From d0f69b355df45a86e90b4eaf9cebeb63c4c5e5d4 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Dag-Erling=20Sm=C3=B8rgrav?= <des@des.no>
Date: Tue, 14 Oct 2025 02:08:44 +0200
Subject: [PATCH] Add archive_string_dirname()

This function performs the equivalent of POSIX dirname(3) on a
struct archive_string.
---
 libarchive/archive_string.c           | 20 ++++++++++++++
 libarchive/archive_string.h           |  4 +++
 libarchive/test/test_archive_string.c | 38 +++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)

diff --git a/libarchive/archive_string.c b/libarchive/archive_string.c
index 3bb978335..740308b6e 100644
--- a/libarchive/archive_string.c
+++ b/libarchive/archive_string.c
@@ -2054,6 +2054,26 @@ archive_strncat_l(struct archive_string *as, const void *_p, size_t n,
 	return (r);
 }
 
+struct archive_string *
+archive_string_dirname(struct archive_string *as)
+{
+	/* strip trailing separators */
+	while (as->length > 1 && as->s[as->length - 1] == '/')
+		as->length--;
+	/* strip final component */
+	while (as->length > 0 && as->s[as->length - 1] != '/')
+		as->length--;
+	/* empty path -> cwd */
+	if (as->length == 0)
+		return (archive_strcat(as, "."));
+	/* strip separator(s) */
+	while (as->length > 1 && as->s[as->length - 1] == '/')
+		as->length--;
+	/* terminate */
+	as->s[as->length] = '\0';
+	return (as);
+}
+
 #if HAVE_ICONV
 
 /*
diff --git a/libarchive/archive_string.h b/libarchive/archive_string.h
index e8987867d..d5f5c03ac 100644
--- a/libarchive/archive_string.h
+++ b/libarchive/archive_string.h
@@ -192,6 +192,10 @@ void	archive_string_vsprintf(struct archive_string *, const char *,
 void	archive_string_sprintf(struct archive_string *, const char *, ...)
 	    __LA_PRINTF(2, 3);
 
+/* Equivalent to dirname(3) */
+struct archive_string *
+archive_string_dirname(struct archive_string *);
+
 /* Translates from MBS to Unicode. */
 /* Returns non-zero if conversion failed in any way. */
 int archive_wstring_append_from_mbs(struct archive_wstring *dest,
diff --git a/libarchive/test/test_archive_string.c b/libarchive/test/test_archive_string.c
index 30f7a800e..bf822c0d5 100644
--- a/libarchive/test/test_archive_string.c
+++ b/libarchive/test/test_archive_string.c
@@ -353,6 +353,43 @@ test_archive_string_sprintf(void)
 	archive_string_free(&s);
 }
 
+static void
+test_archive_string_dirname(void)
+{
+	static struct pair { const char *str, *exp; } pairs[] = {
+		{ "",		"." },
+		{ "/",		"/" },
+		{ "//",		"/" },
+		{ "///",	"/" },
+		{ "./",		"." },
+		{ ".",		"." },
+		{ "..",		"." },
+		{ "foo",	"." },
+		{ "foo/",	"." },
+		{ "foo//",	"." },
+		{ "foo/bar",	"foo" },
+		{ "foo/bar/",	"foo" },
+		{ "foo/bar//",	"foo" },
+		{ "foo//bar",	"foo" },
+		{ "foo//bar/",	"foo" },
+		{ "foo//bar//",	"foo" },
+		{ "/foo",	"/" },
+		{ "//foo",	"/" },
+		{ "//foo/",	"/" },
+		{ "//foo//",	"/" },
+		{ 0 },
+	};
+	struct pair *pair;
+	struct archive_string s;
+
+	archive_string_init(&s);
+	for (pair = pairs; pair->str; pair++) {
+		archive_strcpy(&s, pair->str);
+		archive_string_dirname(&s);
+		assertEqualString(pair->exp, s.s);
+	}
+}
+
 DEFINE_TEST(test_archive_string)
 {
 	test_archive_string_ensure();
@@ -364,6 +401,7 @@ DEFINE_TEST(test_archive_string)
 	test_archive_string_concat();
 	test_archive_string_copy();
 	test_archive_string_sprintf();
+	test_archive_string_dirname();
 }
 
 static const char *strings[] =
-- 
2.47.3