/*
    (C) 1995-96 AROS - The Amiga Replacement OS
    $Id: openiff.c,v 1.1 1997/02/03 16:44:27 digulla Exp $

    Desc:
    Lang: english
*/
#include "iffparse_intern.h"

/*****************************************************************************

    NAME */
#include <proto/iffparse.h>

	AROS_LH2(LONG, OpenIFF,

/*  SYNOPSIS */
	AROS_LHA(struct IFFHandle *, iff, A0),
	AROS_LHA(LONG              , rwMode, D0),

/*  LOCATION */
	struct Library *, IFFParseBase, 6, IFFParse)

/*  FUNCTION
	Initializes an IFFHandle struct for a new session of reading or writing.
	The direction of the I/O is determined by the rwMode flags supplied
	( IFFF_READ or IFFF_WRITE ).

    INPUTS
	iff	  - pointer to IFFHandle struct.
	ewMode	- IFFF_READ or IFFF_WRITE


    RESULT
	error	 -  0 if successfull, IFFERR_#? elsewise.

    NOTES
	 This function tells the custom stream handler to initialize
	by sending it a IFFCMD_INIT IFFStreamCmd.

    EXAMPLE

    BUGS

    SEE ALSO
	CloseIFF(), InitIFF()

    INTERNALS

    HISTORY
  27-11-96    digulla automatically created from
	  iffparse_lib.fd and clib/iffparse_protos.h

*****************************************************************************/
{
    AROS_LIBFUNC_INIT
    AROS_LIBBASE_EXT_DECL(struct Library *,IFFParseBase)


    LONG  err;

    struct IFFStreamCmd cmd;


    struct ContextNode *cn;


    /* Check that a valid StreamHandler Hook has been supplied */
    if
    (
	!( GetIntIH(iff)->iff_StreamHandler )
    )
	return (IFFERR_NOHOOK);
    /* Tell the custom stream to initialize itself */

    cmd.sc_Command = IFFCMD_INIT;
    err = CallHookPkt
    (
	GetIntIH(iff)->iff_StreamHandler,
	iff,
	&cmd
    );
    if (err) return (err);

    /* Set the acess mode, and mark the stream as opened */
    iff->iff_Flags |= (rwMode | IFFF_OPEN);


    /* If we are opend in read mode we should test if we have a valid IFF-File */
    if (rwMode == IFFF_READ)
    {

	/* Get header of iff-stream */
	err = GetChunkHeader(iff, IPB(IFFParseBase));
	/* Valid IFF header ? */
	if (err == IFFERR_MANGLED) return (IFFERR_NOTIFF);

	/* We have now entried the chunk */
	GetIntIH(iff)->iff_CurrentState = IFFSTATE_COMPOSITE;

	cn = TopChunk(iff);

	/* We must see if we have a IFF header ("FORM", "CAT" or "LIST") */
	if (!GetIntCN(cn)->cn_Composite)
	    return (IFFERR_NOTIFF);

    }


    return (NULL); /* No error */

    AROS_LIBFUNC_EXIT
} /* OpenIFF */