// File
//
// If there is an error, it will be of type *Error.
func (mgc *Magic) File(filename string) (string, error) {
mgc.Lock()
defer mgc.Unlock()
runtime.KeepAlive(mgc.magic)
if mgc.cookie == nil {
return "", mgc.error()
}
cfilename := C.CString(filename)
runtime.KeepAlive(cfilename)
defer C.free(unsafe.Pointer(cfilename))
cstring := C.magic_file_wrapper(mgc.cookie, cfilename, C.int(mgc.flags))
if cstring == nil {
rv, err := Version()
if err != nil && err.(*Error).Errno != int(syscall.ENOSYS) {
return "", err
}
// Handle the case when the "ERROR" flag is set regardless
// of the current version of the underlying Magic library.
//
// Prior to version 5.15 the correct behaviour that concerns
// the following IEEE 1003.1 standards was broken:
//
// http://pubs.opengroup.org/onlinepubs/007904975/utilities/file.html
// http://pubs.opengroup.org/onlinepubs/9699919799/utilities/file.html
//
// This is an attempt to mitigate the problem and correct
// it to achieve the desired behaviour as per the standards.
if mgc.flags&ERROR != 0 {
return "", mgc.error()
} else if rv < 515 {
C.magic_errno(mgc.cookie)
cstring = C.magic_error(mgc.cookie)
}
}
// XXX(kwilczynski): This case should not happen, ever.
if cstring == nil {
return "", &Error{-1, "unknown result or nil pointer"}
}
// Depending on the version of the underlying
// Magic library the magic_file() function can
// fail and either yield no results or return
// the "(null)" string instead. Often this
// would indicate that an older version of
// the Magic library is in use.
s := C.GoString(cstring)
if s == "" || s == "(null)" {
return "", &Error{-1, "empty or invalid result"}
}
return s, nil
}
// error retrieves an error from the underlying Magic library.
func (mgc *Magic) error() *Error {
if mgc.cookie == nil {
errno := syscall.EFAULT
return &Error{int(errno), "Magic library is not open"}
}
runtime.KeepAlive(mgc.magic)
cstring := C.magic_error(mgc.cookie)
if cstring != nil {
// Depending on the version of the underlying
// Magic library, the error reporting facilities
// can fail and either yield no results or return
// the "(null)" string instead. Often this would
// indicate that an older version of the Magic
// library is in use.
s := C.GoString(cstring)
if s == "" || s == "(null)" {
return &Error{-1, "empty or invalid error message"}
}
errno := int(C.magic_errno(mgc.cookie))
return &Error{errno, s}
}
return &Error{-1, "unknown error"}
}
func Errno(cookie Magic_t) int {
return (int)(C.magic_errno((C.magic_t)(cookie)))
}