Add HTTP2 HPACK Encoding Support.
Add Dynamic TLS Record support.

Using: patch -p1 < nginx.patch

diff -uNr a/auto/modules b/auto/modules
--- a/auto/modules	2020-03-03 23:04:21.000000000 +0800
+++ b/auto/modules	2020-03-10 15:47:10.738727477 +0800
@@ -423,6 +423,10 @@
         . auto/module
     fi

+    if [ $HTTP_V2_HPACK_ENC = YES ]; then
+        have=NGX_HTTP_V2_HPACK_ENC . auto/have
+    fi
+
     if :; then
         ngx_module_name=ngx_http_static_module
         ngx_module_incs=
diff -uNr a/auto/options b/auto/options
--- a/auto/options	2020-03-03 23:04:21.000000000 +0800
+++ b/auto/options	2020-03-10 15:47:10.739727485 +0800
@@ -59,6 +59,7 @@
 HTTP_GZIP=YES
 HTTP_SSL=NO
 HTTP_V2=NO
+HTTP_V2_HPACK_ENC=NO
 HTTP_SSI=YES
 HTTP_REALIP=NO
 HTTP_XSLT=NO
@@ -224,6 +225,7 @@

         --with-http_ssl_module)          HTTP_SSL=YES               ;;
         --with-http_v2_module)           HTTP_V2=YES                ;;
+        --with-http_v2_hpack_enc)        HTTP_V2_HPACK_ENC=YES      ;;
         --with-http_realip_module)       HTTP_REALIP=YES            ;;
         --with-http_addition_module)     HTTP_ADDITION=YES          ;;
         --with-http_xslt_module)         HTTP_XSLT=YES              ;;
@@ -439,6 +441,7 @@

   --with-http_ssl_module             enable ngx_http_ssl_module
   --with-http_v2_module              enable ngx_http_v2_module
+  --with-http_v2_hpack_enc           enable ngx_http_v2_hpack_enc
   --with-http_realip_module          enable ngx_http_realip_module
   --with-http_addition_module        enable ngx_http_addition_module
   --with-http_xslt_module            enable ngx_http_xslt_module
diff -uNr a/src/core/ngx_murmurhash.c b/src/core/ngx_murmurhash.c
--- a/src/core/ngx_murmurhash.c	2020-03-03 23:04:21.000000000 +0800
+++ b/src/core/ngx_murmurhash.c	2020-03-10 15:47:10.739727485 +0800
@@ -50,3 +50,63 @@

     return h;
 }
+
+
+uint64_t
+ngx_murmur_hash2_64(u_char *data, size_t len, uint64_t seed)
+{
+    uint64_t  h, k;
+
+    h = seed ^ len;
+
+    while (len >= 8) {
+        k  = data[0];
+        k |= data[1] << 8;
+        k |= data[2] << 16;
+        k |= data[3] << 24;
+        k |= (uint64_t)data[4] << 32;
+        k |= (uint64_t)data[5] << 40;
+        k |= (uint64_t)data[6] << 48;
+        k |= (uint64_t)data[7] << 56;
+
+        k *= 0xc6a4a7935bd1e995ull;
+        k ^= k >> 47;
+        k *= 0xc6a4a7935bd1e995ull;
+
+        h ^= k;
+        h *= 0xc6a4a7935bd1e995ull;
+
+        data += 8;
+        len -= 8;
+    }
+
+    switch (len) {
+    case 7:
+        h ^= (uint64_t)data[6] << 48;
+        /* fall through */
+    case 6:
+        h ^= (uint64_t)data[5] << 40;
+        /* fall through */
+    case 5:
+        h ^= (uint64_t)data[4] << 32;
+        /* fall through */
+    case 4:
+        h ^= data[3] << 24;
+        /* fall through */
+    case 3:
+        h ^= data[2] << 16;
+        /* fall through */
+    case 2:
+        h ^= data[1] << 8;
+        /* fall through */
+    case 1:
+        h ^= data[0];
+        h *= 0xc6a4a7935bd1e995ull;
+    }
+
+    h ^= h >> 47;
+    h *= 0xc6a4a7935bd1e995ull;
+    h ^= h >> 47;
+
+    return h;
+}
diff -uNr a/src/core/ngx_murmurhash.h b/src/core/ngx_murmurhash.h
--- a/src/core/ngx_murmurhash.h	2020-03-03 23:04:21.000000000 +0800
+++ b/src/core/ngx_murmurhash.h	2020-03-10 15:47:10.739727485 +0800
@@ -15,5 +15,7 @@

 uint32_t ngx_murmur_hash2(u_char *data, size_t len);

+uint64_t ngx_murmur_hash2_64(u_char *data, size_t len, uint64_t seed);
+

 #endif /* _NGX_MURMURHASH_H_INCLUDED_ */
diff -uNr a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c	2020-03-03 23:04:21.000000000 +0800
+++ b/src/event/ngx_event_openssl.c	2020-03-10 15:47:11.441732971 +0800
@@ -1507,6 +1507,7 @@

     sc->buffer = ((flags & NGX_SSL_BUFFER) != 0);
     sc->buffer_size = ssl->buffer_size;
+    sc->dyn_rec = ssl->dyn_rec;

     sc->session_ctx = ssl->ctx;

@@ -2404,6 +2405,41 @@

     for ( ;; ) {

+        /* Dynamic record resizing:
+           We want the initial records to fit into one TCP segment
+           so we don't get TCP HoL blocking due to TCP Slow Start.
+           A connection always starts with small records, but after
+           a given amount of records sent, we make the records larger
+           to reduce header overhead.
+           After a connection has idled for a given timeout, begin
+           the process from the start. The actual parameters are
+           configurable. If dyn_rec_timeout is 0, we assume dyn_rec is off. */
+
+        if (c->ssl->dyn_rec.timeout > 0 ) {
+
+            if (ngx_current_msec - c->ssl->dyn_rec_last_write >
+                c->ssl->dyn_rec.timeout)
+            {
+                buf->end = buf->start + c->ssl->dyn_rec.size_lo;
+                c->ssl->dyn_rec_records_sent = 0;
+
+            } else {
+                if (c->ssl->dyn_rec_records_sent >
+                    c->ssl->dyn_rec.threshold * 2)
+                {
+                    buf->end = buf->start + c->ssl->buffer_size;
+
+                } else if (c->ssl->dyn_rec_records_sent >
+                           c->ssl->dyn_rec.threshold)
+                {
+                    buf->end = buf->start + c->ssl->dyn_rec.size_hi;
+
+                } else {
+                    buf->end = buf->start + c->ssl->dyn_rec.size_lo;
+                }
+            }
+        }
+
         while (in && buf->last < buf->end && send < limit) {
             if (in->buf->last_buf || in->buf->flush) {
                 flush = 1;
@@ -2511,6 +2547,9 @@

