From 1039bfcfc098b69d56ecb39d198a092552eacf6d Mon Sep 17 00:00:00 2001
From: Lasse Collin <lasse.collin@tukaani.org>
Date: Tue, 5 Apr 2011 15:27:26 +0300
Subject: [PATCH] xz: Use posix_fadvise() if it is available.

---
 configure.ac     |  3 +++
 src/xz/file_io.c | 15 +++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/configure.ac b/configure.ac
index 35720fef..720315f0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -517,6 +517,9 @@ gl_GETOPT
 # Find the best function to set timestamps.
 AC_CHECK_FUNCS([futimens futimes futimesat utimes utime], [break])
 
+# This is nice to have but not mandatory.
+AC_CHECK_FUNCS([posix_fadvise])
+
 TUKLIB_PROGNAME
 TUKLIB_INTEGER
 TUKLIB_PHYSMEM
diff --git a/src/xz/file_io.c b/src/xz/file_io.c
index 09edcca6..56acf3bd 100644
--- a/src/xz/file_io.c
+++ b/src/xz/file_io.c
@@ -293,6 +293,10 @@ io_open_src_real(file_pair *pair)
 		pair->src_fd = STDIN_FILENO;
 #ifdef TUKLIB_DOSLIKE
 		setmode(STDIN_FILENO, O_BINARY);
+#endif
+#ifdef HAVE_POSIX_FADVISE
+		// It will fail if stdin is a pipe and that's fine.
+		(void)posix_fadvise(STDIN_FILENO, 0, 0, POSIX_FADV_SEQUENTIAL);
 #endif
 		return false;
 	}
@@ -497,6 +501,17 @@ io_open_src_real(file_pair *pair)
 	}
 #endif
 
+#ifdef HAVE_POSIX_FADVISE
+	const int fadvise_ret = posix_fadvise(
+			pair->src_fd, 0, 0, POSIX_FADV_SEQUENTIAL);
+
+	// It shouldn't fail, but if it does anyway, it doesn't matter.
+	// Check it with an assertion so that if something gets messed
+	// up in the future, it will get caught when debugging is enabled.
+	assert(fadvise_ret == 0);
+	(void)fadvise_ret;
+#endif
+
 	return false;
 
 error_msg: