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package syscallcompat
import (
"syscall"
"golang.org/x/sys/unix"
)
// Readlinkat exists both in Linux and in MacOS 10.10+. We may add an
// emulated version for users on older MacOS versions if there is
// demand.
// Buffer allocation is handled internally, unlike the bare unix.Readlinkat.
func Readlinkat(dirfd int, path string) (string, error) {
// Allocate the buffer exponentially like os.Readlink does.
for bufsz := 128; ; bufsz *= 2 {
buf := make([]byte, bufsz)
n, err := unix.Readlinkat(dirfd, path, buf)
if err != nil {
return "", err
}
if n < bufsz {
return string(buf[0:n]), nil
}
}
}
// Faccessat exists both in Linux and in MacOS 10.10+, but the Linux version
// DOES NOT support any flags. Emulate AT_SYMLINK_NOFOLLOW like glibc does.
func Faccessat(dirfd int, path string, mode uint32) error {
var st unix.Stat_t
err := Fstatat(dirfd, path, &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
return err
}
if st.Mode&syscall.S_IFMT == syscall.S_IFLNK {
// Pretend that a symlink is always accessible
return nil
}
return unix.Faccessat(dirfd, path, mode, 0)
}
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