NAME
        InitIFF -- initialize an iffhandle structure as a user stream. (v36)

   SYNOPSIS
        InitIFF(iff, flags, streamHook);
                A0   D0     A1

        VOID InitIFF(struct iffhandle *, long, struct hook *);

   FUNCTION
        Initializes an iffhandle as a general user-defined stream by
        allowing the user to declare a hook that the library will call to
        accomplish the low-level reading, writing, and seeking of the stream.
        Flags are the stream I/O flags for the specified stream; typically a
        combination of the IFFF_?SEEK flags.

        The stream vector is called with the following arguments:

                A0:     pointer to streamhook.
                A2:     pointer to iffhandle structure.
                A1:     pointer to iffstreamcmd structure.

        The iffstreamcmd packet appears as follows:

                sc_Command:     Contains an IFFCMD_#? value
                sc_Buf:         Pointer to memory buffer
                sc_NBytes:      Number of bytes involved in operation

        The values taken on by sc_Command, and their meaning, are as follows:

        IFFCMD_INIT:
                Prepare your stream for reading. This is used for certain
                streams that can't be read immediately upon opening, and need
                further preparation. (The clipboard.device is an example of
                such a stream.)  This operation is allowed to fail;  any
                error code will be returned directly to the client. sc_Buf
                and sc_NBytes have no meaning here.
        IFFCMD_CLEANUP:
                Terminate the transaction with the associated stream. This
                is used with streams that can't simply be closed. (Again,
                the clipboard is an example of such a stream.)  This
                operation is not permitted to fail;  any error returned will
                be ignored (best to return 0, though). sc_Buf and sc_NBytes
                have no meaning here.
        IFFCMD_READ:
                read from the stream. you are to read sc_nbytes from the
                stream and place them in the buffer pointed to by sc_Buf.
                Any (non-zero) error returned will be remapped by the parser
                into IFFERR_READ.
        IFFCMD_WRITE:
                write to the stream. you are to write sc_nbytes to the
                stream from the buffer pointed to by sc_Buf. Any (non-zero)
                error returned will be remapped by the parser into
                IFFERR_WRITE.
        IFFCMD_SEEK:
                seek on the stream. you are to perform a seek on the stream
                relative to the current position. sc_NBytes is signed;
                negative values mean seek backward, positive values mean seek
                forward. sc_Buf has no meaning here. Any (non-zero) error
                returned will be remapped by the parser into IFFERR_SEEK.

        All errors are returned in D0. A return of 0 indicates success.
        UNDER NO CIRCUMSTANCES are you permitted to write to the iffstreamcmd
        structure.

   INPUTS
        iff - pointer to iffhandle structure to initialize.
        flags - stream I/O flags for the iffhandle.
        streamHook - pointer to hook structure.

   SEE ALSO
        <utility/hooks.h>, <libraries/iffparse.h>