proc av_cast5_alloc(): ptr AVCAST5 {.importc, cdecl, ...raises: [], tags: [],
                                     forbids: [].}

proc av_cast5_crypt(ctx: ptr AVCAST5; dst, src: ptr uint8; count, decrypt: cint) {.
    importc, cdecl, ...raises: [], tags: [], forbids: [].}

proc av_cast5_crypt2(ctx: ptr AVCAST5; dst, src: ptr uint8; count: cint;
                     iv: ptr uint8; decrypt: cint) {.importc, cdecl, ...raises: [],
    tags: [], forbids: [].}

proc av_cast5_init(ctx: ptr AVCAST5; key: ptr uint8; key_bits: cint): cint {.
    importc, cdecl, ...raises: [], tags: [], forbids: [].}