new file mode 100644
--- /dev/null
+++ b/src/http/v3/ngx_http_v3_parse.c
@@ -0,0 +1,1424 @@
+
+/*
+ * Copyright (C) Roman Arutyunyan
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+ngx_int_t
+ngx_http_v3_parse_varlen_int(ngx_connection_t *c,
+    ngx_http_v3_parse_varlen_int_t *st, u_char ch)
+{
+    enum {
+        sw_start = 0,
+        sw_length_2,
+        sw_length_3,
+        sw_length_4,
+        sw_length_5,
+        sw_length_6,
+        sw_length_7,
+        sw_length_8
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        st->value = ch;
+        if (st->value & 0xc0) {
+            st->state = sw_length_2;
+            break;
+        }
+
+        goto done;
+
+    case sw_length_2:
+
+        st->value = (st->value << 8) + ch;
+        if ((st->value & 0xc000) == 0x4000) {
+            st->value &= 0x3fff;
+            goto done;
+        }
+
+        st->state = sw_length_3;
+        break;
+
+    case sw_length_4:
+
+        st->value = (st->value << 8) + ch;
+        if ((st->value & 0xc0000000) == 0x80000000) {
+            st->value &= 0x3fffffff;
+            goto done;
+        }
+
+        st->state = sw_length_5;
+        break;
+
+    case sw_length_3:
+    case sw_length_5:
+    case sw_length_6:
+    case sw_length_7:
+
+        st->value = (st->value << 8) + ch;
+        st->state++;
+        break;
+
+    case sw_length_8:
+
+        st->value = (st->value << 8) + ch;
+        st->value &= 0x3fffffffffffffff;
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse varlen int %uL", st->value);
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_prefix_int(ngx_connection_t *c,
+    ngx_http_v3_parse_prefix_int_t *st, ngx_uint_t prefix, u_char ch)
+{
+    enum {
+        sw_start = 0,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        st->mask = (1 << prefix) - 1;
+        st->value = (ch & st->mask);
+
+        if (st->value != st->mask) {
+            goto done;
+        }
+
+        st->value = 0;
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        st->value = (st->value << 7) + (ch & 0x7f);
+        if (ch & 0x80) {
+            break;
+        }
+
+        st->value += st->mask;
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse prefix int %uL", st->value);
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_headers(ngx_connection_t *c, ngx_http_v3_parse_headers_t *st,
+    u_char ch)
+{
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_length,
+        sw_prefix,
+        sw_header_rep,
+        sw_done
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse headers");
+
+        if (ch != NGX_HTTP_V3_FRAME_HEADERS) {
+            return NGX_ERROR;
+        }
+
+        st->state = sw_length;
+        break;
+
+    case sw_length:
+
+        if (ngx_http_v3_parse_varlen_int(c, &st->vlint, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->length = st->vlint.value;
+
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse headers len:%ui", st->length);
+
+        st->state = sw_prefix;
+        break;
+
+    case sw_prefix:
+
+        if (st->length-- == 0) {
+            return NGX_ERROR;
+        }
+
+        rc = ngx_http_v3_parse_header_block_prefix(c, &st->prefix, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc != NGX_DONE) {
+            break;
+        }
+
+        if (st->length == 0) {
+            return NGX_ERROR;
+        }
+
+        st->state = sw_header_rep;
+        break;
+
+    case sw_header_rep:
+
+        rc = ngx_http_v3_parse_header_rep(c, &st->header_rep, st->prefix.base,
+                                          ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (--st->length == 0) {
+            if (rc != NGX_DONE) {
+ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "XXX len");
+                return NGX_ERROR;
+            }
+
+            goto done;
+        }
+
+        if (rc == NGX_DONE) {
+            return NGX_OK;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse headers done");
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_block_prefix(ngx_connection_t *c,
+    ngx_http_v3_parse_header_block_prefix_t *st, u_char ch)
+{
+    enum {
+        sw_start = 0,
+        sw_req_insert_count,
+        sw_delta_base,
+        sw_read_delta_base
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse header block prefix");
+
+        st->state = sw_req_insert_count;
+
+        /* fall through */
+
+    case sw_req_insert_count:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 8, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->insert_count = st->pint.value;
+        st->state = sw_delta_base;
+        break;
+
+    case sw_delta_base:
+
+        st->sign = (ch & 0x80) ? 1 : 0;
+        st->state = sw_read_delta_base;
+
+        /* fall through */
+
+    case sw_read_delta_base:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 7, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->delta_base = st->pint.value;
