ludic/examples/lang/json_saves.ludic
Orkuncakilkaya 4499cedcb8 runtime: Json.write_file, and Json.encode through a kept buffer
The encoder appends into RtJsonState's buffer (grown only past the biggest document yet): ints and
Q16.16 fixeds written as digits in place, floats through string() and freed. Json.encode copies the
answer out once; Json.write_file hands the buffer to Fs.write_text (.tmp + rename) and keeps nothing.
json_saves.ludic: exact text, the file equals encode, parse round-trips, 1000 saves grow 0; clean
under MallocScribble. json_quote (the + builder) is gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-09-28 15:32:36 +03:00

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1.9 KiB
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# json_saves.ludic - Json.write_file writes a tree as JSON through a buffer the runtime keeps (the
# .tmp and the rename as Fs.write_text), so a game can save as often as it likes and keep nothing:
# the same text Json.encode gives, read back whole. Prints 1 2 3 and `saves grew 0` (the heap is
# read on the Mac; 0 elsewhere).
program JsonSaves {
function tree(n: int) -> Val {
let o = Value.object()
Value.put(o, "name", Value.str("camp \"north\"\nshore\\"))
Value.put(o, "day", Value.int(n))
Value.put(o, "cold", Value.int(-2147483647))
Value.put(o, "rep", Value.fixed(49152))
Value.put(o, "pace", Value.float(float(7) / float(2)))
Value.put(o, "wet", Value.bool(0))
Value.put(o, "none", Value.null())
let l = Value.list()
for i in 0 .. 40 { Value.add(l, Value.int(i * 37 - 500)) }
Value.put(o, "pack", l)
let inner = Value.object()
Value.put(inner, "x", Value.fixed(-8192))
Value.put(o, "at", inner)
return o
}
entry {
let small = Value.object()
Value.put(small, "a", Value.int(-7))
Value.put(small, "b", Value.fixed(32768))
Value.put(small, "c", Value.str("q\"\\\n"))
let sl = Value.list()
Value.add(sl, Value.bool(1))
Value.add(sl, Value.null())
Value.put(small, "d", sl)
if Json.encode(small) == "{\"a\":-7,\"b\":0.5,\"c\":\"q\\\"\\\\\\n\",\"d\":[true,null]}" { print(1) }
let path = Os.temp_dir() + "/json_saves_" + string(Os.pid()) + ".json"
let t = tree(3)
let wrote = Json.write_file(t, path)
let back = Fs.read_text(path)
let enc = Json.encode(t)
if wrote and back == enc { print(2) }
let again = Json.parse(back)
if Json.encode(again) == enc { print(3) }
for i in 0 .. 20 { Json.write_file(t, path) }
let before = Os.heap_bytes()
for i in 0 .. 1000 { Json.write_file(t, path) }
let grew = Os.heap_bytes() - before
Fs.remove(path)
print(`saves grew {grew}`)
}
}