add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/sum.c

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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>
+
+#define BUFSIZ (512)
+
+int rc = 0;
+
+char *defargv[] = {"-", 0};
+
+main(argc, argv)
+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);
+  }
+  exit(rc);
+}
+
+error(s, f)
+char *s, *f;
+{
+
+  std_err("sum: ");
+  std_err(s);
+
+  if (f) std_err(f);
+  std_err("\n");
+}
+
+sum(fd, fname)
+int fd;
+char *fname;
+{
+  char buf[BUFSIZ];
+  register int i, n;
+  long size = 0;
+  unsigned crc = 0;
+  unsigned tmp, blks;
+
+  while ((n = read(fd, buf, BUFSIZ)) > 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;
+  }
+  putd(crc, 5, 1);
+  blks = (size + (long) BUFSIZ - 1L) / (long) BUFSIZ;
+  putd(blks, 6, 0);
+  if (fname) prints(" %s", fname);
+  prints("\n");
+}
+
+putd(number, fw, zeros)
+int number, fw, zeros;
+{
+/* Put a decimal number, in a field width, to stdout. */
+
+  char buf[10];
+  int n;
+  unsigned num;
+
+  num = (unsigned) number;
+  for (n = 0; n < fw; n++) {
+	if (num || n == 0) {
+		buf[fw - n - 1] = '0' + num % 10;
+		num /= 10;
+	} else
+		buf[fw - n - 1] = zeros ? '0' : ' ';
+  }
+  buf[fw] = 0;
+  prints("%s", buf);
+}