linux-kernel - [PATCH nolibc 20/61] tools/nolibc/stdio: add fwrite() to stdio

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Date:   Mon, 18 Apr 2022 17:41:44 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     gwml@...r.gnuweeb.org, kernel-team@...com, w@....eu,
        Willy Tarreau <w@....eu>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH nolibc 20/61] tools/nolibc/stdio: add fwrite() to stdio

From: Willy Tarreau <w@....eu>

We'll use it to write substrings. It relies on a simpler _fwrite() that
only takes one size. fputs() was also modified to rely on it.

Signed-off-by: Willy Tarreau <w@....eu>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 tools/include/nolibc/stdio.h | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index 149c5ca59aad..996bf89a30d2 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -84,12 +84,14 @@ int putchar(int c)
 }
 
 
-/* puts(), fputs(). Note that puts() emits '\n' but not fputs(). */
+/* fwrite(), puts(), fputs(). Note that puts() emits '\n' but not fputs(). */
 
+/* internal fwrite()-like function which only takes a size and returns 0 on
+ * success or EOF on error. It automatically retries on short writes.
+ */
 static __attribute__((unused))
-int fputs(const char *s, FILE *stream)
+int _fwrite(const void *buf, size_t size, FILE *stream)
 {
-	size_t len = strlen(s);
 	ssize_t ret;
 	int fd;
 
@@ -98,16 +100,35 @@ int fputs(const char *s, FILE *stream)
 
 	fd = 3 + (long)stream;
 
-	while (len > 0) {
-		ret = write(fd, s, len);
+	while (size) {
+		ret = write(fd, buf, size);
 		if (ret <= 0)
 			return EOF;
-		s += ret;
-		len -= ret;
+		size -= ret;
+		buf += ret;
 	}
 	return 0;
 }
 
+static __attribute__((unused))
+size_t fwrite(const void *s, size_t size, size_t nmemb, FILE *stream)
+{
+	size_t written;
+
+	for (written = 0; written < nmemb; written++) {
+		if (_fwrite(s, size, stream) != 0)
+			break;
+		s += size;
+	}
+	return written;
+}
+
+static __attribute__((unused))
+int fputs(const char *s, FILE *stream)
+{
+	return _fwrite(s, strlen(s), stream);
+}
+
 static __attribute__((unused))
 int puts(const char *s)
 {
-- 
2.31.1.189.g2e36527f23