Task 262: .GMK File Format
Task 262: .GMK File Format
1. List of All Properties Intrinsic to the .GMK File Format's File System
The .GMK file format is a binary, chunk-based structure used for GameMaker projects (primarily versions 7.x and 8.x). It features a header followed by fixed-order chunks for settings, resources, and metadata. Resources in version 800+ (GameMaker 8) are Zlib-compressed within their chunks. The intrinsic properties are the structural elements defining the file's organization, versions, counts, sizes, timestamps, and identifiers—excluding individual resource contents (e.g., sprite pixels or script code). Below is a comprehensive list extracted from the format specification:
- Form ID: Integer (fixed value: 1234321, identifies the file as a GameMaker project).
- Format Version: Integer (e.g., 530 for GM6, 600 for GM7, 701 for GM7.1, 800 for GM8; determines compression and features).
- Game ID: Integer (randomized 0–100,000,000; unique identifier for the project).
- DPlay Game GUID: 16-byte binary array (randomized based on Game ID; used for DirectPlay networking).
- GM Version for Game Settings Chunk: Integer (e.g., 530/542/600/702/800; version required to interpret settings).
- Length of Zlib Game Settings Data: Integer (size in bytes of compressed settings data; 0 if uncompressed).
- GM Version for Triggers Chunk: Integer (e.g., 800; version for trigger conditions).
- Number of Triggers: Integer (count of trigger resources).
- Last Time Triggers Changed: Double (Unix timestamp of last modification; version 800+).
- Length of Zlib Triggers Data: Integer (size of compressed triggers data).
- GM Version for Constants Chunk: Integer (e.g., 800; version for named constants).
- Number of Constants: Integer (count of constant definitions).
- Last Time Constants Changed: Double (Unix timestamp; version 800+).
- Length of Zlib Constants Data: Integer (size of compressed constants data).
- Resource Kinds Order: Fixed array of 10 kinds (sounds, sprites, backgrounds, paths, scripts, shaders, fonts, timelines, objects, rooms; defines chunk sequence).
- For each Resource Kind (10 total):
- GM Version for Resource Chunk: Integer (per-kind version, e.g., 400–800).
- Number of Resources: Integer (count for that kind, e.g., number of sprites).
- Last Time Resources Changed: Double (Unix timestamp; version 800+).
- Length of Zlib Resource Data: Integer (size of compressed data for all resources in the kind).
- GM Version for Included Files Chunk: Integer (e.g., 700+; version for external files).
- Number of Included Files: Integer (count of included assets like DLLs).
- Length of Zlib Included Files Data: Integer (size of compressed included files metadata).
- GM Version for Extension Packages Chunk: Integer (e.g., 700; version for extensions).
- Number of Extension Packages: Integer (count of packages).
- For each Extension Package:
- Package Name Length: Integer (byte length of name string).
- Package Name: Length-prefixed ASCII string.
- GM Version for Game Information Chunk: Integer (version for metadata like captions).
- Length of Zlib Game Information Data: Integer (size of compressed info).
- ID of Last Instance Placed: Integer (highest instance ID used in rooms).
- ID of Last Tile Placed: Integer (highest tile ID used in rooms).
- GM Version for Executable Rooms Chunk: Integer (e.g., 500/540/700; version for startup sequence).
- Number of Executable Rooms: Integer (count of rooms in execution order).
- Executable Room Indices: Array of integers (room IDs in startup sequence, one per executable room).
- GM Version for Resource Tree Chunk: Integer (version for resource hierarchy).
- Resource Tree Nodes (hierarchical structure until EOF):
- Node Type: Integer (1=primary, 2=group, 3=secondary).
- Grouping: Integer (1–13; folder category).
- Index: Integer (resource index within kind).
- Name Length: Integer (byte length of node name).
- Node Name: Length-prefixed ASCII string.
- Children Count: Integer (number of child nodes).
- Child Nodes: Recursive sub-nodes (repeat structure for each child).
These properties form the "file system" backbone, enabling navigation, validation, and resource enumeration without decompressing content.
2. Two Direct Download Links for .GMK Files
- https://www.moddb.com/downloads/mirror/163172/206904/fps6.gmk (FPS6 tutorial project for GameMaker 7/8).
- https://archive.org/download/DaveAccelerate/DaveAccelerate.gmk (Dave: Accelerate game source project for GameMaker 8).
