the rest of the current line up to 255 chars
*/
int GetLine(char *s)
{
  if (nextch=='\n') { more; return s[0]=0; }
  if (src==NULL) return scanf("%255[^\n]",s);
  return fscanf(src,"%255[^\n]",s);
}