new file mode 100644
--- /dev/null
+++ b/src/http/ngx_http_write_filter_module.c
@@ -0,0 +1,250 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+#include <ngx_http.h>
+
+
+typedef struct {
+    ngx_chain_t  *out;
+} ngx_http_write_filter_ctx_t;
+
+
+static ngx_int_t ngx_http_write_filter_init(ngx_cycle_t *cycle);
+
+
+ngx_http_module_t  ngx_http_write_filter_module_ctx = {
+    NULL,                                  /* pre conf */
+
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    NULL,                                  /* create server configuration */
+    NULL,                                  /* merge server configuration */
+
+    NULL,                                  /* create location configuration */
+    NULL,                                  /* merge location configuration */
+};
+
+
+ngx_module_t  ngx_http_write_filter_module = {
+    NGX_MODULE,
+    &ngx_http_write_filter_module_ctx,     /* module context */
+    NULL,                                  /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    ngx_http_write_filter_init,            /* init module */
+    NULL                                   /* init process */
+};
+
+
+ngx_int_t
+ngx_http_write_filter(ngx_http_request_t *r, ngx_chain_t *in)
+{
+    off_t                         size, sent;
+    ngx_uint_t                    last, flush;
+    ngx_chain_t                  *cl, *ln, **ll, *chain;
+    ngx_connection_t             *c;
+    ngx_http_core_loc_conf_t     *clcf;
+    ngx_http_write_filter_ctx_t  *ctx;
+
+    ctx = ngx_http_get_module_ctx(r->main ? r->main : r,
+                                  ngx_http_write_filter_module);
+
+    if (ctx == NULL) {
+
+        ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_write_filter_ctx_t));
+        if (ctx == NULL) {
+            return NGX_ERROR;
+        }
+
+        ngx_http_set_ctx(r, ctx, ngx_http_write_filter_module);
+    }
+
+    size = 0;
+    flush = 0;
+    last = 0;
+    ll = &ctx->out;
+
+    /* find the size, the flush point and the last link of the saved chain */
+
+    for (cl = ctx->out; cl; cl = cl->next) {
+        ll = &cl->next;
+
+        ngx_log_debug7(NGX_LOG_DEBUG_EVENT, r->connection->log, 0,
+                       "write old buf t:%d f:%d %p, pos %p, size: %z "
+                       "file: %O, size: %z",
+                       cl->buf->temporary, cl->buf->in_file,
+                       cl->buf->start, cl->buf->pos,
+                       cl->buf->last - cl->buf->pos,
+                       cl->buf->file_pos,
+                       cl->buf->file_last - cl->buf->file_pos);
+
+#if 1
+        if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
+            ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
+                          "zero size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
+#endif
+
+        size += ngx_buf_size(cl->buf);
+
+        if (cl->buf->flush || cl->buf->recycled) {
+            flush = 1;
+        }
+
+        if (cl->buf->last_buf) {
+            last = 1;
+        }
+    }
+
+    /* add the new chain to the existent one */
+
+    for (ln = in; ln; ln = ln->next) {
+        cl = ngx_alloc_chain_link(r->pool);
+        if (cl == NULL) {
+            return NGX_ERROR;
+        }
+
+        cl->buf = ln->buf;
+        *ll = cl;
+        ll = &cl->next;
+
+        ngx_log_debug7(NGX_LOG_DEBUG_EVENT, r->connection->log, 0,
+                       "write new buf t:%d f:%d %p, pos %p, size: %z "
+                       "file: %O, size: %z",
+                       cl->buf->temporary, cl->buf->in_file,
+                       cl->buf->start, cl->buf->pos,
+                       cl->buf->last - cl->buf->pos,
+                       cl->buf->file_pos,
+                       cl->buf->file_last - cl->buf->file_pos);
+
+#if 1
+        if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
+            ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
+                          "zero size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
+#endif
+
+        size += ngx_buf_size(cl->buf);
+
+        if (cl->buf->flush || cl->buf->recycled) {
+            flush = 1;
+        }
+
+        if (cl->buf->last_buf) {
+            last = 1;
+        }
+    }
+
+    *ll = NULL;
+
+    c = r->connection;
+
+    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http write filter: l:%d f:%d s:%O", last, flush, size);
+
+    clcf = ngx_http_get_module_loc_conf(r->main ? r->main : r,
+                                        ngx_http_core_module);
+
+    /*
+     * avoid the output if there is no last buf, no flush point,
+     * there are the incoming bufs and the size of all bufs
+     * is smaller than "postpone_output" directive
+     */
+
+    if (!last && !flush && in && size < (off_t) clcf->postpone_output) {
+        return NGX_OK;
+    }
+
+    if (c->write->delayed) {
+        return NGX_AGAIN;
+    }
+
+    if (size == 0 && !c->buffered) {
+        if (last) {
+            return NGX_OK;
+        }
+
+        if (flush) {
+            do {
+                ctx->out = ctx->out->next;
+            }
+            while (ctx->out);
+
+            return NGX_OK;
+        }
+
+        ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
+                      "the http output chain is empty");
+
+        ngx_debug_point();
+
+        return NGX_ERROR;
+    }
+
+    sent = c->sent;
+
+    chain = c->send_chain(c, ctx->out, clcf->limit_rate);
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http write filter %p", chain);
+
+    if (clcf->limit_rate) {
+        sent = c->sent - sent;
+        c->write->delayed = 1;
+        ngx_add_timer(r->connection->write,
+                      (ngx_msec_t) (sent * 1000 / clcf->limit_rate));
+    }
+
+    if (chain == NGX_CHAIN_ERROR) {
+        return NGX_ERROR;
+    }
+
+    ctx->out = chain;
+
+    if (chain || (last && c->buffered)) {
+        return NGX_AGAIN;
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_write_filter_init(ngx_cycle_t *cycle)
+{
+    ngx_http_top_body_filter = ngx_http_write_filter;
+
+    return NGX_OK;
+}