linux-kernel - [PATCH 31/32] tools/nolibc: implement width padding in printf()

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Message-Id: <20250304-nolibc-kselftest-harness-v1-31-adca7cd231e2@linutronix.de>
Date: Tue, 04 Mar 2025 08:11:01 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Shuah Khan <shuah@...nel.org>, Shuah Khan <skhan@...uxfoundation.org>, 
 Willy Tarreau <w@....eu>, 
 Thomas Weißschuh <linux@...ssschuh.net>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH 31/32] tools/nolibc: implement width padding in printf()

printf can pad each argument to a certain width.
Implement this for compatibility with the kselftest harness.
Currently only padding with spaces is supported.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 tools/include/nolibc/stdio.h                 | 17 ++++++++++++++++-
 tools/testing/selftests/nolibc/nolibc-test.c |  3 +++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index e9f9cb2e8d9877221b442f9f3757d7ace1a5538c..9258cc1c406879b34f65fff442c0f112ede160fa 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -220,7 +220,7 @@ int _printf(_printf_cb cb, intptr_t state, size_t n, const char *fmt, va_list ar
 {
 	char escape, lpref, c;
 	unsigned long long v;
-	unsigned int written;
+	unsigned int written, width;
 	size_t len, ofs, w;
 	char tmpbuf[21];
 	const char *outstr;
@@ -228,10 +228,20 @@ int _printf(_printf_cb cb, intptr_t state, size_t n, const char *fmt, va_list ar
 	written = ofs = escape = lpref = 0;
 	while (1) {
 		c = fmt[ofs++];
+		width = 0;
 
 		if (escape) {
 			/* we're in an escape sequence, ofs == 1 */
 			escape = 0;
+
+			/* width */
+			while (c >= '0' && c <= '9') {
+				width *= 10;
+				width += c - '0';
+
+				c = fmt[ofs++];
+			}
+
 			if (c == 'c' || c == 'd' || c == 'u' || c == 'x' || c == 'p') {
 				char *out = tmpbuf;
 
@@ -309,6 +319,11 @@ int _printf(_printf_cb cb, intptr_t state, size_t n, const char *fmt, va_list ar
 			if (n) {
 				w = len < n ? len : n;
 				n -= w;
+				while (width-- > w) {
+					if (cb(state, " ", 1) != 0)
+						break;
+					written += 1;
+				}
 				if (cb(state, outstr, w) != 0)
 					break;
 			}
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 0a891c40e2afbb398ae39b43dbe977efdab042e2..b801b611e003a6f3ebd5bdbcd4f70961c1279a4d 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1398,6 +1398,9 @@ static int run_printf(int min, int max)
 		CASE_TEST(uintmax_t);    EXPECT_VFPRINTF(20, "18446744073709551615", "%ju", 0xffffffffffffffffULL); break;
 		CASE_TEST(intmax_t);     EXPECT_VFPRINTF(20, "-9223372036854775807", "%jd", 0x8000000000000001LL); break;
 		CASE_TEST(truncation);   EXPECT_VFPRINTF(25, "01234567890123456789", "%s", "0123456789012345678901234"); break;
+		CASE_TEST(string_width); EXPECT_VFPRINTF(10, "         1", "%10s", "1"); break;
+		CASE_TEST(number_width); EXPECT_VFPRINTF(10, "         1", "%10d", 1); break;
+		CASE_TEST(width_trunc);  EXPECT_VFPRINTF(25, "                    ", "%25d", 1); break;
 		CASE_TEST(scanf);        EXPECT_ZR(1, test_scanf()); break;
 		case __LINE__:
 			return ret; /* must be last */

-- 
2.48.1