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os: avoid second fcntl syscall in NewFile on unix 

CL 494915 introduced an additional fcntl(F_GETFL) syscall to determine
whether the file is in append-only mode. The existing unix.IsNonblock
call also issues an fcntl(F_GETFL) syscall. The two can be combined and
both the append-only mode and the non-blocking flags can be determined
from that syscall's result.

Change-Id: I915589ed94e079f6abaa2fd0032ef01f78698f7f
Reviewed-on: https://go-review.googlesource.com/c/go/+/497075
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
This commit is contained in:
Tobias Klauser 2023-05-22 20:37:05 +02:00 committed by Gopher Robot
parent c0b860ba31
commit 3c3a883667
1 changed files with 7 additions and 5 deletions
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12
src/os/file_unix.go
View File

@ -104,13 +104,15 @@ func (f *File) Fd() uintptr {
// constraints apply.
func NewFile(fd uintptr, name string) *File {
kind := kindNewFile
if nb, err := unix.IsNonblock(int(fd)); err == nil && nb {
kind = kindNonBlock
appendMode := false
if flags, err := unix.Fcntl(int(fd), syscall.F_GETFL, 0); err == nil {
if unix.HasNonblockFlag(flags) {
kind = kindNonBlock
}
appendMode = flags&syscall.O_APPEND != 0
}
f := newFile(fd, name, kind)
if flags, err := unix.Fcntl(int(fd), syscall.F_GETFL, 0); err == nil {
f.appendMode = flags&syscall.O_APPEND != 0
}
f.appendMode = appendMode
return f
}