new file mode 100644
--- /dev/null
+++ b/src/http/modules/ngx_http_range_filter.c
@@ -0,0 +1,523 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+/*
+ * the single part format:
+ *
+ * "HTTP/1.0 206 Partial Content" CRLF
+ * ... header ...
+ * "Content-Type: image/jpeg" CRLF
+ * "Content-Length: SIZE" CRLF
+ * "Content-Range: bytes START-END/SIZE" CRLF
+ * CRLF
+ * ... data ...
+ *
+ *
+ * the mutlipart format:
+ *
+ * "HTTP/1.0 206 Partial Content" CRLF
+ * ... header ...
+ * "Content-Type: multipart/byteranges; boundary=0123456789" CRLF
+ * CRLF
+ * CRLF
+ * "--0123456789" CRLF
+ * "Content-Type: image/jpeg" CRLF
+ * "Content-Range: bytes START0-END0/SIZE" CRLF
+ * CRLF
+ * ... data ...
+ * CRLF
+ * "--0123456789" CRLF
+ * "Content-Type: image/jpeg" CRLF
+ * "Content-Range: bytes START1-END1/SIZE" CRLF
+ * CRLF
+ * ... data ...
+ * CRLF
+ * "--0123456789--" CRLF
+ */
+
+
+typedef struct {
+    ngx_str_t  boundary_header;
+} ngx_http_range_filter_ctx_t;
+
+
+static ngx_int_t ngx_http_range_header_filter_init(ngx_cycle_t *cycle);
+static ngx_int_t ngx_http_range_body_filter_init(ngx_cycle_t *cycle);
+
+
+static ngx_http_module_t  ngx_http_range_header_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_range_header_filter_module = {
+    NGX_MODULE,
+    &ngx_http_range_header_filter_module_ctx, /* module context */
+    NULL,                                  /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    ngx_http_range_header_filter_init,     /* init module */
+    NULL                                   /* init child */
+};
+
+
+static ngx_http_module_t  ngx_http_range_body_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_range_body_filter_module = {
+    NGX_MODULE,
+    &ngx_http_range_body_filter_module_ctx, /* module context */
+    NULL,                                  /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    ngx_http_range_body_filter_init,       /* init module */
+    NULL                                   /* init child */
+};
+
+
+static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
+static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;
+
+
+static ngx_int_t ngx_http_range_header_filter(ngx_http_request_t *r)
+{
+    ngx_int_t                     rc;
+    ngx_uint_t                    boundary, suffix, i;
+    u_char                       *p;
+    size_t                        len;
+    off_t                         start, end;
+    ngx_http_range_t             *range;
+    ngx_http_range_filter_ctx_t  *ctx;
+
+    if (r->http_version < NGX_HTTP_VERSION_10
+        || r->headers_out.status != NGX_HTTP_OK
+        || r->headers_out.content_length_n == -1
+        || !r->filter_allow_ranges)
+    {
+        return ngx_http_next_header_filter(r);
+    }
+
+    if (r->headers_in.range == NULL
+        || r->headers_in.range->value.len < 7
+        || ngx_strncasecmp(r->headers_in.range->value.data, "bytes=", 6) != 0)
+    {
+
+        r->headers_out.accept_ranges = ngx_list_push(&r->headers_out.headers);
+        if (r->headers_out.accept_ranges == NULL) {
+            return NGX_ERROR;
+        }
+
+        r->headers_out.accept_ranges->key.len = sizeof("Accept-Ranges") - 1;
+        r->headers_out.accept_ranges->key.data = (u_char *) "Accept-Ranges";
+        r->headers_out.accept_ranges->value.len = sizeof("bytes") - 1;
+        r->headers_out.accept_ranges->value.data = (u_char *) "bytes";
+
+        return ngx_http_next_header_filter(r);
+    }
+
+    ngx_init_array(r->headers_out.ranges, r->pool, 5, sizeof(ngx_http_range_t),
+                   NGX_ERROR);
+
+    rc = 0;
+    range = NULL;
+    p = r->headers_in.range->value.data + 6;
+
+    for ( ;; ) {
+        start = 0;
+        end = 0;
+        suffix = 0;
+
+        while (*p == ' ') { p++; }
+
+        if (*p != '-') {
+            if (*p < '0' || *p > '9') {
+                rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
+                break;
+            }
+
+            while (*p >= '0' && *p <= '9') {
+                start = start * 10 + *p++ - '0';
+            }
+
