From df0c783f4bcbeb93bccd24c33160863563e2f3dc Mon Sep 17 00:00:00 2001 From: Bart Schaefer Date: Thu, 28 Apr 2022 21:06:51 -0700 Subject: 50133: use read-ahead and lseek-rewind for efficient line-buffered input --- Src/input.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'Src/input.c') diff --git a/Src/input.c b/Src/input.c index c59232681..9898a7177 100644 --- a/Src/input.c +++ b/Src/input.c @@ -217,12 +217,34 @@ shinbufrestore(void) static int shingetchar(void) { - int nread; + int nread, rsize = isset(SHINSTDIN) ? 1 : SHINBUFSIZE; if (shinbufptr < shinbufendptr) return STOUC(*shinbufptr++); shinbufreset(); +#ifdef USE_LSEEK + if (rsize == 1 && lseek(SHIN, 0, SEEK_CUR) != (off_t)-1) + rsize = SHINBUFSIZE; + if (rsize > 1) { + do { + errno = 0; + nread = read(SHIN, shinbuffer, rsize); + } while (nread < 0 && errno == EINTR); + if (nread <= 0) + return -1; + if (isset(SHINSTDIN) && + (shinbufendptr = memchr(shinbuffer, '\n', nread))) { + shinbufendptr++; + rsize = (shinbufendptr - shinbuffer); + if (nread > rsize && + lseek(SHIN, -(nread - rsize), SEEK_CUR) < 0) + zerr("lseek(%d, %d): %e", SHIN, -(nread - rsize), errno); + } else + shinbufendptr = shinbuffer + nread; + return STOUC(*shinbufptr++); + } +#endif for (;;) { errno = 0; nread = read(SHIN, shinbufendptr, 1); -- cgit 1.4.1