/*
 * Copyright (C) Roman Arutyunyan
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


/* static table indices */
#define NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO       4
#define NGX_HTTP_V3_HEADER_DATE                      6
#define NGX_HTTP_V3_HEADER_LAST_MODIFIED             10
#define NGX_HTTP_V3_HEADER_LOCATION                  12
#define NGX_HTTP_V3_HEADER_STATUS_200                25
#define NGX_HTTP_V3_HEADER_CONTENT_TYPE_TEXT_PLAIN   53
#define NGX_HTTP_V3_HEADER_VARY_ACCEPT_ENCODING      59
#define NGX_HTTP_V3_HEADER_SERVER                    92


static ngx_int_t ngx_http_v3_process_pseudo_header(ngx_http_request_t *r,
    ngx_str_t *name, ngx_str_t *value);


struct {
    ngx_str_t   name;
    ngx_uint_t  method;
} ngx_http_v3_methods[] = {

    { ngx_string("GET"),       NGX_HTTP_GET },
    { ngx_string("POST"),      NGX_HTTP_POST },
    { ngx_string("HEAD"),      NGX_HTTP_HEAD },
    { ngx_string("OPTIONS"),   NGX_HTTP_OPTIONS },
    { ngx_string("PROPFIND"),  NGX_HTTP_PROPFIND },
    { ngx_string("PUT"),       NGX_HTTP_PUT },
    { ngx_string("MKCOL"),     NGX_HTTP_MKCOL },
    { ngx_string("DELETE"),    NGX_HTTP_DELETE },
    { ngx_string("COPY"),      NGX_HTTP_COPY },
    { ngx_string("MOVE"),      NGX_HTTP_MOVE },
    { ngx_string("PROPPATCH"), NGX_HTTP_PROPPATCH },
    { ngx_string("LOCK"),      NGX_HTTP_LOCK },
    { ngx_string("UNLOCK"),    NGX_HTTP_UNLOCK },
    { ngx_string("PATCH"),     NGX_HTTP_PATCH },
    { ngx_string("TRACE"),     NGX_HTTP_TRACE }
};


ngx_int_t
ngx_http_v3_parse_request(ngx_http_request_t *r, ngx_buf_t *b)
{
    size_t                        len;
    u_char                       *p;
    ngx_int_t                     rc, n;
    ngx_str_t                    *name, *value;
    ngx_connection_t             *c;
    ngx_http_v3_parse_headers_t  *st;

    c = r->connection;
    st = r->h3_parse;

    if (st == NULL) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header");

        st = ngx_pcalloc(c->pool, sizeof(ngx_http_v3_parse_headers_t));
        if (st == NULL) {
            goto failed;
        }

        r->h3_parse = st;
        r->parse_start = b->pos;
        r->state = 1;
    }

    while (b->pos < b->last) {
        rc = ngx_http_v3_parse_headers(c, st, *b->pos);

        if (rc > 0) {
            ngx_http_v3_finalize_connection(c, rc,
                                            "could not parse request headers");
            goto failed;
        }

        if (rc == NGX_ERROR) {
            goto failed;
        }

        if (rc == NGX_BUSY) {
            return NGX_BUSY;
        }

        b->pos++;

        if (rc == NGX_AGAIN) {
            continue;
        }

        name = &st->header_rep.header.name;
        value = &st->header_rep.header.value;

        n = ngx_http_v3_process_pseudo_header(r, name, value);

        if (n == NGX_ERROR) {
            goto failed;
        }

        if (n == NGX_OK && rc == NGX_OK) {
            continue;
        }

        len = (r->method_end - r->method_start) + 1
            + (r->uri_end - r->uri_start) + 1
            + sizeof("HTTP/3") - 1;

        p = ngx_pnalloc(c->pool, len);
        if (p == NULL) {
            goto failed;
        }

        r->request_start = p;

        p = ngx_cpymem(p, r->method_start, r->method_end - r->method_start);
        *p++ = ' ';
        p = ngx_cpymem(p, r->uri_start, r->uri_end - r->uri_start);
        *p++ = ' ';
        p = ngx_cpymem(p, "HTTP/3", sizeof("HTTP/3") - 1);

        r->request_end = p;
        r->state = 0;

        return NGX_OK;
    }

    return NGX_AGAIN;

failed:

