nx_h2_frame.nx

nx_h2_frame.nx -- TUTOR-BOOTSTRAP SCAFFOLD (Claude, authored under the R4-H2 HTTP/2-transport-ladder workflow), NOT credited as team self-authoring. R4-H2-003 of the sovereign HTTP/2 transport ladder (knowledge/specs/2026-06-13-http2-transport-ladder.md). The HTTP/2 frame codec (RFC 9113 §3.4 / §4.1 / §6). The WIRE FORMAT -- the 9-octet generic frame header (Length 24-bit BE, Type 8, Flags 8, R 1 + Stream-ID 31 BE), the 24-octet connection preface, and the per-frame payload layouts of SETTINGS, HEADERS, DATA, RST_STREAM, PING, GOAWAY, WINDOW_UPDATE -- is an allowed internet-boundary requirement: the bytes are dictated by RFC 9113 byte-for- byte so we interoperate, exactly as nx_tls13_ext.nx emits RFC 8446 extension bytes and nx_hpack.nx emits RFC 7541 header blocks. The IMPLEMENTATION is pure NishiLang via nx_cc -> nxasm_x86: no gcc, no openssl, no nghttp2. FOUNDED ON (composes, does not reinvent -- anti-orphan law): - nx_hpack.nx (R4-H2-002, GREEN): the HEADERS frame wraps an HPACK block built by hpack_encode_indexed / hpack_encode_lit_inc_indexed_name; it transitively splices nx_str.nx -> syscalls.nx -> nx_syscalls.nx, so we inherit sys_mmap / sys_write / sys_exit from ONE import (importing nx_str / nx_syscalls directly TOO would be the RC6 double-import landmine). - nx_tls13.nx (no imports; pure byte helpers): we reuse tls_write_u16_be / tls_read_u16_be (nx_tls13.nx:201/205) for the SETTINGS Identifier(16) AND tls_write_u24_be / tls_read_u24_be (nx_tls13.nx:188/192) for the 24-bit frame Length -- the exact same big-endian helpers the TLS handshake-message headers use, NOT reinvented here (Rule-15 DRY). Only the u31/u32 BE pair (which has no TLS counterpart) is added locally. nx_tls13 imports nothing, so importing it alongside nx_hpack does NOT double-import syscalls. No floating capability: HPACK founds this frame codec; the stream state machine (R4-H2-004) founds on this next. BACK-FILL: the team RE-AUTHORS this from the DATA spec via the emitter-of-emitters (X-AUT-006c/e/f) -- this hand-authored scaffold is the sanctioned one-time bootstrap only (meter-integrity, mirror nx_frame_codec.nx:13-16 / nx_hpack.nx:28-31). GATE (main): asserts byte-exact the RFC 9113 known-answers -- the 24-byte connection preface (§3.4), the empty client SETTINGS frame (00 00 00 04 00 00 00 00 00), SETTINGS ACK, a SETTINGS frame carrying INITIAL_WINDOW_SIZE=65535, a HEADERS frame on stream 1 (flags END_STREAM|END_HEADERS = 0x05) wrapping the C.3.1-style HPACK block, plus WINDOW_UPDATE / RST_STREAM / PING / GOAWAY /