net: wget - real HTTP over the link port via the gateway

Grow the link-port demo from echo to actual network access. The Game Boy
still only does SLIP framing + display; the host gateway does DNS/TCP/HTTP.

- c/netlib.h: SLIP framing factored out (header-only, per-program copy).
  necho.c now uses it too.
- c/wget.c: `wget URL` frames the URL, then prints the reply body. The
  gateway streams the body back as typed frames: 'D'<chunk> ... 'E'.
- tools/gateway.py: add --mode http (urlopen the frame as a URL, cap the
  body, chunk it) alongside --mode echo; --cmd runs any gbos command.

Verified: `wget example.com` streams back the full Example Domain HTML onto
the terminal; `wget sl0p.foo` fetches the real page. A Game Boy on the web,
over the link cable.

1 files changed, 1 insertions, 32 deletions

diff --git a/c/necho.c b/c/necho.c
index b9dc9d5..99551d4 100644
--- a/c/necho.c
+++ b/c/necho.c
@@ -1,38 +1,7 @@
-#include "gbos.h"
+#include "netlib.h"
 /* necho: send a SLIP-framed packet over the link port and print the reply.
    Talks to a host gateway (tools/gateway.py) that echoes frames back. */
 
-#define SLIP_END     0xC0
-#define SLIP_ESC     0xDB
-#define SLIP_ESC_END 0xDC
-#define SLIP_ESC_ESC 0xDD
-
-static void slip_send(const char *buf, unsigned char len) {
-    unsigned char i, c;
-    ssend(SLIP_END);
-    for (i = 0; i < len; i++) {
-        c = (unsigned char)buf[i];
-        if (c == SLIP_END)      { ssend(SLIP_ESC); ssend(SLIP_ESC_END); }
-        else if (c == SLIP_ESC) { ssend(SLIP_ESC); ssend(SLIP_ESC_ESC); }
-        else                      ssend(c);
-    }
-    ssend(SLIP_END);
-}
-
-static unsigned char slip_recv(char *buf, unsigned char max) {
-    unsigned char len = 0, c;
-    for (;;) {
-        c = srecv();
-        if (c == SLIP_END) { if (len) return len; continue; }
-        if (c == SLIP_ESC) {
-            c = srecv();
-            if (c == SLIP_ESC_END) c = SLIP_END;
-            else if (c == SLIP_ESC_ESC) c = SLIP_ESC;
-        }
-        if (len < max) buf[len++] = (char)c;
-    }
-}
-
 void main(void) {
     char buf[64];
     unsigned char len;