Claude (auto-RE)
398e8ae0af
The whole retail save is 545 bytes: a GDHA container wrapping a zlib payload,
which is a chunk stream — 'GDAA', a length-prefixed game-phase name (GP_BUNK,
one of the title's GP_* screen ids), a 'GHAD' 122-byte progress block, a
count-prefixed table of 16 20-byte save slots, and a trailer.
None of it is guessed. The layout comes from the serializer at 0x822C00E8 and
its callee 0x822BF678: the writer primitive is 0x821885A8(stream, buf, len), the
slot count 16 and the 20-byte stride are literals, and the GHAD block is ten u32,
a u64, four u32, a raw 4-byte field and a raw 54-byte blob = 122 bytes, which is
exactly what the file carries. savegame.py re-serializes the parse and asserts
byte-identity.
Because the struct is written field-by-field with no packing changes, a payload
offset is also the offset in the live save object -- save+8 for GHAD, save+136
for the slot table, and 136+16*20 = 456 is the serializer's very next access.
Confirmed independently: slot 0's trailing two u32 decode as a FILETIME to
2026-07-23 20:07:23 UTC, and the content header's display string (written by the
game) says 07/23/2026 21:08 at UTC+1; the 15 empty slots hold 2006-01-01 rather
than zero.
Field meanings are left ❔ on purpose -- the naming oracle is a diff of two
saves, and all four copies on disk are byte-identical, so a second save has to
be made first. Nothing has been written back to any save.
138 lines
6.3 KiB
Markdown
138 lines
6.3 KiB
Markdown
# Save file (`savedata`) — container ✅ exact, field meanings ❔ (2026-08-11)
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**Status: ✅ CONFIRMED for the container and the chunk layout** — parsed off the
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title's own serializer, not guessed, and verified by a byte-identical round-trip.
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**❔ for what most of the numbers mean**; those are marked below and none are
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asserted.
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Parser + round-trip check: [`tools/re-capture/savegame.py`](../../../tools/re-capture/savegame.py)
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(`savegame.py <savedata> --verify` re-serializes the parse and asserts equality).
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## Where it lives
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```
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<xenia content>/<XUID>/535107D4/00000001/game01/savedata 545 B payload
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<xenia content>/<XUID>/535107D4/Headers/00000001/game01.header 328 B
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```
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The **header** is the Xbox content header, not game data: a UTF-16BE display
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string (`Game01 07/23/2026 21:08 STAGE02 EASY`), the internal name `game01`, and
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the title id `53 51 07 D4`. It is what the save-select screen lists.
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`savedata` is the whole save. **545 bytes** — there is no second file, so
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everything the game remembers between sessions is in here.
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## Container
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```
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'GDHA' <146-byte header> <zlib stream, 78 DA>
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```
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The deflated payload is 545 bytes. Two of the GDHA header words are a FILETIME
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and a copy of the slot-0 fields; **much of the rest is uninitialised memory** —
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words like `0x828F3DA8`, `0xBD4B6200`, `0x70D8FD50` are guest virtual addresses
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that leaked out of the struct's padding, so the header is not byte-reproducible
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and must not be treated as meaningful. The last four bytes of the file are the
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zlib stream's own Adler-32, and the same value also appears at header offset
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`0x8E`.
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## Payload — a chunk stream written by `0x822C00E8`
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Every element below is read off the serializer, whose writer primitive is
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`0x821885A8(stream, buf, len)`:
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| bytes | what | source |
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|---|---|---|
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| `'GDAA'` | payload magic | `addis 0x4744 / ori 0x4141` at `0x822C00F8` |
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| `u32 len`, `char[len]` | **current game phase**, here `GP_BUNK` | `lwz r11,0(save)`; if `< 29`, index the GP_* name table at `0x820A5680` |
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| `'GHAD'` + 122 B | the progress block | `0x822BF678`, called with `save+8` |
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| `u32 16`, 16 × (`'SHAB'` + 5×u32) | the save-slot table | `addi r28,r0,16` / stride `addi r29,r29,20` |
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| `u32 4`, `"BUNK"`, `'NETA'`, `u32` | trailer | — |
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**The in-memory struct is written field-by-field with no packing changes, so a
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payload offset is also the offset in the live save object**: the GHAD block is
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`save+8`, the slot table is `save+136`, and the serializer's next access after
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the table is `lwz r11,456(save)` — exactly `136 + 16*20`. That makes this doc a
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map of the runtime object too, which is what a live-RAM read would need.