+            while (*p == ' ') { p++; }
+
+            if (*p++ != '-') {
+                rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
+                break;
+            }
+
+            if (start >= r->headers_out.content_length_n) {
+                rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
+                break;
+            }
+
+            while (*p == ' ') { p++; }
+
+            if (*p == ',' || *p == '\0') {
+                ngx_test_null(range, ngx_push_array(&r->headers_out.ranges),
+                              NGX_ERROR);
+                range->start = start;
+                range->end = r->headers_out.content_length_n;
+
+                if (*p++ != ',') {
+                    break;
+                }
+
+                continue;
+            }
+
+        } else {
+            suffix = 1;
+            p++;
+        }
+
+        if (*p < '0' || *p > '9') {
+            rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
+            break;
+        }
+
+        while (*p >= '0' && *p <= '9') {
+            end = end * 10 + *p++ - '0';
+        }
+
+        while (*p == ' ') { p++; }
+
+        if (*p != ',' && *p != '\0') {
+            rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
+            break;
+        }
+
+        if (suffix) {
+           start = r->headers_out.content_length_n - end;
+           end = r->headers_out.content_length_n - 1;
+        }
+
+        if (start > end) {
+            rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
+            break;
+        }
+
+        ngx_test_null(range, ngx_push_array(&r->headers_out.ranges), NGX_ERROR);
+        range->start = start;
+
+        if (end >= r->headers_out.content_length_n) {
+            /*
+             * Download Accelerator sends the last byte position
+             * that equals to the file length
+             */
+            range->end = r->headers_out.content_length_n;
+
+        } else {
+            range->end = end + 1;
+        }
+
+        if (*p++ != ',') {
+            break;
+        }
+    }
+
+    if (rc) {
+
+        /* rc == NGX_HTTP_RANGE_NOT_SATISFIABLE */
+
+        r->headers_out.status = rc;
+        r->headers_out.ranges.nelts = 0;
+
+        r->headers_out.content_range = ngx_list_push(&r->headers_out.headers);
+        if (r->headers_out.content_range == NULL) {
+            return NGX_ERROR;
+        }
+
+        r->headers_out.content_range->key.len = sizeof("Content-Range") - 1;
+        r->headers_out.content_range->key.data = (u_char *) "Content-Range";
+
+        r->headers_out.content_range->value.data =
+                                               ngx_palloc(r->pool, 8 + 20 + 1);
+        if (r->headers_out.content_range->value.data == NULL) {
+            return NGX_ERROR;
+        }
+
+        r->headers_out.content_range->value.len =
+                ngx_snprintf((char *) r->headers_out.content_range->value.data,
+                             8 + 20 + 1, "bytes */" OFF_T_FMT,
+                             r->headers_out.content_length_n);
+
+        r->headers_out.content_length_n = -1;
+        if (r->headers_out.content_length) {
+            r->headers_out.content_length->key.len = 0;
+            r->headers_out.content_length = NULL;
+        }
+
+        return rc;
+
+    } else {
+        r->headers_out.status = NGX_HTTP_PARTIAL_CONTENT;
+
+        if (r->headers_out.ranges.nelts == 1) {
+
+            r->headers_out.content_range =
+                                        ngx_list_push(&r->headers_out.headers);
+            if (r->headers_out.content_range == NULL) {
+                return NGX_ERROR;
+            }
+
+            r->headers_out.content_range->key.len = sizeof("Content-Range") - 1;
+            r->headers_out.content_range->key.data = (u_char *) "Content-Range";
+
+            ngx_test_null(r->headers_out.content_range->value.data,
+                          ngx_palloc(r->pool, 6 + 20 + 1 + 20 + 1 + 20 + 1),
+                          NGX_ERROR);
+
+            /* "Content-Range: bytes SSSS-EEEE/TTTT" header */
+