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    if (st->sign) {
+        st->base = st->insert_count - st->delta_base - 1;
+    } else {
+        st->base = st->insert_count + st->delta_base;
+    }
+
+    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                  "http3 parse header block prefix done "
+                  "i:%ui, s:%ui, d:%ui, base:%uL",
+                  st->insert_count, st->sign, st->delta_base, st->base);
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_rep(ngx_connection_t *c,
+    ngx_http_v3_parse_header_rep_t *st, ngx_uint_t base, u_char ch)
+{
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_header_ri,
+        sw_header_lri,
+        sw_header_l,
+        sw_header_pbi,
+        sw_header_lpbi
+    };
+
+    if (st->state == sw_start) {
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse header representation");
+
+        ngx_memzero(&st->header, sizeof(ngx_http_v3_parse_header_t));
+
+        st->header.base = base;
+
+        if (ch & 0x80) {
+            /* Indexed Header Field */
+
+            st->state = sw_header_ri;
+
+        } else if (ch & 0x40) {
+            /* Literal Header Field With Name Reference */
+
+            st->state = sw_header_lri;
+
+        } else if (ch & 0x20) {
+            /* Literal Header Field Without Name Reference */
+
+            st->state = sw_header_l;
+
+        } else if (ch & 0x10) {
+            /* Indexed Header Field With Post-Base Index */
+
+            st->state = sw_header_pbi;
+
+        } else {
+            /* Literal Header Field With Post-Base Name Reference */
+
+            st->state = sw_header_lpbi;
+        }
+    }
+
+    switch (st->state) {
+
+    case sw_header_ri:
+        rc = ngx_http_v3_parse_header_ri(c, &st->header, ch);
+        break;
+
+    case sw_header_lri:
+        rc = ngx_http_v3_parse_header_lri(c, &st->header, ch);
+        break;
+
+    case sw_header_l:
+        rc = ngx_http_v3_parse_header_l(c, &st->header, ch);
+        break;
+
+    case sw_header_pbi:
+        rc = ngx_http_v3_parse_header_pbi(c, &st->header, ch);
+        break;
+
+    case sw_header_lpbi:
+        rc = ngx_http_v3_parse_header_lpbi(c, &st->header, ch);
+        break;
+
+    default:
+        rc = NGX_OK;
+    }
+
+    if (rc == NGX_ERROR) {
+        return NGX_ERROR;
+    }
+
+    if (rc == NGX_AGAIN) {
+        return NGX_AGAIN;
+    }
+
+    /* rc == NGX_DONE */
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header representation done");
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_literal(ngx_connection_t *c, ngx_http_v3_parse_literal_t *st,
+    u_char ch)
+{
+    ngx_uint_t  n;
+    enum {
+        sw_start = 0,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse literal huff:%ui, len:%ui",
+                       st->huffman, st->length);
+
+        n = st->length;
+
+        if (st->huffman) {
+            n = n * 8 / 5;
+            st->huffstate = 0;
+        }
+
+        st->last = ngx_pnalloc(c->pool, n + 1);
+        if (st->last == NULL) {
+            return NGX_ERROR;
+        }
+
+        st->value.data = st->last;
+        st->state = sw_value;
+
+        /* fall through */
+
+    case sw_value:
+
+        if (st->huffman) {
+            if (ngx_http_v2_huff_decode(&st->huffstate, &ch, 1, &st->last,
+                                        st->length == 1, c->log)
+                != NGX_OK)
+            {
+                return NGX_ERROR;
+            }
+
+        } else {
+            *st->last++ = ch;
+        }
+
+        if (--st->length) {
+            break;
+        }
+
+        st->value.len = st->last - st->value.data;
+        *st->last = '\0';
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse literal done \"%V\"", &st->value);
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_ri(ngx_connection_t *c, ngx_http_v3_parse_header_t *st,
+    u_char ch)
+{
+    ngx_http_v3_header_t  *h;
+    enum {
+        sw_start = 0,
+        sw_index
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header ri");
+
+        st->dynamic = (ch & 0x40) ? 0 : 1;
+        st->state = sw_index;
+
+        /* fall through */
+
+    case sw_index:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 6, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->index = st->pint.value;
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header ri done %s%ui]",
+                   st->dynamic ? "dynamic[-" : "static[", st->index);
+
+    if (st->dynamic) {
+        st->index = st->base - st->index - 1;
+    }
+
+    h = ngx_http_v3_lookup_table(c, st->dynamic, st->index);
+    if (h == NULL) {
+        return NGX_ERROR;
+    }
+
+    st->name = h->name;
+    st->value = h->value;
+    st->state = sw_start;
+
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_lri(ngx_connection_t *c,
+    ngx_http_v3_parse_header_t *st, u_char ch)
+{
+    ngx_int_t              rc;
