/*
   ======================================================================
   surface.c

   Surface functions for an LWO2 reader.

   Ernie Wright  17 Sep 00
   ====================================================================== */

#include "../picointernal.h"
#include "lwo2.h"


/*
   ======================================================================
   lwFreePlugin()

   Free the memory used by an lwPlugin.
   ====================================================================== */

void lwFreePlugin( lwPlugin *p ){
	if ( p ) {
		if ( p->ord ) {
			_pico_free( p->ord );
		}
		if ( p->name ) {
			_pico_free( p->name );
		}
		if ( p->data ) {
			_pico_free( p->data );
		}
		_pico_free( p );
	}
}


/*
   ======================================================================
   lwFreeTexture()

   Free the memory used by an lwTexture.
   ====================================================================== */

void lwFreeTexture( lwTexture *t ){
	if ( t ) {
		if ( t->ord ) {
			_pico_free( t->ord );
		}
		switch ( t->type ) {
		case ID_IMAP:
			if ( t->param.imap.vmap_name ) {
				_pico_free( t->param.imap.vmap_name );
			}
			break;
		case ID_PROC:
			if ( t->param.proc.name ) {
				_pico_free( t->param.proc.name );
			}
			if ( t->param.proc.data ) {
				_pico_free( t->param.proc.data );
			}
			break;
		case ID_GRAD:
			if ( t->param.grad.key ) {
				_pico_free( t->param.grad.key );
			}
			if ( t->param.grad.ikey ) {
				_pico_free( t->param.grad.ikey );
			}
			break;
		}
		_pico_free( t );
	}
}


/*
   ======================================================================
   lwFreeSurface()

   Free the memory used by an lwSurface.
   ====================================================================== */

void lwFreeSurface( lwSurface *surf ){
	if ( surf ) {
		if ( surf->name ) {
			_pico_free( surf->name );
		}
		if ( surf->srcname ) {
			_pico_free( surf->srcname );
		}

		lwListFree( surf->shader, lwFreePlugin );

		lwListFree( surf->color.tex, lwFreeTexture );
		lwListFree( surf->luminosity.tex, lwFreeTexture );
		lwListFree( surf->diffuse.tex, lwFreeTexture );
		lwListFree( surf->specularity.tex, lwFreeTexture );
		lwListFree( surf->glossiness.tex, lwFreeTexture );
		lwListFree( surf->reflection.val.tex, lwFreeTexture );
		lwListFree( surf->transparency.val.tex, lwFreeTexture );
		lwListFree( surf->eta.tex, lwFreeTexture );
		lwListFree( surf->translucency.tex, lwFreeTexture );
		lwListFree( surf->bump.tex, lwFreeTexture );

		_pico_free( surf );
	}
}


/*
   ======================================================================
   lwGetTHeader()

   Read a texture map header from a SURF.BLOK in an LWO2 file.  This is
   the first subchunk in a BLOK, and its contents are common to all three
   texture types.
   ====================================================================== */

int lwGetTHeader( picoMemStream_t *fp, int hsz, lwTexture *tex ){
	unsigned int id;
	unsigned short sz;
	int pos, rlen;


	/* remember where we started */

	set_flen( 0 );
	pos = _pico_memstream_tell( fp );

	/* ordinal string */

	tex->ord = getS0( fp );

	/* first subchunk header */

	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		return 0;
	}

	/* process subchunks as they're encountered */

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_CHAN:
			tex->chan = getU4( fp );
			break;

		case ID_OPAC:
			tex->opac_type = getU2( fp );
			tex->opacity.val = getF4( fp );
			tex->opacity.eindex = getVX( fp );
			break;

		case ID_ENAB:
			tex->enabled = getU2( fp );
			break;

		case ID_NEGA:
			tex->negative = getU2( fp );
			break;

		case ID_AXIS:
			tex->axis = getU2( fp );
			break;

		default:
			break;
		}

		/* error while reading current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			return 0;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the texture header subchunk? */

		if ( hsz <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			return 0;
		}
	}

	set_flen( _pico_memstream_tell( fp ) - pos );
	return 1;
}


/*
   ======================================================================
   lwGetTMap()

   Read a texture map from a SURF.BLOK in an LWO2 file.  The TMAP
   defines the mapping from texture to world or object coordinates.
   ====================================================================== */

int lwGetTMap( picoMemStream_t *fp, int tmapsz, lwTMap *tmap ){
	unsigned int id;
	unsigned short sz;
	int rlen, pos, i;

	pos = _pico_memstream_tell( fp );
	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		return 0;
	}