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The phase name is ✅ real: `GP_BUNK` is one of the title's screen ids, and the
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.pe carries the neighbouring list `GP_HANGAR`, `GP_READY_ROOM`, `GP_BUNK`,
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`GP_MOVIE`, `GP_OPTIONS`, `GP_MISSION_*`. (Note the `SHAB` string that also
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appears in the .pe is a **false hit** — it is inside the RTTI name
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`.?AVSCRIPT_COMMAND_PUSHABLE@SilpheedSCS@@`. The four-character tags are built
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as `lis`/`ori` immediate pairs, so they are not in the string pool at all.)
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### The GHAD block (122 bytes, `0x822BF678`)
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Ten u32, one u64 (`ld r11,40(r30)`), four u32, a raw 4-byte field and a raw
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54-byte blob. 10·4 + 8 + 4·4 + 4 + 54 = **122**, which is exactly what the file
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carries — the layout is closed, with nothing unaccounted for.
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| off | value in this save | reading |
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|---|---|---|
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| +0 | 0 | ❔ |
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| +4 | **324773** | ❔ a large per-save counter — credits/score is the obvious guess, untested |
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| +8 | 5 | ❔ the save-select screen shows this save at **5 %** |
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| +12 | 0 | ❔ |
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| +16 | 1 | ❔ |
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| +20 | 0 | ❔ |
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| +24 | **4101** (`0x1005`) | ❔ same value as +28 and as slot 0's field b |
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| +28 | **4101** (`0x1005`) | ❔ |
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| +32 | 79 | ❔ |
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| +36 | 2 | ❔ equals slot 0's field a; the header calls this save `EASY` |
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| +40 (u64) | 2014400 | ❔ |
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| +48 | 0 | ❔ |
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| +52 | 2 | ❔ |
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| +56 | 2 | ❔ |
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| +60 | 0 | ❔ |
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| +64 (raw 4) | `09 15 00 00` | ❔ the trailer's u32 is the **same** value |
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| +68 (raw 54) | see below | ❔ 54 one-byte entries, values only ∈ {0, 2, 4} |
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The 54-byte blob is the interesting one — a fixed-length array of small
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enumerated states, 20 of the 54 non-zero:
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```
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04 02 00 00 00 02 00 00 00 04 02 00 02 00 00 00 00 00 00 00 00 04 04 00 00 00 04
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02 00 00 00 02 00 04 00 00 00 00 00 04 00 00 00 00 00 04 04 04 00 00 00 00 00 00
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```
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54 matches no count we have already established (22 stages, 110 units, 126
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weapons, ~61 Arsenal entries), so **do not** assume which list it indexes.
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### The slot table (16 × 20 bytes)
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| slot | a | b | c | FILETIME |
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|---|---|---|---|---|
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| 0 | 2 | 4101 | 324773 | **2026-07-23 20:07:23** |
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| 1–15 | 0 | 0 | 0 | 2006-01-01 00:00:00 |
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**The FILETIME reading is ✅ confirmed independently**: the last two u32 of slot 0
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decode as a Windows FILETIME to 2026-07-23 20:07:23 UTC, and the content header's
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own display string — written by the game, parsed by nobody here — says
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`07/23/2026 21:08` (UTC+1). The 15 unused slots all hold 2006-01-01, a plausible
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epoch default rather than zero, which is a second check on the same reading.
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Fields a/b/c of slot 0 are copies of GHAD +36, +24/+28 and +4. So the slot record
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is a **summary** of a save, which is what a slot-select screen needs.
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## What this does and does not unlock
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It settles the format. It does **not** yet settle which field is stage-unlock
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state, so it does not yet answer the question that motivated it — whether stage
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progress can be reached without winning missions
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([mission outcome](../mission-outcome-stage02.md)).
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**The naming oracle is a differential, and only one save exists** (all four
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copies on disk — the live one, both `content-backup-*` snapshots and the `prof2`
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profile — are byte-identical, md5 `142b4f432e0e…`). So the next step is to
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*make* a second save: change one thing in-game that the player can change
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cheaply, save, and diff. Developing or buying a single Arsenal item should move
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+4 (if it is currency) and one entry of the 54-byte blob, which would name two
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fields at once.
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**Nothing here has been written back to a save.** Editing is a separate decision
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and needs the user's go-ahead; the round-trip in `savegame.py` exists so that an
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edit *could* be made safely (parse → change one field → re-serialize → re-deflate
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→ re-wrap), and so that a diff of two saves can be read structurally instead of
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as raw bytes.
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