new file mode 100644
--- /dev/null
+++ b/src/http/modules/ngx_http_range_filter_module.c
@@ -0,0 +1,594 @@
+
+/*
+ * 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 process */
+};
+
+
+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 process */
+};
+
+
+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)
+{
+    u_char                       *p;
+    size_t                        len;
+    off_t                         start, end;
+    ngx_int_t                     rc;
+    ngx_uint_t                    suffix, i;
+    ngx_atomic_uint_t             boundary;
+    ngx_table_elt_t              *content_range;
+    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);
+    }
+
+    if (ngx_array_init(&r->headers_out.ranges, r->pool, 2,
+                                        sizeof(ngx_http_range_t)) == NGX_ERROR)
+    {
+        return 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') {
+                range = ngx_array_push(&r->headers_out.ranges);
+                if (range == NULL) {
+                    return 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;
+        }
+
+        range = ngx_array_push(&r->headers_out.ranges);
+        if (range == NULL) {
+            return 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;
+
+        content_range = ngx_list_push(&r->headers_out.headers);
+        if (content_range == NULL) {
+            return NGX_ERROR;
+        }
+
+        r->headers_out.content_range = content_range;
+
+        content_range->key.len = sizeof("Content-Range") - 1;
+        content_range->key.data = (u_char *) "Content-Range";
+
+        content_range->value.data = ngx_palloc(r->pool,
+                                       sizeof("bytes */") - 1 + NGX_OFF_T_LEN);
+        if (content_range->value.data == NULL) {
+            return NGX_ERROR;
+        }
+
+        content_range->value.len = ngx_sprintf(content_range->value.data,
+                                               "bytes */%O",
+                                               r->headers_out.content_length_n)
+                                   - content_range->value.data;
+
+        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;
+    }
+
+    r->headers_out.status = NGX_HTTP_PARTIAL_CONTENT;
+
+    if (r->headers_out.ranges.nelts == 1) {
+
+        content_range = ngx_list_push(&r->headers_out.headers);
+        if (content_range == NULL) {
+            return NGX_ERROR;
+        }
+
+        r->headers_out.content_range = content_range;
+
+        content_range->key.len = sizeof("Content-Range") - 1;
+        content_range->key.data = (u_char *) "Content-Range";
+
+        content_range->value.data =
+               ngx_palloc(r->pool, sizeof("bytes -/") - 1 + 3 * NGX_OFF_T_LEN);
+        if (content_range->value.data == NULL) {
+            return NGX_ERROR;
+        }
+
+        /* "Content-Range: bytes SSSS-EEEE/TTTT" header */
+
+        content_range->value.len = ngx_sprintf(content_range->value.data,
+                                               "bytes %O-%O/%O",
+                                               range->start, range->end - 1,
+                                               r->headers_out.content_length_n)
+                                   - content_range->value.data;
+
+        r->headers_out.content_length_n = range->end - range->start;
+
+        return ngx_http_next_header_filter(r);
+    }
+
+
+    /* TODO: what if no content_type ?? */
+
+    ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_range_filter_ctx_t));
+    if (ctx == NULL) {
+        return NGX_ERROR;
+    }
+    
+    ngx_http_set_ctx(r, ctx, ngx_http_range_body_filter_module);
+
+
+    len = sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN
+          + sizeof(CRLF "Content-Type: ") - 1
+          + r->headers_out.content_type->value.len
+          + sizeof(CRLF "Content-Range: bytes ") - 1;
+
+    if (r->headers_out.charset.len) {
+        len += sizeof("; charset=") - 1 + r->headers_out.charset.len;
+    }
+
+    ctx->boundary_header.data = ngx_palloc(r->pool, len);
+    if (ctx->boundary_header.data == NULL) {
+        return 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_sprintf(ctx->boundary_header.data,
+                                           CRLF "--%0muA" CRLF
+                                           "Content-Type: %V; charset=%V" CRLF
+                                           "Content-Range: bytes ",
+                                           boundary,
+                                           &r->headers_out.content_type->value,
+                                           &r->headers_out.charset)
+                                   - ctx->boundary_header.data;
