proc av_hmac_alloc(type: AVHMACType): ptr AVHMAC {.importc, cdecl, ...raises: [],
    tags: [], forbids: [].}

proc av_hmac_calc(ctx: ptr AVHMAC; data: ptr uint8; len: cuint; key: ptr uint8;
                  keylen: cuint; out: ptr uint8; outlen: cuint): cint {.importc,
    cdecl, ...raises: [], tags: [], forbids: [].}

proc av_hmac_final(ctx: ptr AVHMAC; out: ptr uint8; outlen: cuint): cint {.
    importc, cdecl, ...raises: [], tags: [], forbids: [].}

proc av_hmac_free(ctx: ptr AVHMAC) {.importc, cdecl, ...raises: [], tags: [],
                                     forbids: [].}

proc av_hmac_init(ctx: ptr AVHMAC; key: ptr uint8; keylen: cuint) {.importc,
    cdecl, ...raises: [], tags: [], forbids: [].}

proc av_hmac_update(ctx: ptr AVHMAC; data: ptr uint8; len: cuint) {.importc,
    cdecl, ...raises: [], tags: [], forbids: [].}