     if (n > 0) {

+        c->ssl->dyn_rec_records_sent++;
+        c->ssl->dyn_rec_last_write = ngx_current_msec;
+
         if (c->ssl->saved_read_handler) {

             c->read->handler = c->ssl->saved_read_handler;
diff -uNr a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
--- a/src/event/ngx_event_openssl.h	2021-04-20 19:35:47.000000000 +0600
+++ b/src/event/ngx_event_openssl.h	2021-04-21 14:47:37.000000000 +0600
@@ -66,11 +66,19 @@

 typedef struct ngx_ssl_ocsp_s  ngx_ssl_ocsp_t;

+typedef struct {
+    ngx_msec_t                  timeout;
+    ngx_uint_t                  threshold;
+    size_t                      size_lo;
+    size_t                      size_hi;
+} ngx_ssl_dyn_rec_t;
+

 struct ngx_ssl_s {
     SSL_CTX                    *ctx;
     ngx_log_t                  *log;
     size_t                      buffer_size;
+    ngx_ssl_dyn_rec_t           dyn_rec;
 };


@@ -106,6 +114,10 @@
     unsigned                    in_ocsp:1;
     unsigned                    early_preread:1;
     unsigned                    write_blocked:1;
+
+    ngx_ssl_dyn_rec_t           dyn_rec;
+    ngx_msec_t                  dyn_rec_last_write;
+    ngx_uint_t                  dyn_rec_records_sent;
 };


@@ -115,7 +127,7 @@
 #define NGX_SSL_DFLT_BUILTIN_SCACHE  -5


-#define NGX_SSL_MAX_SESSION_SIZE  4096
+#define NGX_SSL_MAX_SESSION_SIZE  16384

 typedef struct ngx_ssl_sess_id_s  ngx_ssl_sess_id_t;

diff -uNr a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c
--- a/src/http/modules/ngx_http_ssl_module.c	2021-04-20 19:35:47.000000000 +0600
+++ b/src/http/modules/ngx_http_ssl_module.c	2021-04-21 14:55:37.000000000 +0600
@@ -301,6 +301,41 @@
       offsetof(ngx_http_ssl_srv_conf_t, reject_handshake),
       NULL },

+    { ngx_string("ssl_dyn_rec_enable"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_enable),
+      NULL },
+
+    { ngx_string("ssl_dyn_rec_timeout"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_msec_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_timeout),
+      NULL },
+
+    { ngx_string("ssl_dyn_rec_size_lo"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_size_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_size_lo),
+      NULL },
+
+    { ngx_string("ssl_dyn_rec_size_hi"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_size_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_size_hi),
+      NULL },
+
+    { ngx_string("ssl_dyn_rec_threshold"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_num_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_threshold),
+      NULL },
+
       ngx_null_command
 };

@@ -637,6 +672,11 @@
     sscf->ocsp_cache_zone = NGX_CONF_UNSET_PTR;
     sscf->stapling = NGX_CONF_UNSET;
     sscf->stapling_verify = NGX_CONF_UNSET;
+    sscf->dyn_rec_enable = NGX_CONF_UNSET;
+    sscf->dyn_rec_timeout = NGX_CONF_UNSET_MSEC;
+    sscf->dyn_rec_size_lo = NGX_CONF_UNSET_SIZE;
+    sscf->dyn_rec_size_hi = NGX_CONF_UNSET_SIZE;
+    sscf->dyn_rec_threshold = NGX_CONF_UNSET_UINT;

     return sscf;
 }
@@ -712,6 +752,20 @@
     ngx_conf_merge_str_value(conf->stapling_responder,
                          prev->stapling_responder, "");

+    ngx_conf_merge_value(conf->dyn_rec_enable, prev->dyn_rec_enable, 0);
+    ngx_conf_merge_msec_value(conf->dyn_rec_timeout, prev->dyn_rec_timeout,
+                             1000);
+    /* Default sizes for the dynamic record sizes are defined to fit maximal
+       TLS + IPv6 overhead in a single TCP segment for lo and 3 segments for hi:
+       1369 = 1500 - 40 (IP) - 20 (TCP) - 10 (Time) - 61 (Max TLS overhead) */
+    ngx_conf_merge_size_value(conf->dyn_rec_size_lo, prev->dyn_rec_size_lo,
+                             1369);
+    /* 4229 = (1500 - 40 - 20 - 10) * 3  - 61 */
+    ngx_conf_merge_size_value(conf->dyn_rec_size_hi, prev->dyn_rec_size_hi,
+                             4229);
+    ngx_conf_merge_uint_value(conf->dyn_rec_threshold, prev->dyn_rec_threshold,
+                             40);
+
     conf->ssl.log = cf->log;

     if (conf->enable) {
@@ -943,6 +997,28 @@
         return NGX_CONF_ERROR;
     }

+    if (conf->dyn_rec_enable) {
+        conf->ssl.dyn_rec.timeout = conf->dyn_rec_timeout;
+        conf->ssl.dyn_rec.threshold = conf->dyn_rec_threshold;
+
+        if (conf->buffer_size > conf->dyn_rec_size_lo) {
+            conf->ssl.dyn_rec.size_lo = conf->dyn_rec_size_lo;
+
+        } else {
+            conf->ssl.dyn_rec.size_lo = conf->buffer_size;
+        }
+
+        if (conf->buffer_size > conf->dyn_rec_size_hi) {
+            conf->ssl.dyn_rec.size_hi = conf->dyn_rec_size_hi;
+
+        } else {
+            conf->ssl.dyn_rec.size_hi = conf->buffer_size;
+        }
+
+    } else {
+        conf->ssl.dyn_rec.timeout = 0;
+    }
+
     return NGX_CONF_OK;
 }