3. Ghost Blog Embedded HTML JavaScript for Drag-and-Drop .GMK Property Dump
Drag and drop a .GMK file here to dump properties
Embed this full HTML in a Ghost blog post for drag-and-drop functionality.
4. Python Class for .GMK Handling
import struct
import zlib
import os
class GMK:
def __init__(self, filename):
self.filename = filename
with open(filename, 'rb') as f:
self.data = f.read()
self.pos = 0
self.properties = {}
self.parse()
def read_int(self):
v, = struct.unpack('i', self.data[self.pos:self.pos + 4])
self.pos += 4
return v
def read_double(self):
v, = struct.unpack('d', self.data[self.pos:self.pos + 8])
self.pos += 8
return v
def read_string(self):
l = self.read_int()
if l == -1:
return ''
v = self.data[self.pos:self.pos + l].decode('ascii', errors='ignore')
self.pos += l
return v
def read_guid(self):
v = self.data[self.pos:self.pos + 16]
self.pos += 16
return v.hex()
def skip(self, length):
self.pos += length
def parse(self):
self.properties['form_id'] = self.read_int()
self.properties['version'] = self.read_int()
self.properties['game_id'] = self.read_int()
self.properties['guid'] = self.read_guid()
self.properties['gmver_settings'] = self.read_int()
if self.properties['version'] >= 800:
len_settings = self.read_int()
self.properties['len_settings'] = len_settings
self.skip(len_settings)
self.properties['gmver_triggers'] = self.read_int()
self.properties['num_triggers'] = self.read_int()
if self.properties['version'] >= 800:
self.properties['last_triggers'] = self.read_double()
len_triggers = self.read_int()
self.properties['len_triggers'] = len_triggers
self.skip(len_triggers)
self.properties['gmver_constants'] = self.read_int()
self.properties['num_constants'] = self.read_int()
if self.properties['version'] >= 800:
self.properties['last_constants'] = self.read_double()
len_constants = self.read_int()
self.properties['len_constants'] = len_constants
self.skip(len_constants)
resource_kinds = ['sounds', 'sprites', 'backgrounds', 'paths', 'scripts', 'shaders', 'fonts', 'timelines', 'objects', 'rooms']
self.properties['num_resources'] = {}
self.properties['last_changed'] = {}
for kind in resource_kinds:
gmver = self.read_int()
self.properties['num_resources'][kind] = self.read_int()
if self.properties['version'] >= 800:
self.properties['last_changed'][kind] = self.read_double()
len_data = self.read_int()
self.skip(len_data)
self.properties['gmver_incl'] = self.read_int()
self.properties['num_incl'] = self.read_int()
if self.properties['version'] >= 800:
len_incl = self.read_int()
self.properties['len_incl'] = len_incl
self.skip(len_incl)
self.properties['gmver_ext'] = self.read_int()
self.properties['num_ext'] = self.read_int()
# Skip package names (read/write would need full parse)
for _ in range(self.properties['num_ext']):
name_len = self.read_int()
self.skip(name_len)
self.properties['gmver_info'] = self.read_int()
len_info = self.read_int()
self.properties['len_info'] = len_info
self.skip(len_info)
self.properties['last_instance'] = self.read_int()
self.properties['last_tile'] = self.read_int()
self.properties['gmver_exec'] = self.read_int()
self.properties['num_exec'] = self.read_int()
self.properties['exec_rooms'] = [self.read_int() for _ in range(self.properties['num_exec'])]
self.properties['gmver_tree'] = self.read_int()
# Skip tree data
self.skip(len(self.data) - self.pos)
def print_properties(self):
for key, value in self.properties.items():
if isinstance(value, dict):
print(f"{key}:")
for subkey, subval in value.items():
print(f" {subkey}: {subval}")
else:
print(f"{key}: {value}")
def write(self, output_filename):
# Simple write: copy original (full R/W would reconstruct from properties + content parse)
with open(output_filename, 'wb') as f:
f.write(self.data)
print(f"Wrote to {output_filename}")
# Usage: gmk = GMK('example.gmk'); gmk.print_properties(); gmk.write('output.gmk')
5. Java Class for .GMK Handling
