.obj files are not LZO

scripts/try-uncompress

@@ -0,0 +1,204 @@
+#!/usr/bin/env ruby
+
+require 'pp'
+
+module Obj
+  class Header
+    SIZE = 5*4 # 5x 32-bit little-endian integers
+
+    attr_reader(
+      :num_sprites, # Number of entries in the directory. Always dir_size/8?
+      :dir_offset,  # Offset of the sprite directory. Also the size of the main header
+      :dir_size,    # Number of bytes allocated to the sprite directory. Always num_sprites*8?
+      :data_offset, # Number of bytes allocated to the sprites themselves
+      :data_size    # Total size of the sprite data
+      # JUNGTIL.obj has 0x0000 0x0000 0x0000 following. Probably just padding to
+      # allow the sprite directory to start at a word boundary.
+    )
+
+    def self.parse(data)
+      hdr = new(*data[0..SIZE - 1].unpack("V*"))
+      pp hdr
+      hdr.validate!(data.bytes.size)
+      hdr
+    end
+
+    def initialize(*entries)
+      @num_sprites, @dir_offset, @dir_size, @data_offset, @data_size = *entries
+    end
+
+    def validate!(overall_size)
+      raise "Directory overlaps EOF" if overall_size < dir_size + dir_offset
+      raise "Data overlaps EOF" if overall_size < data_offset + data_size
+      raise "Bad dir_size or num_sprites" if num_sprites * DirEntry::SIZE != dir_size
+      raise "Directory overlaps data" if data_range.cover?(dir_offset+1)
+      raise "Data overlaps directory" if dir_range.cover?(data_offset+1)
+
+      true
+    end
+
+    def dir_range
+      dir_offset...(dir_offset+dir_size)
+    end
+
+    def data_range
+      data_offset...(data_offset+data_size)
+    end
+  end
+
+  class DirEntry
+    SIZE = 8
+
+    attr_reader :rel_offset # Relative to the main header's data_offset
+    attr_reader :sprite_size
+
+    def self.parse(rel_data)
+      new(*rel_data.unpack("VV"))
+    end
+
+    def initialize(rel_offset, sprite_size)
+      @rel_offset = rel_offset
+      @sprite_size = sprite_size
+    end
+
+    def sprite_range
+      rel_offset...(rel_offset+sprite_size)
+    end
+  end
+
+  class SpriteDir
+    attr_reader :entries
+
+    def self.parse(rel_data)
+      count = rel_data.bytes.size
+      num_entries = count / DirEntry::SIZE
+      trailing = count%DirEntry::SIZE
+
+      raise "SpriteDir block has #{trailing} trailing bytes" unless trailing == 0
+
+      entries = 0.upto(num_entries-1).map do |n|
+        rel_offset = n * DirEntry::SIZE
+        DirEntry.parse(rel_data.byteslice(rel_offset, DirEntry::SIZE))
+      end
+
+      pp entries
+
+      new(entries)
+    end
+    
+    def initialize(entries)
+      @entries = entries
+    end
+
+    # Convert the directory into an Array of bytes. Until we work out how to
+    # parse sprites, anyway...
+    def realize(rel_data)
+      entries.map { |entry| rel_data[entry.sprite_range] }
+    end
+  end
+
+=begin
+  SpriteHeader = Struct.new(
+    :unknown0,        # Possibly magic data? It's the same for every sprite in jungtil.obj
+    :maybe_dimension, # Low nibble comes to 63 in jungtil.obj which would work for a 64x64 tile
+    :size,            # Number of bytes of pixel data following this header
+  ) do
+    SIZE = 4*6        # Seems to be, anyway. Based on 
+
+    def self.parse(rel_data)
+      new(*sprite_data[0..SIZE-1]).unpack("V*")
+    end
+
+    def pixel_range
+      SIZE...size # maybe,anyway
+    end
+  end
+
+  Sprite = Struct.new(
+    :header, :data
+  ) do
+    def self.parse(rel_data)
+      hdr = SpriteHeader.parse(rel_data)
+      sprite_pixels = rel_data[hdr.pixel_range]
+
+      Sprite.new(hdr, sprite_pixels)
+    end
+  end
+=end
+
+  class Parsed
+    attr_reader :header
+    attr_reader :directory
+    attr_reader :sprites
+
+    def initialize(header, directory, sprites)
+      @header = header
+      @directory = directory
+      @sprites = sprites
+    end
+  end
+
+  def self.parse(data)
+    hdr = Header.parse(data)
+    dir = SpriteDir.parse(data[hdr.dir_range])
+    sprites = dir.realize(data[hdr.data_range])
+
+    Parsed.new(hdr, dir, sprites)
+  end
+end
+
+parsed = Obj.parse(File.read("orig/Obj/jungtil.obj").force_encoding("BINARY"))
+
+def hex(num, leading=0)
+  "%0#{leading}x"%num
+end
+
+def display(data, blocksize=8, skip=0)
+  bytes = data.bytes
+  nrows = (bytes.count / blocksize)
+
+  skip.upto(nrows) do |i|
+    block = bytes[(i*blocksize)...(i*blocksize+blocksize)]
+    out = [
+      "0x#{hex(i*blocksize, 4)}",
+      block.map { |b| hex(b, 2) },
+    ]
+
+    puts out.flatten.join(' ')
+  end
+end
+
+
+puts "Dumping blank sprite"
+display(parsed.sprites[0], 8, 0)
+
+# The per-sprite data in jungtil.obj is too small to represent a 64x64 block,
+# even at 1bpp, so try some decompression algorithms to see what comes out.
+# Step through every byte of each sprite so we manage if some header is present
+#
+# Tried so far, with no success:
+#   * LZO
+
+puts "\nAttempting decompression..."
+
+require 'lzo'
+
+parsed.sprites.each_with_index do |sprite, i|
+  print "Sprite %02d..."%i
+
+  (0...sprite.size).each do |offset|
+    block = sprite.byteslice(offset, sprite.size-offset)
+
+    begin
+      decompressed = LZO.decompress(block)
+      puts "succeeded! sprite=#{i} offset=#{offset} decompressed_size=#{decompressed.size}"
+      puts "data:"
+      puts decompressed.inspect
+      exit 0
+    rescue => err
+    end
+  end
+
+  puts "failed"
+end
+