diff -uNr a/src/http/modules/ngx_http_ssl_module.h b/src/http/modules/ngx_http_ssl_module.h
--- a/src/http/modules/ngx_http_ssl_module.h	2020-03-03 23:04:21.000000000 +0800
+++ b/src/http/modules/ngx_http_ssl_module.h	2020-03-10 15:47:11.442732979 +0800
@@ -61,6 +61,12 @@

     u_char                         *file;
     ngx_uint_t                      line;
+
+    ngx_flag_t                      dyn_rec_enable;
+    ngx_msec_t                      dyn_rec_timeout;
+    size_t                          dyn_rec_size_lo;
+    size_t                          dyn_rec_size_hi;
+    ngx_uint_t                      dyn_rec_threshold;
 } ngx_http_ssl_srv_conf_t;


diff -uNr a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c	2020-03-03 23:04:21.000000000 +0800
+++ b/src/http/v2/ngx_http_v2.c	2020-03-10 15:47:10.741727500 +0800
@@ -271,6 +271,8 @@

     h2c->frame_size = NGX_HTTP_V2_DEFAULT_FRAME_SIZE;

+    h2c->max_hpack_table_size = NGX_HTTP_V2_DEFAULT_HPACK_TABLE_SIZE;
+
     h2scf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_v2_module);

     h2c->concurrent_pushes = h2scf->concurrent_pushes;
@@ -2098,6 +2100,14 @@
         case NGX_HTTP_V2_HEADER_TABLE_SIZE_SETTING:

             h2c->table_update = 1;
+
+            if (value > NGX_HTTP_V2_MAX_HPACK_TABLE_SIZE) {
+                h2c->max_hpack_table_size = NGX_HTTP_V2_MAX_HPACK_TABLE_SIZE;
+            } else {
+                h2c->max_hpack_table_size = value;
+            }
+
+            h2c->indicate_resize = 1;
             break;

         default:
diff -uNr a/src/http/v2/ngx_http_v2_encode.c b/src/http/v2/ngx_http_v2_encode.c
--- a/src/http/v2/ngx_http_v2_encode.c	2020-03-03 23:04:21.000000000 +0800
+++ b/src/http/v2/ngx_http_v2_encode.c	2020-03-10 15:47:10.742727508 +0800
@@ -10,7 +10,7 @@
 #include <ngx_http.h>


-static u_char *ngx_http_v2_write_int(u_char *pos, ngx_uint_t prefix,
+u_char *ngx_http_v2_write_int(u_char *pos, ngx_uint_t prefix,
     ngx_uint_t value);


@@ -40,7 +40,7 @@
 }


-static u_char *
+u_char *
 ngx_http_v2_write_int(u_char *pos, ngx_uint_t prefix, ngx_uint_t value)
 {
     if (value < prefix) {
diff -uNr a/src/http/v2/ngx_http_v2_filter_module.c b/src/http/v2/ngx_http_v2_filter_module.c
--- a/src/http/v2/ngx_http_v2_filter_module.c	2020-03-03 23:04:21.000000000 +0800
+++ b/src/http/v2/ngx_http_v2_filter_module.c	2020-03-10 15:47:10.743727516 +0800
@@ -23,10 +23,53 @@
 #define ngx_http_v2_literal_size(h)                                           \
     (ngx_http_v2_integer_octets(sizeof(h) - 1) + sizeof(h) - 1)

+#define ngx_http_v2_indexed(i)      (128 + (i))
+#define ngx_http_v2_inc_indexed(i)  (64 + (i))
+
+#define NGX_HTTP_V2_ENCODE_RAW            0
+#define NGX_HTTP_V2_ENCODE_HUFF           0x80
+
+#define NGX_HTTP_V2_AUTHORITY_INDEX       1
+#define NGX_HTTP_V2_METHOD_GET_INDEX      2
+#define NGX_HTTP_V2_PATH_INDEX            4
+
+#define NGX_HTTP_V2_SCHEME_HTTP_INDEX     6
+#define NGX_HTTP_V2_SCHEME_HTTPS_INDEX    7
+
+#define NGX_HTTP_V2_STATUS_INDEX          8
+#define NGX_HTTP_V2_STATUS_200_INDEX      8
+#define NGX_HTTP_V2_STATUS_204_INDEX      9
+#define NGX_HTTP_V2_STATUS_206_INDEX      10
+#define NGX_HTTP_V2_STATUS_304_INDEX      11
+#define NGX_HTTP_V2_STATUS_400_INDEX      12
+#define NGX_HTTP_V2_STATUS_404_INDEX      13
+#define NGX_HTTP_V2_STATUS_500_INDEX      14
+
+#define NGX_HTTP_V2_ACCEPT_ENCODING_INDEX 16
+#define NGX_HTTP_V2_ACCEPT_LANGUAGE_INDEX 17
+#define NGX_HTTP_V2_CONTENT_LENGTH_INDEX  28
+#define NGX_HTTP_V2_CONTENT_TYPE_INDEX    31
+#define NGX_HTTP_V2_DATE_INDEX            33
+#define NGX_HTTP_V2_LAST_MODIFIED_INDEX   44
+#define NGX_HTTP_V2_LOCATION_INDEX        46
+#define NGX_HTTP_V2_SERVER_INDEX          54
+#define NGX_HTTP_V2_USER_AGENT_INDEX      58
+#define NGX_HTTP_V2_VARY_INDEX            59

 #define NGX_HTTP_V2_NO_TRAILERS           (ngx_http_v2_out_frame_t *) -1


+static const struct {
+    u_char        *name;
+    u_char const   len;
+} push_header[] = {
+    { (u_char*)":authority"      , 10 },
+    { (u_char*)"accept-encoding" , 15 },
+    { (u_char*)"accept-language" , 15 },
+    { (u_char*)"user-agent"      , 10 }
+};
+
+
 typedef struct {
     ngx_str_t      name;
     u_char         index;
@@ -155,11 +198,9 @@
 #endif

     static size_t nginx_ver_len = ngx_http_v2_literal_size(NGINX_VER);
-    static u_char nginx_ver[ngx_http_v2_literal_size(NGINX_VER)];

     static size_t nginx_ver_build_len =
                                   ngx_http_v2_literal_size(NGINX_VER_BUILD);
-    static u_char nginx_ver_build[ngx_http_v2_literal_size(NGINX_VER_BUILD)];

     stream = r->stream;

