source: trunk/minix/commands/simple/unexpand.c@ 15

/*  unexpand - convert spaces to tabs   Author: Terrence W. Holm */

/*  Usage:  unexpand  [ -a ]  [ file ... ]  */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#define  TAB   8


int column = 0;                 /* Current column, retained between files  */
int spaces = 0;                 /* Spaces since last tab stop       */
int leading_blank = 1;          /* Only unexpand leading blanks,            */
/* Overruled by -a option                   */

_PROTOTYPE(int main, (int argc, char **argv));
_PROTOTYPE(void Unexpand, (FILE *f, int all));

int main(argc, argv)
int argc;
char *argv[];

{
  int all = 0;                  /* -a flag means unexpand all spaces  */
  int i;
  FILE *f;

  if (argc > 1 && argv[1][0] == '-') {
        if (strcmp(argv[1], "-a") == 0)
                all = 1;
        else {
                fprintf(stderr, "Usage:  unexpand  [ -a ]  [ file ... ]\n");
                exit(1);
        }

        --argc;
        ++argv;
  }
  if (argc == 1)
        Unexpand(stdin, all);
  else
        for (i = 1; i < argc; ++i) {
                if ((f = fopen(argv[i], "r")) == NULL) {
                        perror(argv[i]);
                        exit(1);
                }
                Unexpand(f, all);
                fclose(f);
        }


  /* If there are pending spaces print them.  */

  while (spaces > 0) {
        putchar(' ');
        --spaces;
  }

  return(0);
}

void Unexpand(f, all)
FILE *f;
int all;

{
  int c;

  while ((c = getc(f)) != EOF) {
        if (c == ' ' && (all || leading_blank)) {
                ++column;
                ++spaces;

                /* If we have white space up to a tab stop, then output  */
                /* A tab. If only one space is required, use a ' '.      */

                if (column % TAB == 0) {
                        if (spaces == 1)
                                putchar(' ');
                        else
                                putchar('\t');

                        spaces = 0;
                }
                continue;
        }

        /* If a tab character is encountered in the input then          */
        /* Simply echo it. Any accumulated spaces can only be           */
        /* Since the last tab stop, so ignore them.                     */
        if (c == '\t') {
                column = (column / TAB + 1) * TAB;
                spaces = 0;
                putchar('\t');
                continue;
        }

        /* A non-space character is to be printed. If there   */
        /* Are pending spaces, then print them. There will be */
        /* At most TAB-1 spaces to print.                     */
        while (spaces > 0) {
                putchar(' ');
                --spaces;
        }

        if (c == '\n' || c == '\r') {
                column = 0;
                leading_blank = 1;
                putchar(c);
                continue;
        }
        if (c == '\b')
                column = column > 0 ? column - 1 : 0;
        else
                ++column;

        leading_blank = 0;
        putchar(c);
  }
}