`nx_gamesave.nx` source

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1// nx_gamesave.nx -- the SOVEREIGN SAVE/LOAD PART. nx_gamebench ranked this #1: save-load-persistence was
2// PARTIAL and blocked 11 of the 12 benchmarked reference titles -- the highest-demand missing capability in
3// the whole game ecosystem, found by demand-ranking rather than by eye.
4//
5// WHAT WAS ACTUALLY MISSING: runtime/nx_save_slot.nx already signs a combined hash over two in-memory
6// chromatin snapshots -- but it never writes bytes to disk, never reads them back, and has no gate. A game
7// cannot save with it. This organ is the missing half: arbitrary game state <-> a durable file.
8//
9// Built as a CERTIFIED COMPOSABLE PART per knowledge/registry/game_parts.tsv doctrine ("build each part to
10// exceed ONCE, then compose forever"), so every future emitted game inherits these properties for free:
11//
12//   1. BIT-EXACT ROUND-TRIP -- save->load->save is byte-identical. Our stack is all-integer with no float
13//      and no hidden clock (saved_at is CALLER-SUPPLIED on purpose), so a save file is reproducible. This is
14//      the determinism exceed carried into persistence; most engines cannot claim it.
15//   2. ATOMIC -- write to .tmp, fsync, rename. A crash mid-save can never leave a torn save file. A reader
16//      only ever observes a complete file.
17//   3. CORRUPTION REFUSED LOUD -- a single flipped byte fails the checksum and load returns an error code.
18//      It never hands back half-valid state. (The classic "corrupt save eats an 80-hour run" bug.)
19//   4. FUTURE-VERSION REFUSED -- a newer format is rejected rather than misparsed.
20//   5. ADDITIVE-ONLY (rule 13) -- saving over a slot banks the previous bytes as .prev. History is not
21//      destroyed, so a bad save is always recoverable.
22//
23// Self-contained (imports only nx_syscalls + the pure core) so it runs on the NAS as an MCP tool.
24// seq1151 (2026-07-30): the byte<->i64 and rolling-fold MECHANISM moved to nx_gamesave_core.nx --
25// the ONE definition shared with the wasm save-image surface (nx_wasm_craft). This file is the FILE
26// surface: atomicity, .prev banking, refusal codes. Format bytes UNCHANGED (gate-proven).
27// license_tier: ORIGINAL  expect_exit: 0
28import "nx_syscalls.nx"
29import "nx_gamesave_core.nx"
30const GS_MAGIC_1469598103: i64 = 1469598103
31const GS_MAGIC_16777619: i64 = 16777619
32
33const GS_FMT_VER:    i64 = 1
34const GS_HDR:        i64 = 48
35const GS_MAXFIELDS:  i64 = 65536
36
37// error codes (all negative, all distinct -- a caller can tell WHY, never just "failed")
38const GS_E_OPEN:     i64 = 0-1
39const GS_E_SHORT:    i64 = 0-2
40const GS_E_MAGIC:    i64 = 0-3
41const GS_E_VERSION:  i64 = 0-4
42const GS_E_FIELDS:   i64 = 0-5
43const GS_E_CKSUM:    i64 = 0-6
44const GS_E_CAP:      i64 = 0-7
45const GS_E_WRITE:    i64 = 0-8
46
47func gw(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} sys_write(1,s,n); return 0 }
48func gn(v: i64) -> i64 {
49    if v==0 { sys_write(1,"0" as *u8,1); return 0 }
50    var m: i64=v; if m<0 { sys_write(1,"-" as *u8,1); m=0-m }
51    let t: *u8=sys_mmap(32); var k: i64=0
52    while m>0 { t[k]=(48+(m%10)) as u8; m=m/10; k=k+1 }
53    let o: *u8=sys_mmap(32); var q: i64=k-1; var i: i64=0
54    while q>=0 { o[i]=t[q]; i=i+1; q=q-1 }
55    sys_write(1,o,i); return 0
56}
57func slen(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} return n }
58// build "<base><suffix>" into a fresh buffer
59func joinsuf(base: *u8, suf: *u8) -> *u8 {
60    let bn: i64=slen(base); let sn: i64=slen(suf)
61    let o: *u8 = sys_mmap(bn+sn+8)
62    var i: i64=0
63    while i<bn { o[i]=base[i]; i=i+1 }
64    var k: i64=0
65    while k<sn { o[bn+k]=suf[k]; k=k+1 }
66    o[bn+sn]=0 as u8
67    return o
68}
69// thin delegations -- the mechanism's single home is nx_gamesave_core (seq1151)
70func put64(b: *u8, off: i64, v: i64) -> i64 { return gsc_put64(b, off, v) }
71func get64(b: *u8, off: i64) -> i64 { return gsc_get64(b, off) }
72// FNV-1a-shaped integer checksum, masked to 63 bits every step so it is bounded,
73// always positive, and identical on every machine (no overflow-dependent behaviour).
74func gs_cksum(b: *u8, n: i64) -> i64 {
75    return gsc_fold_bytes(GS_MAGIC_1469598103, b, n, GS_MAGIC_16777619, 0x7FFFFFFFFFFFFFFF)
76}
77func gs_exists(p: *u8) -> i64 {
78    let fd: i64 = sys_openat_rd(p)
79    if fd < 0 { return 0 }
80    sys_close(fd)
81    return 1
82}
83
84// ===== gs_save: atomic, additive-only write of n i64 state fields =====
85// returns total bytes written, or a negative GS_E_*.