@@ -435,7 +476,7 @@
     }

     tmp = ngx_palloc(r->pool, tmp_len);
-    pos = ngx_pnalloc(r->pool, len);
+    pos = ngx_pnalloc(r->pool, len + 15 + 1);

     if (pos == NULL || tmp == NULL) {
         return NGX_ERROR;
@@ -443,11 +484,16 @@

     start = pos;

-    if (h2c->table_update) {
-        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 table size update: 0");
-        *pos++ = (1 << 5) | 0;
-        h2c->table_update = 0;
+    h2c = r->stream->connection;
+
+    if (h2c->indicate_resize) {
+        *pos = 32;
+        pos = ngx_http_v2_write_int(pos, ngx_http_v2_prefix(5),
+                                    h2c->max_hpack_table_size);
+        h2c->indicate_resize = 0;
+#if (NGX_HTTP_V2_HPACK_ENC)
+        ngx_http_v2_table_resize(h2c);
+#endif
     }

     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
@@ -458,67 +504,28 @@
         *pos++ = status;

     } else {
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_STATUS_INDEX);
-        *pos++ = NGX_HTTP_V2_ENCODE_RAW | 3;
-        pos = ngx_sprintf(pos, "%03ui", r->headers_out.status);
+        ngx_sprintf(pos + 8, "%O3ui", r->headers_out.status);
+        pos = ngx_http_v2_write_header(h2c, pos, (u_char *)":status",
+                                       sizeof(":status") - 1, pos + 8, 3, tmp);
     }

     if (r->headers_out.server == NULL) {
-
         if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_ON) {
-            ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                           "http2 output header: \"server: %s\"",
-                           NGINX_VER);
-
-        } else if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_BUILD) {
-            ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                           "http2 output header: \"server: %s\"",
-                           NGINX_VER_BUILD);
-
-        } else {
-            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                           "http2 output header: \"server: nginx\"");
-        }
-
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_SERVER_INDEX);
-
-        if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_ON) {
-            if (nginx_ver[0] == '\0') {
-                p = ngx_http_v2_write_value(nginx_ver, (u_char *) NGINX_VER,
-                                            sizeof(NGINX_VER) - 1, tmp);
-                nginx_ver_len = p - nginx_ver;
-            }
-
-            pos = ngx_cpymem(pos, nginx_ver, nginx_ver_len);
+            pos = ngx_http_v2_write_header_str("server", NGINX_VER);

         } else if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_BUILD) {
-            if (nginx_ver_build[0] == '\0') {
-                p = ngx_http_v2_write_value(nginx_ver_build,
-                                            (u_char *) NGINX_VER_BUILD,
-                                            sizeof(NGINX_VER_BUILD) - 1, tmp);
-                nginx_ver_build_len = p - nginx_ver_build;
-            }
-
-            pos = ngx_cpymem(pos, nginx_ver_build, nginx_ver_build_len);
+            pos = ngx_http_v2_write_header_str("server", NGINX_VER_BUILD);

         } else {
-            pos = ngx_cpymem(pos, nginx, sizeof(nginx));
+            pos = ngx_http_v2_write_header_str("server", "nginx");
         }
     }

     if (r->headers_out.date == NULL) {
-        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 output header: \"date: %V\"",
-                       &ngx_cached_http_time);
-
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_DATE_INDEX);
-        pos = ngx_http_v2_write_value(pos, ngx_cached_http_time.data,
-                                      ngx_cached_http_time.len, tmp);
+        pos = ngx_http_v2_write_header_tbl("date", ngx_cached_http_time);
     }

     if (r->headers_out.content_type.len) {
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_CONTENT_TYPE_INDEX);
-
         if (r->headers_out.content_type_len == r->headers_out.content_type.len
             && r->headers_out.charset.len)
         {
@@ -544,64 +551,36 @@
             r->headers_out.content_type.data = p - len;
         }

-        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 output header: \"content-type: %V\"",
-                       &r->headers_out.content_type);
-
-        pos = ngx_http_v2_write_value(pos, r->headers_out.content_type.data,
-                                      r->headers_out.content_type.len, tmp);
+        pos = ngx_http_v2_write_header_tbl("content-type",
+                                           r->headers_out.content_type);
     }

     if (r->headers_out.content_length == NULL
         && r->headers_out.content_length_n >= 0)
     {
-        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 output header: \"content-length: %O\"",
-                       r->headers_out.content_length_n);
-
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_CONTENT_LENGTH_INDEX);
-
-        p = pos;
-        pos = ngx_sprintf(pos + 1, "%O", r->headers_out.content_length_n);
-        *p = NGX_HTTP_V2_ENCODE_RAW | (u_char) (pos - p - 1);
+        p = ngx_sprintf(pos + 15, "%O", r->headers_out.content_length_n);
+        pos = ngx_http_v2_write_header(h2c, pos, (u_char *)"content-length",
+                                       sizeof("content-length") - 1, pos + 15,
+                                       p - (pos + 15), tmp);
     }

     if (r->headers_out.last_modified == NULL
         && r->headers_out.last_modified_time != -1)
     {
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_LAST_MODIFIED_INDEX);
-
-        ngx_http_time(pos, r->headers_out.last_modified_time);
+        ngx_http_time(pos + 14, r->headers_out.last_modified_time);
         len = sizeof("Wed, 31 Dec 1986 18:00:00 GMT") - 1;
-
-        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 output header: \"last-modified: %*s\"",
-                       len, pos);
-
-        /*
-         * Date will always be encoded using huffman in the temporary buffer,
-         * so it's safe here to use src and dst pointing to the same address.
-         */
-        pos = ngx_http_v2_write_value(pos, pos, len, tmp);
+        pos = ngx_http_v2_write_header(h2c, pos, (u_char *)"last-modified",
+                                       sizeof("last-modified") - 1, pos + 14,
+                                       len, tmp);
     }

     if (r->headers_out.location && r->headers_out.location->value.len) {
-        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 output header: \"location: %V\"",
-                       &r->headers_out.location->value);
-
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_LOCATION_INDEX);
-        pos = ngx_http_v2_write_value(pos, r->headers_out.location->value.data,
-                                      r->headers_out.location->value.len, tmp);
+        pos = ngx_http_v2_write_header_tbl("location", r->headers_out.location->value);
     }

