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// 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 "internal/syscall/unix"
// 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 CopyFileRange(dst, src *FD, remain int64) (written int64, handled bool, err error) {
if !supportCopyFileRange() {
return 0, false, nil
}
for remain > 0 {
max := remain
if max > maxCopyFileRangeRound {
max = maxCopyFileRangeRound
}
n, e := copyFileRange(dst, src, int(max))
if n > 0 {
remain -= n
written += n
}
handled, err = handleCopyFileRangeErr(e, n, written)
if n == 0 || !handled || err != nil {
return
}
}
return written, true, nil
}
// copyFileRange performs one round of copy_file_range(2).
func copyFileRange(dst, src *FD, max int) (written int64, err 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 err := dst.writeLock(); err != nil {
return 0, err
}
defer dst.writeUnlock()
if err := src.readLock(); err != nil {
return 0, err
}
defer src.readUnlock()
return ignoringEINTR2(func() (int64, error) {
n, err := unix.CopyFileRange(src.Sysfd, nil, dst.Sysfd, nil, max, 0)
return int64(n), err
})
}
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