extract from cksum

1 files changed, 157 insertions, 0 deletions

diff --git a/sum.c b/sum.c
new file mode 100644
index 0000000..08f510f
--- /dev/null
+++ b/sum.c
@@ -0,0 +1,157 @@
+/*
+ * UNG's Not GNU
+ *
+ * Copyright (c) 2022, Jakob Kaivo <jkk@ung.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#define _POSIX_C_SOURCE 200809L
+#include <errno.h>
+#include <inttypes.h>
+#include <libgen.h>
+#include <limits.h>
+#include <locale.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define MAX_SUM_WIDTH	(32)
+#define UINT32_BIT	(32)
+#define UINT16_BIT	(16)
+#define BLOCK_SIZE	(512)
+
+enum algorithm { UNSPECIFIED, ALTERNATIVE };
+
+struct sum {
+	uintmax_t size;
+	uintmax_t sum;
+};
+
+static char *progname = NULL;
+
+static uint32_t reverse(uint32_t n, int width)
+{
+	uint32_t r = 0;
+	for (int i = 0; i < width; i++) {
+		r |= (n & 0x1) << ((width - 1) - i);
+		n >>= 1;
+	}
+	return r;
+}
+
+static struct sum sum_obsolete(FILE *f, int alt)
+{
+	struct sum sum = { 0 };
+
+	int c;
+	while ((c = fgetc(f)) != EOF) {
+		sum.size++;
+
+		if (alt) {
+			sum.sum = (sum.sum >> 1) +
+				((sum.sum & 1) << (UINT16_BIT - 1));
+		}
+
+		sum.sum += c;
+
+		if (alt) {
+			sum.sum &= UINT16_MAX;
+		}
+	}
+
+	sum.sum = (sum.sum & UINT16_MAX) + (sum.sum >> UINT16_BIT);
+
+	/* obsolete sum program prints number of 512 byte blocks */
+	if (sum.size % BLOCK_SIZE != 0) {
+		sum.size += BLOCK_SIZE;
+	}
+	sum.size /= BLOCK_SIZE;
+
+	return sum;
+}
+
+static struct sum sum_unspecified(FILE *f)
+{
+	return sum_obsolete(f, 0);
+}
+
+static struct sum sum_alternative(FILE *f)
+{
+	return sum_obsolete(f, 1);
+}
+
+int cksum(const char *path, enum algorithm alg)
+{
+	FILE *f = stdin;
+	if (path && strcmp(path, "-")) {
+		f = fopen(path, "rb");
+	}
+
+	if (f == NULL) {
+		fprintf(stderr, "%s: %s: %s\n", progname, path, strerror(errno));
+		return 1;
+	}
+
+	struct sum sum;
+	switch (alg) {
+	case UNSPECIFIED:
+		sum = sum_unspecified(f);
+		break;
+
+	case ALTERNATIVE:
+		sum = sum_alternative(f);
+		break;
+
+	default:
+		break;
+	}
+
+	printf("%"PRIuMAX" %"PRIuMAX"", sum.sum, sum.size);
+
+	if (f != stdin) {
+		printf(" %s", path);
+		fclose(f);
+	}
+	putchar('\n');
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	setlocale(LC_ALL, "");
+
+	fprintf(stderr, "sum: utility is obsolete; use cksum\n");
+
+	enum algorithm alg = UNSPECIFIED;
+
+	int c;
+	while ((c = getopt(argc, argv, "r")) != -1) {
+		switch (c) {
+		case 'r':
+			alg = ALTERNATIVE;
+			break;
+
+		default:
+			return 1;
+		}
+	}
+
+	int r = 0;
+	do {
+		r |= cksum(argv[optind++], alg);
+	} while (optind < argc);
+	return r;
+}