 #if (NGX_HTTP_GZIP)
     if (r->gzip_vary) {
-        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 output header: \"vary: Accept-Encoding\"");
-
-        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_VARY_INDEX);
-        pos = ngx_cpymem(pos, accept_encoding, sizeof(accept_encoding));
+        pos = ngx_http_v2_write_header_str("vary", "Accept-Encoding");
     }
 #endif

@@ -624,23 +603,10 @@
             continue;
         }

-#if (NGX_DEBUG)
-        if (fc->log->log_level & NGX_LOG_DEBUG_HTTP) {
-            ngx_strlow(tmp, header[i].key.data, header[i].key.len);
-
-            ngx_log_debug3(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                           "http2 output header: \"%*s: %V\"",
-                           header[i].key.len, tmp, &header[i].value);
-        }
-#endif
-
-        *pos++ = 0;
-
-        pos = ngx_http_v2_write_name(pos, header[i].key.data,
-                                     header[i].key.len, tmp);
+        pos = ngx_http_v2_write_header(h2c, pos, header[i].key.data,
+                                       header[i].key.len, header[i].value.data,
+                                       header[i].value.len, tmp);

-        pos = ngx_http_v2_write_value(pos, header[i].value.data,
-                                      header[i].value.len, tmp);
     }

     fin = r->header_only
@@ -998,6 +964,7 @@

     for (i = 0; i < NGX_HTTP_V2_PUSH_HEADERS; i++) {
         len += binary[i].len;
+        len += push_header[i].len + 1;
     }

     pos = ngx_pnalloc(r->pool, len);
@@ -1007,12 +974,17 @@

     start = pos;

-    if (h2c->table_update) {
-        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
-                       "http2 table size update: 0");
-        *pos++ = (1 << 5) | 0;
-        h2c->table_update = 0;
-    }
+    h2c = r->stream->connection;
+
+    if (h2c->indicate_resize) {
+        *pos = 32;
+        pos = ngx_http_v2_write_int(pos, ngx_http_v2_prefix(5),
+                                    h2c->max_hpack_table_size);
+        h2c->indicate_resize = 0;
+#if (NGX_HTTP_V2_HPACK_ENC)
+        ngx_http_v2_table_resize(h2c);
+#endif
+     }

     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
                    "http2 push header: \":method: GET\"");
@@ -1022,8 +994,7 @@
     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
                    "http2 push header: \":path: %V\"", path);

-    *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_PATH_INDEX);
-    pos = ngx_http_v2_write_value(pos, path->data, path->len, tmp);
+    pos = ngx_http_v2_write_header_pot(":path", path);

     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
                    "http2 push header: \":scheme: %V\"", &r->schema);
@@ -1048,11 +1019,15 @@
             continue;
         }

+        value = &(*h)->value;
+
         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, fc->log, 0,
                        "http2 push header: \"%V: %V\"",
                        &ph[i].name, &(*h)->value);

-        pos = ngx_cpymem(pos, binary[i].data, binary[i].len);
+        pos = ngx_http_v2_write_header(h2c, pos,
+                  push_header[i].name, push_header[i].len, value->data, value->len,
+                  tmp);
     }

     frame = ngx_http_v2_create_push_frame(r, start, pos);
diff -uNr a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
--- a/src/http/v2/ngx_http_v2.h	2020-03-03 23:04:21.000000000 +0800
+++ b/src/http/v2/ngx_http_v2.h	2020-03-10 15:47:10.741727500 +0800
@@ -52,6 +52,14 @@
 #define NGX_HTTP_V2_MAX_WINDOW           ((1U << 31) - 1)
 #define NGX_HTTP_V2_DEFAULT_WINDOW       65535

+#define HPACK_ENC_HTABLE_SZ              128 /* better to keep a PoT < 64k */
+#define HPACK_ENC_HTABLE_ENTRIES         ((HPACK_ENC_HTABLE_SZ * 100) / 128)
+#define HPACK_ENC_DYNAMIC_KEY_TBL_SZ     10  /* 10 is sufficient for most */
+#define HPACK_ENC_MAX_ENTRY              512 /* longest header size to match */
+
+#define NGX_HTTP_V2_DEFAULT_HPACK_TABLE_SIZE     4096
+#define NGX_HTTP_V2_MAX_HPACK_TABLE_SIZE         16384 /* < 64k */
+
 #define NGX_HTTP_V2_DEFAULT_WEIGHT       16


@@ -115,6 +123,46 @@
 } ngx_http_v2_hpack_t;


+#if (NGX_HTTP_V2_HPACK_ENC)
+typedef struct {
+    uint64_t                         hash_val;
+    uint32_t                         index;
+    uint16_t                         pos;
+    uint16_t                         klen, vlen;
+    uint16_t                         size;
+    uint16_t                         next;
+} ngx_http_v2_hpack_enc_entry_t;
+
+
+typedef struct {
+    uint64_t                         hash_val;
+    uint32_t                         index;
+    uint16_t                         pos;
+    uint16_t                         klen;
+} ngx_http_v2_hpack_name_entry_t;
+
+
+typedef struct {
+    size_t                           size;    /* size as defined in RFC 7541 */
+    uint32_t                         top;     /* the last entry */
+    uint32_t                         pos;
+    uint16_t                         n_elems; /* number of elements */
+    uint16_t                         base;    /* index of the oldest entry */
+    uint16_t                         last;    /* index of the newest entry */
+
+    /* hash table for dynamic entries, instead using a generic hash table,
+       which would be too slow to process a significant amount of headers,
+       this table is not determenistic, and might ocasionally fail to insert
+       a value, at the cost of slightly worse compression, but significantly
+       faster performance */
+    ngx_http_v2_hpack_enc_entry_t    htable[HPACK_ENC_HTABLE_SZ];
+    ngx_http_v2_hpack_name_entry_t   heads[HPACK_ENC_DYNAMIC_KEY_TBL_SZ];
+    u_char                           storage[NGX_HTTP_V2_MAX_HPACK_TABLE_SIZE +
+                                             HPACK_ENC_MAX_ENTRY];
+} ngx_http_v2_hpack_enc_t;
+#endif
+
+
 struct ngx_http_v2_connection_s {
     ngx_connection_t                *connection;
     ngx_http_connection_t           *http_connection;
@@ -136,6 +184,8 @@

     size_t                           frame_size;