+    ngx_http_v3_header_t  *h;
+    enum {
+        sw_start = 0,
+        sw_index,
+        sw_value_len,
+        sw_read_value_len,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header lri");
+
+        st->dynamic = (ch & 0x10) ? 0 : 1;
+        st->state = sw_index;
+
+        /* fall through */
+
+    case sw_index:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 4, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->index = st->pint.value;
+        st->state = sw_value_len;
+        break;
+
+    case sw_value_len:
+
+        st->literal.huffman = (ch & 0x80) ? 1 : 0;
+        st->state = sw_read_value_len;
+
+        /* fall through */
+
+    case sw_read_value_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 7, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            goto done;
+        }
+
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->value = st->literal.value;
+            goto done;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header lri done %s%ui] \"%V\"",
+                   st->dynamic ? "dynamic[-" : "static[",
+                   st->index, &st->value);
+
+    if (st->dynamic) {
+        st->index = st->base - st->index - 1;
+    }
+
+    h = ngx_http_v3_lookup_table(c, st->dynamic, st->index);
+    if (h == NULL) {
+        return NGX_ERROR;
+    }
+
+    st->name = h->name;
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_l(ngx_connection_t *c,
+    ngx_http_v3_parse_header_t *st, u_char ch)
+{
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_name_len,
+        sw_name,
+        sw_value_len,
+        sw_read_value_len,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header l");
+
+        st->literal.huffman = (ch & 0x08) ? 1 : 0;
+        st->state = sw_name_len;
+
+        /* fall through */
+
+    case sw_name_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 3, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            return NGX_ERROR;
+        }
+
+        st->state = sw_name;
+        break;
+
+    case sw_name:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->name = st->literal.value;
+            st->state = sw_value_len;
+        }
+
+        break;
+
+    case sw_value_len:
+
+        st->literal.huffman = (ch & 0x80) ? 1 : 0;
+        st->state = sw_read_value_len;
+
+        /* fall through */
+
+    case sw_read_value_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 7, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            goto done;
+        }
+
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->value = st->literal.value;
+            goto done;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header l done \"%V\" \"%V\"",
+                   &st->name, &st->value);
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_pbi(ngx_connection_t *c,
+    ngx_http_v3_parse_header_t *st, u_char ch)
+{
+    ngx_http_v3_header_t  *h;
+    enum {
+        sw_start = 0,
+        sw_index
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header pbi");
+
+        st->state = sw_index;
+
+        /* fall through */
+
+    case sw_index:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 4, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->index = st->pint.value;
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header pbi done dynamic[+%ui]", st->index);
+
+    h = ngx_http_v3_lookup_table(c, 1, st->base + st->index);
+    if (h == NULL) {
+        return NGX_ERROR;
+    }
+
+    st->name = h->name;
+    st->value = h->value;
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_lpbi(ngx_connection_t *c,
+    ngx_http_v3_parse_header_t *st, u_char ch)
+{
+    ngx_int_t              rc;
+    ngx_http_v3_header_t  *h;
+    enum {
+        sw_start = 0,
+        sw_index,
+        sw_value_len,
+        sw_read_value_len,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse header lpbi");
+
+        st->state = sw_index;
+
+        /* fall through */
+
+    case sw_index:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 3, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->index = st->pint.value;
+        st->state = sw_value_len;
+        break;
+
+    case sw_value_len:
+
+        st->literal.huffman = (ch & 0x80) ? 1 : 0;
+        st->state = sw_read_value_len;
+
+        /* fall through */
+
+    case sw_read_value_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 7, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            goto done;
+        }
+
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->value = st->literal.value;
+            goto done;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header lpbi done dynamic[+%ui] \"%V\"",
+                   st->index, &st->value);
+
+    h = ngx_http_v3_lookup_table(c, 1, st->base + st->index);
+    if (h == NULL) {
+        return NGX_ERROR;
+    }
+
+    st->name = h->name;
