From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 4/4] syscall: golf + more idiomatic buffer initialization
Date: Mon, 18 Apr 2022 09:50:04 +0000 [thread overview]
Message-ID: <20220418095004.466-5-e@80x24.org> (raw)
In-Reply-To: <20220418095004.466-1-e@80x24.org>
While `vec' is useful for user-supplied buffers to avoid excess
memory traffic, but provides no benefit when we need to allocate
our own buffers as we do in nodatacow_fh, since Perl can't elide
memset(ptr, 0, len). So just use the idiomatic `"\0" x $LEN' here.
---
lib/PublicInbox/Syscall.pm | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/lib/PublicInbox/Syscall.pm b/lib/PublicInbox/Syscall.pm
index cc282f9f..22b779ad 100644
--- a/lib/PublicInbox/Syscall.pm
+++ b/lib/PublicInbox/Syscall.pm
@@ -390,12 +390,10 @@ sub rename_noreplace ($$) {
}
}
-sub nodatacow_fh {
- return if !defined($SYS_fstatfs);
- my $buf = '';
- vec($buf, 120 * 8 - 1, 1) = 0;
+sub nodatacow_fh ($) {
my ($fh) = @_;
- syscall($SYS_fstatfs, fileno($fh), $buf) == 0 or
+ my $buf = "\0" x 120;
+ syscall($SYS_fstatfs // return, fileno($fh), $buf) == 0 or
return warn("fstatfs: $!\n");
my $f_type = unpack('l!', $buf); # statfs.f_type is a signed word
return if $f_type != 0x9123683E; # BTRFS_SUPER_MAGIC
prev parent reply other threads:[~2022-04-18 9:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-18 9:50 [PATCH 0/4] lei: finish wiring up pure-Perl stuff for Linux Eric Wong
2022-04-18 9:50 ` [PATCH 1/4] lei: clobber recvmsg buffer on errors Eric Wong
2022-04-18 9:50 ` [PATCH 2/4] syscall: more idiomatic cmsghdr space allocation Eric Wong
2022-04-18 9:50 ` [PATCH 3/4] lei: wire up pure Perl sendmsg/recvmsg for Linux users Eric Wong
2022-04-18 9:50 ` Eric Wong [this message]
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