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;
public class GMK {
private byte[] data;
private int pos = 0;
private Map<String, Object> properties = new HashMap<>();
public GMK(String filename) throws IOException {
data = Files.readAllBytes(Paths.get(filename));
parse();
}
private int readInt() {
int v = ByteBuffer.wrap(data, pos, 4).order(ByteOrder.BIG_ENDIAN).getInt();
pos += 4;
return v;
}
private double readDouble() {
double v = ByteBuffer.wrap(data, pos, 8).order(ByteOrder.BIG_ENDIAN).getDouble();
pos += 8;
return v;
}
private String readString() {
int len = readInt();
if (len == -1) return "";
String s = new String(data, pos, len);
pos += len;
return s;
}
private String readGuid() {
byte[] guidBytes = Arrays.copyOfRange(data, pos, pos + 16);
pos += 16;
StringBuilder sb = new StringBuilder();
for (byte b : guidBytes) {
sb.append(String.format("%02x", b));
}
return sb.toString();
}
private void skip(int length) {
pos += length;
}
private void parse() {
properties.put("form_id", readInt());
properties.put("version", readInt());
properties.put("game_id", readInt());
properties.put("guid", readGuid());
properties.put("gmver_settings", readInt());
int version = (int) properties.get("version");
if (version >= 800) {
int lenSettings = readInt();
properties.put("len_settings", lenSettings);
skip(lenSettings);
}
properties.put("gmver_triggers", readInt());
properties.put("num_triggers", readInt());
if (version >= 800) {
properties.put("last_triggers", readDouble());
int lenTriggers = readInt();
properties.put("len_triggers", lenTriggers);
skip(lenTriggers);
}
properties.put("gmver_constants", readInt());
properties.put("num_constants", readInt());
if (version >= 800) {
properties.put("last_constants", readDouble());
int lenConstants = readInt();
properties.put("len_constants", lenConstants);
skip(lenConstants);
}
String[] resourceKinds = {"sounds", "sprites", "backgrounds", "paths", "scripts", "shaders", "fonts", "timelines", "objects", "rooms"};
Map<String, Integer> numResources = new HashMap<>();
Map<String, Double> lastChanged = new HashMap<>();
properties.put("num_resources", numResources);
properties.put("last_changed", lastChanged);
for (String kind : resourceKinds) {
int gmver = readInt();
int num = readInt();
numResources.put(kind, num);
if (version >= 800) {
lastChanged.put(kind, readDouble());
int lenData = readInt();
skip(lenData);
}
}
properties.put("gmver_incl", readInt());
properties.put("num_incl", readInt());
if (version >= 800) {
int lenIncl = readInt();
properties.put("len_incl", lenIncl);
skip(lenIncl);
}
properties.put("gmver_ext", readInt());
int numExt = readInt();
properties.put("num_ext", numExt);
// Skip packages
for (int i = 0; i < numExt; i++) {
int nameLen = readInt();
skip(nameLen);
}
properties.put("gmver_info", readInt());
int lenInfo = readInt();
properties.put("len_info", lenInfo);
skip(lenInfo);
properties.put("last_instance", readInt());
properties.put("last_tile", readInt());
properties.put("gmver_exec", readInt());
int numExec = readInt();
properties.put("num_exec", numExec);
List<Integer> execRooms = new ArrayList<>();
for (int i = 0; i < numExec; i++) execRooms.add(readInt());
properties.put("exec_rooms", execRooms);
properties.put("gmver_tree", readInt());
// Skip tree
skip(data.length - pos);
}
public void printProperties() {
for (Map.Entry<String, Object> entry : properties.entrySet()) {
System.out.println(entry.getKey() + ": " + entry.getValue());
}
}
public void write(String outputFilename) throws IOException {
// Simple copy (full R/W would reconstruct)
Files.write(Paths.get(outputFilename), data);
System.out.println("Wrote to " + outputFilename);
}
// Usage: GMK gmk = new GMK("example.gmk"); gmk.printProperties(); gmk.write("output.gmk");
}
6. JavaScript Class for .GMK Handling (Node.js Compatible)
const fs = require('fs');
class GMK {
constructor(filename) {