    return NGX_HTTP_PARSE_INVALID_REQUEST;
}


ngx_int_t
ngx_http_v3_parse_header(ngx_http_request_t *r, ngx_buf_t *b,
    ngx_uint_t allow_underscores)
{
    u_char                        ch;
    ngx_int_t                     rc;
    ngx_str_t                    *name, *value;
    ngx_uint_t                    hash, i, n;
    ngx_connection_t             *c;
    ngx_http_v3_parse_headers_t  *st;
    enum {
        sw_start = 0,
        sw_done,
        sw_next,
        sw_header
    };

    c = r->connection;
    st = r->h3_parse;

    switch (r->state) {

    case sw_start:
        r->parse_start = b->pos;

        if (st->state) {
            r->state = sw_next;
            goto done;
        }

        name = &st->header_rep.header.name;

        if (name->len && name->data[0] != ':') {
            r->state = sw_done;
            goto done;
        }

        /* fall through */

    case sw_done:
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 parse header done");
        return NGX_HTTP_PARSE_HEADER_DONE;

    case sw_next:
        r->parse_start = b->pos;
        r->invalid_header = 0;
        break;

    case sw_header:
        break;
    }

    while (b->pos < b->last) {
        rc = ngx_http_v3_parse_headers(c, st, *b->pos++);

        if (rc > 0) {
            ngx_http_v3_finalize_connection(c, rc,
                                            "could not parse request headers");
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (rc == NGX_ERROR) {
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (rc == NGX_DONE) {
            r->state = sw_done;
            goto done;
        }

        if (rc == NGX_OK) {
            r->state = sw_next;
            goto done;
        }
    }

    r->state = sw_header;
    return NGX_AGAIN;

done:

    name = &st->header_rep.header.name;
    value = &st->header_rep.header.value;

    r->header_name_start = name->data;
    r->header_name_end = name->data + name->len;
    r->header_start = value->data;
    r->header_end = value->data + value->len;

    hash = 0;
    i = 0;

    for (n = 0; n < name->len; n++) {
        ch = name->data[n];

        if (ch >= 'A' && ch <= 'Z') {
            /*
             * A request or response containing uppercase
             * header field names MUST be treated as malformed
             */
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (ch == '\0') {
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (ch == '_' && !allow_underscores) {
            r->invalid_header = 1;
            continue;
        }

        if ((ch < 'a' || ch > 'z')
            && (ch < '0' || ch > '9')
            && ch != '-' && ch != '_')
        {
            r->invalid_header = 1;
            continue;
        }

        hash = ngx_hash(hash, ch);
        r->lowcase_header[i++] = ch;
        i &= (NGX_HTTP_LC_HEADER_LEN - 1);
    }

    r->header_hash = hash;
    r->lowcase_index = i;

    return NGX_OK;
}


static ngx_int_t
ngx_http_v3_process_pseudo_header(ngx_http_request_t *r, ngx_str_t *name,
    ngx_str_t *value)
{
    ngx_uint_t         i;
    ngx_connection_t  *c;

    if (name->len == 0 || name->data[0] != ':') {
        return NGX_DONE;
    }

    c = r->connection;

    if (name->len == 7 && ngx_strncmp(name->data, ":method", 7) == 0) {
        r->method_start = value->data;
        r->method_end = value->data + value->len;

        for (i = 0; i < sizeof(ngx_http_v3_methods)
                        / sizeof(ngx_http_v3_methods[0]); i++)
        {
            if (value->len == ngx_http_v3_methods[i].name.len
                && ngx_strncmp(value->data, ngx_http_v3_methods[i].name.data,
                               value->len) == 0)
            {
                r->method = ngx_http_v3_methods[i].method;
                break;
            }
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 method \"%V\" %ui", value, r->method);
        return NGX_OK;
    }

    if (name->len == 5 && ngx_strncmp(name->data, ":path", 5) == 0) {
        r->uri_start = value->data;
        r->uri_end = value->data + value->len;

        if (ngx_http_parse_uri(r) != NGX_OK) {
            ngx_log_error(NGX_LOG_INFO, c->log, 0,
                          "client sent invalid :path header: \"%V\"", value);
            return NGX_ERROR;
        }

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 path \"%V\"", value);

        return NGX_OK;
    }

    if (name->len == 7 && ngx_strncmp(name->data, ":scheme", 7) == 0) {
        r->schema_start = value->data;
        r->schema_end = value->data + value->len;

