[klibc] fwrite: use memrchr() to find the final '\n' in _IOLBF mode

In line buffered mode, we need to split the write at the final '\n'
(which usually, but not always, is the last character in the string.)

Use memrchr() instead of open-coding it.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 4 insertions, 9 deletions

diff --git a/usr/klibc/stdio/fwrite.c b/usr/klibc/stdio/fwrite.c
index 5d2c3f01343eb..71ee75cc95892 100644
--- a/usr/klibc/stdio/fwrite.c
+++ b/usr/klibc/stdio/fwrite.c
@@ -59,6 +59,7 @@ size_t _fwrite(const void *buf, size_t count, FILE *file)
 	size_t bytes = 0;
 	size_t pf_len, pu_len;
 	const char *p = buf;
+	const char *q;
 
 	/* We divide the data into two chunks, flushed (pf)
 	   and unflushed (pu) depending on buffering mode
@@ -67,23 +68,16 @@ size_t _fwrite(const void *buf, size_t count, FILE *file)
 	switch (f->bufmode) {
 	case _IOFBF:
 		pf_len = 0;
-		pu_len = count;
 		break;
 
 	case _IOLBF:
-		pf_len = count;
-		pu_len = 0;
-
-		while (pf_len && p[pf_len-1] != '\n') {
-			pf_len--;
-			pu_len++;
-		}
+		q = memrchr(p, '\n', count);
+		pf_len = q ? q - p + 1 : 0;
 		break;
 
 	case _IONBF:
 	default:
 		pf_len = count;
-		pu_len = 0;
 		break;
 	}
 
@@ -94,6 +88,7 @@ size_t _fwrite(const void *buf, size_t count, FILE *file)
 			return bytes;
 	}
 
+	pu_len = count - pf_len;
 	if (pu_len)
 		bytes += fwrite_noflush(p, pu_len, f);