+
+        r->headers_out.charset.len = 0;
+
+    } else {
+        ctx->boundary_header.len = ngx_sprintf(ctx->boundary_header.data,
+                                           CRLF "--%0muA" CRLF
+                                           "Content-Type: %V" CRLF
+                                           "Content-Range: bytes ",
+                                           boundary,
+                                           &r->headers_out.content_type->value)
+                                   - ctx->boundary_header.data;
+    }
+
+    r->headers_out.content_type->value.data =
+         ngx_palloc(r->pool,
+                    sizeof("Content-Type: multipart/byteranges; boundary=") - 1
+                    + NGX_ATOMIC_T_LEN);
+
+    if (r->headers_out.content_type->value.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    /* "Content-Type: multipart/byteranges; boundary=0123456789" */
+
+    r->headers_out.content_type->value.len =
+                           ngx_sprintf(r->headers_out.content_type->value.data,
+                                       "multipart/byteranges; boundary=%0muA",
+                                       boundary)
+                           - r->headers_out.content_type->value.data;
+
+
+    /* the size of the last boundary CRLF "--0123456789--" CRLF */
+
+    len = sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN + sizeof("--" CRLF) - 1;
+
+    range = r->headers_out.ranges.elts;
+    for (i = 0; i < r->headers_out.ranges.nelts; i++) {
+
+        /* the size of the range: "SSSS-EEEE/TTTT" CRLF CRLF */
+
+        range[i].content_range.data =
+                                ngx_palloc(r->pool, 3 * NGX_OFF_T_LEN + 2 + 4);
+
+        if (range[i].content_range.data == NULL) {
+            return NGX_ERROR;
+        }
+
+        range[i].content_range.len = ngx_sprintf(range[i].content_range.data,
+                                               "%O-%O/%O" CRLF CRLF,
+                                               range[i].start, range[i].end - 1,
+                                               r->headers_out.content_length_n)
+                                     - range[i].content_range.data;
+
+        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 "
+             */
+
+            b = ngx_calloc_buf(r->pool);
+            if (b == NULL) {
+                return NGX_ERROR;
+            }
+
+            b->memory = 1;
+            b->pos = ctx->boundary_header.data;
+            b->last = ctx->boundary_header.data + ctx->boundary_header.len;
+
+            hcl = ngx_alloc_chain_link(r->pool);
+            if (hcl == NULL) {
+                return NGX_ERROR;
+            }
+
+            hcl->buf = b;
+
+
+            /* "SSSS-EEEE/TTTT" CRLF CRLF */
+
+            b = ngx_calloc_buf(r->pool);
+            if (b == NULL) {
+                return NGX_ERROR;
+            }
+
+            b->temporary = 1;
+            b->pos = range[i].content_range.data;
+            b->last = range[i].content_range.data + range[i].content_range.len;
+
+            rcl = ngx_alloc_chain_link(r->pool);
+            if (rcl == NULL) {
+                return NGX_ERROR;
+            }
+
+            rcl->buf = b;
+
+
+            /* the range data */
+
+            b = ngx_calloc_buf(r->pool);
+            if (b == NULL) {
+                return NGX_ERROR;
+            }
+
+            b->in_file = 1;
+            b->file_pos = range[i].start;
+            b->file_last = range[i].end;
+            b->file = in->buf->file;
+
+            dcl = ngx_alloc_chain_link(r->pool);
+            if (dcl == NULL) {
+                return NGX_ERROR;
+            }
+
+            dcl->buf = b;
+
+            *ll = hcl;
+            hcl->next = rcl;
+            rcl->next = dcl;
+            ll = &dcl->next;
+        }
+
+        /* the last boundary CRLF "--0123456789--" CRLF  */
+
+        b = ngx_calloc_buf(r->pool);
+        if (b == NULL) {
+            return NGX_ERROR;
+        }
+
+        b->temporary = 1;
+        b->last_buf = 1;
+
+        b->pos = ngx_palloc(r->pool, sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN
+                                     + sizeof("--" CRLF) - 1);
+        if (b->pos == NULL) {
+            return NGX_ERROR;
+        }
+
+        b->last = ngx_cpymem(b->pos, ctx->boundary_header.data, 4 + 10);
+        *b->last++ = '-'; *b->last++ = '-';
+        *b->last++ = CR; *b->last++ = LF;
+
+        hcl = ngx_alloc_chain_link(r->pool);
+        if (hcl == NULL) {
+            return NGX_ERROR;
+        }
+
+        hcl->buf = b;
+        hcl->next = NULL;
+
+        *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;
+}