+            r->headers_out.content_range->value.len =
+                   ngx_snprintf((char *)
+                                r->headers_out.content_range->value.data,
+                                6 + 20 + 1 + 20 + 1 + 20 + 1,
+                                "bytes " OFF_T_FMT "-" OFF_T_FMT "/" OFF_T_FMT,
+                                range->start, range->end - 1,
+                                r->headers_out.content_length_n);
+
+            r->headers_out.content_length_n = range->end - range->start;
+
+        } else {
+
+#if 0
+            /* TODO: what if no content_type ?? */
+
+            if (!(r->headers_out.content_type =
+                   ngx_http_add_header(&r->headers_out, ngx_http_headers_out)))
+            {
+                return NGX_ERROR;
+            }
+#endif
+
+            ngx_http_create_ctx(r, ctx, ngx_http_range_body_filter_module,
+                                sizeof(ngx_http_range_filter_ctx_t), NGX_ERROR);
+
+            len = 4 + 10 + 2 + 14 + r->headers_out.content_type->value.len
+                                  + 2 + 21 + 1;
+
+            if (r->headers_out.charset.len) {
+                len += 10 + r->headers_out.charset.len;
+            }
+
+            ngx_test_null(ctx->boundary_header.data, ngx_palloc(r->pool, len),
+                          NGX_ERROR);
+
+            boundary = ngx_next_temp_number(0);
+
+            /*
+             * The boundary header of the range:
+             * CRLF
+             * "--0123456789" CRLF
+             * "Content-Type: image/jpeg" CRLF
+             * "Content-Range: bytes "
+             */
+
+            if (r->headers_out.charset.len) {
+                ctx->boundary_header.len =
+                         ngx_snprintf((char *) ctx->boundary_header.data, len,
+                                      CRLF "--%010" NGX_UINT_T_FMT CRLF
+                                      "Content-Type: %s; charset=%s" CRLF
+                                      "Content-Range: bytes ",
+                                      boundary,
+                                      r->headers_out.content_type->value.data,
+                                      r->headers_out.charset.data);
+
+                r->headers_out.charset.len = 0;
+
+            } else {
+                ctx->boundary_header.len =
+                         ngx_snprintf((char *) ctx->boundary_header.data, len,
+                                      CRLF "--%010" NGX_UINT_T_FMT CRLF
+                                      "Content-Type: %s" CRLF
+                                      "Content-Range: bytes ",
+                                      boundary,
+                                      r->headers_out.content_type->value.data);
+            }
+
+            ngx_test_null(r->headers_out.content_type->value.data,
+                          ngx_palloc(r->pool, 31 + 10 + 1),
+                          NGX_ERROR);
+
+            /* "Content-Type: multipart/byteranges; boundary=0123456789" */
+
+            r->headers_out.content_type->value.len =
+                      ngx_snprintf((char *)
+                                   r->headers_out.content_type->value.data,
+                                   31 + 10 + 1,
+                                   "multipart/byteranges; boundary=%010"
+                                   NGX_UINT_T_FMT,
+                                   boundary);
+
+            /* the size of the last boundary CRLF "--0123456789--" CRLF */
+            len = 4 + 10 + 4;
+
+            range = r->headers_out.ranges.elts;
+            for (i = 0; i < r->headers_out.ranges.nelts; i++) {
+                ngx_test_null(range[i].content_range.data,
+                              ngx_palloc(r->pool, 20 + 1 + 20 + 1 + 20 + 5),
+                              NGX_ERROR);
+
+                /* the size of the range: "SSSS-EEEE/TTTT" CRLF CRLF */
+
+                range[i].content_range.len =
+                  ngx_snprintf((char *) range[i].content_range.data,
+                               20 + 1 + 20 + 1 + 20 + 5,
