1 files changed, 48 insertions, 0 deletions
diff --git a/ips-patcher.lua b/ips-patcher.lua
new file mode 100644
index 0000000..316f8da
--- /dev/null
+++ b/ips-patcher.lua
@@ -0,0 +1,48 @@
+-- based on http://zerosoft.zophar.net/ips.php (note the data is big endian - this isn't clear from the text)
+
+local function read_some_bytes(fin, siz)
+    local ret = 0
+
+    for _ = 1, siz do
+        ret = ret * 256 + fin:readU8()
+    end
+
+    return ret
+end
+
+function ips_patch(buffer, ips)
+    local header, offset, size, b = "", 0, 0
+    
+    for _ = 1, 5 do
+        header = header .. string.char(ips:readU8())
+    end
+    
+    if header ~= "PATCH" then error "Wrong IPS file format - bad header" end
+    
+    while true do
+        offset = read_some_bytes(ips, 3)
+    
+        -- that's one of the most stupid thing ever... you can NOT patch the offset
+        -- 0x454F46 since this is the end of the ips file marker... whomever came
+        -- with this brillant design needs a smack in the face.
+        if offset == 0x454F46 then
+            break
+        end
+    
+        buffer:seek(offset)
+        if buffer.wseek then buffer:wseek(offset) end
+
+        size = read_some_bytes(ips, 2)
+
+        if size == 0 then
+            size = read_some_bytes(ips, 2)
+            b = ips:readU8()
+            for _ = 1, size do buffer:writeU8(b) end
+        else
+            ips:copyto(buffer, size)
+        end
+    end
+
+    buffer:seek(0)
+    if buffer.wseek then buffer:wseek(0) end
+end