string-util: tweak cellescape() a bit

For short buffer sizes cellescape() was a bit wasteful, as it might
suffice to to drop a single character to find enough place for the full
four byte ellipsis, if that one character was a four character escape.
With this rework we'll guarantee to drop the minimum number of
characters from the end to fit in the ellipsis.

If the buffers we write to are large this doesn't matter much. However,
if they are short (as they are when talking about the process comm
field) then it starts to matter that we put as much information as we
can in the space we get.

1 files changed, 68 insertions, 10 deletions

diff --git a/src/test/test-string-util.c b/src/test/test-string-util.c
index 413adfda7d..8b176781de 100644
--- a/src/test/test-string-util.c
+++ b/src/test/test-string-util.c
@@ -81,21 +81,79 @@ static void test_ascii_strcasecmp_nn(void) {
 static void test_cellescape(void) {
         char buf[40];
 
-        assert_se(streq(cellescape(buf, 10, "1"), "1"));
-        assert_se(streq(cellescape(buf, 10, "12"), "12"));
-        assert_se(streq(cellescape(buf, 10, "123"), is_locale_utf8() ? "1…" : "1..."));
-
-        assert_se(streq(cellescape(buf, 10, "1\011"), "1\\t"));
-        assert_se(streq(cellescape(buf, 10, "1\020"), "1\\020"));
-        assert_se(streq(cellescape(buf, 10, "1\020x"), is_locale_utf8() ? "1…" : "1..."));
+        assert_se(streq(cellescape(buf, 1, ""), ""));
+        assert_se(streq(cellescape(buf, 1, "1"), ""));
+        assert_se(streq(cellescape(buf, 1, "12"), ""));
+
+        assert_se(streq(cellescape(buf, 2, ""), ""));
+        assert_se(streq(cellescape(buf, 2, "1"), "1"));
+        assert_se(streq(cellescape(buf, 2, "12"), "."));
+        assert_se(streq(cellescape(buf, 2, "123"), "."));
+
+        assert_se(streq(cellescape(buf, 3, ""), ""));
+        assert_se(streq(cellescape(buf, 3, "1"), "1"));
+        assert_se(streq(cellescape(buf, 3, "12"), "12"));
+        assert_se(streq(cellescape(buf, 3, "123"), ".."));
+        assert_se(streq(cellescape(buf, 3, "1234"), ".."));
+
+        assert_se(streq(cellescape(buf, 4, ""), ""));
+        assert_se(streq(cellescape(buf, 4, "1"), "1"));
+        assert_se(streq(cellescape(buf, 4, "12"), "12"));
+        assert_se(streq(cellescape(buf, 4, "123"), "123"));
+        assert_se(streq(cellescape(buf, 4, "1234"), is_locale_utf8() ? "…" : "..."));
+        assert_se(streq(cellescape(buf, 4, "12345"), is_locale_utf8() ? "…" : "..."));
+
+        assert_se(streq(cellescape(buf, 5, ""), ""));
+        assert_se(streq(cellescape(buf, 5, "1"), "1"));
+        assert_se(streq(cellescape(buf, 5, "12"), "12"));
+        assert_se(streq(cellescape(buf, 5, "123"), "123"));
+        assert_se(streq(cellescape(buf, 5, "1234"), "1234"));
+        assert_se(streq(cellescape(buf, 5, "12345"), is_locale_utf8() ? "1…" : "1..."));
+        assert_se(streq(cellescape(buf, 5, "123456"), is_locale_utf8() ? "1…" : "1..."));
+
+        assert_se(streq(cellescape(buf, 1, "\020"), ""));
+        assert_se(streq(cellescape(buf, 2, "\020"), "."));
+        assert_se(streq(cellescape(buf, 3, "\020"), ".."));
+        assert_se(streq(cellescape(buf, 4, "\020"), "…"));
+        assert_se(streq(cellescape(buf, 5, "\020"), "\\020"));
+
+        assert_se(streq(cellescape(buf, 5, "1234\020"), "1…"));
+        assert_se(streq(cellescape(buf, 6, "1234\020"), "12…"));
+        assert_se(streq(cellescape(buf, 7, "1234\020"), "123…"));
+        assert_se(streq(cellescape(buf, 8, "1234\020"), "1234…"));
+        assert_se(streq(cellescape(buf, 9, "1234\020"), "1234\\020"));
+
+        assert_se(streq(cellescape(buf, 1, "\t\n"), ""));
+        assert_se(streq(cellescape(buf, 2, "\t\n"), "."));
+        assert_se(streq(cellescape(buf, 3, "\t\n"), ".."));
+        assert_se(streq(cellescape(buf, 4, "\t\n"), "…"));
+        assert_se(streq(cellescape(buf, 5, "\t\n"), "\\t\\n"));
+
+        assert_se(streq(cellescape(buf, 5, "1234\t\n"), "1…"));
+        assert_se(streq(cellescape(buf, 6, "1234\t\n"), "12…"));
+        assert_se(streq(cellescape(buf, 7, "1234\t\n"), "123…"));
+        assert_se(streq(cellescape(buf, 8, "1234\t\n"), "1234…"));
+        assert_se(streq(cellescape(buf, 9, "1234\t\n"), "1234\\t\\n"));
+
+        assert_se(streq(cellescape(buf, 4, "x\t\020\n"), "…"));
+        assert_se(streq(cellescape(buf, 5, "x\t\020\n"), "x…"));
+        assert_se(streq(cellescape(buf, 6, "x\t\020\n"), "x…"));
+        assert_se(streq(cellescape(buf, 7, "x\t\020\n"), "x\\t…"));
+        assert_se(streq(cellescape(buf, 8, "x\t\020\n"), "x\\t…"));
+        assert_se(streq(cellescape(buf, 9, "x\t\020\n"), "x\\t…"));
+        assert_se(streq(cellescape(buf, 10, "x\t\020\n"), "x\\t\\020\\n"));
+
+        assert_se(streq(cellescape(buf, 6, "1\011"), "1\\t"));
+        assert_se(streq(cellescape(buf, 6, "1\020"), "1\\020"));
+        assert_se(streq(cellescape(buf, 6, "1\020x"), is_locale_utf8() ? "1…" : "1..."));
 
