russell@unturf.com
574ddc50d7
Fuses portal (Scheme-source-as-interchange) with sockets (bytes over the network). Wire protocol: one S-expression per connection. Same server + client .lsp runs byte-identically in Python, C, and asm. New primitives in all three impls: - read-from-string — parse one sexp from a string Asm gets two more: - symbol->string — standard R7RS, was missing - eval — evaluate a Scheme value in the global env (Python + C had it as a special form; asm exposes it as a builtin) examples/rpc-server.lsp (port 9080): - Whitelisted dispatch: ping / add / mul / fib / echo - Never calls eval on client input; safe by construction - Uses heap-snapshot/restore for O(1) memory on asm - ~90 lines, portable examples/rpc-client.lsp: - Sends one request, reads one response, displays both - 45 lines, portable examples/repl-server.lsp (port 9081): - DANGER: full remote eval. Any Scheme form accepted and evaluated in the server's global env. Persistent across connections. - Deliberately does NOT use heap-snapshot — remote (define x ...) lives in the global env above any snapshot point; rewinding would invalidate the new binding. The ulimit -v 512 MB safety net (documented in CLAUDE.md) ensures an escaped process can't crash the machine. - ~70 lines, portable. Demonstrates what "the language IS the interchange format" gets you at the limit: a single socket and a single primitive (eval) carry a full-powered REPL. Verified 3×3 server×client matrix: all 9 combinations green. All 132 asm + 571 py + 189 shared + 83 c tests still pass. One quirk discovered and worked around: in asm, a closure captures its env chain by pointer at define time. Forward-referenced names in mutually-recursive toplevel defines can fail under specific heap-restore patterns — see the leaf-first ordering note in rpc-server.lsp.
110 lines
4.2 KiB
Text
110 lines
4.2 KiB
Text
;;; rpc-server.lsp — S-expression RPC with a whitelisted dispatch table.
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;;;
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;;; Wire protocol: each connection carries ONE request S-expression and
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;;; returns ONE response S-expression. Bytes on the wire are Scheme source;
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;;; the parser on each side is already the right tool.
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;;;
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;;; Runs byte-identically in Python, C, and asm:
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;;; python3 uncommonlisp.py --fast examples/rpc-server.lsp
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;;; ./c/uncommonlisp examples/rpc-server.lsp
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;;; ./asm/uncommonlisp < examples/rpc-server.lsp
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;;;
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;;; Request examples (send as plain text, one per connection):
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;;; (ping) -> pong
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;;; (add 1 2 3) -> 6
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;;; (mul 6 7) -> 42
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;;; (fib 30) -> 832040
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;;; (echo (1 2 3)) -> (1 2 3)
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;;; (nope whatever) -> (error "unknown op: nope")
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;;;
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;;; The server never calls (eval) on client input. Only whitelisted ops
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;;; run. This is the safe RPC pattern. For full remote eval see
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;;; examples/repl-server.lsp.
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(define *port* 9080)
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(define *max-requests* 100000)
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;;; ── Whitelisted handlers ────────────────────────────────────
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(define (do-ping args) 'pong)
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(define (do-echo args) (if (pair? args) (car args) '()))
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(define (do-add args)
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(if (null? args) 0
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(+ (car args) (do-add (cdr args)))))
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(define (do-mul args)
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(if (null? args) 1
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(* (car args) (do-mul (cdr args)))))
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(define (do-fib args)
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(let loop ((a 0) (b 1) (i 0) (n (car args)))
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(if (= i n) a (loop b (+ a b) (+ i 1) n))))
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(define (dispatch op args)
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(cond
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((eqv? op 'ping) (do-ping args))
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((eqv? op 'echo) (do-echo args))
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((eqv? op 'add) (do-add args))
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((eqv? op 'mul) (do-mul args))
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((eqv? op 'fib) (do-fib args))
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(else (list 'error (string-append "unknown op: " (symbol->string op))))))
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;;; ── Wire handler ────────────────────────────────────────────
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(define (handle-request raw)
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;; raw is a string like "(add 1 2)". Parse, dispatch, return a string.
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(let ((form (read-from-string raw)))
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(if (pair? form)
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(let ((op (car form)) (args (cdr form)))
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(response->string (dispatch op args)))
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(response->string (list 'error "malformed request")))))
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;; Defined leaf-first so closures never capture a forward reference —
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;; which the asm impl resolves at define time via env-chain pointer
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;; and therefore cannot see a name bound later.
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(define (atom->string v)
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(cond
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((number? v) (number->string v))
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((symbol? v) (symbol->string v))
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((null? v) "()")
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((pair? v) (string-append "(" (list->string v) ")"))
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((string? v) (string-append "\"" v "\""))
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(else "#<unknown>")))
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(define (list->string lst)
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(cond
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((null? lst) "")
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((null? (cdr lst)) (atom->string (car lst)))
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(else (string-append (atom->string (car lst)) " " (list->string (cdr lst))))))
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(define (response->string v)
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;; Custom readable serializer — avoids open-output-string so this runs
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;; unchanged in asm (which lacks mutable string ports). Covers the
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;; response shapes our dispatch table can return.
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(cond
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((number? v) (string-append (number->string v) "\n"))
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((symbol? v) (string-append (symbol->string v) "\n"))
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((null? v) "()\n")
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((pair? v) (string-append "(" (list->string v) ")\n"))
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((string? v) (string-append "\"" v "\"\n"))
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(else "#<unknown>\n")))
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;;; ── Main loop ───────────────────────────────────────────────
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(define server (tcp-listen *port*))
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(define (server-loop n snap)
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(if (>= n *max-requests*)
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(begin (display "request cap reached, exiting\n") (tcp-close server))
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(begin
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(let ((client (tcp-accept server)))
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(let ((req (tcp-recv client 4096)))
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(if (and req (> (string-length req) 0))
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(tcp-send client (handle-request req))
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#f))
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(tcp-close client))
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(heap-restore snap)
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(server-loop (+ n 1) snap))))
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(display "rpc-server on :") (display *port*)
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(display " (whitelisted: ping echo add mul fib)") (newline)
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(server-loop 0 (heap-snapshot))
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