read ifds for tiff files

extra/graphics/tiff/tiff.factor

@@ -1,15 +1,28 @@
 ! Copyright (C) 2009 Doug Coleman.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors combinators io io.encodings.binary io.files
-kernel pack endian ;
+kernel pack endian tools.hexdump constructors sequences arrays
+sorting.slots math.order ;
 IN: graphics.tiff
 
 TUPLE: tiff
 endianness
 the-answer
 ifd-offset
+ifds
 ;
 
+CONSTRUCTOR: tiff ( -- tiff )
+    V{ } clone >>ifds ;
+
+TUPLE: ifd count ifd-entries ;
+
+CONSTRUCTOR: ifd ( count ifd-entries -- ifd ) ;
+
+TUPLE: ifd-entry tag type count offset ;
+
+CONSTRUCTOR: ifd-entry ( tag type count offset -- ifd-entry ) ;
+
 
 ERROR: bad-tiff-magic bytes ;
 
@@ -20,6 +33,9 @@ ERROR: bad-tiff-magic bytes ;
         [ bad-tiff-magic ]
     } case ;
 
+: with-tiff-endianness ( tiff quot -- tiff )
+    [ dup endianness>> ] dip with-endianness ; inline
+
 : read-header ( tiff -- tiff )
     2 read tiff-endianness [ >>endianness ] keep
     [
@@ -27,10 +43,27 @@ ERROR: bad-tiff-magic bytes ;
         4 read endian> >>ifd-offset
     ] with-endianness ;
 
+: push-ifd ( tiff ifd -- tiff )
+    over ifds>> push ;
+
+: read-ifd ( -- ifd )
+    2 read endian>
+    2 read endian>
+    4 read endian>
+    4 read endian> <ifd-entry> ;
+
+: read-ifds ( tiff -- tiff )
+    [
+        dup ifd-offset>> seek
+        2 read endian>
+        dup [ read-ifd ] replicate <ifd> >>ifds
+    ] with-tiff-endianness ;
+
 : (load-tiff) ( path -- tiff )
     binary [
         tiff new
         read-header
+        read-ifds
     ] with-file-reader ;
 
 : load-tiff ( path -- tiff )