From 3ebbd00cf3c5a7c6f90e2fed8adaf0c5145fb4ac Mon Sep 17 00:00:00 2001 From: Jim Hill Date: Sun, 31 May 2015 11:16:45 -0700 Subject: [PATCH] strbuf_read(): skip unnecessary strbuf_grow() at eof The loop in strbuf_read() uses xread() repeatedly while extending the strbuf until the call returns zero. If the buffer is sufficiently large to begin with, this results in xread() returning the remainder of the file to the end (returning non-zero), the loop extending the strbuf, and then making another call to xread() to have it return zero. By using read_in_full(), we can tell when the read reached the end of file: when it returns less than was requested, it's eof. This way we can avoid an extra iteration that allocates an extra 8kB that is never used. Signed-off-by: Jim Hill Reviewed-by: Jeff King Signed-off-by: Junio C Hamano --- strbuf.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/strbuf.c b/strbuf.c index ee96dcfb816625..ede99d372fe4d2 100644 --- a/strbuf.c +++ b/strbuf.c @@ -348,19 +348,19 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint) strbuf_grow(sb, hint ? hint : 8192); for (;;) { - ssize_t cnt; + ssize_t want = sb->alloc - sb->len - 1; + ssize_t got = read_in_full(fd, sb->buf + sb->len, want); - cnt = xread(fd, sb->buf + sb->len, sb->alloc - sb->len - 1); - if (cnt < 0) { + if (got < 0) { if (oldalloc == 0) strbuf_release(sb); else strbuf_setlen(sb, oldlen); return -1; } - if (!cnt) + sb->len += got; + if (got < want) break; - sb->len += cnt; strbuf_grow(sb, 8192); }