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_SIZE:
			for ( i = 0; i < 3; i++ )
				tmap->size.val[ i ] = getF4( fp );
			tmap->size.eindex = getVX( fp );
			break;

		case ID_CNTR:
			for ( i = 0; i < 3; i++ )
				tmap->center.val[ i ] = getF4( fp );
			tmap->center.eindex = getVX( fp );
			break;

		case ID_ROTA:
			for ( i = 0; i < 3; i++ )
				tmap->rotate.val[ i ] = getF4( fp );
			tmap->rotate.eindex = getVX( fp );
			break;

		case ID_FALL:
			tmap->fall_type = getU2( fp );
			for ( i = 0; i < 3; i++ )
				tmap->falloff.val[ i ] = getF4( fp );
			tmap->falloff.eindex = getVX( fp );
			break;

		case ID_OREF:
			tmap->ref_object = getS0( fp );
			break;

		case ID_CSYS:
			tmap->coord_sys = getU2( fp );
			break;

		default:
			break;
		}

		/* error while reading the current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			return 0;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the TMAP subchunk? */

		if ( tmapsz <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			return 0;
		}
	}

	set_flen( _pico_memstream_tell( fp ) - pos );
	return 1;
}


/*
   ======================================================================
   lwGetImageMap()

   Read an lwImageMap from a SURF.BLOK in an LWO2 file.
   ====================================================================== */

int lwGetImageMap( picoMemStream_t *fp, int rsz, lwTexture *tex ){
	unsigned int id;
	unsigned short sz;
	int rlen, pos;

	pos = _pico_memstream_tell( fp );
	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		return 0;
	}

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_TMAP:
			if ( !lwGetTMap( fp, sz, &tex->tmap ) ) {
				return 0;
			}
			break;

		case ID_PROJ:
			tex->param.imap.projection = getU2( fp );
			break;

		case ID_VMAP:
			tex->param.imap.vmap_name = getS0( fp );
			break;

		case ID_AXIS:
			tex->param.imap.axis = getU2( fp );
			break;

		case ID_IMAG:
			tex->param.imap.cindex = getVX( fp );
			break;

		case ID_WRAP:
			tex->param.imap.wrapw_type = getU2( fp );
			tex->param.imap.wraph_type = getU2( fp );
			break;

		case ID_WRPW:
			tex->param.imap.wrapw.val = getF4( fp );
			tex->param.imap.wrapw.eindex = getVX( fp );
			break;

		case ID_WRPH:
			tex->param.imap.wraph.val = getF4( fp );
			tex->param.imap.wraph.eindex = getVX( fp );
			break;

		case ID_AAST:
			tex->param.imap.aas_flags = getU2( fp );
			tex->param.imap.aa_strength = getF4( fp );
			break;

		case ID_PIXB:
			tex->param.imap.pblend = getU2( fp );
			break;

		case ID_STCK:
			tex->param.imap.stck.val = getF4( fp );
			tex->param.imap.stck.eindex = getVX( fp );
			break;

		case ID_TAMP:
			tex->param.imap.amplitude.val = getF4( fp );
			tex->param.imap.amplitude.eindex = getVX( fp );
			break;

		default:
			break;
		}

		/* error while reading the current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			return 0;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the image map? */

		if ( rsz <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			return 0;
		}
	}

	set_flen( _pico_memstream_tell( fp ) - pos );
	return 1;
}


/*
   ======================================================================
   lwGetProcedural()

   Read an lwProcedural from a SURF.BLOK in an LWO2 file.
   ====================================================================== */

int lwGetProcedural( picoMemStream_t *fp, int rsz, lwTexture *tex ){
	unsigned int id;
	unsigned short sz;
	int rlen, pos;

	pos = _pico_memstream_tell( fp );
	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		return 0;
	}

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_TMAP:
			if ( !lwGetTMap( fp, sz, &tex->tmap ) ) {
				return 0;
			}
			break;

		case ID_AXIS:
			tex->param.proc.axis = getU2( fp );
			break;

		case ID_VALU:
			tex->param.proc.value[ 0 ] = getF4( fp );
			if ( sz >= 8 ) {
				tex->param.proc.value[ 1 ] = getF4( fp );
			}
			if ( sz >= 12 ) {
				tex->param.proc.value[ 2 ] = getF4( fp );
			}
			break;

		case ID_FUNC:
			tex->param.proc.name = getS0( fp );
			rlen = get_flen();
			tex->param.proc.data = getbytes( fp, sz - rlen );
			break;

		default:
			break;
		}

		/* error while reading the current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			return 0;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the procedural block? */

		if ( rsz <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			return 0;
		}
	}

	set_flen( _pico_memstream_tell( fp ) - pos );
	return 1;
}


/*
   ======================================================================
   lwGetGradient()

