diff options
| author | Bill Morgan <arthurwilliammorgan@gmail.com> | 2026-01-18 14:11:05 +0000 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2026-01-22 13:07:52 -0800 |
| commit | a006e17162ddf70b7ee23a8ec2e3e064d0102bd5 (patch) | |
| tree | a804165f8c71433befe32597f0f42de3ae0a4631 | |
| parent | 858d4bf8511a7741cf5c21f1d51b23ed180fd450 (diff) | |
| download | go-a006e17162ddf70b7ee23a8ec2e3e064d0102bd5.tar.xz | |
syscall: document Sendfile semantics
syscall.Sendfile behavior differs significantly between operating
systems.
Document the platform-specific behavior for the offset argument and
partial write reporting on Linux versus BSD-derived systems.
Fixes #64044
Change-Id: I93f740c3e2df911a10bf0884ffab218d4bb4e5fc
GitHub-Last-Rev: a11b898bb98f2a136caaba875033f1c155c1c872
GitHub-Pull-Request: golang/go#77224
Reviewed-on: https://go-review.googlesource.com/c/go/+/737122
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
| -rw-r--r-- | src/syscall/syscall_unix.go | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go index 60173f6d16..ffe4112ad6 100644 --- a/src/syscall/syscall_unix.go +++ b/src/syscall/syscall_unix.go @@ -525,6 +525,22 @@ func Socketpair(domain, typ, proto int) (fd [2]int, err error) { return } +// Sendfile copies up to count bytes from file descriptor infd to file descriptor outfd. +// +// It wraps the sendfile system call. The behavior varies by operating system, +// particularly regarding the offset argument and how partial writes are reported. +// +// On Linux, if offset is nil, Sendfile uses and updates the current file +// position of infd. If offset is non-nil, the current file position is +// unchanged, and the offset pointer is updated to reflect the bytes written. +// A non-nil error typically implies that no bytes were written. +// +// On BSD-derived systems (including macOS), if offset is nil, Sendfile panics. +// The offset argument is not updated by the system call; the caller must manually +// update the offset using the number of bytes written. These systems may +// return a non-zero byte count together with an error (for example, EAGAIN). +// +// For precise semantics, see the system documentation (e.g., man 2 sendfile). func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) { if race.Enabled { race.ReleaseMerge(unsafe.Pointer(&ioSync)) |