The chunk checksum is just a CRC32. It seems to be a slighty weird one in that there seems to be signed/unsigned difficulties. This is fixed in the javascript for all my test cases. Right now it does nothing except check the signatures of each chunk.
It is easy to add json serialization/unserialization later.
| { | |
| "name": "patchnode-19232", | |
| "version": "1.0.0", | |
| "description": "", | |
| "main": "patch.js", | |
| "dependencies": { | |
| "crc-32": "^1.0.1" | |
| }, | |
| "devDependencies": {}, | |
| "scripts": { | |
| "test": "echo \"Error: no test specified\" && exit 1" | |
| }, | |
| "author": "Tim Peters", | |
| "license": "ISC" | |
| } |
| const CRC32 = require('crc-32'); | |
| const fs = require('fs'); | |
| const buffer = fs.readFileSync('./patch_v3.lvl.3'); | |
| const header = buffer.slice(0,8); | |
| const maps = buffer.readUInt32LE(4); | |
| console.log(maps); | |
| for(let index = 0; index < maps; index++) { | |
| let chunk = buffer.slice(8+185344*index,8+185344*(index+1)); | |
| let checksum = chunk.readUInt32LE(4); | |
| chunk[4] = 0; | |
| chunk[5] = 0; | |
| chunk[6] = 0; | |
| chunk[7] = 0; | |
| // checksum seems to be inverted. | |
| // So invert & treat as unsigned. | |
| let crc = ~CRC32.buf(chunk) >>> 0; | |
| console.log(checksum.toString(16), crc.toString(16)); | |
| } |