[PERLIO] In line-buffered mode, flush on the *last* newline,

not on every newline.

p4raw-id: //depot/perl@22478

1 files changed, 16 insertions, 21 deletions

diff --git a/perlio.c b/perlio.c
index 87ac75f4a5..da4a1822b6 100644
--- a/perlio.c
+++ b/perlio.c
@@ -3691,6 +3691,7 @@ PerlIOBuf_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
     PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
     const STDCHAR *buf = (const STDCHAR *) vbuf;
+    const STDCHAR *flushptr = buf;
     Size_t written = 0;
     if (!b->buf)
 	PerlIO_get_base(f);
@@ -3701,32 +3702,26 @@ PerlIOBuf_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 	    return 0;
 	}
     }	
+    if (PerlIOBase(f)->flags & PERLIO_F_LINEBUF) {
+	flushptr = buf + count;
+	while (flushptr > buf && *(flushptr - 1) != '\n')
+	    --flushptr;
+    }
     while (count > 0) {
 	SSize_t avail = b->bufsiz - (b->ptr - b->buf);
 	if ((SSize_t) count < avail)
 	    avail = count;
+	if (flushptr > buf && flushptr <= buf + avail)
+	    avail = flushptr - buf;
 	PerlIOBase(f)->flags |= PERLIO_F_WRBUF;
-	if (PerlIOBase(f)->flags & PERLIO_F_LINEBUF) {
-	    while (avail > 0) {
-		int ch = *buf++;
-		*(b->ptr)++ = ch;
-		count--;
-		avail--;
-		written++;
-		if (ch == '\n') {
-		    PerlIO_flush(f);
-		    break;
-		}
-	    }
-	}
-	else {
-	    if (avail) {
-		Copy(buf, b->ptr, avail, STDCHAR);
-		count -= avail;
-		buf += avail;
-		written += avail;
-		b->ptr += avail;
-	    }
+	if (avail) {
+	    Copy(buf, b->ptr, avail, STDCHAR);
+	    count -= avail;
+	    buf += avail;
+	    written += avail;
+	    b->ptr += avail;
+	    if (buf == flushptr)
+		PerlIO_flush(f);
 	}
 	if (b->ptr >= (b->buf + b->bufsiz))
 	    PerlIO_flush(f);