   Read an lwGradient from a SURF.BLOK in an LWO2 file.
   ====================================================================== */

int lwGetGradient( picoMemStream_t *fp, int rsz, lwTexture *tex ){
	unsigned int id;
	unsigned short sz;
	int rlen, pos, i, j, nkeys;

	pos = _pico_memstream_tell( fp );
	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		return 0;
	}

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_TMAP:
			if ( !lwGetTMap( fp, sz, &tex->tmap ) ) {
				return 0;
			}
			break;

		case ID_PNAM:
			tex->param.grad.paramname = getS0( fp );
			break;

		case ID_INAM:
			tex->param.grad.itemname = getS0( fp );
			break;

		case ID_GRST:
			tex->param.grad.start = getF4( fp );
			break;

		case ID_GREN:
			tex->param.grad.end = getF4( fp );
			break;

		case ID_GRPT:
			tex->param.grad.repeat = getU2( fp );
			break;

		case ID_FKEY:
			nkeys = sz / sizeof( lwGradKey );
			tex->param.grad.key = _pico_calloc( nkeys, sizeof( lwGradKey ) );
			if ( !tex->param.grad.key ) {
				return 0;
			}
			for ( i = 0; i < nkeys; i++ ) {
				tex->param.grad.key[ i ].value = getF4( fp );
				for ( j = 0; j < 4; j++ )
					tex->param.grad.key[ i ].rgba[ j ] = getF4( fp );
			}
			break;

		case ID_IKEY:
			nkeys = sz / 2;
			tex->param.grad.ikey = _pico_calloc( nkeys, sizeof( short ) );
			if ( !tex->param.grad.ikey ) {
				return 0;
			}
			for ( i = 0; i < nkeys; i++ )
				tex->param.grad.ikey[ i ] = getU2( fp );
			break;

		default:
			break;
		}

		/* error while reading the current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			return 0;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the gradient? */

		if ( rsz <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			return 0;
		}
	}

	set_flen( _pico_memstream_tell( fp ) - pos );
	return 1;
}


/*
   ======================================================================
   lwGetTexture()

   Read an lwTexture from a SURF.BLOK in an LWO2 file.
   ====================================================================== */

lwTexture *lwGetTexture( picoMemStream_t *fp, int bloksz, unsigned int type ){
	lwTexture *tex;
	unsigned short sz;
	int ok;

	tex = _pico_calloc( 1, sizeof( lwTexture ) );
	if ( !tex ) {
		return NULL;
	}

	tex->type = type;
	tex->tmap.size.val[ 0 ] =
		tex->tmap.size.val[ 1 ] =
			tex->tmap.size.val[ 2 ] = 1.0f;
	tex->opacity.val = 1.0f;
	tex->enabled = 1;

	sz = getU2( fp );
	if ( !lwGetTHeader( fp, sz, tex ) ) {
		_pico_free( tex );
		return NULL;
	}

	sz = bloksz - sz - 6;
	switch ( type ) {
	case ID_IMAP:  ok = lwGetImageMap( fp, sz, tex );  break;
	case ID_PROC:  ok = lwGetProcedural( fp, sz, tex );  break;
	case ID_GRAD:  ok = lwGetGradient( fp, sz, tex );  break;
	default:
		ok = !_pico_memstream_seek( fp, sz, PICO_SEEK_CUR );
	}

	if ( !ok ) {
		lwFreeTexture( tex );
		return NULL;
	}

	set_flen( bloksz );
	return tex;
}


/*
   ======================================================================
   lwGetShader()

   Read a shader record from a SURF.BLOK in an LWO2 file.
   ====================================================================== */

lwPlugin *lwGetShader( picoMemStream_t *fp, int bloksz ){
	lwPlugin *shdr;
	unsigned int id;
	unsigned short sz;
	int hsz, rlen, pos;

	shdr = _pico_calloc( 1, sizeof( lwPlugin ) );
	if ( !shdr ) {
		return NULL;
	}

	pos = _pico_memstream_tell( fp );
	set_flen( 0 );
	hsz = getU2( fp );
	shdr->ord = getS0( fp );
	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		goto Fail;
	}

	while ( hsz > 0 ) {
		sz += sz & 1;
		hsz -= sz;
		if ( id == ID_ENAB ) {
			shdr->flags = getU2( fp );
			break;
		}
		else {
			_pico_memstream_seek( fp, sz, PICO_SEEK_CUR );
			id = getU4( fp );
			sz = getU2( fp );
		}
	}