+    size_t                           max_hpack_table_size;
+
     ngx_queue_t                      waiting;

     ngx_http_v2_state_t              state;
@@ -163,6 +213,11 @@
     unsigned                         blocked:1;
     unsigned                         goaway:1;
     unsigned                         push_disabled:1;
+    unsigned                         indicate_resize:1;
+
+#if (NGX_HTTP_V2_HPACK_ENC)
+    ngx_http_v2_hpack_enc_t          hpack_enc;
+#endif
 };


@@ -206,6 +261,8 @@

     ngx_array_t                     *cookies;

+    size_t                           header_limit;
+
     ngx_pool_t                      *pool;

     unsigned                         waiting:1;
@@ -418,4 +475,35 @@
     u_char *tmp, ngx_uint_t lower);


+u_char *ngx_http_v2_string_encode(u_char *dst, u_char *src, size_t len,
+    u_char *tmp, ngx_uint_t lower);
+
+u_char *
+ngx_http_v2_write_int(u_char *pos, ngx_uint_t prefix, ngx_uint_t value);
+
+#define ngx_http_v2_write_name(dst, src, len, tmp)                            \
+    ngx_http_v2_string_encode(dst, src, len, tmp, 1)
+#define ngx_http_v2_write_value(dst, src, len, tmp)                           \
+    ngx_http_v2_string_encode(dst, src, len, tmp, 0)
+
+u_char *
+ngx_http_v2_write_header(ngx_http_v2_connection_t *h2c, u_char *pos,
+    u_char *key, size_t key_len, u_char *value, size_t value_len,
+    u_char *tmp);
+
+void
+ngx_http_v2_table_resize(ngx_http_v2_connection_t *h2c);
+
+#define ngx_http_v2_write_header_str(key, value)                        \
+    ngx_http_v2_write_header(h2c, pos, (u_char *) key, sizeof(key) - 1, \
+    (u_char *) value, sizeof(value) - 1, tmp);
+
+#define ngx_http_v2_write_header_tbl(key, val)                          \
+    ngx_http_v2_write_header(h2c, pos, (u_char *) key, sizeof(key) - 1, \
+    val.data, val.len, tmp);
+
+#define ngx_http_v2_write_header_pot(key, val)                          \
+    ngx_http_v2_write_header(h2c, pos, (u_char *) key, sizeof(key) - 1, \
+    val->data, val->len, tmp);
+
 #endif /* _NGX_HTTP_V2_H_INCLUDED_ */
diff -uNr a/src/http/v2/ngx_http_v2_table.c b/src/http/v2/ngx_http_v2_table.c
--- a/src/http/v2/ngx_http_v2_table.c	2020-03-03 23:04:21.000000000 +0800
+++ b/src/http/v2/ngx_http_v2_table.c	2020-03-10 15:47:10.743727516 +0800
@@ -361,3 +361,434 @@