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 schema \"%V\"", value);

        return NGX_OK;
    }

    if (name->len == 10 && ngx_strncmp(name->data, ":authority", 10) == 0) {
        r->host_start = value->data;
        r->host_end = value->data + value->len;

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 authority \"%V\"", value);

        return NGX_OK;
    }

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 unknown pseudo header \"%V\" \"%V\"", name, value);

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_parse_request_body(ngx_http_request_t *r, ngx_buf_t *b,
    ngx_http_chunked_t *ctx)
{
    ngx_int_t                  rc;
    ngx_connection_t          *c;
    ngx_http_v3_parse_data_t  *st;

    c = r->connection;
    st = ctx->h3_parse;

    if (st == NULL) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 parse request body");

        st = ngx_pcalloc(c->pool, sizeof(ngx_http_v3_parse_data_t));
        if (st == NULL) {
            goto failed;
        }

        r->h3_parse = st;
    }

    if (ctx->size) {
        ctx->length = ctx->size + 1;
        return (b->pos == b->last) ? NGX_AGAIN : NGX_OK;
    }

    while (b->pos < b->last) {
        rc = ngx_http_v3_parse_data(c, st, *b->pos++);

        if (rc > 0) {
            ngx_http_v3_finalize_connection(c, rc,
                                            "could not parse request body");
            goto failed;
        }

        if (rc == NGX_ERROR) {
            goto failed;
        }

        if (rc == NGX_AGAIN) {
            continue;
        }

        /* rc == NGX_DONE */

        ctx->size = st->length;
        return NGX_OK;
    }

    if (!b->last_buf) {
        ctx->length = 1;
        return NGX_AGAIN;
    }

    if (st->state) {
        goto failed;
    }

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header done");

    return NGX_DONE;

failed:

    return NGX_ERROR;
}


ngx_chain_t *
ngx_http_v3_create_header(ngx_http_request_t *r)
{
    u_char                    *p;
    size_t                     len, n;
    ngx_buf_t                 *b;
    ngx_str_t                  host;
    ngx_uint_t                 i, port;
    ngx_chain_t               *hl, *cl, *bl;
    ngx_list_part_t           *part;
    ngx_table_elt_t           *header;
    ngx_connection_t          *c;
    ngx_http_core_loc_conf_t  *clcf;
    ngx_http_core_srv_conf_t  *cscf;
    u_char                     addr[NGX_SOCKADDR_STRLEN];

    c = r->connection;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 create header");

    len = ngx_http_v3_encode_header_block_prefix(NULL, 0, 0, 0);

    if (r->headers_out.status == NGX_HTTP_OK) {
        len += ngx_http_v3_encode_header_ri(NULL, 0,
                                            NGX_HTTP_V3_HEADER_STATUS_200);

    } else {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                             NGX_HTTP_V3_HEADER_STATUS_200,
                                             NULL, 3);
    }

    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

    if (r->headers_out.server == NULL) {
        if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_ON) {
            n = sizeof(NGINX_VER) - 1;

        } else if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_BUILD) {
            n = sizeof(NGINX_VER_BUILD) - 1;

        } else {
            n = sizeof("nginx") - 1;
        }

        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                             NGX_HTTP_V3_HEADER_SERVER,
                                             NULL, n);
    }

    if (r->headers_out.date == NULL) {
        len += ngx_http_v3_encode_header_lri(NULL, 0, NGX_HTTP_V3_HEADER_DATE,
                                             NULL, ngx_cached_http_time.len);
    }

    if (r->headers_out.content_type.len) {
        n = r->headers_out.content_type.len;

        if (r->headers_out.content_type_len == r->headers_out.content_type.len
            && r->headers_out.charset.len)
        {
            n += sizeof("; charset=") - 1 + r->headers_out.charset.len;
        }

        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                    NGX_HTTP_V3_HEADER_CONTENT_TYPE_TEXT_PLAIN,
                                    NULL, n);
    }

    if (r->headers_out.content_length == NULL) {
        if (r->headers_out.content_length_n > 0) {
            len += ngx_http_v3_encode_header_lri(NULL, 0,
                                        NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO,
                                        NULL, NGX_OFF_T_LEN);