this.data = new Uint8Array(fs.readFileSync(filename));
this.pos = 0;
this.properties = {};
this.parse();
}
readInt() {
const v = this.data[this.pos] << 24 | this.data[this.pos + 1] << 16 | this.data[this.pos + 2] << 8 | this.data[this.pos + 3];
this.pos += 4;
return v;
}
readDouble() {
const buf = this.data.slice(this.pos, this.pos + 8);
let v = 0;
for (let i = 0; i < 8; i++) v = (v * 256) + buf[i];
this.pos += 8;
return v; // Simplified; use full IEEE754 parser for accuracy
}
readString() {
const len = this.readInt();
if (len === -1) return '';
const str = new TextDecoder().decode(this.data.slice(this.pos, this.pos + len));
this.pos += len;
return str;
}
readGuid() {
const guid = this.data.slice(this.pos, this.pos + 16);
this.pos += 16;
return Array.from(guid).map(b => b.toString(16).padStart(2, '0')).join('');
}
skip(length) {
this.pos += length;
}
parse() {
this.properties.form_id = this.readInt();
this.properties.version = this.readInt();
this.properties.game_id = this.readInt();
this.properties.guid = this.readGuid();
this.properties.gmver_settings = this.readInt();
if (this.properties.version >= 800) {
this.properties.len_settings = this.readInt();
this.skip(this.properties.len_settings);
}
this.properties.gmver_triggers = this.readInt();
this.properties.num_triggers = this.readInt();
if (this.properties.version >= 800) {
this.properties.last_triggers = this.readDouble();
this.properties.len_triggers = this.readInt();
this.skip(this.properties.len_triggers);
}
this.properties.gmver_constants = this.readInt();
this.properties.num_constants = this.readInt();
if (this.properties.version >= 800) {
this.properties.last_constants = this.readDouble();
this.properties.len_constants = this.readInt();
this.skip(this.properties.len_constants);
}
const resourceKinds = ['sounds', 'sprites', 'backgrounds', 'paths', 'scripts', 'shaders', 'fonts', 'timelines', 'objects', 'rooms'];
this.properties.num_resources = {};
this.properties.last_changed = {};
resourceKinds.forEach(kind => {
this.properties.num_resources[kind] = this.readInt();
if (this.properties.version >= 800) {
this.properties.last_changed[kind] = this.readDouble();
this.skip(this.readInt());
}
});
this.properties.gmver_incl = this.readInt();
this.properties.num_incl = this.readInt();
if (this.properties.version >= 800) {
this.properties.len_incl = this.readInt();
this.skip(this.properties.len_incl);
}
this.properties.gmver_ext = this.readInt();
this.properties.num_ext = this.readInt();
for (let i = 0; i < this.properties.num_ext; i++) {
this.skip(this.readInt());
}
this.properties.gmver_info = this.readInt();
this.properties.len_info = this.readInt();
this.skip(this.properties.len_info);
this.properties.last_instance = this.readInt();
this.properties.last_tile = this.readInt();
this.properties.gmver_exec = this.readInt();
this.properties.num_exec = this.readInt();
this.properties.exec_rooms = [];
for (let i = 0; i < this.properties.num_exec; i++) {
this.properties.exec_rooms.push(this.readInt());
}
this.properties.gmver_tree = this.readInt();
this.skip(this.data.length - this.pos);
}
printProperties() {
console.log(this.properties);
}
write(outputFilename) {
// Simple copy
fs.writeFileSync(outputFilename, this.data);
console.log(`Wrote to ${outputFilename}`);
}
}
// Usage: const gmk = new GMK('example.gmk'); gmk.printProperties(); gmk.write('output.gmk');
7. C Class (Struct) for .GMK Handling
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <zlib.h> // For potential decompression, but skipped here
typedef struct {
int32_t form_id;
int32_t version;
int32_t game_id;
uint8_t guid[16];
// Add other properties as needed
int32_t gmver_settings;
int32_t len_settings;
int32_t gmver_triggers;
int32_t num_triggers;
double last_triggers;
int32_t len_triggers;
// ... (similar for constants, resources, etc.)
int32_t num_resources[10]; // 0=sounds, 1=sprites, etc.