	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		goto Fail;
	}

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_FUNC:
			shdr->name = getS0( fp );
			rlen = get_flen();
			shdr->data = getbytes( fp, sz - rlen );
			break;

		default:
			break;
		}

		/* error while reading the current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			goto Fail;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the shader block? */

		if ( bloksz <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			goto Fail;
		}
	}

	set_flen( _pico_memstream_tell( fp ) - pos );
	return shdr;

Fail:
	lwFreePlugin( shdr );
	return NULL;
}


/*
   ======================================================================
   compare_textures()
   compare_shaders()

   Callbacks for the lwListInsert() function, which is called to add
   textures to surface channels and shaders to surfaces.
   ====================================================================== */

static int compare_textures( lwTexture *a, lwTexture *b ){
	return strcmp( a->ord, b->ord );
}


static int compare_shaders( lwPlugin *a, lwPlugin *b ){
	return strcmp( a->ord, b->ord );
}


/*
   ======================================================================
   add_texture()

   Finds the surface channel (lwTParam or lwCParam) to which a texture is
   applied, then calls lwListInsert().
   ====================================================================== */

static int add_texture( lwSurface *surf, lwTexture *tex ){
	lwTexture **list;

	switch ( tex->chan ) {
	case ID_COLR:  list = &surf->color.tex;             break;
	case ID_LUMI:  list = &surf->luminosity.tex;        break;
	case ID_DIFF:  list = &surf->diffuse.tex;           break;
	case ID_SPEC:  list = &surf->specularity.tex;       break;
	case ID_GLOS:  list = &surf->glossiness.tex;        break;
	case ID_REFL:  list = &surf->reflection.val.tex;    break;
	case ID_TRAN:  list = &surf->transparency.val.tex;  break;
	case ID_RIND:  list = &surf->eta.tex;               break;
	case ID_TRNL:  list = &surf->translucency.tex;      break;
	case ID_BUMP:  list = &surf->bump.tex;              break;
	default:  return 0;
	}

	lwListInsert( list, tex, compare_textures );
	return 1;
}


/*
   ======================================================================
   lwDefaultSurface()

   Allocate and initialize a surface.
   ====================================================================== */

lwSurface *lwDefaultSurface( void ){
	lwSurface *surf;

	surf = _pico_calloc( 1, sizeof( lwSurface ) );
	if ( !surf ) {
		return NULL;
	}

	surf->color.rgb[ 0 ] = 0.78431f;
	surf->color.rgb[ 1 ] = 0.78431f;
	surf->color.rgb[ 2 ] = 0.78431f;
	surf->diffuse.val    = 1.0f;
	surf->glossiness.val = 0.4f;
	surf->bump.val       = 1.0f;
	surf->eta.val        = 1.0f;
	surf->sideflags      = 1;

	return surf;
}


/*
   ======================================================================
   lwGetSurface()

   Read an lwSurface from an LWO2 file.
   ====================================================================== */

lwSurface *lwGetSurface( picoMemStream_t *fp, int cksize ){
	lwSurface *surf;
	lwTexture *tex;
	lwPlugin *shdr;
	unsigned int id, type;
	unsigned short sz;
	int pos, rlen;


	/* allocate the Surface structure */

	surf = _pico_calloc( 1, sizeof( lwSurface ) );
	if ( !surf ) {
		goto Fail;
	}

	/* non-zero defaults */

	surf->color.rgb[ 0 ] = 0.78431f;
	surf->color.rgb[ 1 ] = 0.78431f;
	surf->color.rgb[ 2 ] = 0.78431f;
	surf->diffuse.val    = 1.0f;
	surf->glossiness.val = 0.4f;
	surf->bump.val       = 1.0f;
	surf->eta.val        = 1.0f;
	surf->sideflags      = 1;

	/* remember where we started */

	set_flen( 0 );
	pos = _pico_memstream_tell( fp );

	/* names */

	surf->name = getS0( fp );
	surf->srcname = getS0( fp );

