Fix zlib compression for save file writing #3

Merged

Leon Schmidt merged 1 commit from cloudy/Anno2205-Savegame-Modifier:main into main

2026-03-31 21:24:22 +02:00

Cloudy (Bot) commented

2026-03-31 20:49:43 +02:00

Collaborator

Fixes #2

The set command was already implemented, but the save_file function produced corrupted save files.

Problem: zlib.compress() produces a 78 9c zlib header, but Anno 2205 expects 78 da (default compression level header).

Solution: Build the zlib stream manually:

78 da header
Raw deflate data (wbits=-15)
Adler-32 checksum trailer

Testing:

DifficultyMilitaryInvasions: 1 → 0 ✓
DifficultyTraderPrices: 0 → 100 ✓
Both modified files can be re-read and dumped correctly

Fixes #2 The `set` command was already implemented, but the `save_file` function produced corrupted save files. **Problem:** `zlib.compress()` produces a `78 9c` zlib header, but Anno 2205 expects `78 da` (default compression level header). **Solution:** Build the zlib stream manually: - `78 da` header - Raw deflate data (wbits=-15) - Adler-32 checksum trailer **Testing:** - `DifficultyMilitaryInvasions`: 1 → 0 ✓ - `DifficultyTraderPrices`: 0 → 100 ✓ - Both modified files can be re-read and dumped correctly

Cloudy (Bot) added 1 commit

2026-03-31 20:49:43 +02:00

Fix zlib compression for save file writing 30b5de7657

The original implementation used zlib.compress() which produces 78 9c header,
but Anno 2205 expects 78 da (default compression level header).

Build the zlib stream manually with:
- 78 da header
- Raw deflate data (wbits=-15)
- Adler-32 checksum trailer

Tested successfully with DifficultyMilitaryInvasions and DifficultyTraderPrices.

Cloudy (Bot) referenced this pull request

2026-03-31 20:49:50 +02:00

Implement the set command #2