ludic/runtime/native/base64.ludic
Orkuncakilkaya bf36bc8a8f refactor(runtime,packages,examples): named constants, package enums, idiom sweep
- runtime: HEADLESS_FRAME_PATH, STICK_DEADZONE / STICK_LEFT_X/Y, key and
  byte codes as char literals throughout (`k == 'w'`, `fill(rt_map, ' ', …)`)
- ludic.gameplay/stats: drop the duplicate `stat_field` (it answered "atk"
  for every build stat); Stats.base uses stats_field_name
- ludic.shooter: compare aim modes and fire patterns with AimMode.* and
  WeaponPattern.* instead of raw ints; STICK_RIGHT_X/Y
- ludic.npcai: DecisionMade / brain_set_state use AiState.*
- examples/games/menu.ludic uses Font.load / Ui.* with FONT_PATH and
  BACKDROP named; strings.ludic header says what it prints
- whole tree: `x = x + 1` → `x += 1` (single-term right-hand sides only),
  `0 - x` → `-x`, ASCII codes → char literals; every .ludic and every
  ```ludic fence reformatted with the fixed formatter (whitespace only)

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
2026-09-05 01:12:26 +03:00

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# ============================================================================
# base64.ludic — standard base64 (RFC 4648) encode + decode, in Ludic (`Base64.*`).
#
# `Crypto.base64` already encodes (hand-written IR, tied to the crypto prelude);
# the Tiled data pipeline (issue #67) needs a *decoder* — base64 layer data feeds
# the DEFLATE inflater. This is that decoder, plus a matching pure-Ludic encoder
# so the namespace is self-contained and spliceable on its own (no crypto prelude
# dependency). Deterministic, allocation the only cost.
#
# ludicc splices this file when a program mentions `Base64.*` (parse.ludic). The
# decoder ignores ASCII whitespace (TMX embeds newlines/indentation in its base64
# `<data>`), and '=' padding ends the stream.
# ============================================================================
# the standard alphabet value of a base64 character, or -1 for anything else
# (whitespace, '=', stray bytes — the decoder skips them / stops on '=').
function b64_val(c: int) -> int {
if c >= 'A' and c <= 'Z' { return c - 65 } # 'A'..'Z' -> 0..25
if c >= 'a' and c <= 'z' { return c - 71 } # 'a'..'z' -> 26..51
if c >= '0' and c <= '9' { return c + 4 } # '0'..'9' -> 52..61
if c == '+' { return 62 } # '+'
if c == '/' { return 63 } # '/'
return -1
}
# decode NUL-terminated base64 `src` into the caller's `out` buffer; returns the
# number of bytes written. Whitespace is ignored; '=' padding terminates. `out`
# must hold at least (len(src)*3)/4 bytes.
function b64_decode(src: pointer, out: pointer) -> int {
var acc = 0
var nbits = 0
var w = 0
var i = 0
var c = src[i]
while c != 0 {
if c == '=' { return w } # '=' -> done
let v = b64_val(c)
if v >= 0 {
acc = (acc << 6) | v
nbits += 6
if nbits >= 8 {
nbits -= 8
out[w] = (acc >> nbits) & 255
w += 1
}
}
i += 1
c = src[i]
}
return w
}
# decode base64 text -> a fresh NUL-terminated string of the decoded bytes.
# (For binary payloads that may contain NUL, decode into a sized buffer with
# `b64_decode` and track the returned length instead.)
function base64_decode(src: pointer) -> pointer {
let cap = len(src) + 4
let out = bytes(cap)
let w = b64_decode(src, out)
out[w] = 0
return out
}
# encode the bytes of NUL-terminated `src` as standard base64 (with '=' padding).
function base64_encode(src: pointer) -> pointer {
let tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
let n = len(src)
var out = ""
var i = 0
while i < n {
let b0 = src[i]
var b1 = 0
var b2 = 0
var have = 1
if i + 1 < n { b1 = src[i + 1]; have = 2 }
if i + 2 < n { b2 = src[i + 2]; have = 3 }
let e0 = b0 >> 2
let e1 = ((b0 & 3) << 4) | (b1 >> 4)
let e2 = ((b1 & 15) << 2) | (b2 >> 6)
let e3 = b2 & 63
out = out + tab[e0..e0 + 1] + tab[e1..e1 + 1]
if have >= 2 { out += tab[e2..e2 + 1] } else { out += "=" }
if have >= 3 { out += tab[e3..e3 + 1] } else { out += "=" }
i += 3
}
return out
}