     return NGX_OK;
 }
+
+
+#if (NGX_HTTP_V2_HPACK_ENC)
+
+static ngx_int_t
+hpack_get_static_index(ngx_http_v2_connection_t *h2c, u_char *val, size_t len);
+
+static ngx_int_t
+hpack_get_dynamic_index(ngx_http_v2_connection_t *h2c, uint64_t key_hash,
+                        uint8_t *key, size_t key_len);
+
+
+void
+ngx_http_v2_table_resize(ngx_http_v2_connection_t *h2c)
+{
+    ngx_http_v2_hpack_enc_entry_t  *table;
+    uint64_t                        idx;
+
+    table = h2c->hpack_enc.htable;
+
+    while (h2c->hpack_enc.size > h2c->max_hpack_table_size) {
+        idx = h2c->hpack_enc.base;
+        h2c->hpack_enc.base = table[idx].next;
+        h2c->hpack_enc.size -= table[idx].size;
+        table[idx].hash_val = 0;
+        h2c->hpack_enc.n_elems--;
+    }
+}
+
+
+/* checks if a header is in the hpack table - if so returns the table entry,
+   otherwise encodes and inserts into the table and returns 0,
+   if failed to insert into table, returns -1 */
+static ngx_int_t
+ngx_http_v2_table_encode_strings(ngx_http_v2_connection_t *h2c,
+    size_t key_len, size_t val_len, uint8_t *key, uint8_t *val,
+    ngx_int_t *header_idx)
+{
+    uint64_t  hash_val, key_hash, idx, lru;
+    int       i;
+    size_t    size = key_len + val_len + 32;
+    uint8_t  *storage = h2c->hpack_enc.storage;
+
+    ngx_http_v2_hpack_enc_entry_t   *table;
+    ngx_http_v2_hpack_name_entry_t  *name;
+
+    *header_idx = NGX_ERROR;
+    /* step 1: compute the hash value of header */
+    if (size > HPACK_ENC_MAX_ENTRY || size > h2c->max_hpack_table_size) {
+        return NGX_ERROR;
+    }
+
+    key_hash = ngx_murmur_hash2_64(key, key_len, 0x01234);
+    hash_val = ngx_murmur_hash2_64(val, val_len, key_hash);
+
+    if (hash_val == 0) {
+        return NGX_ERROR;
+    }
+
+    /* step 2: check if full header in the table */
+    idx = hash_val;
+    i = -1;
+    while (idx) {
+         /* at most 8 locations are checked, but most will be done in 1 or 2 */
+        table = &h2c->hpack_enc.htable[idx % HPACK_ENC_HTABLE_SZ];
+        if (table->hash_val == hash_val
+            && table->klen == key_len
+            && table->vlen == val_len
+            && ngx_memcmp(key, storage + table->pos, key_len) == 0
+            && ngx_memcmp(val, storage + table->pos + key_len, val_len) == 0)
+        {
+            return (h2c->hpack_enc.top - table->index) + 61;
+        }
+
+        if (table->hash_val == 0 && i == -1) {
+            i = idx % HPACK_ENC_HTABLE_SZ;
+            break;
+        }
+
+        idx >>= 8;
+    }
+
+    /* step 3: check if key is in one of the tables */
+    *header_idx = hpack_get_static_index(h2c, key, key_len);
+
+    if (i == -1) {
+        return NGX_ERROR;
+    }
+
+    if (*header_idx == NGX_ERROR) {
+        *header_idx = hpack_get_dynamic_index(h2c, key_hash, key, key_len);
+    }
+
+    /* step 4: store the new entry */
+    table =  h2c->hpack_enc.htable;
+
+    if (h2c->hpack_enc.top == 0xffffffff) {
+        /* just to be on the safe side, avoid overflow */
+        ngx_memset(&h2c->hpack_enc, 0, sizeof(ngx_http_v2_hpack_enc_t));
+    }
+
+    while ((h2c->hpack_enc.size + size > h2c->max_hpack_table_size)
+           || h2c->hpack_enc.n_elems == HPACK_ENC_HTABLE_ENTRIES) {
+        /* make space for the new entry first */
+        idx = h2c->hpack_enc.base;
+        h2c->hpack_enc.base = table[idx].next;
+        h2c->hpack_enc.size -= table[idx].size;
+        table[idx].hash_val = 0;
+        h2c->hpack_enc.n_elems--;
+    }
+
+    table[i] = (ngx_http_v2_hpack_enc_entry_t){.hash_val = hash_val,
+                                               .index = h2c->hpack_enc.top,
+                                               .pos = h2c->hpack_enc.pos,
+                                               .klen = key_len,
+                                               .vlen = val_len,
+                                               .size = size,
+                                               .next = 0};
+
+    table[h2c->hpack_enc.last].next = i;
+    if (h2c->hpack_enc.n_elems == 0) {
+        h2c->hpack_enc.base = i;
+    }
+
+    h2c->hpack_enc.last = i;
+    h2c->hpack_enc.top++;
+    h2c->hpack_enc.size += size;
+    h2c->hpack_enc.n_elems++;
+
+    /* update header name lookup */
+    if (*header_idx == NGX_ERROR ) {
+        lru = h2c->hpack_enc.top;
+
+        for (i=0; i<HPACK_ENC_DYNAMIC_KEY_TBL_SZ; i++) {
+
+            name = &h2c->hpack_enc.heads[i];
+
+            if ( name->hash_val == 0 || (name->hash_val == key_hash
+                && ngx_memcmp(storage + name->pos, key, key_len) == 0) )
+            {
+                name->hash_val = key_hash;
+                name->pos = h2c->hpack_enc.pos;
+                name->index = h2c->hpack_enc.top - 1;
+                break;
+            }
+
+            if (lru > name->index) {
+                lru = name->index;
+                idx = i;
+            }
+        }
+
+        if (i == HPACK_ENC_DYNAMIC_KEY_TBL_SZ) {
+            name = &h2c->hpack_enc.heads[idx];
+            name->hash_val = hash_val;
+            name->pos = h2c->hpack_enc.pos;
+            name->index = h2c->hpack_enc.top - 1;
+        }
+    }
+
+    ngx_memcpy(storage + h2c->hpack_enc.pos, key, key_len);
+    ngx_memcpy(storage + h2c->hpack_enc.pos + key_len, val, val_len);
+
+    h2c->hpack_enc.pos += size;
+    if (h2c->hpack_enc.pos > NGX_HTTP_V2_MAX_HPACK_TABLE_SIZE) {
+        h2c->hpack_enc.pos = 0;
+    }
+
+    return NGX_OK;
+}
+
+
+u_char *
+ngx_http_v2_write_header(ngx_http_v2_connection_t *h2c, u_char *pos,
+                         u_char *key, size_t key_len,
+                         u_char *value, size_t value_len,
+                         u_char *tmp)
+{
+    ngx_int_t idx, header_idx;
+
+    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                   "http2 output header: %*s: %*s", key_len, key, value_len,
+                   value);
+
+    /* attempt to find the value in the dynamic table */
+    idx = ngx_http_v2_table_encode_strings(h2c, key_len, value_len, key, value,
+                                           &header_idx);
+
+    if (idx > 0) {
+        /* positive index indicates success */
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                       "http2 hpack encode: Indexed Header Field: %ud", idx);
+
+        *pos = 128;
+        pos = ngx_http_v2_write_int(pos, ngx_http_v2_prefix(7), idx);
+
+    } else {
+
+        if (header_idx == NGX_ERROR) { /* if key is not present */
+
+            if (idx == NGX_ERROR) {    /* if header was not added */
+                *pos++ = 0;
+
+                ngx_log_debug0(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                              "http2 hpack encode: Literal Header Field without"
+                              " Indexing — New Name");
+            } else {                   /* if header was added */
+                *pos++ = 64;
+
+                ngx_log_debug0(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                              "http2 hpack encode: Literal Header Field with "