         assert_se(streq(cellescape(buf, 40, "1\020"), "1\\020"));
         assert_se(streq(cellescape(buf, 40, "1\020x"), "1\\020x"));
 
         assert_se(streq(cellescape(buf, 40, "\a\b\f\n\r\t\v\\\"'"), "\\a\\b\\f\\n\\r\\t\\v\\\\\\\"\\'"));
-        assert_se(streq(cellescape(buf, 10, "\a\b\f\n\r\t\v\\\"'"), is_locale_utf8() ? "\\a…" : "\\a..."));
-        assert_se(streq(cellescape(buf, 11, "\a\b\f\n\r\t\v\\\"'"), is_locale_utf8() ? "\\a…" : "\\a..."));
-        assert_se(streq(cellescape(buf, 12, "\a\b\f\n\r\t\v\\\"'"), is_locale_utf8() ? "\\a\\b…" : "\\a\\b..."));
+        assert_se(streq(cellescape(buf, 6, "\a\b\f\n\r\t\v\\\"'"), is_locale_utf8() ? "\\a…" : "\\a..."));
+        assert_se(streq(cellescape(buf, 7, "\a\b\f\n\r\t\v\\\"'"), is_locale_utf8() ? "\\a…" : "\\a..."));
+        assert_se(streq(cellescape(buf, 8, "\a\b\f\n\r\t\v\\\"'"), is_locale_utf8() ? "\\a\\b…" : "\\a\\b..."));
 
         assert_se(streq(cellescape(buf, sizeof buf, "1\020"), "1\\020"));
         assert_se(streq(cellescape(buf, sizeof buf, "1\020x"), "1\\020x"));