comm.c

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/* comm - select lines from two sorted files    Author: Martin C. Atkins */

/*
 *      This program was written by:
 *              Martin C. Atkins,
 *              University of York,
 *              Heslington,
 *              York. Y01 5DD
 *              England
 *      and is released into the public domain, on the condition
 *      that this comment is always included without alteration.
 */

#include <sys/types.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <minix/minlib.h>
#include <stdio.h>

#define BUFFER_SIZE (512)
#define LINMAX (600)

struct file {
  char *name;                   /* the file's name */
  int fd;                       /* the file descripter */
  char buf[BUFFER_SIZE];                /* buffer storage */
  char *next;                   /* the next character to read */
  char *endp;                   /* the first invalid character */
  int seeneof;                  /* an end of file has been seen */
} files[2];

char lines[2][LINMAX];

int colflgs[3] = {1, 2, 3};     /* number of tabs + 1: 0 => no column */

static char *umsg = "Usage: comm [-[123]] file1 file2\n";

_PROTOTYPE(int main, (int argc, char **argv));
_PROTOTYPE(void usage, (void));
_PROTOTYPE(void error, (char *s, char *f));
_PROTOTYPE(void eopen, (char *fn, struct file *file));
_PROTOTYPE(int getbuf, (struct file *file));
_PROTOTYPE(int readline, (int fno));
_PROTOTYPE(void comm, (void));
_PROTOTYPE(void putcol, (int col, char *buf));
_PROTOTYPE(void cpycol, (int col));

int main(argc, argv)
int argc;
char *argv[];
{
  int cnt;
  if (argc > 1 && argv[1][0] == '-' && argv[1][1] != '\0') {
        char *ap;
        for (ap = &argv[1][1]; *ap; ap++) switch (*ap) {
                    case '1':
                    case '2':
                    case '3':
                        cnt = *ap - '1';
                        if (colflgs[cnt] == 0) break;
                        colflgs[cnt] = 0;
                        for (cnt++; cnt < 3; cnt++) colflgs[cnt]--;
                        break;
                    default:    usage();
                }
        argc--;
        argv++;
  }
  if (argc != 3) usage();
  eopen(argv[1], &files[0]);
  eopen(argv[2], &files[1]);
  comm();
  return(0);
}

void usage()
{

  std_err(umsg);
  exit(1);
}

void error(s, f)
char *s, *f;
{
  std_err("comm: ");
  std_err(s);
  if (f) std_err(f);
  std_err("\n");
  exit(1);
}

void eopen(fn, file)
char *fn;
struct file *file;
{
  file->name = fn;
  file->next = file->endp = &file->buf[0];
  file->seeneof = 0;
  if (fn[0] == '-' && fn[1] == '\0')
        file->fd = 0;
  else if ((file->fd = open(fn, O_RDONLY)) < 0)
        error("can't open ", fn);
}


int getbuf(file)
struct file *file;
{
/* Get a buffer-full from the file.  Return true if no characters
 * were obtained because we are at end of file.
 */
  int n;

  if (file->seeneof) return(1);
  if ((n = read(file->fd, &file->buf[0], BUFFER_SIZE)) < 0)
        error("read error on ", file->name);
  if (n == 0) {
        file->seeneof++;
        return 1;
  }
  file->next = &file->buf[0];
  file->endp = &file->buf[n];
  return(0);
}


int readline(fno)
int fno;
{
/* Read up to the next '\n' character to buf.
 * Return a complete line, even if end of file occurs within a line.
 * Return false at end of file/
 */
  register struct file *file = &files[fno];
  char *buf = lines[fno];

  if (file->next == file->endp && getbuf(file)) return(0);
  while ((*buf++ = *file->next++) != '\n')
        if (file->next == file->endp && getbuf(file)) {
                *buf++ = '\n';
                *buf = '\0';
                return(1);
        }
  *buf = '\0';
  return(1);
}

void comm()
{
  register int res;

  if (!readline(0)) {
        cpycol(1);
        return;
  }
  if (!readline(1)) {
        putcol(0, lines[0]);
        cpycol(0);
        return;
  }
  for (;;) {
        if ((res = strcmp(lines[0], lines[1])) != 0) {
                res = res > 0;
                putcol(res, lines[res]);
                if (!readline(res)) {
                        putcol(!res, lines[!res]);
                        cpycol(!res);
                        return;
                }
        } else {
                putcol(2, lines[0]);    /* files[1]lin == f2lin */
                if (!readline(0)) {
                        cpycol(1);
                        return;
                }
                if (!readline(1)) {
                        putcol(0, lines[0]);
                        cpycol(0);
                        return;
                }
        }
  }

  /* NOTREACHED */
}

void putcol(col, buf)
int col;
char *buf;
{
  int cnt;

  if (colflgs[col] == 0) return;
  for (cnt = 0; cnt < colflgs[col] - 1; cnt++) printf("\t");
  printf("%s", buf);
}

void cpycol(col)
int col;
{
  if (colflgs[col]) while (readline(col))
                putcol(col, lines[col]);
}

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