rot13->rot

rot/Makefile

@@ -0,0 +1,9 @@
+rot-ascii.o: rot-ascii.c rot-ascii.h
+
+rot-ascii: rot-ascii.o
+	$(CC) $(CFLAGS) -c -o rot.o -include "rot-ascii.h" rot.c
+	$(CC) $(CFLAGS) -o rot-ascii rot.o rot-ascii.o
+
+rot-unicode: rot-unicode.o
+	$(CC) $(CFLAGS) -c -o rot.o -include "rot-unicode.h" rot.c
+	$(CC) $(CFLAGS) -o rot-unicode rot.o rot-unicode.o

rot/rot-ascii.c

@@ -0,0 +1,30 @@
+#include "rot-ascii.h"
+
+#include <stdlib.h> /* size_t */
+
+static CHAR
+caesar_lower(CHAR c, size_t r){
+	static char alpha_lower[] = "abcdefghijklmnopqrstuvwxyz"
+	                            "abcdefghijklmnopqrstuvwxyz";
+
+	return alpha_lower[c - alpha_lower[0]
+		+ r % 26 /* length of alphabet */];
+}
+
+static CHAR
+caesar_upper(CHAR c, size_t r){
+	static char alpha_upper[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	                            "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+	return alpha_upper[c - alpha_upper[0]
+		+ r % 26 /* length of alphabet */];
+}
+
+CHAR
+caesar(CHAR c, size_t r){
+	return !ISALPHA(c)
+		? c
+		: ISLOWER(c)
+			? caesar_lower(c, r)
+			: caesar_upper(c, r);
+}

rot/rot-ascii.h

@@ -0,0 +1,10 @@
+typedef int CHAR;
+#include <ctype.h> /* isalpha(3), islower(3), isupper(3) */
+#define ISALPHA(a) (((a) < 0x80) && isalpha(a))
+#define ISLOWER(a) (((a) < 0x80) && islower(a))
+#define ISUPPER(a) (((a) < 0x80) && isupper(a))
+#include <stdio.h> /* getc(3), putc(3), stdin, stdout, EOF */
+#define ENDOFFILE EOF
+#define GETC getc
+#define PUTC putc
+/* #include <stdlib.h> /* size_t */

rot/rot-unicode.c

@@ -0,0 +1,33 @@
+#include "rot-unicode.h"
+
+#include <stdlib.h> /* size_t */
+
+/* this file is essentially the same as rot-ascii.c */
+/* TODO: multilingual rot */
+
+static CHAR
+caesar_lower(CHAR c, size_t r){
+	static char alpha_lower[] = "abcdefghijklmnopqrstuvwxyz"
+	                            "abcdefghijklmnopqrstuvwxyz";
+
+	return : alpha_lower[c - alpha_lower[0]
+		+ r % 26 /* length of alphabet */];
+}
+
+static CHAR
+caesar_upper(CHAR c, size_t r){
+	static char alpha_upper[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	                            "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+	return alpha_upper[c - alpha_upper[0]
+		+ r % 26 /* length of alphabet */];
+}
+
+CHAR
+caesar(CHAR c, size_t r){
+	return !ISALPHA(c)
+		? c
+		: ISLOWER(c)
+			? caesar_lower(c, r)
+			: caesar_upper(c, r);
+}

rot/rot-unicode.h

@@ -0,0 +1,13 @@
+#include <utypes.h> /* UChar32 */
+typedef UChar32 CHAR;
+#include <uchar.h> /* u_islower(3), u_isupper(3) */
+#include <ctype.h> /* isalpha(3) */
+#define ISALPHA(a) (((a) < 0x80) && isalpha(a))
+#define ISLOWER u_islower
+#define ISUPPER u_isupper
+#include <ustdio.h> /* u_fgetc(3), u_fputc(3), U_EOF */
+#define ENDOFFILE U_EOF
+#define GETC u_fgetc
+#define PUTC u_fputc
+#include <stdio.h> /* stdin, stdout */
+/* #include <stdlib.h> /* size_t */

rot/rot.c

@@ -0,0 +1,37 @@
+#include <errno.h> /* errno */
+#include <stdlib.h> /* strtol(3), size_t */
+#if !defined EX_OK || !defined EX_USAGE
+#	include <sysexits.h> /* EX_OK, EX_USAGE */
+#endif
+
+CHAR caesar(CHAR c, size_t r);
+
+static char *program_name = "rot";
+
+int main(int argc, char *argv[]){
+	CHAR c;
+	size_t r;
+
+	if(argc > 2){
+		fprintf(stderr, "Usage: %s (rotation)\n",
+			argv[0] == NULL ? program_name : argv[0]
+		);
+		return EX_USAGE;
+	}
+
+	if(argc == 2){
+		r = strtol(argv[1], &argv[1], 10);
+		if(*argv[1] != '\0' || errno != 0){
+			fprintf(stderr, "%s: Invalid rotation\n", argv[0]);
+			return EX_USAGE;
+		}
+	}else
+		r = 13; /* default to rot13 */
+
+
+	while((c = GETC(stdin)) != ENDOFFILE)
+		if(PUTC(caesar(c, r), stdout) == ENDOFFILE)
+			break;
+	
+	return EX_OK;
+}

rot/rot13

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec rot 13

rot/rot13.1

@@ -0,0 +1,32 @@
+.TH ROT13 1
+
+.SH NAME
+
+rot13 \- decrypt/encrypt 13-degree caesar-rotated text
+
+.SH DESCRIPTION
+
+.B rot13
+is a filter program that writes to standard output each Alphabet character from standard input, rotated 13 places.
+Non-Alphabet characters are ignored.
+
+.SH DIAGNOSTICS
+
+.B rot13
+will exit with the appropriate status from sysexits(3) if executed improperly.
+Otherwise,
+.B rot13
+will always exit with status 0, unless there are any unforeseen errors, in which case it will crash without grace. 
+
+
+.SH BUGS
+
+Not Unicode compatible.
+
+.SH COPYRIGHT
+
+Public domain.
+
+.SH SEE ALSO
+
+caesar(1)