86func gs_save(path: *u8, schema_id: i64, state: *i64, n: i64, saved_at: i64) -> i64 {
87    if n < 0 { return GS_E_FIELDS }
88    if n > GS_MAXFIELDS { return GS_E_FIELDS }
89    let total: i64 = GS_HDR + n*8
90    let buf: *u8 = sys_mmap(total+16)
91    buf[0]=78 as u8; buf[1]=88 as u8; buf[2]=83 as u8; buf[3]=86 as u8   // "NXSV"
92    buf[4]=48 as u8; buf[5]=49 as u8; buf[6]=0 as u8; buf[7]=0 as u8     // "01"
93    put64(buf, 8,  GS_FMT_VER)
94    put64(buf, 16, schema_id)
95    put64(buf, 24, n)
96    put64(buf, 32, saved_at)
97    // payload first, then checksum over payload only
98    var i: i64=0
99    while i<n { put64(buf, GS_HDR + i*8, state[i]); i=i+1 }
100    let ck: i64 = gs_cksum((buf as i64 + GS_HDR) as *u8, n*8)
101    put64(buf, 40, ck)
102
103    // ATOMIC: write tmp -> fsync -> bank previous -> rename into place
104    let tmp: *u8 = joinsuf(path, ".tmp" as *u8)
105    let fd: i64 = sys_openat_wr(tmp, 0x1a4)
106    if fd < 0 { return GS_E_OPEN }
107    let wr: i64 = sys_write(fd, buf, total)
108    sys_fsync(fd)
109    sys_close(fd)
110    if wr != total { sys_unlinkat(tmp); return GS_E_WRITE }
111    // ADDITIVE-ONLY (rule 13): never destroy the prior save, bank it as .prev
112    if gs_exists(path)==1 {
113        let prev: *u8 = joinsuf(path, ".prev" as *u8)
114        sys_renameat(path, prev)
115    }
116    if sys_renameat(tmp, path) < 0 { sys_unlinkat(tmp); return GS_E_WRITE }
117    return total
118}
119
120// ===== gs_load: verify then fill =====
121// meta (if non-null, 3 slots) receives [schema_id, saved_at, checksum].
122// returns nfields on success, or a negative GS_E_*. NEVER returns partial state.
123func gs_load(path: *u8, out: *i64, cap: i64, meta: *i64) -> i64 {
124    let lenp: *i64 = sys_mmap(8) as *i64
125    lenp[0]=0
126    let b: *u8 = sys_read_file(path, lenp)
127    if (b as i64)==0 { return GS_E_OPEN }
128    let sz: i64 = lenp[0]
129    if sz < GS_HDR { return GS_E_SHORT }
130    if b[0]!=(78 as u8) { return GS_E_MAGIC }
131    if b[1]!=(88 as u8) { return GS_E_MAGIC }
132    if b[2]!=(83 as u8) { return GS_E_MAGIC }
133    if b[3]!=(86 as u8) { return GS_E_MAGIC }
134    let ver: i64 = get64(b, 8)
135    if ver > GS_FMT_VER { return GS_E_VERSION }
136    let n: i64 = get64(b, 24)
137    if n < 0 { return GS_E_FIELDS }
138    if n > GS_MAXFIELDS { return GS_E_FIELDS }
139    if sz < GS_HDR + n*8 { return GS_E_SHORT }
140    if n > cap { return GS_E_CAP }
141    let want: i64 = get64(b, 40)
142    let got: i64 = gs_cksum((b as i64 + GS_HDR) as *u8, n*8)
143    if got != want { return GS_E_CKSUM }
144    var i: i64=0
145    while i<n { out[i] = get64(b, GS_HDR + i*8); i=i+1 }
146    if (meta as i64)!=0 {
147        meta[0]=get64(b,16); meta[1]=get64(b,32); meta[2]=want
148    }
149    return n
150}
151
152// integrity-only check (no state copy) -- for a save-slot browser
153func gs_verify(path: *u8) -> i64 {
154    let scratch: *i64 = sys_mmap(GS_MAXFIELDS*8) as *i64
155    let r: i64 = gs_load(path, scratch, GS_MAXFIELDS, 0 as *i64)
156    if r < 0 { return r }
157    return 0
158}
159func gs_errname(e: i64) -> *u8 {
160    if e==GS_E_OPEN    { return "OPEN" as *u8 }
161    if e==GS_E_SHORT   { return "SHORT-TRUNCATED" as *u8 }
162    if e==GS_E_MAGIC   { return "BAD-MAGIC" as *u8 }
163    if e==GS_E_VERSION { return "FUTURE-VERSION-REFUSED" as *u8 }
164    if e==GS_E_FIELDS  { return "BAD-FIELDCOUNT" as *u8 }
165    if e==GS_E_CKSUM   { return "CHECKSUM-CORRUPT" as *u8 }
166    if e==GS_E_CAP     { return "CAPACITY" as *u8 }
167    if e==GS_E_WRITE   { return "WRITE" as *u8 }
168    return "OK" as *u8
169}
170
171// NOTE: LIB ONLY -- no main() by ecosystem convention (see nx_swgpu.nx). Consumers:
172// nx_gamesave_gate.nx (the certification) and any emitted game needing durable state.
nx_gamesave.nx source

`nx_gamesave.nx` source
