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 <>
This commit is contained in:
Jim Hill 2015-05-31 11:16:45 -07:00 committed by Junio C Hamano
parent 282616c72d
commit 3ebbd00cf3
1 changed files with 5 additions and 5 deletions

View File

@ -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_setlen(sb, oldlen);
return -1;
if (!cnt)
sb->len += got;
if (got < want)
sb->len += cnt;
strbuf_grow(sb, 8192);