Creates ips patch from .json

ips.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
import os
import sys
import json

class IPSRecord:
    def __init__(self):
        self.offset = 0
        self.data   = None
        self.repeat = 0
        
class IPSPatch:
    def __init__(self):
        self.records = []
    
    def add(self, record):
        self.records.append(record)
    
    def write(self, filename):
        header = b'PATCH'
        footer = b'EOF'
        
        recordHeader = bytearray(5)
        rleData      = bytearray(3)
        
        output = open(filename, 'wb')
        output.write(header)
        
        for item in self.records:
            recordData = None
            # serialize offset
            recordHeader[0] = (item.offset >> 16) & 0xff
            recordHeader[1] = (item.offset >>  8) & 0xff
            recordHeader[2] = (item.offset      ) & 0xff
            if None == item.repeat:
                # serialize size
                size = len(item.data)
                recordHeader[3] = (size >> 8) & 0xff;
                recordHeader[4] = (size     ) & 0xff;
                # item data
                recordData = item.data
            else:
                # empty size
                recordHeader[3] = 0
                recordHeader[4] = 0
                # record data is 3 bytes long.
                # -- 1st and 2nd bytes are repeat count
                rleData[0] = (item.repeat >> 8) & 0xff 
                rleData[1] = (item.repeat     ) & 0xff
                # -- 3rd byte is the repeated data
                rleData[2] = item.data & 0xff
                recordData = rleData
            # output record header
            output.write(recordHeader)
            # output record data
            output.write(recordData)
        output.write(footer)
        output.close()
    
    def read(self, filename):
        inputFile = open(filename)
        data = json.load(inputFile)
        inputFile.close()
        
        for entry in data:
            item = None
            if 'filename' in entry:
                item = IPSRecord
                fh = open(entry['filename'])
                item.data = bytearray(fh.read())
                fh.close()
            elif 'data' in entry:
                item = IPSRecord
                item.data = bytearray.fromhex(entry['data'])
            elif 'repeat' in entry:
                item = IPSRecord
                item.data   = int(entry['repeat'], 16)
                item.repeat = entry['count']
            if None == item:
                raise Exception("Missing filename, data or repeat option.") 
            item.offset = entry['offset']
            self.add(item)
        

if __name__ == "__main__":
    ips = IPSPatch()
    ips.read("patch.json")
    ips.write("bla.ips")

patch.json

[
    {
        "offset": 222,
        "filename": "bla.bin"
    },
    {
        "offset": 200,
        "data": "29ff01ef"
    },
    {
        "offset": 155,
        "repeat": "ff",
        "count": 16
    }
]