	/* first subchunk header */

	id = getU4( fp );
	sz = getU2( fp );
	if ( 0 > get_flen() ) {
		goto Fail;
	}

	/* process subchunks as they're encountered */

	while ( 1 ) {
		sz += sz & 1;
		set_flen( 0 );

		switch ( id ) {
		case ID_COLR:
			surf->color.rgb[ 0 ] = getF4( fp );
			surf->color.rgb[ 1 ] = getF4( fp );
			surf->color.rgb[ 2 ] = getF4( fp );
			surf->color.eindex = getVX( fp );
			break;

		case ID_LUMI:
			surf->luminosity.val = getF4( fp );
			surf->luminosity.eindex = getVX( fp );
			break;

		case ID_DIFF:
			surf->diffuse.val = getF4( fp );
			surf->diffuse.eindex = getVX( fp );
			break;

		case ID_SPEC:
			surf->specularity.val = getF4( fp );
			surf->specularity.eindex = getVX( fp );
			break;

		case ID_GLOS:
			surf->glossiness.val = getF4( fp );
			surf->glossiness.eindex = getVX( fp );
			break;

		case ID_REFL:
			surf->reflection.val.val = getF4( fp );
			surf->reflection.val.eindex = getVX( fp );
			break;

		case ID_RFOP:
			surf->reflection.options = getU2( fp );
			break;

		case ID_RIMG:
			surf->reflection.cindex = getVX( fp );
			break;

		case ID_RSAN:
			surf->reflection.seam_angle = getF4( fp );
			break;

		case ID_TRAN:
			surf->transparency.val.val = getF4( fp );
			surf->transparency.val.eindex = getVX( fp );
			break;

		case ID_TROP:
			surf->transparency.options = getU2( fp );
			break;

		case ID_TIMG:
			surf->transparency.cindex = getVX( fp );
			break;

		case ID_RIND:
			surf->eta.val = getF4( fp );
			surf->eta.eindex = getVX( fp );
			break;

		case ID_TRNL:
			surf->translucency.val = getF4( fp );
			surf->translucency.eindex = getVX( fp );
			break;

		case ID_BUMP:
			surf->bump.val = getF4( fp );
			surf->bump.eindex = getVX( fp );
			break;

		case ID_SMAN:
			surf->smooth = getF4( fp );
			break;

		case ID_SIDE:
			surf->sideflags = getU2( fp );
			break;

		case ID_CLRH:
			surf->color_hilite.val = getF4( fp );
			surf->color_hilite.eindex = getVX( fp );
			break;

		case ID_CLRF:
			surf->color_filter.val = getF4( fp );
			surf->color_filter.eindex = getVX( fp );
			break;

		case ID_ADTR:
			surf->add_trans.val = getF4( fp );
			surf->add_trans.eindex = getVX( fp );
			break;

		case ID_SHRP:
			surf->dif_sharp.val = getF4( fp );
			surf->dif_sharp.eindex = getVX( fp );
			break;

		case ID_GVAL:
			surf->glow.val = getF4( fp );
			surf->glow.eindex = getVX( fp );
			break;

		case ID_LINE:
			surf->line.enabled = 1;
			if ( sz >= 2 ) {
				surf->line.flags = getU2( fp );
			}
			if ( sz >= 6 ) {
				surf->line.size.val = getF4( fp );
			}
			if ( sz >= 8 ) {
				surf->line.size.eindex = getVX( fp );
			}
			break;

		case ID_ALPH:
			surf->alpha_mode = getU2( fp );
			surf->alpha = getF4( fp );
			break;

		case ID_AVAL:
			surf->alpha = getF4( fp );
			break;

		case ID_BLOK:
			type = getU4( fp );

			switch ( type ) {
			case ID_IMAP:
			case ID_PROC:
			case ID_GRAD:
				tex = lwGetTexture( fp, sz - 4, type );
				if ( !tex ) {
					goto Fail;
				}
				if ( !add_texture( surf, tex ) ) {
					lwFreeTexture( tex );
				}
				set_flen( 4 + get_flen() );
				break;
			case ID_SHDR:
				shdr = lwGetShader( fp, sz - 4 );
				if ( !shdr ) {
					goto Fail;
				}
				lwListInsert( &surf->shader, shdr, compare_shaders );
				++surf->nshaders;
				set_flen( 4 + get_flen() );
				break;
			}
			break;

		default:
			break;
		}

		/* error while reading current subchunk? */

		rlen = get_flen();
		if ( rlen < 0 || rlen > sz ) {
			goto Fail;
		}

		/* skip unread parts of the current subchunk */

		if ( rlen < sz ) {
			_pico_memstream_seek( fp, sz - rlen, PICO_SEEK_CUR );
		}

		/* end of the SURF chunk? */

		if ( cksize <= _pico_memstream_tell( fp ) - pos ) {
			break;
		}

		/* get the next subchunk header */

		set_flen( 0 );
		id = getU4( fp );
		sz = getU2( fp );
		if ( 6 != get_flen() ) {
			goto Fail;
		}
	}

	return surf;

Fail:
	if ( surf ) {
		lwFreeSurface( surf );
	}
	return NULL;
}