        } else if (r->headers_out.content_length_n == 0) {
            len += ngx_http_v3_encode_header_ri(NULL, 0,
                                       NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO);
        }
    }

    if (r->headers_out.last_modified == NULL
        && r->headers_out.last_modified_time != -1)
    {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                  NGX_HTTP_V3_HEADER_LAST_MODIFIED, NULL,
                                  sizeof("Mon, 28 Sep 1970 06:00:00 GMT") - 1);
    }

    if (r->headers_out.location
        && r->headers_out.location->value.len
        && r->headers_out.location->value.data[0] == '/'
        && clcf->absolute_redirect)
    {
        r->headers_out.location->hash = 0;

        if (clcf->server_name_in_redirect) {
            cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);
            host = cscf->server_name;

        } else if (r->headers_in.server.len) {
            host = r->headers_in.server;

        } else {
            host.len = NGX_SOCKADDR_STRLEN;
            host.data = addr;

            if (ngx_connection_local_sockaddr(c, &host, 0) != NGX_OK) {
                return NULL;
            }
        }

        port = ngx_inet_get_port(c->local_sockaddr);

        n = sizeof("https://") - 1 + host.len
            + r->headers_out.location->value.len;

        if (clcf->port_in_redirect) {
            port = (port == 443) ? 0 : port;

        } else {
            port = 0;
        }

        if (port) {
            n += sizeof(":65535") - 1;
        }

        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                         NGX_HTTP_V3_HEADER_LOCATION, NULL, n);

    } else {
        ngx_str_null(&host);
        port = 0;
    }

#if (NGX_HTTP_GZIP)
    if (r->gzip_vary) {
        if (clcf->gzip_vary) {
            len += ngx_http_v3_encode_header_ri(NULL, 0,
                                      NGX_HTTP_V3_HEADER_VARY_ACCEPT_ENCODING);

        } else {
            r->gzip_vary = 0;
        }
    }
#endif

    part = &r->headers_out.headers.part;
    header = part->elts;

    for (i = 0; /* void */; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }

            part = part->next;
            header = part->elts;
            i = 0;
        }

        if (header[i].hash == 0) {
            continue;
        }

        len += ngx_http_v3_encode_header_l(NULL, &header[i].key,
                                           &header[i].value);
    }

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 header len:%uz", len);

    b = ngx_create_temp_buf(r->pool, len);
    if (b == NULL) {
        return NULL;
    }

    b->last = (u_char *) ngx_http_v3_encode_header_block_prefix(b->last,
                                                                0, 0, 0);

    if (r->headers_out.status == NGX_HTTP_OK) {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                                NGX_HTTP_V3_HEADER_STATUS_200);

    } else {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                 NGX_HTTP_V3_HEADER_STATUS_200,
                                                 NULL, 3);
        b->last = ngx_sprintf(b->last, "%03ui", r->headers_out.status);
    }

    if (r->headers_out.server == NULL) {
        if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_ON) {
            p = (u_char *) NGINX_VER;
            n = sizeof(NGINX_VER) - 1;

        } else if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_BUILD) {
            p = (u_char *) NGINX_VER_BUILD;
            n = sizeof(NGINX_VER_BUILD) - 1;

        } else {
            p = (u_char *) "nginx";
            n = sizeof("nginx") - 1;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                     NGX_HTTP_V3_HEADER_SERVER,
                                                     p, n);
    }

    if (r->headers_out.date == NULL) {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                     NGX_HTTP_V3_HEADER_DATE,
                                                     ngx_cached_http_time.data,
                                                     ngx_cached_http_time.len);
    }

    if (r->headers_out.content_type.len) {
        n = r->headers_out.content_type.len;

        if (r->headers_out.content_type_len == r->headers_out.content_type.len
            && r->headers_out.charset.len)
        {
            n += sizeof("; charset=") - 1 + r->headers_out.charset.len;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                    NGX_HTTP_V3_HEADER_CONTENT_TYPE_TEXT_PLAIN,
                                    NULL, n);

        p = b->last;
        b->last = ngx_cpymem(b->last, r->headers_out.content_type.data,
                             r->headers_out.content_type.len);

        if (r->headers_out.content_type_len == r->headers_out.content_type.len
            && r->headers_out.charset.len)
        {
            b->last = ngx_cpymem(b->last, "; charset=",
                                 sizeof("; charset=") - 1);
            b->last = ngx_cpymem(b->last, r->headers_out.charset.data,
                                 r->headers_out.charset.len);