+                              "Incremental Indexing — New Name");
+            }
+
+            pos = ngx_http_v2_write_name(pos, key, key_len, tmp);
+
+        } else {                       /* if key is present */
+
+            if (idx == NGX_ERROR) {
+                *pos = 0;
+                pos = ngx_http_v2_write_int(pos, ngx_http_v2_prefix(4), header_idx);
+
+                ngx_log_debug1(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                              "http2 hpack encode: Literal Header Field without"
+                              " Indexing — Indexed Name: %ud", header_idx);
+            } else {
+                *pos = 64;
+                pos = ngx_http_v2_write_int(pos, ngx_http_v2_prefix(6), header_idx);
+
+                ngx_log_debug1(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                              "http2 hpack encode: Literal Header Field with "
+                              "Incremental Indexing — Indexed Name: %ud", header_idx);
+            }
+        }
+
+        pos = ngx_http_v2_write_value(pos, value, value_len, tmp);
+    }
+
+    return pos;
+}
+
+
+static ngx_int_t
+hpack_get_dynamic_index(ngx_http_v2_connection_t *h2c, uint64_t key_hash,
+                        uint8_t *key, size_t key_len)
+{
+    ngx_http_v2_hpack_name_entry_t  *name;
+    int                              i;
+
+    for (i=0; i<HPACK_ENC_DYNAMIC_KEY_TBL_SZ; i++) {
+        name = &h2c->hpack_enc.heads[i];
+
+        if (name->hash_val == key_hash
+            && ngx_memcmp(h2c->hpack_enc.storage + name->pos, key, key_len) == 0)
+        {
+            if (name->index >= h2c->hpack_enc.top - h2c->hpack_enc.n_elems) {
+                return (h2c->hpack_enc.top - name->index) + 61;
+            }
+            break;
+        }
+    }
+
+    return NGX_ERROR;
+}
+
+
+/* decide if a given header is present in the static dictionary, this could be
+   done in several ways, but it seems the fastest one is "exhaustive" search */
+static ngx_int_t
+hpack_get_static_index(ngx_http_v2_connection_t *h2c, u_char *val, size_t len)
+{
+    /* the static dictionary of response only headers,
+       although response headers can be put by origin,
+       that would be rare */
+    static const struct {
+        u_char         len;
+        const u_char   val[28];
+        u_char         idx;
+    } server_headers[] = {
+        { 3, "age",                         21},//0
+        { 3, "via",                         60},
+        { 4, "date",                        33},//2
+        { 4, "etag",                        34},
+        { 4, "link",                        45},
+        { 4, "vary",                        59},
+        { 5, "allow",                       22},//6
+        { 6, "server",                      54},//7
+        { 7, "expires",                     36},//8
+        { 7, "refresh",                     52},
+        { 8, "location",                    46},//10
+        {10, "set-cookie",                  55},//11
+        {11, "retry-after",                 53},//12
+        {12, "content-type",                31},//13
+        {13, "content-range",               30},//14
+        {13, "accept-ranges",               18},
+        {13, "cache-control",               24},
+        {13, "last-modified",               44},
+        {14, "content-length",              28},//18
+        {16, "content-encoding",            26},//19
+        {16, "content-language",            27},
+        {16, "content-location",            29},
+        {16, "www-authenticate",            61},
+        {17, "transfer-encoding",           57},//23
+        {18, "proxy-authenticate",          48},//24
+        {19, "content-disposition",         25},//25
+        {25, "strict-transport-security",   56},//26
+        {27, "access-control-allow-origin", 20},//27
+        {99, "",                            99},
+    }, *header;
+
+    /* for a given length, where to start the search
+       since minimal length is 3, the table has a -3
+       offset */
+    static const int8_t start_at[] = {
+        [3-3]  = 0,
+        [4-3]  = 2,
+        [5-3]  = 6,
+        [6-3]  = 7,
+        [7-3]  = 8,
+        [8-3]  = 10,
+        [9-3]  = -1,
+        [10-3] = 11,
+        [11-3] = 12,
+        [12-3] = 13,
+        [13-3] = 14,
+        [14-3] = 18,
+        [15-3] = -1,
+        [16-3] = 19,
+        [17-3] = 23,
+        [18-3] = 24,
+        [19-3] = 25,
+        [20-3] = -1,
+        [21-3] = -1,
+        [22-3] = -1,
+        [23-3] = -1,
+        [24-3] = -1,
+        [25-3] = 26,
+        [26-3] = -1,
+        [27-3] = 27,
+    };
+
+    uint64_t pref;
+    size_t   save_len = len, i;
+    int8_t   start;
+
+    /* early exit for out of bounds lengths */
+    if (len < 3 || len > 27) {
+        return NGX_ERROR;
+    }
+
+    start = start_at[len - 3];
+    if (start == -1) {
+        /* exit for non existent lengths */
+        return NGX_ERROR;
+    }
+
+    header = &server_headers[start_at[len - 3]];
+
+    /* load first 8 bytes of key, for fast comparison */
+    if (len < 8) {
+        pref = 0;
+        if (len >= 4) {
+            pref = *(uint32_t *)(val + len - 4) | 0x20202020;
+            len -= 4;
+        }
+        while (len > 0) { /* 3 iterations at most */
+            pref = (pref << 8) ^ (val[len - 1] | 0x20);
+            len--;
+        }
+    } else {
+        pref = *(uint64_t *)val | 0x2020202020202020;
+        len -= 8;
+    }
+
+    /* iterate over headers with the right length */
+    while (header->len == save_len) {
+        /* quickly compare the first 8 bytes, most tests will end here */
+        if (pref != *(uint64_t *) header->val) {
+            header++;
+            continue;
+        }
+
+        if (len == 0) {
+            /* len == 0, indicates prefix held the entire key */
+            return header->idx;
+        }
+        /* for longer keys compare the rest */
+        i = 1 + (save_len + 7) % 8; /* align so we can compare in quadwords */
+
+        while (i + 8 <= save_len) { /* 3 iterations at most */
+            if ( *(uint64_t *)&header->val[i]
+                 != (*(uint64_t *) &val[i]| 0x2020202020202020) )
+            {
+                header++;
+                i = 0;
+                break;
+            }
+            i += 8;
+        }
+
+        if (i == 0) {
+            continue;
+        }
+
+        /* found the corresponding entry in the static dictionary */
+        return header->idx;
+    }
+
+    return NGX_ERROR;
+}
+
+#else
+
+u_char *
+ngx_http_v2_write_header(ngx_http_v2_connection_t *h2c, u_char *pos,
+                         u_char *key, size_t key_len,
+                         u_char *value, size_t value_len,
+                         u_char *tmp)
+{
+    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                   "http2 output header: %*s: %*s", key_len, key, value_len,
+                   value);
+
+    *pos++ = 64;
+    pos = ngx_http_v2_write_name(pos, key, key_len, tmp);
+    pos = ngx_http_v2_write_value(pos, value, value_len, tmp);
+
+    return pos;
+}
+
+#endif
