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/* sum - checksum a file		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 <unistd.h>
#include <string.h>
#include <stdio.h>

int rc = 0;
char *defargv[] = {"-", 0};
static char buf[2048];

void error(char *s, char *f)
{
  fprintf(stderr, "sum: ");
  fprintf(stderr, s);

  if (f) 
	fprintf(stderr, f);
  fprintf(stderr, "\n");
}

void sum(int fd, char *fname)
{
  register int i, n;
  long size = 0;
  unsigned crc = 0;
  unsigned tmp;

  while ((n = read(fd, buf, sizeof(buf))) > 0) {
	for (i = 0; i < n; i++) {
		crc = (crc >> 1) + ((crc & 1) ? 0x8000 : 0);
		tmp = buf[i] & 0377;
		crc += tmp;
		crc &= 0xffff;
	}
	size++;
  }

  if (n < 0) {
	if (fname)
		error("read error on ", fname);
	else
		error("read error", (char *) 0);
	rc = 1;
	return;
  }
  printf("%05u %6ld", crc, size);
  if (fname) printf(" %s", fname);
  printf("\n");
}

int main(int argc, char **argv)
{
  register int fd;

  if (*++argv == 0) argv = defargv;
  for (; *argv; argv++) {
	if (argv[0][0] == '-' && argv[0][1] == '\0')
		fd = 0;
	else
		fd = open(*argv, O_RDONLY);

	if (fd == -1) {
		error("can't open ", *argv);
		rc = 1;
		continue;
	}
	sum(fd, (argc > 2) ? *argv : (char *) 0);
	if (fd != 0) close(fd);
  }
  return(rc);
}

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