            /* update r->headers_out.content_type for possible logging */

            r->headers_out.content_type.len = b->last - p;
            r->headers_out.content_type.data = p;
        }
    }

    if (r->headers_out.content_length == NULL) {
        if (r->headers_out.content_length_n > 0) {
            p = ngx_sprintf(b->last, "%O", r->headers_out.content_length_n);
            n = p - b->last;

            b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                        NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO,
                                        NULL, n);

            b->last = ngx_sprintf(b->last, "%O",
                                  r->headers_out.content_length_n);

        } else if (r->headers_out.content_length_n == 0) {
            b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                       NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO);
        }
    }

    if (r->headers_out.last_modified == NULL
        && r->headers_out.last_modified_time != -1)
    {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                  NGX_HTTP_V3_HEADER_LAST_MODIFIED, NULL,
                                  sizeof("Mon, 28 Sep 1970 06:00:00 GMT") - 1);

        b->last = ngx_http_time(b->last, r->headers_out.last_modified_time);
    }

    if (host.data) {
        n = sizeof("https://") - 1 + host.len
            + r->headers_out.location->value.len;

        if (port) {
            n += ngx_sprintf(b->last, ":%ui", port) - b->last;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                   NGX_HTTP_V3_HEADER_LOCATION,
                                                   NULL, n);

        p = b->last;
        b->last = ngx_cpymem(b->last, "https://", sizeof("https://") - 1);
        b->last = ngx_cpymem(b->last, host.data, host.len);

        if (port) {
            b->last = ngx_sprintf(b->last, ":%ui", port);
        }

        b->last = ngx_cpymem(b->last, r->headers_out.location->value.data,
                             r->headers_out.location->value.len);

        /* update r->headers_out.location->value for possible logging */

        r->headers_out.location->value.len = b->last - p;
        r->headers_out.location->value.data = p;
        ngx_str_set(&r->headers_out.location->key, "Location");
    }

#if (NGX_HTTP_GZIP)
    if (r->gzip_vary) {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                      NGX_HTTP_V3_HEADER_VARY_ACCEPT_ENCODING);
    }
#endif

    part = &r->headers_out.headers.part;
    header = part->elts;

    for (i = 0; /* void */; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }

            part = part->next;
            header = part->elts;
            i = 0;
        }

        if (header[i].hash == 0) {
            continue;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_l(b->last,
                                                         &header[i].key,
                                                         &header[i].value);
    }

    if (r->header_only) {
        b->last_buf = 1;
    }

    cl = ngx_alloc_chain_link(c->pool);
    if (cl == NULL) {
        return NULL;
    }

    cl->buf = b;
    cl->next = NULL;

    n = b->last - b->pos;

    len = 1 + ngx_http_v3_encode_varlen_int(NULL, n);

    b = ngx_create_temp_buf(c->pool, len);
    if (b == NULL) {
        return NULL;
    }

    *b->last++ = NGX_HTTP_V3_FRAME_HEADERS;
    b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last, n);

    hl = ngx_alloc_chain_link(c->pool);
    if (hl == NULL) {
        return NULL;
    }

    hl->buf = b;
    hl->next = cl;

    if (r->headers_out.content_length_n >= 0 && !r->header_only) {
        len = 1 + ngx_http_v3_encode_varlen_int(NULL,
                                              r->headers_out.content_length_n);

        b = ngx_create_temp_buf(c->pool, len);
        if (b == NULL) {
            return NULL;
        }

        *b->last++ = NGX_HTTP_V3_FRAME_DATA;
        b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last,
                                              r->headers_out.content_length_n);

        bl = ngx_alloc_chain_link(c->pool);
        if (bl == NULL) {
            return NULL;
        }

        bl->buf = b;
        bl->next = NULL;
        cl->next = bl;
    }

    return hl;
}


ngx_chain_t *
ngx_http_v3_create_trailers(ngx_http_request_t *r)
{
    ngx_buf_t    *b;
    ngx_chain_t  *cl;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http3 create trailers");

    /* XXX */

    b = ngx_calloc_buf(r->pool);
    if (b == NULL) {
        return NULL;
    }

    b->last_buf = 1;

    cl = ngx_alloc_chain_link(r->pool);
    if (cl == NULL) {
        return NULL;
    }

    cl->buf = b;
    cl->next = NULL;

    return cl;
}