Support large WebKit Inspector messages (heap snapshots)

[nnemirovsky]

Problem

The WebKit Inspector Protocol's Heap.startTracking command returns a trackingStart event containing a full heap snapshot. On real-world pages, this snapshot can be 20-200+ MB. Currently, iwdp fails to relay these messages due to three issues:

1. MAX_BODY_LENGTH is 64 MB — messages larger than this are silently rejected as "Invalid packet header", breaking the entire event pipeline for that inspector session
2. Single WebSocket frame — the full payload is buffered into one WebSocket frame, causing peak memory ~2x the payload size on the outgoing side
3. UTF-8 validation — byte-by-byte validation of 50-200 MB payloads is expensive and unnecessary since the data is always valid JSON from WebKit

Changes

1. Raise MAX_BODY_LENGTH from 64 MB to 256 MB (webinspector.c)

Also adds parentheses to the #define to fix a latent operator precedence issue (1<<26 without parens is ambiguous in compound expressions).

2. WebSocket continuation frames for large payloads (ios_webkit_debug_proxy.c)

Messages larger than 1 MB are split into 1 MB chunks sent as RFC 6455 continuation frames. This reduces peak memory on the outgoing side since ws_send_frame only buffers one chunk at a time.

Small messages (≤1 MB) take the existing single-frame fast path — no behavior change for the vast majority of messages.

3. Skip UTF-8 validation for large payloads (websocket.c)

Payloads larger than 1 MB skip the byte-by-byte UTF-8 validation loop. The data is JSON from WebKit Inspector and is always valid UTF-8.

Also fixes ws_send_frame to clear continued_opcode on FIN frames, matching the receive-side behavior at line 740. Without this fix, sending continuation frames leaves stale state that corrupts subsequent single-frame sends.

Testing

Tested with a connected iPhone running Safari on a Google Shopping page:

• Heap.enable → Heap.gc → Heap.startTracking → Heap.gc → Heap.stopTracking
• 33 MB heap snapshot received successfully via continuation frames in ~2 seconds
• GC events dispatched correctly after the large snapshot
• No errors in iwdp output
• Builds clean with -Wall -Werror

[muratpekff]

Great improvement. This was definitely needed. Thanks for tackling it

[Mizzery47]

Literally good decision. Respect