NTSTRSAFE_UNICODE_STRING_MAX_CCH - NtDoc

#ifndef _NTSTRSAFE_H_INCLUDED_
// The user may override NTSTRSAFE_UNICODE_STRING_MAX_CCH, but it must always be less than (USHORT_MAX / sizeof(wchar_t))
#ifndef NTSTRSAFE_UNICODE_STRING_MAX_CCH

#define NTSTRSAFE_UNICODE_STRING_MAX_CCH    (0xffff / sizeof(wchar_t))  // max buffer size, in characters, for a UNICODE_STRING

#endif
#endif
View code on GitHub