Ruby zlib::Gzip not working properly

Question

I was in the middle of creating an inport/export system that could encode a costume data structure in an xml tree and then read it back and recreate the object. I got the xml part to work fine but when I discovered that the xml file was 1.5mb when the original ruby::Marshal file was only 105kb I decided that it would be a good idea to compress the file. so I did this

require "rexml/document"
require "zlib"
include REXML

tilesetfile = File.new( "tilesets.rmpy", "w+" )
buffer = ""
tilesetgz = Zlib::GzipWriter.new(tilesetfile)
puts "Compressing output for: tilesets.rxdata ..."
tilesetdoc.write(buffer, 0)
tilesetgz.write(buffer)
tilesetgz.close

then I tried to get the buffer string back so that I could phrase it as xml again like so

require "rexml/document"
require "zlib"
include REXML

tilesetfile = File.open("tilesets.rmpy", "r")
tilesetgz = Zlib::GzipReader.new(tilesetfile)
testfile = File.new("importtest.txt", "w")
tilesetdoc = Document.new tilesetgz

it should be noted that neither of these spinets contains the entire system, just the require header and the last few lines that do the compression

but I get a phrasing error because the xml document has bee corrupted some how

this is the out put of the import scrupt before I Gziped it (tracated of course the file is 1.5mb after all)

<tilesetdata>
<tileset>
<id>
1
</id>
<022-Roof01/>
<tileset_name>
019-DesertTown01
</tileset_name>
<autotile_names>
<item>
015-Sa_Water01
</item>
<item>
016-Sa_Shadow01
</item>
<item>
018-Sa_Ground01
</item>
<item>
019-Sa_Grass02
</item>
<item>
020-Sa_Grass03
</item>
<item>
021-Sa_Road01
</item>
<item>
022-Roof01
</item>
</autotile_names>
<panorama_name>
</panorama_name>
<panorama_hue>
0
</panorama_hue>
<fog_name>
</fog_name>
<fog_hue>
0
</fog_hue>
<fog_opacity>
64
</fog_opacity>
<fog_blend_type>
0
</fog_blend_type>
<fog_zoom>
200
</fog_zoom>
<fog_sx>
0
</fog_sx>
<fog_sy>
0
</fog_sy>
<battleback_name>
</battleback_name>
<passages>
<item>
15
</item>
<item>
15
</item>
<item>
15
</item>
<item>
15
</item>
<item>
15
</item>
<item>
15
</item>

on the import side I intercepted the the unGziped file strangely enough the file is 1.3mb this time

<tilesetdata>
<tileset>
<id>
 1
</id>
<022-Roof01/>
<tileset_name>
019-DesertTown01
</tileset_name>
<autotile_names>
<item>
015-Sa_Water01
</item>
<item>
016-Sa_Shadow01
</item>
<item>
018-Sa_Ground01
</item>
<item>
019-Sa_Grass02
</item>
<item>
020-Sa_Grass03
</item>
<item>
021-Sa_Road01
</item>
<item>
022-Roof01
</item>
</autotile_names>
<panorama_name>
</panorama_name>
<panorama_hue>
0
</panorama_hue>
<fog_name>
</fog_name>
<fog_hue>
0
</fog_hue>
<fog_opacity>
64
</fog_opacity>
<fog_blend_type>
0
</fog_blend_type>
<fog_zoom>
200
</fog_zoom>
<fog_sx>
0
</fog_sx>
<fog_syy>
0
</fog_sx>
<fog_syy>
0
</fog_sx>
<fog_syy>
0
</fog_sx>
<fog_syy>
0
</fog_sx>
<fog_syy>
0
</fog_sx>

the corruption of the original only gets worse from here on

to clarify I ran the import script and it generated the file tilesets.rmpy (at 18kb) and the i ran the import to test the system and discovered this.

any idea what whent wrong? or if not how fix it, an alternative?

Answer 1

It seems that Gzip only works properly with files open in binary mode

require "rexml/document"
require "zlib"
include REXML

tilesetfile = File.new( "tilesets.rmpy", "wb" )
buffer = ""
tilesetgz = Zlib::GzipWriter.new(tilesetfile)
puts "Compressing output for: tilesets.rxdata ..."
tilesetdoc.write(buffer, 0)
tilesetgz.write(buffer)
tilesetgz.close

and

require "rexml/document"
require "zlib"
include REXML

tilesetfile = File.open("tilesets.rmpy", "rb")
tilesetgz = Zlib::GzipReader.new(tilesetfile)
tilesetdoc = Document.new tilesetgz.read.to_s

worked with out any problems