+                               OFF_T_FMT "-" OFF_T_FMT "/" OFF_T_FMT CRLF CRLF,
+                               range[i].start, range[i].end - 1,
+                               r->headers_out.content_length_n);
+
+                len += ctx->boundary_header.len + range[i].content_range.len
+                                    + (size_t) (range[i].end - range[i].start);
+            }
+
+            r->headers_out.content_length_n = len;
+            r->headers_out.content_length = NULL;
+        }
+    }
+
+    return ngx_http_next_header_filter(r);
+}
+
+
+static ngx_int_t ngx_http_range_body_filter(ngx_http_request_t *r,
+                                            ngx_chain_t *in)
+{
+    ngx_uint_t                    i;
+    ngx_buf_t                    *b;
+    ngx_chain_t                  *out, *hcl, *rcl, *dcl, **ll;
+    ngx_http_range_t             *range;
+    ngx_http_range_filter_ctx_t  *ctx;
+
+    if (r->headers_out.ranges.nelts == 0) {
+        return ngx_http_next_body_filter(r, in);
+    }
+
+    /*
+     * the optimized version for the static files only
+     * that are passed in the single file buf
+     */
+
+    if (in && in->buf->in_file && in->buf->last_buf) {
+        range = r->headers_out.ranges.elts;
+
+        if (r->headers_out.ranges.nelts == 1) {
+            in->buf->file_pos = range->start;
+            in->buf->file_last = range->end;
+
+            return ngx_http_next_body_filter(r, in);
+        }
+
+        ctx = ngx_http_get_module_ctx(r, ngx_http_range_body_filter_module);
+        ll = &out;
+
+        for (i = 0; i < r->headers_out.ranges.nelts; i++) {
+
+            /*
+             * The boundary header of the range:
+             * CRLF
+             * "--0123456789" CRLF
+             * "Content-Type: image/jpeg" CRLF
+             * "Content-Range: bytes "
+             */
+
+            ngx_test_null(b, ngx_calloc_buf(r->pool), NGX_ERROR);
+            b->memory = 1;
+            b->pos = ctx->boundary_header.data;
+            b->last = ctx->boundary_header.data + ctx->boundary_header.len;
+
+            ngx_test_null(hcl, ngx_alloc_chain_link(r->pool), NGX_ERROR);
+            hcl->buf = b;
+
+            /* "SSSS-EEEE/TTTT" CRLF CRLF */
+
+            ngx_test_null(b, ngx_calloc_buf(r->pool), NGX_ERROR);
+            b->temporary = 1;
+            b->pos = range[i].content_range.data;
+            b->last = range[i].content_range.data + range[i].content_range.len;
+
+            ngx_test_null(rcl, ngx_alloc_chain_link(r->pool), NGX_ERROR);
+            rcl->buf = b;
+
+            /* the range data */
+
+            ngx_test_null(b, ngx_calloc_buf(r->pool), NGX_ERROR);
+            b->in_file = 1;
+            b->file_pos = range[i].start;
+            b->file_last = range[i].end;
+            b->file = in->buf->file;
+
+            ngx_alloc_link_and_set_buf(dcl, b, r->pool, NGX_ERROR);
+
+            *ll = hcl;
+            hcl->next = rcl;
+            rcl->next = dcl;
+            ll = &dcl->next;
+        }
+
+        /* the last boundary CRLF "--0123456789--" CRLF  */
+
+        ngx_test_null(b, ngx_calloc_buf(r->pool), NGX_ERROR);
+        b->temporary = 1;
+        b->last_buf = 1;
+        ngx_test_null(b->pos, ngx_palloc(r->pool, 4 + 10 + 4), NGX_ERROR);
+        b->last = ngx_cpymem(b->pos, ctx->boundary_header.data, 4 + 10);
+        *b->last++ = '-'; *b->last++ = '-';
+        *b->last++ = CR; *b->last++ = LF;
+
+        ngx_alloc_link_and_set_buf(hcl, b, r->pool, NGX_ERROR);
+        *ll = hcl;
+
+        return ngx_http_next_body_filter(r, out);
+    }
+
+    /* TODO: alert */
+
+    return ngx_http_next_body_filter(r, in);
+}
+
+
+static ngx_int_t ngx_http_range_header_filter_init(ngx_cycle_t *cycle)
+{
+    ngx_http_next_header_filter = ngx_http_top_header_filter;
+    ngx_http_top_header_filter = ngx_http_range_header_filter;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t ngx_http_range_body_filter_init(ngx_cycle_t *cycle)
+{
+    ngx_http_next_body_filter = ngx_http_top_body_filter;
+    ngx_http_top_body_filter = ngx_http_range_body_filter;
+
+    return NGX_OK;
+}