shared: add nm_strquote() util

We already have nm_strquote_a(). That is useful, but uses alloca(), hence it
is ill suited to be called from a macro, inside a loop, or from a function
that should be inlined.

Instead, add nm_strquote() that has the same purpose but writes to a provided
string buffer.

libnm-core/tests/test-general.c

@@ -4852,6 +4852,88 @@ test_hexstr2bin (void)
 
 /*****************************************************************************/
 
+static void
+_do_strquote (const char *str, gsize buf_len, const char *expected)
+{
+	char canary = (char) nmtst_get_rand_int ();
+	gs_free char *buf_full = g_malloc (buf_len + 2);
+	char *buf = &buf_full[1];
+	const char *b;
+
+	buf[-1] = canary;
+	buf[buf_len] = canary;
+
+	if (buf_len == 0) {
+		b = nm_strquote (NULL, 0, str);
+		g_assert (b == NULL);
+		g_assert (expected == NULL);
+		b = nm_strquote (buf, 0, str);
+		g_assert (b == buf);
+	} else {
+		b = nm_strquote (buf, buf_len, str);
+		g_assert (b == buf);
+		g_assert (strlen (b) < buf_len);
+		g_assert_cmpstr (expected, ==, b);
+	}
+
+	g_assert (buf[-1] == canary);
+	g_assert (buf[buf_len] == canary);
+}
+
+static void
+test_nm_strquote (void)
+{
+	_do_strquote (NULL, 0, NULL);
+	_do_strquote ("", 0, NULL);
+	_do_strquote ("a", 0, NULL);
+	_do_strquote ("ab", 0, NULL);
+
+	_do_strquote (NULL, 1, "");
+	_do_strquote (NULL, 2, "(");
+	_do_strquote (NULL, 3, "(n");
+	_do_strquote (NULL, 4, "(nu");
+	_do_strquote (NULL, 5, "(nul");
+	_do_strquote (NULL, 6, "(null");
+	_do_strquote (NULL, 7, "(null)");
+	_do_strquote (NULL, 8, "(null)");
+	_do_strquote (NULL, 100, "(null)");
+
+	_do_strquote ("", 1, "");
+	_do_strquote ("", 2, "^");
+	_do_strquote ("", 3, "\"\"");
+	_do_strquote ("", 4, "\"\"");
+	_do_strquote ("", 5, "\"\"");
+	_do_strquote ("", 100, "\"\"");
+
+	_do_strquote ("a", 1, "");
+	_do_strquote ("a", 2, "^");
+	_do_strquote ("a", 3, "\"^");
+	_do_strquote ("a", 4, "\"a\"");
+	_do_strquote ("a", 5, "\"a\"");
+	_do_strquote ("a", 6, "\"a\"");
+	_do_strquote ("a", 100, "\"a\"");
+
+	_do_strquote ("ab", 1, "");
+	_do_strquote ("ab", 2, "^");
+	_do_strquote ("ab", 3, "\"^");
+	_do_strquote ("ab", 4, "\"a^");
+	_do_strquote ("ab", 5, "\"ab\"");
+	_do_strquote ("ab", 6, "\"ab\"");
+	_do_strquote ("ab", 7, "\"ab\"");
+	_do_strquote ("ab", 100, "\"ab\"");
+
+	_do_strquote ("abc", 1, "");
+	_do_strquote ("abc", 2, "^");
+	_do_strquote ("abc", 3, "\"^");
+	_do_strquote ("abc", 4, "\"a^");
+	_do_strquote ("abc", 5, "\"ab^");
+	_do_strquote ("abc", 6, "\"abc\"");
+	_do_strquote ("abc", 7, "\"abc\"");
+	_do_strquote ("abc", 100, "\"abc\"");
+}
+
+/*****************************************************************************/
+
 #define UUID_NIL        "00000000-0000-0000-0000-000000000000"
 #define UUID_NS_DNS     "6ba7b810-9dad-11d1-80b4-00c04fd430c8"
 
@@ -6366,6 +6448,7 @@ int main (int argc, char **argv)
 	g_test_add_func ("/core/general/test_setting_user_data", test_setting_user_data);
 
 	g_test_add_func ("/core/general/hexstr2bin", test_hexstr2bin);
+	g_test_add_func ("/core/general/nm_strquote", test_nm_strquote);
 	g_test_add_func ("/core/general/test_nm_utils_uuid_generate_from_string", test_nm_utils_uuid_generate_from_string);
 	g_test_add_func ("/core/general/_nm_utils_uuid_generate_from_strings", test_nm_utils_uuid_generate_from_strings);
 

shared/nm-utils/nm-shared-utils.c

@@ -115,6 +115,78 @@ nm_utils_strbuf_append (char **buf, gsize *len, const char *format, ...)
 
 /*****************************************************************************/
 
+/**
+ * nm_strquote:
+ * @buf: the output buffer of where to write the quoted @str argument.
+ * @buf_len: the size of @buf.
+ * @str: (allow-none): the string to quote.
+ *
+ * Writes @str to @buf with quoting. The resulting buffer
+ * is always NUL terminated, unless @buf_len is zero.
+ * If @str is %NULL, it writes "(null)".
+ *
+ * If @str needs to be truncated, the closing quote is '^' instead
+ * of '"'.
+ *
+ * This is similar to nm_strquote_a(), which however uses alloca()
+ * to allocate a new buffer. Also, here @buf_len is the size of @buf,
+ * while nm_strquote_a() has the number of characters to print. The latter
+ * doesn't include the quoting.
+ *
+ * Returns: the input buffer with the quoted string. */
+const char *
+nm_strquote (char *buf, gsize buf_len, const char *str)
+{
+	const char *const buf0 = buf;
+
+	if (!str) {
+		nm_utils_strbuf_append_str (&buf, &buf_len, "(null)");
+		goto out;
+	}
+
+	if (G_UNLIKELY (buf_len <= 2)) {
+		switch (buf_len) {
+		case 2:
+			*(buf++) = '^';
+			/* fall-through*/
+		case 1:
+			*(buf++) = '\0';
+			break;
+		}
+		goto out;
+	}
+
+	*(buf++) = '"';
+	buf_len--;
+
+	nm_utils_strbuf_append_str (&buf, &buf_len, str);
+
+	/* if the string was too long we indicate truncation with a
+	 * '^' instead of a closing quote. */
+	if (G_UNLIKELY (buf_len <= 1)) {
+		switch (buf_len) {
+		case 1:
+			buf[-1] = '^';
+			break;
+		case 0:
+			buf[-2] = '^';
+			break;
+		default:
+			nm_assert_not_reached ();
+			break;
+		}
+	} else {
+		nm_assert (buf_len >= 2);
+		*(buf++) = '"';
+		*(buf++) = '\0';
+	}
+
+out:
+	return buf0;
+}
+
+/*****************************************************************************/
+
 char _nm_utils_to_string_buffer[];
 
 void

shared/nm-utils/nm-shared-utils.h

@@ -166,6 +166,8 @@ void nm_utils_strbuf_append (char **buf, gsize *len, const char *format, ...) _n
 void nm_utils_strbuf_append_c (char **buf, gsize *len, char c);
 void nm_utils_strbuf_append_str (char **buf, gsize *len, const char *str);
 
+const char *nm_strquote (char *buf, gsize buf_len, const char *str);
+
 /*****************************************************************************/
 
 const char **nm_utils_strsplit_set (const char *str, const char *delimiters);