Re-design of the original gocryptfs code to work as a library.
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libgocryptfs/internal/syscallcompat/sys_common.go

77 lines
2.1 KiB

package syscallcompat
import (
"syscall"
"golang.org/x/sys/unix"
)
// PATH_MAX is the maximum allowed path length on Linux.
// It is not defined on Darwin, so we use the Linux value.
const PATH_MAX = 4096
// Readlinkat is a convenience wrapper around unix.Readlinkat() that takes
// care of buffer sizing. Implemented like os.Readlink().
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
}
}
}
// Openat wraps the Openat syscall.
// Retries on EINTR.
func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
if flags&syscall.O_CREAT == 0 {
// If O_CREAT is not used, we should use O_NOFOLLOW
if flags&syscall.O_NOFOLLOW == 0 {
flags |= syscall.O_NOFOLLOW
}
}
fd, err = retryEINTR2(func() (int, error) {
return unix.Openat(dirfd, path, flags, mode)
})
return fd, err
}
// Fstatat syscall.
// Retries on EINTR.
func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?
if flags&unix.AT_SYMLINK_NOFOLLOW == 0 {
flags |= unix.AT_SYMLINK_NOFOLLOW
}
err = retryEINTR(func() error {
return unix.Fstatat(dirfd, path, stat, flags)
})
return err
}
// Fstatat2 is a more convenient version of Fstatat. It allocates a Stat_t
// for you and also handles the Unix2syscall conversion.
// Retries on EINTR.
func Fstatat2(dirfd int, path string, flags int) (*syscall.Stat_t, error) {
var stUnix unix.Stat_t
err := Fstatat(dirfd, path, &stUnix, flags)
if err != nil {
return nil, err
}
st := Unix2syscall(stUnix)
return &st, nil
}
const XATTR_SIZE_MAX = 65536
// Make the buffer 1kB bigger so we can detect overflows. Unfortunately,
// slices larger than 64kB are always allocated on the heap.
const XATTR_BUFSZ = XATTR_SIZE_MAX + 1024
// We try with a small buffer first - this one can be allocated on the stack.
const XATTR_BUFSZ_SMALL = 500