Source File
copy_file_range_unix.go
Belonging Package
internal/poll
// Copyright 2024 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build freebsd || linux
package poll
import
// CopyFileRange copies at most remain bytes of data from src to dst, using
// the copy_file_range system call. dst and src must refer to regular files.
func (, *FD, int64) ( int64, bool, error) {
if !supportCopyFileRange() {
return 0, false, nil
}
for > 0 {
:=
if > maxCopyFileRangeRound {
= maxCopyFileRangeRound
}
, := copyFileRange(, , int())
if > 0 {
-=
+=
}
, = handleCopyFileRangeErr(, , )
if == 0 || ! || != nil {
return
}
}
return , true, nil
}
// copyFileRange performs one round of copy_file_range(2).
func (, *FD, int) ( int64, error) {
// For Linux, the signature of copy_file_range(2) is:
//
// ssize_t copy_file_range(int fd_in, loff_t *off_in,
// int fd_out, loff_t *off_out,
// size_t len, unsigned int flags);
//
// For FreeBSD, the signature of copy_file_range(2) is:
//
// ssize_t
// copy_file_range(int infd, off_t *inoffp, int outfd, off_t *outoffp,
// size_t len, unsigned int flags);
//
// Note that in the call to unix.CopyFileRange below, we use nil
// values for off_in/off_out and inoffp/outoffp, which means "the file
// offset for infd(fd_in) or outfd(fd_out) respectively will be used and
// updated by the number of bytes copied".
//
// That is why we must acquire locks for both file descriptors (and why
// this whole machinery is in the internal/poll package to begin with).
if := .writeLock(); != nil {
return 0,
}
defer .writeUnlock()
if := .readLock(); != nil {
return 0,
}
defer .readUnlock()
return ignoringEINTR2(func() (int64, error) {
, := unix.CopyFileRange(.Sysfd, nil, .Sysfd, nil, , 0)
return int64(),
})
}
The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)