NAME
        PushChunk -- push a new context node on the context stack. (V36)

   SYNOPSIS
        error = PushChunk(iff, type, id, size);
        D0                A0   D0    D1  D2

        long pushchunk(struct iffhandle *, long, long, long);

   FUNCTION
        Pushes a new context node on the context stack by reading it from the
        stream if this is a read file, or by creating it from the passed
        parameters if this is a write file. Normally this function is only
        called in write mode, where the type and id codes specify the new
        chunk to create. If this is a leaf chunk, i.e. a local chunk inside
        a FORM or PROP chunk, then the type argument is ignored. If the size
        is specified then the chunk writing functions will enforce this size.
        If the size is given as IFFSIZE_UNKNOWN, the chunk will expand to
        accommodate whatever is written into it.

   INPUTS
        iff - pointer to iffhandle structure.
        type - chunk type specifier (ex. ILBM) (ignored for read mode or
               leaf chunks).
        id - chunk id specifier (ex. CMAP) (ignored for read mode).
        size - size of the chunk to create or IFFSIZE_UNKNOWN (ignored for
               read mode).

   RESULT
        error - 0 if successful or an IFFERR_#? error code if not unsuccessful.

   SEE ALSO
        popchunk(), writechunkrecords(), writechunkbytes(),
        <libraries/iffparse.h>