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_control(ngx_connection_t *c, void *data, u_char ch)
+{
+    ngx_http_v3_parse_control_t *st = data;
+
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_type,
+        sw_length,
+        sw_settings,
+        sw_max_push_id,
+        sw_skip
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse control");
+
+        st->state = sw_type;
+
+        /* fall through */
+
+    case sw_type:
+
+        if (ngx_http_v3_parse_varlen_int(c, &st->vlint, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->type = st->vlint.value;
+
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse frame type:%ui", st->type);
+
+        st->state = sw_length;
+        break;
+
+    case sw_length:
+
+        if (ngx_http_v3_parse_varlen_int(c, &st->vlint, ch) != NGX_DONE) {
+            break;
+        }
+
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse frame len:%uL", st->vlint.value);
+
+        st->length = st->vlint.value;
+        if (st->length == 0) {
+            st->state = sw_type;
+            break;
+        }
+
+        switch (st->type) {
+
+        case NGX_HTTP_V3_FRAME_SETTINGS:
+            st->state = sw_settings;
+            break;
+
+        case NGX_HTTP_V3_FRAME_MAX_PUSH_ID:
+            st->state = sw_max_push_id;
+            break;
+
+        default:
+            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                           "http3 parse skip unknown frame");
+            st->state = sw_skip;
+        }
+
+        break;
+
+    case sw_settings:
+
+        rc = ngx_http_v3_parse_settings(c, &st->settings, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (--st->length > 0) {
+            break;
+        }
+
+        if (rc != NGX_DONE) {
+            return NGX_ERROR;
+        }
+
+        st->state = sw_type;
+        break;
+
+    case sw_max_push_id:
+
+        if (ngx_http_v3_parse_varlen_int(c, &st->vlint, ch) != NGX_DONE) {
+            break;
+        }
+
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse MAX_PUSH_ID:%uL", st->vlint.value);
+
+        st->state = sw_type;
+        break;
+
+    case sw_skip:
+
+        if (--st->length == 0) {
+            st->state = sw_type;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_settings(ngx_connection_t *c,
+    ngx_http_v3_parse_settings_t *st, u_char ch)
+{
+    enum {
+        sw_start = 0,
+        sw_id,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse settings");
+
+        st->state = sw_id;
+
+        /* fall through */
+
+    case sw_id:
+
+        if (ngx_http_v3_parse_varlen_int(c, &st->vlint, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->id = st->vlint.value;
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        if (ngx_http_v3_parse_varlen_int(c, &st->vlint, ch) != NGX_DONE) {
+            break;
+        }
+
+        if (ngx_http_v3_set_param(c, st->id, st->vlint.value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse settings done");
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_encoder(ngx_connection_t *c, void *data, u_char ch)
+{
+    ngx_http_v3_parse_encoder_t *st = data;
+
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_inr,
+        sw_iwnr,
+        sw_capacity,
+        sw_duplicate
+    };
+
+    if (st->state == sw_start) {
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse encoder instruction");
+
+        if (ch & 0x80) {
+            /* Insert With Name Reference */
+
+            st->state = sw_inr;
+
+        } else if (ch & 0x40) {
+            /*  Insert Without Name Reference */
+
+            st->state = sw_iwnr;
+
+        } else if (ch & 0x20) {
+            /*  Set Dynamic Table Capacity */
+
+            st->state = sw_capacity;
+
+        } else {
+            /* Duplicate */
+
+            st->state = sw_duplicate;
+        }
+    }
+
+    switch (st->state) {
+
+    case sw_inr:
+
+        rc = ngx_http_v3_parse_header_inr(c, &st->header, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc != NGX_DONE) {
+            break;
+        }
+
+        goto done;
+
+    case sw_iwnr:
+
+        rc = ngx_http_v3_parse_header_iwnr(c, &st->header, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc != NGX_DONE) {
+            break;
+        }
+
+        goto done;
+
+    case sw_capacity:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 5, ch) != NGX_DONE) {
+            break;
+        }
+
+        if (ngx_http_v3_set_capacity(c, st->pint.value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto done;
+
+    case sw_duplicate:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 5, ch) != NGX_DONE) {
+            break;
+        }
+
+        if (ngx_http_v3_duplicate(c, st->pint.value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse encoder instruction done");
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_inr(ngx_connection_t *c,
+    ngx_http_v3_parse_header_t *st, u_char ch)
+{
