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140 lines
3.8 KiB
140 lines
3.8 KiB
From cbe8d2bcdc20682464217856aa48628804637f28 Mon Sep 17 00:00:00 2001
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From: Bart Schaefer <schaefer@zsh.org>
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Date: Thu, 28 Apr 2022 21:06:51 -0700
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Subject: [PATCH] 50133: use read-ahead and lseek-rewind for efficient
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line-buffered input
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---
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ChangeLog | 6 ++++++
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Src/input.c | 24 ++++++++++++++++++++-
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configure.ac | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
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3 files changed, 88 insertions(+), 1 deletion(-)
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diff --git a/ChangeLog b/ChangeLog
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index cae2fc4e3..79c77741b 100644
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--- a/ChangeLog
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+++ b/ChangeLog
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@@ -1,3 +1,9 @@
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+2022-04-28 Bart Schaefer <schaefer@zsh.org>
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+
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+ * 50133 (Bart, PWS, Jun-ichi): Src/input.c, configure.ac: when
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+ lseek(2) is available, use it to check for and rewind read-ahead
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+ for more efficient line-buffered input.
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+
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2022-03-03 Peter Stephenson <p.w.stephenson@ntlworld.com>
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* 49792: Src/input.c, Test/A01grammar.ztst: Use line buffering
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diff --git a/Src/input.c b/Src/input.c
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index caa8e23b0..6cc1b8a51 100644
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--- a/Src/input.c
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+++ b/Src/input.c
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@@ -217,12 +217,34 @@ shinbufrestore(void)
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static int
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shingetchar(void)
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{
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- int nread;
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+ int nread, rsize = isset(SHINSTDIN) ? 1 : SHINBUFSIZE;
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if (shinbufptr < shinbufendptr)
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return STOUC(*shinbufptr++);
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shinbufreset();
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+#ifdef USE_LSEEK
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+ if (rsize == 1 && lseek(SHIN, 0, SEEK_CUR) != (off_t)-1)
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+ rsize = SHINBUFSIZE;
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+ if (rsize > 1) {
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+ do {
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+ errno = 0;
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+ nread = read(SHIN, shinbuffer, rsize);
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+ } while (nread < 0 && errno == EINTR);
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+ if (nread <= 0)
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+ return -1;
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+ if (isset(SHINSTDIN) &&
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+ (shinbufendptr = memchr(shinbuffer, '\n', nread))) {
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+ shinbufendptr++;
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+ rsize = (shinbufendptr - shinbuffer);
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+ if (nread > rsize &&
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+ lseek(SHIN, -(nread - rsize), SEEK_CUR) < 0)
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+ zerr("lseek(%d, %d): %e", SHIN, -(nread - rsize), errno);
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+ } else
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+ shinbufendptr = shinbuffer + nread;
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+ return STOUC(*shinbufptr++);
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+ }
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+#endif
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for (;;) {
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errno = 0;
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nread = read(SHIN, shinbufendptr, 1);
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diff --git a/configure.ac b/configure.ac
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index af8c5bba8..42f2837cd 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -2304,6 +2304,65 @@ if test x$zsh_cv_sys_fifo = xyes; then
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AC_DEFINE(HAVE_FIFOS)
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fi
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+dnl -----------
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+dnl check that lseek() correctly reports seekability.
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+dnl -----------
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+AC_CACHE_CHECK(if lseek() correctly reports seekability,
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+zsh_cv_sys_lseek,
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+[AC_RUN_IFELSE([AC_LANG_SOURCE([[
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+#include <stdio.h>
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+#include <sys/types.h>
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+#include <fcntl.h>
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+#include <unistd.h>
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+#include <sys/socket.h>
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+#include <sys/stat.h>
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+int main() {
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+ int pipefd[2], fd;
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+ off_t ret;
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+ char* tmpfile = "seekfiletest.tmp";
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+ if ((fd = open(tmpfile, O_CREAT, S_IRUSR)) < 0) {
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+ fprintf(stderr, "creating file failed\n");
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+ return 1;
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+ }
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+ ret = lseek(fd, 0, SEEK_CUR);
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+ close(fd);
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+ unlink(tmpfile);
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+ if (ret == (off_t)-1) {
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+ fprintf(stderr, "lseek on regular file failed\n");
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+ return 1;
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+ }
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+ if (pipe(pipefd) < 0) {
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+ fprintf(stderr, "creating pipe failed\n");
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+ return 1;
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+ }
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+ write(pipefd[1], "abcdefgh", 8);
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+ ret = lseek(pipefd[0], 0, SEEK_CUR);
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+ close(pipefd[0]);
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+ close(pipefd[1]);
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+ if (ret != (off_t)-1) {
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+ fprintf(stderr, "lseek on pipe succeeded\n");
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+ return 1;
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+ }
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+ if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
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+ fprintf(stderr, "creating UNIX domain socket failed\n");
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+ return 1;
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+ }
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+ ret = lseek(fd, 0, SEEK_CUR);
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+ close(fd);
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+ if (ret != (off_t)-1) {
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+ fprintf(stderr, "lseek on UNIX domain socket succeeded\n");
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+ return 1;
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+ }
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+ return 0;
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+}
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+]])],[zsh_cv_sys_lseek=yes],[zsh_cv_sys_lseek=no],[zsh_cv_sys_lseek=yes])
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+])
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+AH_TEMPLATE([USE_LSEEK],
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+[Define to 1 if lseek() can be used for SHIN.])
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+if test x$zsh_cv_sys_lseek = xyes; then
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+ AC_DEFINE(USE_LSEEK)
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+fi
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+
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dnl -----------
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dnl test for whether link() works
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dnl for instance, BeOS R4.51 doesn't support hard links yet
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--
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2.36.0
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