From c9076497c235510f9358f9e3eadfe91fbfa9d5e3 Mon Sep 17 00:00:00 2001
From: Philipp Takacs <philipp@bureaucracy.de>
Date: Fri, 25 Aug 2023 20:28:55 +0200
Subject: [PATCH] mhbuild implement header folding

---
 h/mh.h                          |    2 ++
 h/prototypes.h                  |    1 +
 sbr/Makefile.in                 |    3 +-
 sbr/fold.c                      |   61 +++++++++++++++++++++++++++++++++++++++
 test/tests/mhbuild/test-folding |   35 ++++++++++++++++++++++
 uip/mhoutsbr.c                  |    5 +++-
 6 files changed, 105 insertions(+), 2 deletions(-)
 create mode 100644 sbr/fold.c
 create mode 100644 test/tests/mhbuild/test-folding

diff --git a/h/mh.h b/h/mh.h
index 3326185..280249e 100644
--- a/h/mh.h
+++ b/h/mh.h
@@ -221,6 +221,8 @@ struct msgs {
                            ** terminating NULL.
                            */
 
+#define MAXTEXTPERLN 78
+
 /* m_getfld2() returned data */
 struct field {
 	char name[NAMESZ];
diff --git a/h/prototypes.h b/h/prototypes.h
index fad1af4..182cf1c 100644
--- a/h/prototypes.h
+++ b/h/prototypes.h
@@ -114,6 +114,7 @@ void unquote_string(const char *input, char *output);
 int uprf(char *, char *);
 int vfgets(FILE *, char **);
 char *write_charset_8bit(void);
+void fold(charstring_t, size_t, const char *restrict);
 
 
 
diff --git a/sbr/Makefile.in b/sbr/Makefile.in
index cee1c45..ca8b20d 100644
--- a/sbr/Makefile.in
+++ b/sbr/Makefile.in
@@ -54,7 +54,8 @@ SRCS = addrsbr.c ambigsw.c brkstring.c  \
 	cpydata.c crawl_folders.c  \
 	charstring.c \
 	dtime.c dtimep.c  \
-	error.c execprog.c ext_hook.c folder_addmsg.c folder_delmsgs.c  \
+	error.c execprog.c ext_hook.c fold.c  \
+	folder_addmsg.c folder_delmsgs.c  \
 	folder_free.c folder_read.c  \
 	folder_realloc.c gans.c getans.c getanswer.c  \
 	getarguments.c \
diff --git a/sbr/fold.c b/sbr/fold.c
new file mode 100644
index 0000000..0189382
--- /dev/null
+++ b/sbr/fold.c
@@ -0,0 +1,61 @@
+/* fold.c -- fold a mail header field
+ *
+ * This code is Copyright (c), by the authors of nmh.  See the
+ * COPYRIGHT file in the root directory of the nmh distribution for
+ * complete copyright information. */
+
+#include <h/mh.h>
+#include <stdio.h>
+
+void
+fold(charstring_t dst, size_t namelen, const char *restrict body)
+{
+	const char *restrict body_next;
+	const char *restrict wsp;
+	const char *restrict wsp_next;
+	const int crlf = strchr(body, '\r') != NULL;
+	charstring_clear(dst);
+	namelen++;
+
+	while (*body) {
+		body_next = strchr(body, '\n');
+		if ((unsigned long) (body_next - body) <= MAXTEXTPERLN - namelen) {
+			charstring_push_back_chars(dst, body, body_next - body + 1);
+			namelen = 0;
+			body = body_next + 1;
+			continue;
+		}
+		wsp = body;
+		while (namelen == 0 && (*wsp == ' ' || *wsp == '\t')) {
+			wsp++;
+		}
+		wsp = wsp_next = strpbrk(wsp, " \t");
+
+		/* if now whitespace is in the current line just print the curret line as is */
+		if (!wsp_next || wsp_next > body_next) {
+			charstring_push_back_chars(dst, body, body_next - body + 1);
+			namelen = 0;
+			body = body_next + 1;
+			continue;
+		}
+
+		while ((unsigned long)(wsp_next - body) <= MAXTEXTPERLN - namelen) {
+			wsp = wsp_next;
+			wsp_next = strpbrk(wsp+1, " \t");
+			if (!wsp_next) {
+				break;
+			}
+			if (wsp_next > body_next) {
+				break;
+			}
+		}
+
+		charstring_push_back_chars(dst, body, wsp - body);
+		if (crlf) {
+			charstring_push_back(dst, '\r');
+		}
+		charstring_push_back(dst, '\n');
+		namelen = 0;
+		body = wsp;
+	}
+}
diff --git a/test/tests/mhbuild/test-folding b/test/tests/mhbuild/test-folding
new file mode 100644
index 0000000..366f82b
--- /dev/null
+++ b/test/tests/mhbuild/test-folding
@@ -0,0 +1,35 @@
+# test mhbuild linebreak for quoted-printable
+
+. "$MH_TEST_COMMON"
+
+
+draft="$MH_TEST_DIR/mhbuild-$$.draft"
+
+cat >"$draft" <<!
+From: meillo
+To: meillo
+Date: Thursday, 28 Sep 2006 00:02:00
+Subject: mhbuild header folding
+References: <aaaaaaaaaaaaaaaaaaaaaaaaaaa@example.com> <aaaaaaaaaaaaaaaaaaaaaaaaaab@example.com> <c@example.com>
+----------------
+Das ist ein test
+!
+
+
+
+runandcheck 'mhbuild "$draft"' <<!
+!
+
+runandcheck 'sed "/^Content-ID:/s/:.*/: <TESTID>/" "$draft"' <<!
+From: meillo
+To: meillo
+Date: Thursday, 28 Sep 2006 00:02:00
+Subject: mhbuild header folding
+References: <aaaaaaaaaaaaaaaaaaaaaaaaaaa@example.com>
+ <aaaaaaaaaaaaaaaaaaaaaaaaaab@example.com> <c@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="us-ascii"
+Content-ID: <TESTID>
+
+Das ist ein test
+!
diff --git a/uip/mhoutsbr.c b/uip/mhoutsbr.c
index 87e7943..2915afe 100644
--- a/uip/mhoutsbr.c
+++ b/uip/mhoutsbr.c
@@ -161,12 +161,15 @@ static void
 output_headers(CT ct, FILE *out)
 {
 	HF hp;
+	charstring_t body = charstring_create(0);
 
 	hp = ct->c_first_hf;
 	while (hp) {
-		fprintf(out, "%s:%s", hp->name, hp->value);
+		fold(body, strlen(hp->name), hp->value);
+		fprintf(out, "%s:%s", hp->name, charstring_buffer(body));
 		hp = hp->next;
 	}
+	charstring_free(body);
 }
 
 
-- 
1.7.10.4