calendar: use iconv to respect the output encoding

calendar(1) can have input in various encoding, specifying
LANG=<locale_name> to enable calendar(1) to determine which one to use.

The problem is the content of the calendar itself is exposed as is making it
unreadable in many cases. For example french calendar which is encoded
ISO8859-1 is rendered badly in a fr_FR.UTF-8 environment.

Using iconv allows to solve this issue.
This will also allow to keep only 1 encoding in base for those files without
breaking user existing setup

Reported by:	many
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D19221

1 files changed, 119 insertions, 15 deletions

diff --git a/usr.bin/calendar/events.c b/usr.bin/calendar/events.c
index 113962bc8a03..84f8f2b41a8b 100644
--- a/usr.bin/calendar/events.c
+++ b/usr.bin/calendar/events.c
@@ -35,10 +35,120 @@ __FBSDID("$FreeBSD$");
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#ifdef WITH_ICONV
+#include <iconv.h>
+#include <errno.h>
+#include <langinfo.h>
+
+static iconv_t conv = (iconv_t)-1;
+static char *currentEncoding = NULL;
+
+#endif
 
 #include "pathnames.h"
 #include "calendar.h"
 
+#ifdef WITH_ICONV
+void
+set_new_encoding(void)
+{
+	const char *newenc;
+
+	newenc = nl_langinfo(CODESET);
+	if (currentEncoding == NULL) {
+		currentEncoding = strdup(newenc);
+		if (currentEncoding == NULL)
+			errx(1, "set_new_encoding: cannot allocate memory");
+		return;
+	}
+	if (strcmp(currentEncoding, newenc) == 0)
+		return;
+	free(currentEncoding);
+	currentEncoding = strdup(newenc);
+	if (currentEncoding == NULL)
+		errx(1, "set_new_encoding: cannot allocate memory");
+	if (conv != (iconv_t) -1) {
+		iconv_close(conv);
+		conv = (iconv_t) -1;
+	}
+}
+#endif
+
+static char *
+convert(char *input)
+{
+	char *output;
+#ifdef WITH_ICONV
+	size_t inleft, outleft, converted = 0;
+	char *outbuf, *tmp;
+	char *inbuf;
+	size_t outlen;
+
+	if (currentEncoding == NULL) {
+		output = strdup(input);
+		if (output == NULL)
+			errx(1, "convert: cannot allocate memory");
+		return (output);
+	}
+	if (conv == (iconv_t)-1) {
+		conv = iconv_open(outputEncoding, currentEncoding);
+		if (conv == (iconv_t)-1) {
+			if (errno == EINVAL)
+				errx(1, "Conversion is not supported");
+			else
+				err(1, "Initialization failure");
+		}
+	}
+
+	inleft = strlen(input);
+	inbuf = input;
+
+	outlen = inleft;
+	if ((output = malloc(outlen + 1)) == NULL)
+		errx(1, "convert: cannot allocate memory");
+
+	for (;;) {
+		errno = 0;
+		outbuf = output + converted;
+		outleft = outlen - converted;
+
+		converted = iconv(conv, (char **) &inbuf, &inleft, &outbuf, &outleft);
+		if (converted != (size_t) -1 || errno == EINVAL) {
+			/* finished or invalid multibyte, so truncate and ignore */
+			break;
+		}
+
+		if (errno != E2BIG) {
+			free(output);
+			err(1, "convert");
+		}
+
+		converted = outbuf - output;
+		outlen += inleft * 2;
+
+		if ((tmp = realloc(output, outlen + 1)) == NULL) {
+			free(output);
+			errx(1, "convert: cannot allocate memory");
+		}
+
+		output = tmp;
+		outbuf = output + converted;
+	}
+
+	/* flush the iconv conversion */
+	iconv(conv, NULL, NULL, &outbuf, &outleft);
+
+	/* null terminate the string */
+	*outbuf = '\0';
+#else
+	output = strdup(input);
+	if (output == NULL)
+		errx(1, "convert: cannot allocate memory");
+#endif
+
+	return (output);
+}
+
 struct event *
 event_add(int year, int month, int day, char *date, int var, char *txt,
     char *extra)
@@ -58,15 +168,15 @@ event_add(int year, int month, int day, char *date, int var, char *txt,
 	e->month = month;
 	e->day = day;
 	e->var = var;
-	e->date = strdup(date);
+	e->date = convert(date);
 	if (e->date == NULL)
 		errx(1, "event_add: cannot allocate memory");
-	e->text = strdup(txt);
+	e->text = convert(txt);
 	if (e->text == NULL)
 		errx(1, "event_add: cannot allocate memory");
 	e->extra = NULL;
 	if (extra != NULL && extra[0] != '\0')
-		e->extra = strdup(extra);
+		e->extra = convert(extra);
 	addtodate(e, year, month, day);
 	return (e);
 }
@@ -74,23 +184,17 @@ event_add(int year, int month, int day, char *date, int var, char *txt,
 void
 event_continue(struct event *e, char *txt)
 {
-	char *text;
+	char *oldtext, *text;
 
-	/*
-	 * Adding text to the event:
-	 * - Save a copy of the old text (unknown length, so strdup())
-	 * - Allocate enough space for old text + \n + new text + 0
-	 * - Store the old text + \n + new text
-	 * - Destroy the saved copy.
-	 */
-	text = strdup(e->text);
-	if (text == NULL)
+	text = convert(txt);
+	oldtext = e->text;
+	if (oldtext == NULL)
 		errx(1, "event_continue: cannot allocate memory");
 
-	free(e->text);
-	asprintf(&e->text, "%s\n%s", text, txt);
+	asprintf(&e->text, "%s\n%s", oldtext, text);
 	if (e->text == NULL)
 		errx(1, "event_continue: cannot allocate memory");
+	free(oldtext);
 	free(text);
 
 	return;