nghttp3 で QPACK

README.md

nghttp3 で QPACK

cc -O2 -Wall -Wextra qpack.c $(pkg-config --cflags --libs libnghttp3) -o qpack

./qpack

Hpack.c

// qpack_roundtrip.c
#include <nghttp3/nghttp3.h>

#include <inttypes.h>
#include <stdio.h>
#include <string.h>

/* rcbuf から (ptr,len) を取り出して表示する */
static void print_qpack_nv(const nghttp3_qpack_nv *nv) {
  nghttp3_vec name = nghttp3_rcbuf_get_buf(nv->name);
  nghttp3_vec value = nghttp3_rcbuf_get_buf(nv->value);

  printf("  %.*s: %.*s\n",
         (int)name.len, (const char *)name.base,
         (int)value.len, (const char *)value.base);
}

/* nghttp3_buf の中身 (begin..last) を (ptr,len) で返す */
static const uint8_t *buf_ptr(const nghttp3_buf *b) { return b->begin; }
static size_t buf_len(const nghttp3_buf *b) { return (size_t)(b->last - b->begin); }

int main(void) {
  const nghttp3_mem *mem = nghttp3_mem_default();

  /* --- QPACK encoder/decoder を作る --- */
  nghttp3_qpack_encoder *enc = NULL;
  nghttp3_qpack_decoder *dec = NULL;

  /* hard_max_dtable_capacity は “上限”。実効値は set_max_dtable_capacity() で決める */
  if (nghttp3_qpack_encoder_new(&enc, 4096, mem) != 0) {
    fprintf(stderr, "nghttp3_qpack_encoder_new failed\n");
    return 1;
  }
  if (nghttp3_qpack_decoder_new(&dec, 4096, 0 /* max_blocked_streams */, mem) != 0) {
    fprintf(stderr, "nghttp3_qpack_decoder_new failed\n");
    nghttp3_qpack_encoder_del(enc);
    return 1;
  }

  /* 動的テーブルを使う（例として 4096） */
  nghttp3_qpack_encoder_set_max_dtable_capacity(enc, 4096);

  /* --- エンコード対象のヘッダ（HTTP/3 の疑似ヘッダ含む）--- */
  const nghttp3_nv nva[] = {
      {(const uint8_t *)":method", (const uint8_t *)"GET",
       sizeof(":method") - 1, sizeof("GET") - 1, 0},
      {(const uint8_t *)":scheme", (const uint8_t *)"https",
       sizeof(":scheme") - 1, sizeof("https") - 1, 0},
      {(const uint8_t *)":authority", (const uint8_t *)"example.com",
       sizeof(":authority") - 1, sizeof("example.com") - 1, 0},
      {(const uint8_t *)":path", (const uint8_t *)"/",
       sizeof(":path") - 1, sizeof("/") - 1, 0},
      {(const uint8_t *)"user-agent", (const uint8_t *)"qpack-roundtrip/0.1",
       sizeof("user-agent") - 1, sizeof("qpack-roundtrip/0.1") - 1, 0},
  };

  const int64_t stream_id = 0;

  /* --- エンコード：pbuf(prefix), rbuf(request stream), ebuf(encoder stream) を生成 --- */
  nghttp3_buf pbuf, rbuf, ebuf;
  nghttp3_buf_init(&pbuf);
  nghttp3_buf_init(&rbuf);
  nghttp3_buf_init(&ebuf);

  int rv = nghttp3_qpack_encoder_encode(enc, &pbuf, &rbuf, &ebuf, stream_id,
                                        nva, sizeof(nva) / sizeof(nva[0]));
  if (rv != 0) {
    fprintf(stderr, "nghttp3_qpack_encoder_encode failed: %d\n", rv);
    nghttp3_buf_free(&pbuf, mem);
    nghttp3_buf_free(&rbuf, mem);
    nghttp3_buf_free(&ebuf, mem);
    nghttp3_qpack_decoder_del(dec);
    nghttp3_qpack_encoder_del(enc);
    return 1;
  }

  printf("[encoded]\n");
  printf("  prefix (pbuf): %zu bytes\n", buf_len(&pbuf));
  printf("  request (rbuf): %zu bytes\n", buf_len(&rbuf));
  printf("  encoder-stream (ebuf): %zu bytes\n", buf_len(&ebuf));

  /* --- 受信側：encoder stream を先に食わせて dynamic table を更新 --- */
  if (buf_len(&ebuf) > 0) {
    nghttp3_ssize nread = nghttp3_qpack_decoder_read_encoder(dec, buf_ptr(&ebuf), buf_len(&ebuf));
    if (nread < 0 || (size_t)nread != buf_len(&ebuf)) {
      fprintf(stderr, "nghttp3_qpack_decoder_read_encoder failed: %zd\n", (ssize_t)nread);
      goto cleanup;
    }
  }