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_name_index,
+        sw_value_len,
+        sw_read_value_len,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header inr");
+
+        st->dynamic = (ch & 0x40) ? 0 : 1;
+        st->state = sw_name_index;
+
+        /* fall through */
+
+    case sw_name_index:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 6, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->index = st->pint.value;
+        st->state = sw_value_len;
+        break;
+
+    case sw_value_len:
+
+        st->literal.huffman = (ch & 0x80) ? 1 : 0;
+        st->state = sw_read_value_len;
+
+        /* fall through */
+
+    case sw_read_value_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 7, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            goto done;
+        }
+
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->value = st->literal.value;
+            goto done;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header inr done %s[%ui] \"%V\"",
+                   st->dynamic ? "dynamic" : "static",
+                   st->index, &st->value);
+
+    if (ngx_http_v3_ref_insert(c, st->dynamic, st->index, &st->value) != NGX_OK)
+    {
+        return NGX_ERROR;
+    }
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_header_iwnr(ngx_connection_t *c,
+    ngx_http_v3_parse_header_t *st, u_char ch)
+{
+    ngx_int_t  rc;
+    enum {
+        sw_start = 0,
+        sw_name_len,
+        sw_name,
+        sw_value_len,
+        sw_read_value_len,
+        sw_value
+    };
+
+    switch (st->state) {
+
+    case sw_start:
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse header iwnr");
+
+        st->literal.huffman = (ch & 0x20) ? 1 : 0;
+        st->state = sw_name_len;
+
+        /* fall through */
+
+    case sw_name_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 5, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            return NGX_ERROR;
+        }
+
+        st->state = sw_name;
+        break;
+
+    case sw_name:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->name = st->literal.value;
+            st->state = sw_value_len;
+        }
+
+        break;
+
+    case sw_value_len:
+
+        st->literal.huffman = (ch & 0x80) ? 1 : 0;
+        st->state = sw_read_value_len;
+
+        /* fall through */
+
+    case sw_read_value_len:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 7, ch) != NGX_DONE) {
+            break;
+        }
+
+        st->literal.length = st->pint.value;
+        if (st->literal.length == 0) {
+            goto done;
+        }
+
+        st->state = sw_value;
+        break;
+
+    case sw_value:
+
+        rc = ngx_http_v3_parse_literal(c, &st->literal, ch);
+
+        if (rc == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+
+        if (rc == NGX_DONE) {
+            st->value = st->literal.value;
+            goto done;
+        }
+
+        break;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse header iwnr done \"%V\":\"%V\"",
+                   &st->name, &st->value);
+
+    if (ngx_http_v3_insert(c, &st->name, &st->value) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    st->state = sw_start;
+    return NGX_DONE;
+}
+
+
+ngx_int_t
+ngx_http_v3_parse_decoder(ngx_connection_t *c, void *data, u_char ch)
+{
+    ngx_http_v3_parse_decoder_t *st = data;
+
+    enum {
+        sw_start = 0,
+        sw_ack_header,
+        sw_cancel_stream,
+        sw_inc_insert_count
+    };
+
+    if (st->state == sw_start) {
+
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "http3 parse decoder instruction");
+
+        if (ch & 0x80) {
+            /* Header Acknowledgement */
+
+            st->state = sw_ack_header;
+
+        } else if (ch & 0x40) {
+            /*  Stream Cancellation */
+
+            st->state = sw_cancel_stream;
+
+        }  else {
+            /*  Insert Count Increment */
+
+            st->state = sw_inc_insert_count;
+        }
+    }
+
+    switch (st->state) {
+
+    case sw_ack_header:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 6, ch) != NGX_DONE) {
+            break;
+        }
+
+        if (ngx_http_v3_ack_header(c, st->pint.value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto done;
+
+    case sw_cancel_stream:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 6, ch) != NGX_DONE) {
+            break;
+        }
+
+        if (ngx_http_v3_cancel_stream(c, st->pint.value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto done;
+
+    case sw_inc_insert_count:
+
+        if (ngx_http_v3_parse_prefix_int(c, &st->pint, 6, ch) != NGX_DONE) {
+            break;
+        }
+
+        if (ngx_http_v3_inc_insert_count(c, st->pint.value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto done;
+    }
+
+    return NGX_AGAIN;
+
+done:
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 parse decoder instruction done");
+
+    st->state = sw_start;
+    return NGX_DONE;
+}