double last_changed[10];
int32_t gmver_incl;
int32_t num_incl;
int32_t len_incl;
int32_t gmver_ext;
int32_t num_ext;
int32_t gmver_info;
int32_t len_info;
int32_t last_instance;
int32_t last_tile;
int32_t gmver_exec;
int32_t num_exec;
int32_t exec_rooms[100]; // Assume max 100
int32_t gmver_tree;
} GMKProperties;
typedef struct {
uint8_t* data;
size_t size;
size_t pos;
GMKProperties props;
} GMK;
int32_t read_int(GMK* gmk) {
int32_t v = (gmk->data[gmk->pos] << 24) | (gmk->data[gmk->pos + 1] << 16) |
(gmk->data[gmk->pos + 2] << 8) | gmk->data[gmk->pos + 3];
gmk->pos += 4;
return v;
}
double read_double(GMK* gmk) {
// Simplified; use full double parse
uint64_t bits = 0;
for (int i = 0; i < 8; i++) {
bits = (bits << 8) | gmk->data[gmk->pos + i];
}
gmk->pos += 8;
return *(double*)&bits; // Unsafe; use proper union
}
void read_guid(GMK* gmk) {
memcpy(gmk->props.guid, &gmk->data[gmk->pos], 16);
gmk->pos += 16;
}
void skip(GMK* gmk, size_t len) {
gmk->pos += len;
}
void parse(GMK* gmk) {
gmk->props.form_id = read_int(gmk);
gmk->props.version = read_int(gmk);
gmk->props.game_id = read_int(gmk);
read_guid(gmk);
gmk->props.gmver_settings = read_int(gmk);
if (gmk->props.version >= 800) {
gmk->props.len_settings = read_int(gmk);
skip(gmk, gmk->props.len_settings);
}
gmk->props.gmver_triggers = read_int(gmk);
gmk->props.num_triggers = read_int(gmk);
if (gmk->props.version >= 800) {
gmk->props.last_triggers = read_double(gmk);
gmk->props.len_triggers = read_int(gmk);
skip(gmk, gmk->props.len_triggers);
}
// Similar for constants...
gmk->props.gmver_constants = read_int(gmk);
gmk->props.num_constants = read_int(gmk);
if (gmk->props.version >= 800) {
gmk->props.last_constants = read_double(gmk);
gmk->props.len_constants = read_int(gmk);
skip(gmk, gmk->props.len_constants);
}
const char* kinds[10] = {"sounds", "sprites", "backgrounds", "paths", "scripts", "shaders", "fonts", "timelines", "objects", "rooms"};
for (int i = 0; i < 10; i++) {
read_int(gmk); // gmver
gmk->props.num_resources[i] = read_int(gmk);
if (gmk->props.version >= 800) {
gmk->props.last_changed[i] = read_double(gmk);
skip(gmk, read_int(gmk));
}
}
// Similar for included, extensions (skip names), info, options, exec rooms, tree...
gmk->props.gmver_incl = read_int(gmk);
gmk->props.num_incl = read_int(gmk);
if (gmk->props.version >= 800) {
gmk->props.len_incl = read_int(gmk);
skip(gmk, gmk->props.len_incl);
}
gmk->props.gmver_ext = read_int(gmk);
gmk->props.num_ext = read_int(gmk);
for (int i = 0; i < gmk->props.num_ext; i++) {
skip(gmk, read_int(gmk));
}
gmk->props.gmver_info = read_int(gmk);
gmk->props.len_info = read_int(gmk);
skip(gmk, gmk->props.len_info);
gmk->props.last_instance = read_int(gmk);
gmk->props.last_tile = read_int(gmk);
gmk->props.gmver_exec = read_int(gmk);
gmk->props.num_exec = read_int(gmk);
for (int i = 0; i < gmk->props.num_exec; i++) {
gmk->props.exec_rooms[i] = read_int(gmk);
}
gmk->props.gmver_tree = read_int(gmk);
skip(gmk, gmk->size - gmk->pos);
}
void print_properties(GMK* gmk) {
printf("Form ID: %d\n", gmk->props.form_id);
printf("Version: %d\n", gmk->props.version);
// ... print all
printf("Game ID: %d\n", gmk->props.game_id);
// GUID as hex...
for (int i = 0; i < 10; i++) printf("Num %s: %d\n", /*kind*/, gmk->props.num_resources[i]);
// etc.
}
void write(GMK* gmk, const char* output) {
FILE* f = fopen(output, "wb");
fwrite(gmk->data, 1, gmk->size, f);
fclose(f);
printf("Wrote to %s\n", output);
}
int main() {
GMK gmk;
// Load file into gmk.data, gmk.size
FILE* f = fopen("example.gmk", "rb");
fseek(f, 0, SEEK_END);
gmk.size = ftell(f);
fseek(f, 0, SEEK_SET);
gmk.data = malloc(gmk.size);
fread(gmk.data, 1, gmk.size, f);
fclose(f);
gmk.pos = 0;
parse(&gmk);
print_properties(&gmk);
write(&gmk, "output.gmk");
free(gmk.data);
return 0;
}