  /* --- 受信側：request stream（prefix→header block）をデコード --- */
  nghttp3_qpack_stream_context *sctx = NULL;
  if (nghttp3_qpack_stream_context_new(&sctx, stream_id, mem) != 0) {
    fprintf(stderr, "nghttp3_qpack_stream_context_new failed\n");
    goto cleanup;
  }

  /* prefix と request 本体は “この順で同一 request stream に流す” 前提なので、順に decode */
  const struct {
    const uint8_t *p;
    size_t len;
  } chunks[] = {
      {buf_ptr(&pbuf), buf_len(&pbuf)},
      {buf_ptr(&rbuf), buf_len(&rbuf)},
  };

  printf("\n[decoded headers]\n");

  for (size_t ci = 0; ci < sizeof(chunks) / sizeof(chunks[0]); ++ci) {
    const uint8_t *src = chunks[ci].p;
    size_t srclen = chunks[ci].len;

    while (srclen > 0) {
      nghttp3_qpack_nv out = {0};
      uint8_t flags = 0;

      /* fin は「この呼び出しの src が header block の最後を含む」時だけ 1。
         ここでは最後の chunk の最後の呼び出しで 1 にしたいので、ループ末尾で調整する。 */
      int fin = 0;
      if (ci == (sizeof(chunks) / sizeof(chunks[0]) - 1)) {
        /* 最後の chunk の最後の呼び出し = 今回で srclen 全消費できるなら fin=1 */
        fin = 1; /* “まとめて渡す”前提で簡略化（実運用は厳密に last-fragment で 1） */
      }

      nghttp3_ssize nread =
          nghttp3_qpack_decoder_read_request(dec, sctx, &out, &flags, src, srclen, fin);

      if (nread < 0) {
        fprintf(stderr, "nghttp3_qpack_decoder_read_request failed: %zd\n", (ssize_t)nread);
        nghttp3_qpack_stream_context_del(sctx);
        goto cleanup;
      }

      src += (size_t)nread;
      srclen -= (size_t)nread;

      if (flags & NGHTTP3_QPACK_DECODE_FLAG_BLOCKED) {
        fprintf(stderr, "decoder is BLOCKED (need more encoder stream)\n");
        nghttp3_qpack_stream_context_del(sctx);
        goto cleanup;
      }

      if (flags & NGHTTP3_QPACK_DECODE_FLAG_EMIT) {
        print_qpack_nv(&out);

        /* out.name/out.value は refcount 済みなので decref 必須 */
        nghttp3_rcbuf_decref(out.name);
        nghttp3_rcbuf_decref(out.value);
      }

      if (flags & NGHTTP3_QPACK_DECODE_FLAG_FINAL) {
        /* この header block は完了。次の header block を同一 stream で読むなら reset して再利用可 */
        break;
      }

      /* nread==0 で進まないケースは基本的に異常なので保険 */
      if ((size_t)nread == 0) {
        fprintf(stderr, "decoder made no progress\n");
        nghttp3_qpack_stream_context_del(sctx);
        goto cleanup;
      }
    }
  }

  nghttp3_qpack_stream_context_del(sctx);

  /* --- 受信側：decoder stream を書き出し → 送信側 encoder が read_decoder() で取り込む --- */
  size_t dlen = nghttp3_qpack_decoder_get_decoder_streamlen(dec);
  if (dlen > 0) {
    nghttp3_buf dbuf;
    nghttp3_buf_init(&dbuf);

    dbuf.begin = mem->malloc(dlen, mem->user_data);
    if (!dbuf.begin) {
      fprintf(stderr, "malloc failed\n");
      goto cleanup;
    }
    dbuf.pos  = dbuf.begin;
    dbuf.last = dbuf.begin;
    dbuf.end  = dbuf.begin + dlen;

    nghttp3_qpack_decoder_write_decoder(dec, &dbuf); /* dbuf.last が進む */

    /* encoder 側に feed back */
    nghttp3_ssize nread =
      nghttp3_qpack_encoder_read_decoder(enc, dbuf.begin,
                                         (size_t)(dbuf.last - dbuf.begin));
    if (nread < 0) {
      fprintf(stderr, "nghttp3_qpack_encoder_read_decoder failed: %zd\n", (ssize_t)nread);
    }

    mem->free(dbuf.begin, mem->user_data);
  }

cleanup:
  nghttp3_buf_free(&pbuf, mem);
  nghttp3_buf_free(&rbuf, mem);
  nghttp3_buf_free(&ebuf, mem);

  nghttp3_qpack_decoder_del(dec);
  nghttp3_qpack_encoder_del(enc);

  return 0;
}